轉自：http://blog.chinaunix.net/uid-27717694-id-3493611.html

8250串口的初始化：

（1）定義uart_driver、uart_ops、uart_port等結構體的實例并在適當的地方更具具體的硬件驅動情況初始化他們，當然具體設備xxx的驅動可以將這些結構體套在新定義的xxx_uart_driver、xxx_uart_ops、xxx_uart_port之內。

（2）在模塊初始化調用uart_register()和uart_add_one_port()以注冊UART驅動并添加端口，在模塊卸載時調用uart_unregister_driver()和uart_remove_one_port()以注銷UART驅動以移除端口。

（3）根據具體硬件的uart_ops中的成員函數，這些函數的實現成為UART驅動的主體工作。
1.串口結構體,他們之間的關系如圖所示：

//（1）串口驅動結構體
struct uart_driver {??
??? struct module?? *owner; //模塊所有者???
??? const char? *driver_name;?? //驅動名???
??? const char? *dev_name;? //設備名???
??? int? major; //主設備號???
??? int? minor; //次設備號???
??? int? nr;??? //支持串口個數???
??? struct console? *cons;//控制臺設備???
??? struct uart_state?? *state; //串口狀態???
??? struct tty_driver?? *tty_driver; //tty設備???
};?

//（2）串口端口結構體
struct uart_port {??
??? spinlock_t? lock;??
??? unsigned long?? iobase; //io端口基地址???
??? unsigned char __iomem?? *membase; //內存端口基地址???
??? unsigned int??? (*serial_in)(struct uart_port *, int); //串口讀函數?
??? void??? (*serial_out)(struct uart_port *, int, int); //串口寫方法
??? void??? (*set_termios)(struct uart_port *,struct ktermios *new,struct ktermios *old); //串口配置方法函數
??? void??? (*pm)(struct uart_port *, unsigned int state,unsigned int old);??
??? unsigned int??? irq;??? //中斷號???
??? unsigned long?? irqflags;?? //中斷標志???
??? unsigned int??? uartclk;?? //串口時鐘
??? unsigned int??? fifosize;?? //fifo大小???????
??? unsigned char?? x_char;??
??? unsigned char?? regshift;?? //寄存器偏移值???????
??? unsigned char?? iotype; //io訪問類型???
??? unsigned char?? unused1;??
??? unsigned int??? read_status_mask;??
??? unsigned int??? ignore_status_mask;??
??? struct uart_state?? *state; //uart_state結構體????
??? struct uart_icount? icount; //串口使用計數???
??? struct console? *cons;? //console控制臺???
#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(SUPPORT_SYSRQ)???
??? unsigned long?? sysrq;??
#endif???
??? upf_t?? flags;??
??? unsigned int??? mctrl;??
??? unsigned int??? timeout;??
??? unsigned int??? type; //串口類型?
??? const struct uart_ops?? *ops;?? //串口操作函數集???
??? unsigned int??? custom_divisor;??
??? unsigned int??? line;?? //端口號???
??? resource_size_t mapbase; //串口寄存器基地址（物理地址）
??? struct device?? *dev;?? //設備文件???
??? unsigned char?? hub6;??
??? unsigned char?? suspended;??
??? unsigned char?? irq_wake;??
??? unsigned char?? unused[2];??
??? void??? *private_data;??
};?

//（3）操作函數集
struct uart_ops {??
??? unsigned int??? (*tx_empty)(struct uart_port *);??? //發送緩沖區為空???
??? void??? (*set_mctrl)(struct uart_port *, unsigned int mctrl);?? //設置串口modem控制模式???
??? unsigned int??? (*get_mctrl)(struct uart_port *);?? //獲取串口modem控制模式???
??? void??? (*stop_tx)(struct uart_port *); //停止發送???
??? void??? (*start_tx)(struct uart_port *);??? //開始發送???
??? void??? (*send_xchar)(struct uart_port *, char ch);??
??? void??? (*stop_rx)(struct uart_port *); //停止接收???
??? void??? (*enable_ms)(struct uart_port *);?? //使能modem狀態信息???
??? void??? (*break_ctl)(struct uart_port *, int ctl);??
??? int (*startup)(struct uart_port *); //打開串口???
??? void??? (*shutdown)(struct uart_port *);??? //關閉串口???
??? void??? (*flush_buffer)(struct uart_port *);??
??? void??? (*set_termios)(struct uart_port *, struct ktermios *new,struct ktermios *old);? //設置串口參數???
??? void??? (*set_ldisc)(struct uart_port *, int new);??
??? void??? (*pm)(struct uart_port *, unsigned int state,unsigned int oldstate);??
??? int (*set_wake)(struct uart_port *, unsigned int state);??
??? const char *(*type)(struct uart_port *);??
??? void??? (*release_port)(struct uart_port *);??? //釋放端口???
??? int (*request_port)(struct uart_port *);??? //請求端口???
??? void??? (*config_port)(struct uart_port *, int);??? //配置端口???
??? int (*verify_port)(struct uart_port *, struct serial_struct *); //校驗端口???
??? int (*ioctl)(struct uart_port *, unsigned int, unsigned long);? //控制???
#ifdef CONFIG_CONSOLE_POLL???
??? void??? (*poll_put_char)(struct uart_port *, unsigned char);??
??? int (*poll_get_char)(struct uart_port *);??
#endif???
};?

//（4）uart_state
struct uart_state {??
??? struct tty_port port;??
??? int???? pm_state;??
??? struct circ_buf xmit;??
??? struct tasklet_struct?? tlet;??
??? struct uart_port??? *uart_port;//指向對應的串口結構??
};?

2.串口初始化
static int __init serial8250_init(void)
{
?int ret;

?if (nr_uarts > UART_NR)//UART_NR =3
??nr_uarts = UART_NR;//串口數量最多設為3個

?printk(KERN_INFO "Serial: 8250/16550 driver, ""%d ports, IRQ sharing %sabled\n", nr_uarts,share_irqs ? "en" : "dis");

?serial8250_reg.nr = UART_NR;//串口數量
?/*
??static struct uart_driver serial8250_reg = