前面介绍了tty核心分析及tty驱动开发的方法，tty设备包括串口、终端、伪终端三大类，其中终端和伪终端驱动内核都帮我们实现好了，很少需要改动。因此我们主要介绍串口驱动的开发及其在内核中的构架（其核心实现源码主要在/drivers/serial_core.c中），这一节中我们主要分析向内核中加入一个serial驱动用到的数据结构。

      serial core是构建在tty core之上的。注册一个串口驱动即在tty core层注册一个tty驱动。下面我们看看串口驱动中用到的两个最重要的数据机构 struct uart_driver 表示一个serial驱动，struct uart_port 表示一个串口端口。

struct uart_driver {
 struct module  *owner;
 const char  *driver_name;  //驱动名称
 const char  *dev_name;     //设备名基础
 int    major;                         //主设备号
 int    minor;                         //起始次设备号
 int    nr;                              //设备个数
 struct console  *cons;        //关联的控制台

 /*
  * these are private; the low level driver should not
  * touch these; they should be initialised to NULL
  */
 struct uart_state *state;        //串口驱动操作设备数组
 struct tty_driver *tty_driver;  //表征串口驱动的tty驱动
};

 

      上面结构中struct uart_state *state指向驱动操作的串口设备相关数据结构，其中struct uart_port *port就是我们下面要介绍的描述串口设备的结构，struct uart_info *info 指向相关联的struct tty_struct 结构和数据发射时环形缓冲区struct circ_buf xmit，即串口打开时的描述信息。uart_info有两个成员在底层串口驱动会用到：xmit和tty。用户空间程序通过串口发送数据时，上层驱动将用户数据保存在xmit；而串口发送中断处理函数就是通过xmit获取到用户数据并将它们发送出去。串口接收中断处理函数需要通过tty将接收到的数据传递给行规则层。具体的成员分析我们在后面介绍具体的操作时再分析。

 

struct uart_port {
 spinlock_t  lock;   /* port lock */   //串口端口锁
 unsigned int  iobase;   /* in/out[bwl] */    //io端口基地址
 unsigned char __iomem *membase;  /* read/write[bwl] */  //io内存基地址，虚拟地址
 unsigned int  irq;   /* irq number */      //中断号
 unsigned int  uartclk;  /* base uart clock */  //串口时钟
 unsigned int  fifosize;  /* tx fifo size */       //串口fifo缓冲大小
 unsigned char  x_char;   /* xon/xoff char */  //xon/xoff字符
 unsigned char  regshift;  /* reg offset shift */       //j寄存器移位       
 unsigned char  iotype;   /* io access style */    //io访问方式
 unsigned char  unused1;

#define UPIO_PORT  (0)   //端口
#define UPIO_HUB6  (1)
#define UPIO_MEM  (2)    //内存
#define UPIO_MEM32  (3)
#define UPIO_AU   (4)   /* Au1x00 type IO */
#define UPIO_TSI  (5)   /* Tsi108/109 type IO */
#define UPIO_DWAPB  (6)   /* DesignWare APB UART */
#define UPIO_RM9000  (7)   /* RM9000 type IO */

 unsigned int  read_status_mask; /* driver specific */  //关心的rx error status
 unsigned int  ignore_status_mask; /* driver specific */ //忽略的rx error status

 struct uart_info *info;   /* pointer to parent info */
 struct uart_icount icount;   /* statistics */

 struct console  *cons;   /* struct console, if any */
#ifdef CONFIG_SERIAL_CORE_CONSOLE
 unsigned long  sysrq;   /* sysrq timeout */
#endif

 upf_t   flags;

#define UPF_FOURPORT  ((__force upf_t) (1 << 1))
#define UPF_SAK   ((__force upf_t) (1 << 2))
#define UPF_SPD_MASK  ((__force upf_t) (0x1030))
#define UPF_SPD_HI  ((__force upf_t) (0x0010))
#define UPF_SPD_VHI  ((__force upf_t) (0x0020))
#define UPF_SPD_CUST  ((__force upf_t) (0x0030))
#define UPF_SPD_SHI  ((__force upf_t) (0x1000))
#define UPF_SPD_WARP  ((__force upf_t) (0x1010))
#define UPF_SKIP_TEST  ((__force upf_t) (1 << 6))
#define UPF_AUTO_IRQ  ((__force upf_t) (1 << 7))
#define UPF_HARDPPS_CD  ((__force upf_t) (1 << 11))
#define UPF_LOW_LATENCY  ((__force upf_t) (1 << 13))
#define UPF_BUGGY_UART  ((__force upf_t) (1 << 14))
#define UPF_MAGIC_MULTIPLIER ((__force upf_t) (1 << 16))
#define UPF_CONS_FLOW  ((__force upf_t) (1 << 23))
#define UPF_SHARE_IRQ  ((__force upf_t) (1 << 24))
#define UPF_BOOT_AUTOCONF ((__force upf_t) (1 << 28))
#define UPF_FIXED_PORT  ((__force upf_t) (1 << 29))
#define UPF_DEAD  ((__force upf_t) (1 << 30))
#define UPF_IOREMAP  ((__force upf_t) (1 << 31))

#define UPF_CHANGE_MASK  ((__force upf_t) (0x17fff))
#define UPF_USR_MASK  ((__force upf_t) (UPF_SPD_MASK|UPF_LOW_LATENCY))

 unsigned int  mctrl;   /* current modem ctrl settings */
 unsigned int  timeout;  /* character-based timeout */
 unsigned int  type;   /* port type */
 const struct uart_ops *ops;   //具体端口的相关操作函数
 unsigned int  custom_divisor;
 unsigned int  line;   /* port index */
 resource_size_t  mapbase;  /* for ioremap */  //io内存物理地址
 struct device  *dev;   /* parent device */
 unsigned char  hub6;   /* this should be in the 8250 driver */
 unsigned char  suspended;
 unsigned char  unused[2]; //允许串口收发字符标志
 void   *private_data;  /* generic platform data pointer */
};

uart_iconut为串口信息计数器，包含了发送字符计数、接收字符计数等。在串口的发送中断处理函数和接收中断处理函数中，我们需要管理这些计数。

struct uart_icount {
 __u32 cts;
 __u32 dsr;
 __u32 rng;
 __u32 dcd;
 __u32 rx;             //接收字符数
 __u32 tx;             //发送字符数
 __u32 frame;       //错误帧计数
 __u32 overrun;    //rx fifo溢出计数
 __u32 parity;        //帧校验错误计数
 __u32 brk;            //break计数
 __u32 buf_overrun;
};

对于实现一个串口驱动，主要的工作量就是实现struct uart_ops *ops中的各个操作函数。
 * This structure describes all the operations that can be
 * done on the physical hardware.
 */
struct uart_ops {
 unsigned int (*tx_empty)(struct uart_port *);  //串口tx FIFO缓存是否为空
 void  (*set_mctrl)(struct uart_port *, unsigned int mctrl);  //设置串口modem控制
 unsigned int (*get_mctrl)(struct uart_port *);                    //获得串口的modem控制
 void  (*stop_tx)(struct uart_port *);                                   //停止串口发送
 void  (*start_tx)(struct uart_port *);                                   //使能串口发送
 void  (*send_xchar)(struct uart_port *, char ch);                //发送xchar
 void  (*stop_rx)(struct uart_port *);                                   //禁止串口接收
 void  (*enable_ms)(struct uart_port *);                              //使能modem状态信号
 void  (*break_ctl)(struct uart_port *, int ctl);                      //设置break信号
 int  (*startup)(struct uart_port *);                                      //启动串口
 void  (*shutdown)(struct uart_port *);                                //关闭串口
 void  (*flush_buffer)(struct uart_port *);                             //刷新缓存
 void  (*set_termios)(struct uart_port *, struct ktermios *new,
           struct ktermios *old);                                               //设置串口参数
 void  (*set_ldisc)(struct uart_port *);                                 //设置线路规程
 void  (*pm)(struct uart_port *, unsigned int state,
         unsigned int oldstate);    //电源管理
 int  (*set_wake)(struct uart_port *, unsigned int state);

 

 

 /*
  * Return a string describing the type of the port
  */
 const char *(*type)(struct uart_port *);

 /*
  * Release IO and memory resources used by the port.
  * This includes iounmap if necessary.
  */
 void  (*release_port)(struct uart_port *);

 /*
  * Request IO and memory resources used by the port.
  * This includes iomapping the port if necessary.
  */
 int  (*request_port)(struct uart_port *);
 void  (*config_port)(struct uart_port *, int);   //执行串口所需的自动配置
 int  (*verify_port)(struct uart_port *, struct serial_struct *);  //核实串口信息
 int  (*ioctl)(struct uart_port *, unsigned int, unsigned long);
#ifdef CONFIG_CONSOLE_POLL
 void (*poll_put_char)(struct uart_port *, unsigned char);
 int  (*poll_get_char)(struct uart_port *);
#endif
};

 

上节介绍了serial驱动核心提供的重要数据结构，这一节将介绍serial核心提供给驱动开发的核心函数uart_register_driver向内核注册serial驱动（具体操作就是向内核注册一个tty_driver）以及uart_unregister_driver注销serial驱动。uart_add_one_port用于为串口驱动添加一个串口端口（在总线型设备驱动中，通常用于探测函数probe中），uart_remove_one_port用于删除一个已经添加到驱动中的串口端口（通常在卸载函数中调用）。

 

//uart_register_driver就是初始化一个tty_driver并把其加入tty core层，并对uart_state做一些初始化,起始就是写一个tty类驱动。

/**
 * uart_register_driver - register a driver with the uart core layer
 * @drv: low level driver structure
 *
 * Register a uart driver with the core driver.  We in turn register
 * with the tty layer, and initialise the core driver per-port state.
 *
 * We have a proc file in /proc/tty/driver which is named after the
 * normal driver.
 *
 * drv->port should be NULL, and the per-port structures should be
 * registered using uart_add_one_port after this call has succeeded.
 */
int uart_register_driver(struct uart_driver *drv)
{
 struct tty_driver *normal = NULL;  //定义一个tty_driver驱动指针
 int i, retval;

 BUG_ON(drv->state);      

 /*
  * Maybe we should be using a slab cache for this, especially if
  * we have a large number of ports to handle.
  */
 drv->state = kzalloc(sizeof(struct uart_state) * drv->nr, GFP_KERNEL); //为串口设备管理分配空间即uart_state数组
 retval = -ENOMEM;
 if (!drv->state)
  goto out;

 normal  = alloc_tty_driver(drv->nr);
 if (!normal)
  goto out;

 drv->tty_driver = normal;

 normal->owner  = drv->owner;
 normal->driver_name = drv->driver_name;
 normal->name  = drv->dev_name;
 normal->major  = drv->major;
 normal->minor_start = drv->minor;
 normal->type  = TTY_DRIVER_TYPE_SERIAL;  //tty设备类型
 normal->subtype  = SERIAL_TYPE_NORMAL;  //tty设备子类型
 normal->init_termios = tty_std_termios;
 normal->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL; //串口默认控制参数
 normal->init_termios.c_ispeed = normal->init_termios.c_ospeed = 9600;

//TTY_DRIVER_DYNAMIC_DEV是不会在初始化的时候去注册device.也就是说在/dev/下没有动态生成结点

 normal->flags  = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
 normal->driver_state    = drv; //便于查找uart_driver
 tty_set_operations(normal, &uart_ops);

 /*
  * Initialise the UART state(s).
  */
 for (i = 0; i < drv->nr; i++) {
  struct uart_state *state = drv->state + i;

  state->close_delay     = 500; /* .5 seconds */
  state->closing_wait    = 30000; /* 30 seconds */

  mutex_init(&state->mutex);
 }

 retval = tty_register_driver(normal); //把normal加入到tty core中
 out:
 if (retval < 0) {
  put_tty_driver(normal);
  kfree(drv->state);
 }
 return retval;
}

 

//uart_unregister_driver完成与上面代码相反的操作

 /**
 * uart_unregister_driver - remove a driver from the uart core layer
 * @drv: low level driver structure
 *
 * Remove all references to a driver from the core driver.  The low
 * level driver must have removed all its ports via the
 * uart_remove_one_port() if it registered them with uart_add_one_port().
 * (ie, drv->port == NULL)
 */
void uart_unregister_driver(struct uart_driver *drv)
{
 struct tty_driver *p = drv->tty_driver;
 tty_unregister_driver(p);
 put_tty_driver(p);
 kfree(drv->state);
 drv->tty_driver = NULL;
}

 

//uart_add_one_port 向uart_driver加入一个可操作的端口，注意serial驱动的核心在端口的操作函数上

//即const struct uart_ops *ops的成员函数上，每个端口对应一个uart_state结构

 /**
 * uart_add_one_port - attach a driver-defined port structure
 * @drv: pointer to the uart low level driver structure for this port
 * @port: uart port structure to use for this port.
 *
 * This allows the driver to register its own uart_port structure
 * with the core driver.  The main purpose is to allow the low
 * level uart drivers to expand uart_port, rather than having yet
 * more levels of structures.
 */
int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
{
 struct uart_state *state;
 int ret = 0;
 struct device *tty_dev;

 BUG_ON(in_interrupt());  //函数不能在中断环境中调用

 if (port->line >= drv->nr)  //port->line 指在uart_state数组中的索引
  return -EINVAL;

 state = drv->state + port->line;

 mutex_lock(&port_mutex);
 mutex_lock(&state->mutex);
 if (state->port) {
  ret = -EINVAL;
  goto out;
 }

 state->port = port;
 state->pm_state = -1;

 port->cons = drv->cons;
 port->info = state->info;  //两者指向同一个uart_info结构

 /*
  * If this port is a console, then the spinlock is already
  * initialised.
  */
 if (!(uart_console(port) && (port->cons->flags & CON_ENABLED))) {
  spin_lock_init(&port->lock);
  lockdep_set_class(&port->lock, &port_lock_key);
 }

 uart_configure_port(drv, state, port); //配置端口 下面具体分析

 /*
  * Register the port whether it's detected or not.  This allows
  * setserial to be used to alter this ports parameters.
  */
 tty_dev = tty_register_device(drv->tty_driver, port->line, port->dev); //注册tty设备
 if (likely(!IS_ERR(tty_dev))) { //设置设备的唤醒状态
  device_init_wakeup(tty_dev, 1);
  device_set_wakeup_enable(tty_dev, 0);
 } else
  printk(KERN_ERR "Cannot register tty device on line %d/n",
         port->line);

 /*
  * Ensure UPF_DEAD is not set.
  */
 port->flags &= ~UPF_DEAD;

 out:
 mutex_unlock(&state->mutex);
 mutex_unlock(&port_mutex);

 return ret;
}

 

//端口为配置的情况下调用端口的自动配置函数，否则直接报告端口信息以及modem控制设置等操作

static void uart_configure_port(struct uart_driver *drv, struct uart_state *state,
      struct uart_port *port)
{
 unsigned int flags;

 /*
  * If there isn't a port here, don't do anything further.
  */
 if (!port->iobase && !port->mapbase && !port->membase) //设备不存在
  return;

 /*
  * Now do the auto configuration stuff.  Note that config_port
  * is expected to claim the resources and map the port for us.
  */
 flags = UART_CONFIG_TYPE;
 if (port->flags & UPF_AUTO_IRQ)
  flags |= UART_CONFIG_IRQ;
 if (port->flags & UPF_BOOT_AUTOCONF) {
  port->type = PORT_UNKNOWN;
  port->ops->config_port(port, flags); //调用设备的自动配置函数，在后面的serial驱动例子中可以看看具体看什么
 }

 if (port->type != PORT_UNKNOWN) {
  unsigned long flags;

  uart_report_port(drv, port);  //输出端口的相关信息

  /* Power up port for set_mctrl() */
  uart_change_pm(state, 0); //改变端口的电源状态

  /* 
   * Ensure that the modem control lines are de-activated.
   * keep the DTR setting that is set in uart_set_options()
   * We probably don't need a spinlock around this, but
   */
  spin_lock_irqsave(&port->lock, flags);
  port->ops->set_mctrl(port, port->mctrl & TIOCM_DTR); //设置串口modem控制
  spin_unlock_irqrestore(&port->lock, flags);

  /*
   * If this driver supports console, and it hasn't been
   * successfully registered yet, try to re-register it.
   * It may be that the port was not available.
   */
  if (port->cons && !(port->cons->flags & CON_ENABLED))
   register_console(port->cons);

  /*
   * Power down all ports by default, except the
   * console if we have one.
   */
  if (!uart_console(port))
   uart_change_pm(state, 3);
 }
}

 

//uart_remove_one_port完成uart_add_one_port相反操作，删除一个已加入的串口端口

 

/**
 * uart_remove_one_port - detach a driver defined port structure
 * @drv: pointer to the uart low level driver structure for this port
 * @port: uart port structure for this port
 *
 * This unhooks (and hangs up) the specified port structure from the
 * core driver.  No further calls will be made to the low-level code
 * for this port.
 */
int uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
{
 struct uart_state *state = drv->state + port->line;
 struct uart_info *info;

 BUG_ON(in_interrupt());

 if (state->port != port)  //删除端口与驱动对应端口不匹配
  printk(KERN_ALERT "Removing wrong port: %p != %p/n",
   state->port, port);

 mutex_lock(&port_mutex);

 /*
  * Mark the port "dead" - this prevents any opens from
  * succeeding while we shut down the port.
  */
 mutex_lock(&state->mutex);
 port->flags |= UPF_DEAD;   //设置端口不可用标志
 mutex_unlock(&state->mutex);

 /*
  * Remove the devices from the tty layer
  */
 tty_unregister_device(drv->tty_driver, port->line); //端口对应设备从内核注销掉

 info = state->info;
 if (info && info->port.tty)
  tty_vhangup(info->port.tty);//处理tty挂起相关操作do_tty_hungup函数

 /*
  * All users of this port should now be disconnected from
  * this driver, and the port shut down.  We should be the
  * only thread fiddling with this port from now on.
  */
 state->info = NULL;

 /*
  * Free the port IO and memory resources, if any.
  */
 if (port->type != PORT_UNKNOWN)
  port->ops->release_port(port); //释放端口资源

 /*
  * Indicate that there isn't a port here anymore.
  */
 port->type = PORT_UNKNOWN;

 /*
  * Kill the tasklet, and free resources.
  */
 if (info) {
  tasklet_kill(&info->tlet);//下半部机制确保tasklet不再被调用
  kfree(info);
 }

 state->port = NULL;
 mutex_unlock(&port_mutex);

 return 0;
}

 

这一节我们将介绍一个serial驱动的实例，后面各节中也将以这个例子来分析串口各种操作的实际情景(例子是at91sam9260板子的串口驱动)。

  

更详细platform资料可参考网上相关文章。

 

/*
 *  linux/drivers/char/atmel_serial.c
 *
 *  Driver for Atmel AT91 / AT32 Serial ports
 *  Copyright (C) 2003 Rick Bronson
 *
 *  Based on drivers/char/serial_sa1100.c, by Deep Blue Solutions Ltd.
 *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 *
 *  DMA support added by Chip Coldwell.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */
#include <linux/module.h>
#include <linux/tty.h>
#include <linux/ioport.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/serial.h>
#include <linux/clk.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/tty_flip.h>
#include <linux/platform_device.h>
#include <linux/dma-mapping.h>
#include <linux/atmel_pdc.h>
#include <linux/atmel_serial.h>

#include <asm/io.h>

#include <asm/mach/serial_at91.h>
#include <mach/board.h>

#ifdef CONFIG_ARM
#include <mach/cpu.h>
#include <mach/gpio.h>
#endif

#define PDC_BUFFER_SIZE  512
/* Revisit: We should calculate this based on the actual port settings */
#define PDC_RX_TIMEOUT  (3 * 10)  /* 3 bytes */

#if defined(CONFIG_SERIAL_ATMEL_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#include <linux/serial_core.h>

#ifdef CONFIG_SERIAL_ATMEL_TTYAT

/* Use device name ttyAT, major 204 and minor 154-169.  This is necessary if we
 * should coexist with the 8250 driver, such as if we have an external 16C550
 * UART. */
#define SERIAL_ATMEL_MAJOR 204
#define MINOR_START  154
#define ATMEL_DEVICENAME "ttyAT"

#else

/* Use device name ttyS, major 4, minor 64-68.  This is the usual serial port
 * name, but it is legally reserved for the 8250 driver. */
#define SERIAL_ATMEL_MAJOR TTY_MAJOR
#define MINOR_START  64
#define ATMEL_DEVICENAME "ttyS"

#endif

#define ATMEL_ISR_PASS_LIMIT 256

/* UART registers. CR is write-only, hence no GET macro */
#define UART_PUT_CR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_CR)
#define UART_GET_MR(port) __raw_readl((port)->membase + ATMEL_US_MR)
#define UART_PUT_MR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_MR)
#define UART_PUT_IER(port,v) __raw_writel(v, (port)->membase + ATMEL_US_IER)
#define UART_PUT_IDR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_IDR)
#define UART_GET_IMR(port) __raw_readl((port)->membase + ATMEL_US_IMR)
#define UART_GET_CSR(port) __raw_readl((port)->membase + ATMEL_US_CSR)
#define UART_GET_CHAR(port) __raw_readl((port)->membase + ATMEL_US_RHR)
#define UART_PUT_CHAR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_THR)
#define UART_GET_BRGR(port) __raw_readl((port)->membase + ATMEL_US_BRGR)
#define UART_PUT_BRGR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_BRGR)
#define UART_PUT_RTOR(port,v) __raw_writel(v, (port)->membase + ATMEL_US_RTOR)

 /* PDC registers */
#define UART_PUT_PTCR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_PTCR)
#define UART_GET_PTSR(port) __raw_readl((port)->membase + ATMEL_PDC_PTSR)

#define UART_PUT_RPR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_RPR)
#define UART_GET_RPR(port) __raw_readl((port)->membase + ATMEL_PDC_RPR)
#define UART_PUT_RCR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_RCR)
#define UART_PUT_RNPR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_RNPR)
#define UART_PUT_RNCR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_RNCR)

#define UART_PUT_TPR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_TPR)
#define UART_PUT_TCR(port,v) __raw_writel(v, (port)->membase + ATMEL_PDC_TCR)
#define UART_GET_TCR(port) __raw_readl((port)->membase + ATMEL_PDC_TCR)

static int (*atmel_open_hook)(struct uart_port *);
static void (*atmel_close_hook)(struct uart_port *);

struct atmel_dma_buffer {
 unsigned char *buf;
 dma_addr_t dma_addr;
 unsigned int dma_size;
 unsigned int ofs;
};

struct atmel_uart_char {
 u16  status;
 u16  ch;
};

#define ATMEL_SERIAL_RINGSIZE 1024

/*
 * We wrap our port structure around the generic uart_port.
 */
struct atmel_uart_port {
 struct uart_port uart;  /* uart */
 struct clk  *clk;  /* uart clock */
 int   may_wakeup; /* cached value of device_may_wakeup for times we need to disable it */
 u32   backup_imr; /* IMR saved during suspend */
 int   break_active; /* break being received */

 short   use_dma_rx; /* enable PDC receiver */
 short   pdc_rx_idx; /* current PDC RX buffer */
 struct atmel_dma_buffer pdc_rx[2]; /* PDC receier */

 short   use_dma_tx; /* enable PDC transmitter */
 struct atmel_dma_buffer pdc_tx;  /* PDC transmitter */

 struct tasklet_struct tasklet;
 unsigned int  irq_status;
 unsigned int  irq_status_prev;

 struct circ_buf  rx_ring;
};

static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART];

#ifdef SUPPORT_SYSRQ
static struct console atmel_console;
#endif

static inline struct atmel_uart_port *
to_atmel_uart_port(struct uart_port *uart)
{
 return container_of(uart, struct atmel_uart_port, uart);
}

#ifdef CONFIG_SERIAL_ATMEL_PDC
static bool atmel_use_dma_rx(struct uart_port *port)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

 return atmel_port->use_dma_rx;
}

static bool atmel_use_dma_tx(struct uart_port *port)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

 return atmel_port->use_dma_tx;
}
#else
static bool atmel_use_dma_rx(struct uart_port *port)
{
 return false;
}

static bool atmel_use_dma_tx(struct uart_port *port)
{
 return false;
}
#endif

/*
 * Return TIOCSER_TEMT when transmitter FIFO and Shift register is empty.
 */
static u_int atmel_tx_empty(struct uart_port *port)
{
 return (UART_GET_CSR(port) & ATMEL_US_TXEMPTY) ? TIOCSER_TEMT : 0;
}

/*
 * Set state of the modem control output lines
 */
static void atmel_set_mctrl(struct uart_port *port, u_int mctrl)
{
 unsigned int control = 0;
 unsigned int mode;

#ifdef CONFIG_ARCH_AT91RM9200
 if (cpu_is_at91rm9200()) {
  /*
   * AT91RM9200 Errata #39: RTS0 is not internally connected
   * to PA21. We need to drive the pin manually.
   */
  if (port->mapbase == AT91RM9200_BASE_US0) {
   if (mctrl & TIOCM_RTS)
    at91_set_gpio_value(AT91_PIN_PA21, 0);
   else
    at91_set_gpio_value(AT91_PIN_PA21, 1);
  }
 }
#endif

 if (mctrl & TIOCM_RTS)
  control |= ATMEL_US_RTSEN;
 else
  control |= ATMEL_US_RTSDIS;

 if (mctrl & TIOCM_DTR)
  control |= ATMEL_US_DTREN;
 else
  control |= ATMEL_US_DTRDIS;

 UART_PUT_CR(port, control);

 /* Local loopback mode? */
 mode = UART_GET_MR(port) & ~ATMEL_US_CHMODE;
 if (mctrl & TIOCM_LOOP)
  mode |= ATMEL_US_CHMODE_LOC_LOOP;
 else
  mode |= ATMEL_US_CHMODE_NORMAL;
 UART_PUT_MR(port, mode);
}

/*
 * Get state of the modem control input lines
 */
static u_int atmel_get_mctrl(struct uart_port *port)
{
 unsigned int status, ret = 0;

 status = UART_GET_CSR(port);

 /*
  * The control signals are active low.
  */
 if (!(status & ATMEL_US_DCD))
  ret |= TIOCM_CD;
 if (!(status & ATMEL_US_CTS))
  ret |= TIOCM_CTS;
 if (!(status & ATMEL_US_DSR))
  ret |= TIOCM_DSR;
 if (!(status & ATMEL_US_RI))
  ret |= TIOCM_RI;

 return ret;
}

/*
 * Stop transmitting.
 */
static void atmel_stop_tx(struct uart_port *port)
{
 if (atmel_use_dma_tx(port)) {
  /* disable PDC transmit */
  UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);
  UART_PUT_IDR(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
 } else
  UART_PUT_IDR(port, ATMEL_US_TXRDY);
}

/*
 * Start transmitting.
 */
static void atmel_start_tx(struct uart_port *port)
{
 if (atmel_use_dma_tx(port)) {
  if (UART_GET_PTSR(port) & ATMEL_PDC_TXTEN)
   /* The transmitter is already running.  Yes, we
      really need this.*/
   return;

  UART_PUT_IER(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
  /* re-enable PDC transmit */
  UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);
 } else
  UART_PUT_IER(port, ATMEL_US_TXRDY);
}

/*
 * Stop receiving - port is in process of being closed.
 */
static void atmel_stop_rx(struct uart_port *port)
{
 if (atmel_use_dma_rx(port)) {
  /* disable PDC receive */
  UART_PUT_PTCR(port, ATMEL_PDC_RXTDIS);
  UART_PUT_IDR(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
 } else
  UART_PUT_IDR(port, ATMEL_US_RXRDY);
}

/*
 * Enable modem status interrupts
 */
static void atmel_enable_ms(struct uart_port *port)
{
 UART_PUT_IER(port, ATMEL_US_RIIC | ATMEL_US_DSRIC
   | ATMEL_US_DCDIC | ATMEL_US_CTSIC);
}

/*
 * Control the transmission of a break signal
 */
static void atmel_break_ctl(struct uart_port *port, int break_state)
{
 if (break_state != 0)
  UART_PUT_CR(port, ATMEL_US_STTBRK); /* start break */
 else
  UART_PUT_CR(port, ATMEL_US_STPBRK); /* stop break */
}

/*
 * Stores the incoming character in the ring buffer
 */
static void
atmel_buffer_rx_char(struct uart_port *port, unsigned int status,
       unsigned int ch)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 struct circ_buf *ring = &atmel_port->rx_ring;
 struct atmel_uart_char *c;

 if (!CIRC_SPACE(ring->head, ring->tail, ATMEL_SERIAL_RINGSIZE))
  /* Buffer overflow, ignore char */
  return;

 c = &((struct atmel_uart_char *)ring->buf)[ring->head];
 c->status = status;
 c->ch  = ch;

 /* Make sure the character is stored before we update head. */
 smp_wmb();

 ring->head = (ring->head + 1) & (ATMEL_SERIAL_RINGSIZE - 1);
}

/*
 * Deal with parity, framing and overrun errors.
 */
static void atmel_pdc_rxerr(struct uart_port *port, unsigned int status)
{
 /* clear error */
 UART_PUT_CR(port, ATMEL_US_RSTSTA);

 if (status & ATMEL_US_RXBRK) {
  /* ignore side-effect */
  status &= ~(ATMEL_US_PARE | ATMEL_US_FRAME);
  port->icount.brk++;
 }
 if (status & ATMEL_US_PARE)
  port->icount.parity++;
 if (status & ATMEL_US_FRAME)
  port->icount.frame++;
 if (status & ATMEL_US_OVRE)
  port->icount.overrun++;
}

/*
 * Characters received (called from interrupt handler)
 */
static void atmel_rx_chars(struct uart_port *port)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 unsigned int status, ch;

 status = UART_GET_CSR(port);
 while (status & ATMEL_US_RXRDY) {
  ch = UART_GET_CHAR(port);

  /*
   * note that the error handling code is
   * out of the main execution path
   */
  if (unlikely(status & (ATMEL_US_PARE | ATMEL_US_FRAME
           | ATMEL_US_OVRE | ATMEL_US_RXBRK)
        || atmel_port->break_active)) {

   /* clear error */
   UART_PUT_CR(port, ATMEL_US_RSTSTA);

   if (status & ATMEL_US_RXBRK
       && !atmel_port->break_active) {
    atmel_port->break_active = 1;
    UART_PUT_IER(port, ATMEL_US_RXBRK);
   } else {
    /*
     * This is either the end-of-break
     * condition or we've received at
     * least one character without RXBRK
     * being set. In both cases, the next
     * RXBRK will indicate start-of-break.
     */
    UART_PUT_IDR(port, ATMEL_US_RXBRK);
    status &= ~ATMEL_US_RXBRK;
    atmel_port->break_active = 0;
   }
  }

  atmel_buffer_rx_char(port, status, ch);
  status = UART_GET_CSR(port);
 }

 tasklet_schedule(&atmel_port->tasklet);
}

/*
 * Transmit characters (called from tasklet with TXRDY interrupt
 * disabled)
 */
static void atmel_tx_chars(struct uart_port *port)
{
 struct circ_buf *xmit = &port->info->xmit;

 if (port->x_char && UART_GET_CSR(port) & ATMEL_US_TXRDY) {
  UART_PUT_CHAR(port, port->x_char);
  port->icount.tx++;
  port->x_char = 0;
 }
 if (uart_circ_empty(xmit) || uart_tx_stopped(port))
  return;

 while (UART_GET_CSR(port) & ATMEL_US_TXRDY) {
  UART_PUT_CHAR(port, xmit->buf[xmit->tail]);
  xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
  port->icount.tx++;
  if (uart_circ_empty(xmit))
   break;
 }

 if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
  uart_write_wakeup(port);

 if (!uart_circ_empty(xmit))
  UART_PUT_IER(port, ATMEL_US_TXRDY);
}

/*
 * receive interrupt handler.
 */
static void
atmel_handle_receive(struct uart_port *port, unsigned int pending)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

 if (atmel_use_dma_rx(port)) {
  /*
   * PDC receive. Just schedule the tasklet and let it
   * figure out the details.
   *
   * TODO: We're not handling error flags correctly at
   * the moment.
   */
  if (pending & (ATMEL_US_ENDRX | ATMEL_US_TIMEOUT)) {
   UART_PUT_IDR(port, (ATMEL_US_ENDRX
      | ATMEL_US_TIMEOUT));
   tasklet_schedule(&atmel_port->tasklet);
  }

  if (pending & (ATMEL_US_RXBRK | ATMEL_US_OVRE |
    ATMEL_US_FRAME | ATMEL_US_PARE))
   atmel_pdc_rxerr(port, pending);
 }

 /* Interrupt receive */
 if (pending & ATMEL_US_RXRDY)
  atmel_rx_chars(port);
 else if (pending & ATMEL_US_RXBRK) {
  /*
   * End of break detected. If it came along with a
   * character, atmel_rx_chars will handle it.
   */
  UART_PUT_CR(port, ATMEL_US_RSTSTA);
  UART_PUT_IDR(port, ATMEL_US_RXBRK);
  atmel_port->break_active = 0;
 }
}

/*
 * transmit interrupt handler. (Transmit is IRQF_NODELAY safe)
 */
static void
atmel_handle_transmit(struct uart_port *port, unsigned int pending)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

 if (atmel_use_dma_tx(port)) {
  /* PDC transmit */
  if (pending & (ATMEL_US_ENDTX | ATMEL_US_TXBUFE)) {
   UART_PUT_IDR(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
   tasklet_schedule(&atmel_port->tasklet);
  }
 } else {
  /* Interrupt transmit */
  if (pending & ATMEL_US_TXRDY) {
   UART_PUT_IDR(port, ATMEL_US_TXRDY);
   tasklet_schedule(&atmel_port->tasklet);
  }
 }
}

/*
 * status flags interrupt handler.
 */
static void
atmel_handle_status(struct uart_port *port, unsigned int pending,
      unsigned int status)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

 if (pending & (ATMEL_US_RIIC | ATMEL_US_DSRIC | ATMEL_US_DCDIC
    | ATMEL_US_CTSIC)) {
  atmel_port->irq_status = status;
  tasklet_schedule(&atmel_port->tasklet);
 }
}

/*
 * Interrupt handler
 */
static irqreturn_t atmel_interrupt(int irq, void *dev_id)
{
 struct uart_port *port = dev_id;
 unsigned int status, pending, pass_counter = 0;

 do {
  status = UART_GET_CSR(port);
  pending = status & UART_GET_IMR(port);
  if (!pending)
   break;

  atmel_handle_receive(port, pending);
  atmel_handle_status(port, pending, status);
  atmel_handle_transmit(port, pending);
 } while (pass_counter++ < ATMEL_ISR_PASS_LIMIT);

 return pass_counter ? IRQ_HANDLED : IRQ_NONE;
}

/*
 * Called from tasklet with ENDTX and TXBUFE interrupts disabled.
 */
static void atmel_tx_dma(struct uart_port *port)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 struct circ_buf *xmit = &port->info->xmit;
 struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;
 int count;

 /* nothing left to transmit? */
 if (UART_GET_TCR(port))
  return;

 xmit->tail += pdc->ofs;
 xmit->tail &= UART_XMIT_SIZE - 1;

 port->icount.tx += pdc->ofs;
 pdc->ofs = 0;

 /* more to transmit - setup next transfer */

 /* disable PDC transmit */
 UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);

 if (!uart_circ_empty(xmit)) {
  dma_sync_single_for_device(port->dev,
        pdc->dma_addr,
        pdc->dma_size,
        DMA_TO_DEVICE);

  count = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
  pdc->ofs = count;

  UART_PUT_TPR(port, pdc->dma_addr + xmit->tail);
  UART_PUT_TCR(port, count);
  /* re-enable PDC transmit and interrupts */
  UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);
  UART_PUT_IER(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE);
 }

 if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
  uart_write_wakeup(port);
}

static void atmel_rx_from_ring(struct uart_port *port)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 struct circ_buf *ring = &atmel_port->rx_ring;
 unsigned int flg;
 unsigned int status;

 while (ring->head != ring->tail) {
  struct atmel_uart_char c;

  /* Make sure c is loaded after head. */
  smp_rmb();

  c = ((struct atmel_uart_char *)ring->buf)[ring->tail];

  ring->tail = (ring->tail + 1) & (ATMEL_SERIAL_RINGSIZE - 1);

  port->icount.rx++;
  status = c.status;
  flg = TTY_NORMAL;

  /*
   * note that the error handling code is
   * out of the main execution path
   */
  if (unlikely(status & (ATMEL_US_PARE | ATMEL_US_FRAME
           | ATMEL_US_OVRE | ATMEL_US_RXBRK))) {
   if (status & ATMEL_US_RXBRK) {
    /* ignore side-effect */
    status &= ~(ATMEL_US_PARE | ATMEL_US_FRAME);

    port->icount.brk++;
    if (uart_handle_break(port))
     continue;
   }
   if (status & ATMEL_US_PARE)
    port->icount.parity++;
   if (status & ATMEL_US_FRAME)
    port->icount.frame++;
   if (status & ATMEL_US_OVRE)
    port->icount.overrun++;

   status &= port->read_status_mask;

   if (status & ATMEL_US_RXBRK)
    flg = TTY_BREAK;
   else if (status & ATMEL_US_PARE)
    flg = TTY_PARITY;
   else if (status & ATMEL_US_FRAME)
    flg = TTY_FRAME;
  }

  if (uart_handle_sysrq_char(port, c.ch))
   continue;

  uart_insert_char(port, status, ATMEL_US_OVRE, c.ch, flg);
 }

 /*
  * Drop the lock here since it might end up calling
  * uart_start(), which takes the lock.
  */
 spin_unlock(&port->lock);
 tty_flip_buffer_push(port->info->port.tty);
 spin_lock(&port->lock);
}

static void atmel_rx_from_dma(struct uart_port *port)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 struct tty_struct *tty = port->info->port.tty;
 struct atmel_dma_buffer *pdc;
 int rx_idx = atmel_port->pdc_rx_idx;
 unsigned int head;
 unsigned int tail;
 unsigned int count;

 do {
  /* Reset the UART timeout early so that we don't miss one */
  UART_PUT_CR(port, ATMEL_US_STTTO);

  pdc = &atmel_port->pdc_rx[rx_idx];
  head = UART_GET_RPR(port) - pdc->dma_addr;
  tail = pdc->ofs;

  /* If the PDC has switched buffers, RPR won't contain
   * any address within the current buffer. Since head
   * is unsigned, we just need a one-way comparison to
   * find out.
   *
   * In this case, we just need to consume the entire
   * buffer and resubmit it for DMA. This will clear the
   * ENDRX bit as well, so that we can safely re-enable
   * all interrupts below.
   */
  head = min(head, pdc->dma_size);

  if (likely(head != tail)) {
   dma_sync_single_for_cpu(port->dev, pdc->dma_addr,
     pdc->dma_size, DMA_FROM_DEVICE);

   /*
    * head will only wrap around when we recycle
    * the DMA buffer, and when that happens, we
    * explicitly set tail to 0. So head will
    * always be greater than tail.
    */
   count = head - tail;

   tty_insert_flip_string(tty, pdc->buf + pdc->ofs, count);

   dma_sync_single_for_device(port->dev, pdc->dma_addr,
     pdc->dma_size, DMA_FROM_DEVICE);

   port->icount.rx += count;
   pdc->ofs = head;
  }

  /*
   * If the current buffer is full, we need to check if
   * the next one contains any additional data.
   */
  if (head >= pdc->dma_size) {
   pdc->ofs = 0;
   UART_PUT_RNPR(port, pdc->dma_addr);
   UART_PUT_RNCR(port, pdc->dma_size);

   rx_idx = !rx_idx;
   atmel_port->pdc_rx_idx = rx_idx;
  }
 } while (head >= pdc->dma_size);

 /*
  * Drop the lock here since it might end up calling
  * uart_start(), which takes the lock.
  */
 spin_unlock(&port->lock);
 tty_flip_buffer_push(tty);
 spin_lock(&port->lock);

 UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
}

/*
 * tasklet handling tty stuff outside the interrupt handler.
 */
static void atmel_tasklet_func(unsigned long data)
{
 struct uart_port *port = (struct uart_port *)data;
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 unsigned int status;
 unsigned int status_change;

 /* The interrupt handler does not take the lock */
 spin_lock(&port->lock);

 if (atmel_use_dma_tx(port))
  atmel_tx_dma(port);
 else
  atmel_tx_chars(port);

 status = atmel_port->irq_status;
 status_change = status ^ atmel_port->irq_status_prev;

 if (status_change & (ATMEL_US_RI | ATMEL_US_DSR
    | ATMEL_US_DCD | ATMEL_US_CTS)) {
  /* TODO: All reads to CSR will clear these interrupts! */
  if (status_change & ATMEL_US_RI)
   port->icount.rng++;
  if (status_change & ATMEL_US_DSR)
   port->icount.dsr++;
  if (status_change & ATMEL_US_DCD)
   uart_handle_dcd_change(port, !(status & ATMEL_US_DCD));
  if (status_change & ATMEL_US_CTS)
   uart_handle_cts_change(port, !(status & ATMEL_US_CTS));

  wake_up_interruptible(&port->info->delta_msr_wait);

  atmel_port->irq_status_prev = status;
 }

 if (atmel_use_dma_rx(port))
  atmel_rx_from_dma(port);
 else
  atmel_rx_from_ring(port);

 spin_unlock(&port->lock);
}

/*
 * Perform initialization and enable port for reception
 */
static int atmel_startup(struct uart_port *port)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 struct tty_struct *tty = port->info->port.tty;
 int retval;

 /*
  * Ensure that no interrupts are enabled otherwise when
  * request_irq() is called we could get stuck trying to
  * handle an unexpected interrupt
  */
 UART_PUT_IDR(port, -1);

 /*
  * Allocate the IRQ
  */
 retval = request_irq(port->irq, atmel_interrupt, IRQF_SHARED,
   tty ? tty->name : "atmel_serial", port);
 if (retval) {
  printk("atmel_serial: atmel_startup - Can't get irq/n");
  return retval;
 }

 /*
  * Initialize DMA (if necessary)
  */
 if (atmel_use_dma_rx(port)) {
  int i;

  for (i = 0; i < 2; i++) {
   struct atmel_dma_buffer *pdc = &atmel_port->pdc_rx[i];

   pdc->buf = kmalloc(PDC_BUFFER_SIZE, GFP_KERNEL);
   if (pdc->buf == NULL) {
    if (i != 0) {
     dma_unmap_single(port->dev,
      atmel_port->pdc_rx[0].dma_addr,
      PDC_BUFFER_SIZE,
      DMA_FROM_DEVICE);
     kfree(atmel_port->pdc_rx[0].buf);
    }
    free_irq(port->irq, port);
    return -ENOMEM;
   }
   pdc->dma_addr = dma_map_single(port->dev,
             pdc->buf,
             PDC_BUFFER_SIZE,
             DMA_FROM_DEVICE);
   pdc->dma_size = PDC_BUFFER_SIZE;
   pdc->ofs = 0;
  }

  atmel_port->pdc_rx_idx = 0;

  UART_PUT_RPR(port, atmel_port->pdc_rx[0].dma_addr);
  UART_PUT_RCR(port, PDC_BUFFER_SIZE);

  UART_PUT_RNPR(port, atmel_port->pdc_rx[1].dma_addr);
  UART_PUT_RNCR(port, PDC_BUFFER_SIZE);
 }
 if (atmel_use_dma_tx(port)) {
  struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;
  struct circ_buf *xmit = &port->info->xmit;

  pdc->buf = xmit->buf;
  pdc->dma_addr = dma_map_single(port->dev,
            pdc->buf,
            UART_XMIT_SIZE,
            DMA_TO_DEVICE);
  pdc->dma_size = UART_XMIT_SIZE;
  pdc->ofs = 0;
 }

 /*
  * If there is a specific "open" function (to register
  * control line interrupts)
  */
 if (atmel_open_hook) {
  retval = atmel_open_hook(port);
  if (retval) {
   free_irq(port->irq, port);
   return retval;
  }
 }

 /*
  * Finally, enable the serial port
  */
 UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
 /* enable xmit & rcvr */
 UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);

 if (atmel_use_dma_rx(port)) {
  /* set UART timeout */
  UART_PUT_RTOR(port, PDC_RX_TIMEOUT);
  UART_PUT_CR(port, ATMEL_US_STTTO);

  UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);
  /* enable PDC controller */
  UART_PUT_PTCR(port, ATMEL_PDC_RXTEN);
 } else {
  /* enable receive only */
  UART_PUT_IER(port, ATMEL_US_RXRDY);
 }

 return 0;
}

/*
 * Disable the port
 */
static void atmel_shutdown(struct uart_port *port)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 /*
  * Ensure everything is stopped.
  */
 atmel_stop_rx(port);
 atmel_stop_tx(port);

 /*
  * Shut-down the DMA.
  */
 if (atmel_use_dma_rx(port)) {
  int i;

  for (i = 0; i < 2; i++) {
   struct atmel_dma_buffer *pdc = &atmel_port->pdc_rx[i];

   dma_unmap_single(port->dev,
      pdc->dma_addr,
      pdc->dma_size,
      DMA_FROM_DEVICE);
   kfree(pdc->buf);
  }
 }
 if (atmel_use_dma_tx(port)) {
  struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx;

  dma_unmap_single(port->dev,
     pdc->dma_addr,
     pdc->dma_size,
     DMA_TO_DEVICE);
 }

 /*
  * Disable all interrupts, port and break condition.
  */
 UART_PUT_CR(port, ATMEL_US_RSTSTA);
 UART_PUT_IDR(port, -1);

 /*
  * Free the interrupt
  */
 free_irq(port->irq, port);

 /*
  * If there is a specific "close" function (to unregister
  * control line interrupts)
  */
 if (atmel_close_hook)
  atmel_close_hook(port);
}

/*
 * Flush any TX data submitted for DMA. Called when the TX circular
 * buffer is reset.
 */
static void atmel_flush_buffer(struct uart_port *port)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

 if (atmel_use_dma_tx(port)) {
  UART_PUT_TCR(port, 0);
  atmel_port->pdc_tx.ofs = 0;
 }
}

/*
 * Power / Clock management.
 */
static void atmel_serial_pm(struct uart_port *port, unsigned int state,
       unsigned int oldstate)
{
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

 switch (state) {
 case 0:
  /*
   * Enable the peripheral clock for this serial port.
   * This is called on uart_open() or a resume event.
   */
  clk_enable(atmel_port->clk);

  /* re-enable interrupts if we disabled some on suspend */
  UART_PUT_IER(port, atmel_port->backup_imr);
  break;
 case 3:
  /* Back up the interrupt mask and disable all interrupts */
  atmel_port->backup_imr = UART_GET_IMR(port);
  UART_PUT_IDR(port, -1);

  /*
   * Disable the peripheral clock for this serial port.
   * This is called on uart_close() or a suspend event.
   */
  clk_disable(atmel_port->clk);
  break;
 default:
  printk(KERN_ERR "atmel_serial: unknown pm %d/n", state);
 }
}

/*
 * Change the port parameters
 */
static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
         struct ktermios *old)
{
 unsigned long flags;
 unsigned int mode, imr, quot, baud;

 /* Get current mode register */
 mode = UART_GET_MR(port) & ~(ATMEL_US_USCLKS | ATMEL_US_CHRL
     | ATMEL_US_NBSTOP | ATMEL_US_PAR);

 baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16);
 quot = uart_get_divisor(port, baud);

 if (quot > 65535) { /* BRGR is 16-bit, so switch to slower clock */
  quot /= 8;
  mode |= ATMEL_US_USCLKS_MCK_DIV8;
 }

 /* byte size */
 switch (termios->c_cflag & CSIZE) {
 case CS5:
  mode |= ATMEL_US_CHRL_5;
  break;
 case CS6:
  mode |= ATMEL_US_CHRL_6;
  break;
 case CS7:
  mode |= ATMEL_US_CHRL_7;
  break;
 default:
  mode |= ATMEL_US_CHRL_8;
  break;
 }

 /* stop bits */
 if (termios->c_cflag & CSTOPB)
  mode |= ATMEL_US_NBSTOP_2;

 /* parity */
 if (termios->c_cflag & PARENB) {
  /* Mark or Space parity */
  if (termios->c_cflag & CMSPAR) {
   if (termios->c_cflag & PARODD)
    mode |= ATMEL_US_PAR_MARK;
   else
    mode |= ATMEL_US_PAR_SPACE;
  } else if (termios->c_cflag & PARODD)
   mode |= ATMEL_US_PAR_ODD;
  else
   mode |= ATMEL_US_PAR_EVEN;
 } else
  mode |= ATMEL_US_PAR_NONE;

 spin_lock_irqsave(&port->lock, flags);

 port->read_status_mask = ATMEL_US_OVRE;
 if (termios->c_iflag & INPCK)
  port->read_status_mask |= (ATMEL_US_FRAME | ATMEL_US_PARE);
 if (termios->c_iflag & (BRKINT | PARMRK))
  port->read_status_mask |= ATMEL_US_RXBRK;

 if (atmel_use_dma_rx(port))
  /* need to enable error interrupts */
  UART_PUT_IER(port, port->read_status_mask);

 /*
  * Characters to ignore
  */
 port->ignore_status_mask = 0;
 if (termios->c_iflag & IGNPAR)
  port->ignore_status_mask |= (ATMEL_US_FRAME | ATMEL_US_PARE);
 if (termios->c_iflag & IGNBRK) {
  port->ignore_status_mask |= ATMEL_US_RXBRK;
  /*
   * If we're ignoring parity and break indicators,
   * ignore overruns too (for real raw support).
   */
  if (termios->c_iflag & IGNPAR)
   port->ignore_status_mask |= ATMEL_US_OVRE;
 }
 /* TODO: Ignore all characters if CREAD is set.*/

 /* update the per-port timeout */
 uart_update_timeout(port, termios->c_cflag, baud);

 /* save/disable interrupts and drain transmitter */
 imr = UART_GET_IMR(port);
 UART_PUT_IDR(port, -1);
 while (!(UART_GET_CSR(port) & ATMEL_US_TXEMPTY))
  cpu_relax();

 /* disable receiver and transmitter */
 UART_PUT_CR(port, ATMEL_US_TXDIS | ATMEL_US_RXDIS);

 /* set the parity, stop bits and data size */
 UART_PUT_MR(port, mode);

 /* set the baud rate */
 UART_PUT_BRGR(port, quot);
 UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
 UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);

 /* restore interrupts */
 UART_PUT_IER(port, imr);

 /* CTS flow-control and modem-status interrupts */
 if (UART_ENABLE_MS(port, termios->c_cflag))
  port->ops->enable_ms(port);

 spin_unlock_irqrestore(&port->lock, flags);
}

/*
 * Return string describing the specified port
 */
static const char *atmel_type(struct uart_port *port)
{
 return (port->type == PORT_ATMEL) ? "ATMEL_SERIAL" : NULL;
}

/*
 * Release the memory region(s) being used by 'port'.
 */
static void atmel_release_port(struct uart_port *port)
{
 struct platform_device *pdev = to_platform_device(port->dev);
 int size = pdev->resource[0].end - pdev->resource[0].start + 1;

 release_mem_region(port->mapbase, size);

 if (port->flags & UPF_IOREMAP) {
  iounmap(port->membase);
  port->membase = NULL;
 }
}

/*
 * Request the memory region(s) being used by 'port'.
 */
static int atmel_request_port(struct uart_port *port)
{
 struct platform_device *pdev = to_platform_device(port->dev);
 int size = pdev->resource[0].end - pdev->resource[0].start + 1;

 if (!request_mem_region(port->mapbase, size, "atmel_serial"))
  return -EBUSY;

 if (port->flags & UPF_IOREMAP) {
  port->membase = ioremap(port->mapbase, size);
  if (port->membase == NULL) {
   release_mem_region(port->mapbase, size);
   return -ENOMEM;
  }
 }

 return 0;
}

/*
 * Configure/autoconfigure the port.
 */
static void atmel_config_port(struct uart_port *port, int flags)
{
 if (flags & UART_CONFIG_TYPE) {
  port->type = PORT_ATMEL;
  atmel_request_port(port);
 }
}

/*
 * Verify the new serial_struct (for TIOCSSERIAL).
 */
static int atmel_verify_port(struct uart_port *port, struct serial_struct *ser)
{
 int ret = 0;
 if (ser->type != PORT_UNKNOWN && ser->type != PORT_ATMEL)
  ret = -EINVAL;
 if (port->irq != ser->irq)
  ret = -EINVAL;
 if (ser->io_type != SERIAL_IO_MEM)
  ret = -EINVAL;
 if (port->uartclk / 16 != ser->baud_base)
  ret = -EINVAL;
 if ((void *)port->mapbase != ser->iomem_base)
  ret = -EINVAL;
 if (port->iobase != ser->port)
  ret = -EINVAL;
 if (ser->hub6 != 0)
  ret = -EINVAL;
 return ret;
}

static struct uart_ops atmel_pops = {
 .tx_empty = atmel_tx_empty,
 .set_mctrl = atmel_set_mctrl,
 .get_mctrl = atmel_get_mctrl,
 .stop_tx = atmel_stop_tx,
 .start_tx = atmel_start_tx,
 .stop_rx = atmel_stop_rx,
 .enable_ms = atmel_enable_ms,
 .break_ctl = atmel_break_ctl,
 .startup = atmel_startup,
 .shutdown = atmel_shutdown,
 .flush_buffer = atmel_flush_buffer,
 .set_termios = atmel_set_termios,
 .type  = atmel_type,
 .release_port = atmel_release_port,
 .request_port = atmel_request_port,
 .config_port = atmel_config_port,
 .verify_port = atmel_verify_port,
 .pm  = atmel_serial_pm,
};

 

/*
 * Configure the port from the platform device resource info.
 */
static void __devinit atmel_init_port(struct atmel_uart_port *atmel_port,
          struct platform_device *pdev)
{
 struct uart_port *port = &atmel_port->uart;
 struct atmel_uart_data *data = pdev->dev.platform_data; //访问方式管理

 port->iotype = UPIO_MEM;       //访问方式为内存方式
 port->flags = UPF_BOOT_AUTOCONF;  //配置方式设置
 port->ops = &atmel_pops;              //串口的具体操作，串口驱动的关键实现
 port->fifosize = 1;                            //FIFO缓存的大小         
 port->line = pdev->id;
 port->dev = &pdev->dev;

 port->mapbase = pdev->resource[0].start;   //物理内存
 port->irq = pdev->resource[1].start;             //中断号

 tasklet_init(&atmel_port->tasklet, atmel_tasklet_func,
   (unsigned long)port);   

 memset(&atmel_port->rx_ring, 0, sizeof(atmel_port->rx_ring));

 if (data->regs)
  /* Already mapped by setup code */
  port->membase = data->regs;
 else {
  port->flags |= UPF_IOREMAP;
  port->membase = NULL;
 }

 /* for console, the clock could already be configured */
 if (!atmel_port->clk) {
  atmel_port->clk = clk_get(&pdev->dev, "usart");
  clk_enable(atmel_port->clk);
  port->uartclk = clk_get_rate(atmel_port->clk);
 }

 atmel_port->use_dma_rx = data->use_dma_rx;
 atmel_port->use_dma_tx = data->use_dma_tx;
 if (atmel_use_dma_tx(port))
  port->fifosize = PDC_BUFFER_SIZE;
}

 

 

/*
 * Register board-specific modem-control line handlers.
 */
void __init atmel_register_uart_fns(struct atmel_port_fns *fns)
{
 if (fns->enable_ms)
  atmel_pops.enable_ms = fns->enable_ms;
 if (fns->get_mctrl)
  atmel_pops.get_mctrl = fns->get_mctrl;
 if (fns->set_mctrl)
  atmel_pops.set_mctrl = fns->set_mctrl;
 atmel_open_hook  = fns->open;
 atmel_close_hook = fns->close;
 atmel_pops.pm  = fns->pm;
 atmel_pops.set_wake = fns->set_wake;
}

#ifdef CONFIG_SERIAL_ATMEL_CONSOLE
static void atmel_console_putchar(struct uart_port *port, int ch)
{
 while (!(UART_GET_CSR(port) & ATMEL_US_TXRDY))
  cpu_relax();
 UART_PUT_CHAR(port, ch);
}

/*
 * Interrupts are disabled on entering
 */
static void atmel_console_write(struct console *co, const char *s, u_int count)
{
 struct uart_port *port = &atmel_ports[co->index].uart;
 unsigned int status, imr;
 unsigned int pdc_tx;

 /*
  * First, save IMR and then disable interrupts
  */
 imr = UART_GET_IMR(port);
 UART_PUT_IDR(port, ATMEL_US_RXRDY | ATMEL_US_TXRDY);

 /* Store PDC transmit status and disable it */
 pdc_tx = UART_GET_PTSR(port) & ATMEL_PDC_TXTEN;
 UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS);

 uart_console_write(port, s, count, atmel_console_putchar);

 /*
  * Finally, wait for transmitter to become empty
  * and restore IMR
  */
 do {
  status = UART_GET_CSR(port);
 } while (!(status & ATMEL_US_TXRDY));

 /* Restore PDC transmit status */
 if (pdc_tx)
  UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);

 /* set interrupts back the way they were */
 UART_PUT_IER(port, imr);
}

/*
 * If the port was already initialised (eg, by a boot loader),
 * try to determine the current setup.
 */
static void __init atmel_console_get_options(struct uart_port *port, int *baud,
          int *parity, int *bits)
{
 unsigned int mr, quot;

 /*
  * If the baud rate generator isn't running, the port wasn't
  * initialized by the boot loader.
  */
 quot = UART_GET_BRGR(port) & ATMEL_US_CD;
 if (!quot)
  return;

 mr = UART_GET_MR(port) & ATMEL_US_CHRL;
 if (mr == ATMEL_US_CHRL_8)
  *bits = 8;
 else
  *bits = 7;

 mr = UART_GET_MR(port) & ATMEL_US_PAR;
 if (mr == ATMEL_US_PAR_EVEN)
  *parity = 'e';
 else if (mr == ATMEL_US_PAR_ODD)
  *parity = 'o';

 /*
  * The serial core only rounds down when matching this to a
  * supported baud rate. Make sure we don't end up slightly
  * lower than one of those, as it would make us fall through
  * to a much lower baud rate than we really want.
  */
 *baud = port->uartclk / (16 * (quot - 1));
}

static int __init atmel_console_setup(struct console *co, char *options)
{
 struct uart_port *port = &atmel_ports[co->index].uart;
 int baud = 115200;
 int bits = 8;
 int parity = 'n';
 int flow = 'n';

 if (port->membase == NULL) {
  /* Port not initialized yet - delay setup */
  return -ENODEV;
 }

 UART_PUT_IDR(port, -1);
 UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
 UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);

 if (options)
  uart_parse_options(options, &baud, &parity, &bits, &flow);
 else
  atmel_console_get_options(port, &baud, &parity, &bits);

 return uart_set_options(port, co, baud, parity, bits, flow);
}

static struct uart_driver atmel_uart;

static struct console atmel_console = {
 .name  = ATMEL_DEVICENAME,
 .write  = atmel_console_write,
 .device  = uart_console_device,
 .setup  = atmel_console_setup,
 .flags  = CON_PRINTBUFFER,
 .index  = -1,
 .data  = &atmel_uart,
};

#define ATMEL_CONSOLE_DEVICE &atmel_console

/*
 * Early console initialization (before VM subsystem initialized).
 */
static int __init atmel_console_init(void)
{
 if (atmel_default_console_device) {
  add_preferred_console(ATMEL_DEVICENAME,
          atmel_default_console_device->id, NULL);
  atmel_init_port(&atmel_ports[atmel_default_console_device->id],
    atmel_default_console_device);
  register_console(&atmel_console);
 }

 return 0;
}

console_initcall(atmel_console_init);

/*
 * Late console initialization.
 */
static int __init atmel_late_console_init(void)
{
 if (atmel_default_console_device
     && !(atmel_console.flags & CON_ENABLED))
  register_console(&atmel_console);

 return 0;
}

core_initcall(atmel_late_console_init);

static inline bool atmel_is_console_port(struct uart_port *port)
{
 return port->cons && port->cons->index == port->line;
}

#else
#define ATMEL_CONSOLE_DEVICE NULL

static inline bool atmel_is_console_port(struct uart_port *port)
{
 return false;
}
#endif

static struct uart_driver atmel_uart = {
 .owner  = THIS_MODULE,
 .driver_name = "atmel_serial",
 .dev_name = ATMEL_DEVICENAME,
 .major  = SERIAL_ATMEL_MAJOR,
 .minor  = MINOR_START,
 .nr  = ATMEL_MAX_UART,
 .cons  = ATMEL_CONSOLE_DEVICE,
};

#ifdef CONFIG_PM
static bool atmel_serial_clk_will_stop(void)
{
#ifdef CONFIG_ARCH_AT91
 return at91_suspend_entering_slow_clock();
#else
 return false;
#endif
}

static int atmel_serial_suspend(struct platform_device *pdev,
    pm_message_t state)
{
 struct uart_port *port = platform_get_drvdata(pdev);
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

 if (atmel_is_console_port(port) && console_suspend_enabled) {
  /* Drain the TX shifter */
  while (!(UART_GET_CSR(port) & ATMEL_US_TXEMPTY))
   cpu_relax();
 }

 /* we can not wake up if we're running on slow clock */
 atmel_port->may_wakeup = device_may_wakeup(&pdev->dev);
 if (atmel_serial_clk_will_stop())
  device_set_wakeup_enable(&pdev->dev, 0);

 uart_suspend_port(&atmel_uart, port);

 return 0;
}

static int atmel_serial_resume(struct platform_device *pdev)
{
 struct uart_port *port = platform_get_drvdata(pdev);
 struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);

 uart_resume_port(&atmel_uart, port);
 device_set_wakeup_enable(&pdev->dev, atmel_port->may_wakeup);

 return 0;
}
#else
#define atmel_serial_suspend NULL
#define atmel_serial_resume NULL
#endif

 

//根据平台设备的资源构建一个atmle_uart_port结构，并将相关联的uart_port结构和uart_driver关联

static int __devinit atmel_serial_probe(struct platform_device *pdev)
{
 struct atmel_uart_port *port;
 void *data;
 int ret;

 BUILD_BUG_ON(!is_power_of_2(ATMEL_SERIAL_RINGSIZE));

 port = &atmel_ports[pdev->id];   //串口都保存在atmel_ports数组中，平台设备的id即为数组索引
 port->backup_imr = 0;

 atmel_init_port(port, pdev);  //构建uart_port结构

 if (!atmel_use_dma_rx(&port->uart)) {
  ret = -ENOMEM;
  data = kmalloc(sizeof(struct atmel_uart_char) //使用DMA时DMA缓存分配
    * ATMEL_SERIAL_RINGSIZE, GFP_KERNEL);
  if (!data)
   goto err_alloc_ring;
  port->rx_ring.buf = data;
 }

 ret = uart_add_one_port(&atmel_uart, &port->uart);//把分配的端口加到uart_driver中
 if (ret)
  goto err_add_port;

 device_init_wakeup(&pdev->dev, 1);
 platform_set_drvdata(pdev, port);

 return 0;

err_add_port:
 kfree(port->rx_ring.buf);
 port->rx_ring.buf = NULL;
err_alloc_ring:
 if (!atmel_is_console_port(&port->uart)) {
  clk_disable(port->clk);
  clk_put(port->clk);
  port->clk = NULL;
 }

 return ret;
}

 

11:35:00static struct platform_driver atmel_serial_driver = {
 .probe  = atmel_serial_probe,
 .remove  = __devexit_p(atmel_serial_remove),
 .suspend = atmel_serial_suspend,
 .resume  = atmel_serial_resume,
 .driver  = {
  .name = "atmel_usart",
  .owner = THIS_MODULE,
 },
};

 

static int __init atmel_serial_init(void)
{
 int ret;

 ret = uart_register_driver(&atmel_uart); //注册串口驱动
 if (ret)
  return ret;

 ret = platform_driver_register(&atmel_serial_driver);//注册平台驱动
 if (ret)
  uart_unregister_driver(&atmel_uart);

 return ret;
}

 

static void __exit atmel_serial_exit(void)
{
 platform_driver_unregister(&atmel_serial_driver);
 uart_unregister_driver(&atmel_uart);
}

module_init(atmel_serial_init);
module_exit(atmel_serial_exit);

MODULE_AUTHOR("Rick Bronson");
MODULE_DESCRIPTION("Atmel AT91 / AT32 serial port driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:atmel_usart");

 

我们顺着驱动加载流程对上面代码做简要分析：

      1）当加载驱动时，代码首先执行atmel_serial_init函数，该函数向内核注册了两个驱动分别是struct uart_driver atmel_uart（我们的串口驱动）和struct platform_driver atmel_serial_driver(平台设备驱动，主要用于串口设备的探测和移除工作)，注意两个驱动的名称分别是atmel_serial和atmel_usart。

     2）当平台驱动加载后会执行平台驱动的probe函数即atmel_serial_probe.在我们的驱动平台设备的加入是在arch/arm/mach-at91/at91sam9260_devices.c中加入的。具体相关代码如下：

/* --------------------------------------------------------------------
 *  UART
 * -------------------------------------------------------------------- */
#if defined(CONFIG_SERIAL_ATMEL)
static struct resource dbgu_resources[] = {
 [0] = {
  .start = AT91_VA_BASE_SYS + AT91_DBGU,
  .end = AT91_VA_BASE_SYS + AT91_DBGU + SZ_512 - 1,
  .flags = IORESOURCE_MEM,
 },
 [1] = {
  .start = AT91_ID_SYS,
  .end = AT91_ID_SYS,
  .flags = IORESOURCE_IRQ,
 },
};

static struct atmel_uart_data dbgu_data = {
 .use_dma_tx = 0,
 .use_dma_rx = 0,  /* DBGU not capable of receive DMA */
 .regs  = (void __iomem *)(AT91_VA_BASE_SYS + AT91_DBGU),
};

static u64 dbgu_dmamask = DMA_BIT_MASK(32);

static struct platform_device at91sam9260_dbgu_device = {
 .name  = "atmel_usart",
 .id  = 0,
 .dev  = {
    .dma_mask  = &dbgu_dmamask,
    .coherent_dma_mask = DMA_BIT_MASK(32),
    .platform_data  = &dbgu_data,
 },
 .resource = dbgu_resources,
 .num_resources = ARRAY_SIZE(dbgu_resources),
};

static inline void configure_dbgu_pins(void)
{
 at91_set_A_periph(AT91_PIN_PB14, 0);  /* DRXD */
 at91_set_A_periph(AT91_PIN_PB15, 1);  /* DTXD */
}

static struct resource uart0_resources[] = {
 [0] = {
  .start = AT91SAM9260_BASE_US0,
  .end = AT91SAM9260_BASE_US0 + SZ_16K - 1,
  .flags = IORESOURCE_MEM,
 },
 [1] = {
  .start = AT91SAM9260_ID_US0,
  .end = AT91SAM9260_ID_US0,
  .flags = IORESOURCE_IRQ,
 },
};

static struct atmel_uart_data uart0_data = {
 .use_dma_tx = 1,
 .use_dma_rx = 1,
};

static u64 uart0_dmamask = DMA_BIT_MASK(32);

static struct platform_device at91sam9260_uart0_device = {
 .name  = "atmel_usart",
 .id  = 1,
 .dev  = {
    .dma_mask  = &uart0_dmamask,
    .coherent_dma_mask = DMA_BIT_MASK(32),
    .platform_data  = &uart0_data,
 },
 .resource = uart0_resources,
 .num_resources = ARRAY_SIZE(uart0_resources),
};

static inline void configure_usart0_pins(unsigned pins)
{
 at91_set_A_periph(AT91_PIN_PB4, 1);  /* TXD0 */
 at91_set_A_periph(AT91_PIN_PB5, 0);  /* RXD0 */

 if (pins & ATMEL_UART_RTS)
  at91_set_A_periph(AT91_PIN_PB26, 0); /* RTS0 */
 if (pins & ATMEL_UART_CTS)
  at91_set_A_periph(AT91_PIN_PB27, 0); /* CTS0 */
 if (pins & ATMEL_UART_DTR)
  at91_set_A_periph(AT91_PIN_PB24, 0); /* DTR0 */
 if (pins & ATMEL_UART_DSR)
  at91_set_A_periph(AT91_PIN_PB22, 0); /* DSR0 */
 if (pins & ATMEL_UART_DCD)
  at91_set_A_periph(AT91_PIN_PB23, 0); /* DCD0 */
 if (pins & ATMEL_UART_RI)
  at91_set_A_periph(AT91_PIN_PB25, 0); /* RI0 */
}

static struct resource uart1_resources[] = {
 [0] = {
  .start = AT91SAM9260_BASE_US1,
  .end = AT91SAM9260_BASE_US1 + SZ_16K - 1,
  .flags = IORESOURCE_MEM,
 },
 [1] = {
  .start = AT91SAM9260_ID_US1,
  .end = AT91SAM9260_ID_US1,
  .flags = IORESOURCE_IRQ,
 },
};

static struct atmel_uart_data uart1_data = {
 .use_dma_tx = 1,
 .use_dma_rx = 1,
};

static u64 uart1_dmamask = DMA_BIT_MASK(32);

static struct platform_device at91sam9260_uart1_device = {
 .name  = "atmel_usart",
 .id  = 2,
 .dev  = {
    .dma_mask  = &uart1_dmamask,
    .coherent_dma_mask = DMA_BIT_MASK(32),
    .platform_data  = &uart1_data,
 },
 .resource = uart1_resources,
 .num_resources = ARRAY_SIZE(uart1_resources),
};

static inline void configure_usart1_pins(unsigned pins)
{
 /*add by shadow*/
 at91_set_A_periph(AT91_PIN_PB6, 1);  /* TXD1 */
 /*shadow end*/
 at91_set_A_periph(AT91_PIN_PB7, 0);  /* RXD1 */

 if (pins & ATMEL_UART_RTS)
  at91_set_A_periph(AT91_PIN_PB28, 0); /* RTS1 */
 if (pins & ATMEL_UART_CTS)
  at91_set_A_periph(AT91_PIN_PB29, 0); /* CTS1 */
}

static struct resource uart2_resources[] = {
 [0] = {
  .start = AT91SAM9260_BASE_US2,
  .end = AT91SAM9260_BASE_US2 + SZ_16K - 1,
  .flags = IORESOURCE_MEM,
 },
 [1] = {
  .start = AT91SAM9260_ID_US2,
  .end = AT91SAM9260_ID_US2,
  .flags = IORESOURCE_IRQ,
 },
};

static struct atmel_uart_data uart2_data = {
 .use_dma_tx = 1,
 .use_dma_rx = 1,
};

static u64 uart2_dmamask = DMA_BIT_MASK(32);

static struct platform_device at91sam9260_uart2_device = {
 .name  = "atmel_usart",
 .id  = 3,
 .dev  = {
    .dma_mask  = &uart2_dmamask,
    .coherent_dma_mask = DMA_BIT_MASK(32),
    .platform_data  = &uart2_data,
 },
 .resource = uart2_resources,
 .num_resources = ARRAY_SIZE(uart2_resources),
};

static inline void configure_usart2_pins(unsigned pins)
{
 at91_set_A_periph(AT91_PIN_PB8, 1);  /* TXD2 */
 at91_set_A_periph(AT91_PIN_PB9, 0);  /* RXD2 */

 if (pins & ATMEL_UART_RTS)
  at91_set_A_periph(AT91_PIN_PA4, 0); /* RTS2 */
 if (pins & ATMEL_UART_CTS)
  at91_set_A_periph(AT91_PIN_PA5, 0); /* CTS2 */
}

static struct resource uart3_resources[] = {
 [0] = {
  .start = AT91SAM9260_BASE_US3,
  .end = AT91SAM9260_BASE_US3 + SZ_16K - 1,
  .flags = IORESOURCE_MEM,
 },
 [1] = {
  .start = AT91SAM9260_ID_US3,
  .end = AT91SAM9260_ID_US3,
  .flags = IORESOURCE_IRQ,
 },
};

static struct atmel_uart_data uart3_data = {
 .use_dma_tx = 1,
 .use_dma_rx = 1,
};

static u64 uart3_dmamask = DMA_BIT_MASK(32);

static struct platform_device at91sam9260_uart3_device = {
 .name  = "atmel_usart",
 .id  = 4,
 .dev  = {
    .dma_mask  = &uart3_dmamask,
    .coherent_dma_mask = DMA_BIT_MASK(32),
    .platform_data  = &uart3_data,
 },
 .resource = uart3_resources,
 .num_resources = ARRAY_SIZE(uart3_resources),
};

static inline void configure_usart3_pins(unsigned pins)
{
 at91_set_A_periph(AT91_PIN_PB10, 1);  /* TXD3 */
 at91_set_A_periph(AT91_PIN_PB11, 0);  /* RXD3 */

 if (pins & ATMEL_UART_RTS)
  at91_set_B_periph(AT91_PIN_PC8, 0); /* RTS3 */
 if (pins & ATMEL_UART_CTS)
  at91_set_B_periph(AT91_PIN_PC10, 0); /* CTS3 */
}

static struct resource uart4_resources[] = {
 [0] = {
  .start = AT91SAM9260_BASE_US4,
  .end = AT91SAM9260_BASE_US4 + SZ_16K - 1,
  .flags = IORESOURCE_MEM,
 },
 [1] = {
  .start = AT91SAM9260_ID_US4,
  .end = AT91SAM9260_ID_US4,
  .flags = IORESOURCE_IRQ,
 },
};

static struct atmel_uart_data uart4_data = {
 .use_dma_tx = 1,
 .use_dma_rx = 1,
};

static u64 uart4_dmamask = DMA_BIT_MASK(32);

static struct platform_device at91sam9260_uart4_device = {
 .name  = "atmel_usart",
 .id  = 5,
 .dev  = {
    .dma_mask  = &uart4_dmamask,
    .coherent_dma_mask = DMA_BIT_MASK(32),
    .platform_data  = &uart4_data,
 },
 .resource = uart4_resources,
 .num_resources = ARRAY_SIZE(uart4_resources),
};

static inline void configure_usart4_pins(void)
{
 at91_set_B_periph(AT91_PIN_PA31, 1);  /* TXD4 */
 at91_set_B_periph(AT91_PIN_PA30, 0);  /* RXD4 */
}

static struct resource uart5_resources[] = {
 [0] = {
  .start = AT91SAM9260_BASE_US5,
  .end = AT91SAM9260_BASE_US5 + SZ_16K - 1,
  .flags = IORESOURCE_MEM,
 },
 [1] = {
  .start = AT91SAM9260_ID_US5,
  .end = AT91SAM9260_ID_US5,
  .flags = IORESOURCE_IRQ,
 },
};

static struct atmel_uart_data uart5_data = {
 .use_dma_tx = 1,
 .use_dma_rx = 1,
};

static u64 uart5_dmamask = DMA_BIT_MASK(32);

static struct platform_device at91sam9260_uart5_device = {
 .name  = "atmel_usart",
 .id  = 6,
 .dev  = {
    .dma_mask  = &uart5_dmamask,
    .coherent_dma_mask = DMA_BIT_MASK(32),
    .platform_data  = &uart5_data,
 },
 .resource = uart5_resources,
 .num_resources = ARRAY_SIZE(uart5_resources),
};

static inline void configure_usart5_pins(void)
{
 at91_set_A_periph(AT91_PIN_PB12, 1);  /* TXD5 */
 at91_set_A_periph(AT91_PIN_PB13, 0);  /* RXD5 */
}

static struct platform_device *__initdata at91_uarts[ATMEL_MAX_UART]; /* the UARTs to use */
struct platform_device *atmel_default_console_device; /* the serial console device */

void __init at91_register_uart(unsigned id, unsigned portnr, unsigned pins)
{
 struct platform_device *pdev;

 switch (id) {
  case 0:  /* DBGU */
   pdev = &at91sam9260_dbgu_device;
   configure_dbgu_pins();
   at91_clock_associate("mck", &pdev->dev, "usart");
   break;
  case AT91SAM9260_ID_US0:
   pdev = &at91sam9260_uart0_device;
   configure_usart0_pins(pins);
   at91_clock_associate("usart0_clk", &pdev->dev, "usart");
   break;
  case AT91SAM9260_ID_US1:
   pdev = &at91sam9260_uart1_device;
   configure_usart1_pins(pins);
   at91_clock_associate("usart1_clk", &pdev->dev, "usart");
   break;
  case AT91SAM9260_ID_US2:
   pdev = &at91sam9260_uart2_device;
   configure_usart2_pins(pins);
   at91_clock_associate("usart2_clk", &pdev->dev, "usart");
   break;
  case AT91SAM9260_ID_US3:
   pdev = &at91sam9260_uart3_device;
   configure_usart3_pins(pins);
   at91_clock_associate("usart3_clk", &pdev->dev, "usart");
   break;
  case AT91SAM9260_ID_US4:
   pdev = &at91sam9260_uart4_device;
   configure_usart4_pins();
   at91_clock_associate("usart4_clk", &pdev->dev, "usart");
   break;
  case AT91SAM9260_ID_US5:
   pdev = &at91sam9260_uart5_device;
   configure_usart5_pins();
   at91_clock_associate("usart5_clk", &pdev->dev, "usart");
   break;
  default:
   return;
 }
 pdev->id = portnr;  /* update to mapped ID */

 if (portnr < ATMEL_MAX_UART)
  at91_uarts[portnr] = pdev;
}

void __init at91_set_serial_console(unsigned portnr)
{
 if (portnr < ATMEL_MAX_UART)
  atmel_default_console_device = at91_uarts[portnr];
}

void __init at91_add_device_serial(void)
{
 int i;

 for (i = 0; i < ATMEL_MAX_UART; i++) {
  if (at91_uarts[i])
   platform_device_register(at91_uarts[i]);
 }

 if (!atmel_default_console_device)
  printk(KERN_INFO "AT91: No default serial console defined./n");
}
#else
void __init at91_register_uart(unsigned id, unsigned portnr, unsigned pins) {}
void __init at91_set_serial_console(unsigned portnr) {}
void __init at91_add_device_serial(void) {}
#endif
      在atmel_serial_probe函数中传入的参数就是上面加入的平台设备，注意这里的平台设备和平台驱动具有相同的名字。而前面加载的两个驱动的关联也在这个探测函数中得以体现，具体见上面的代码注解。其他比较好理解就是对uart_ops的实现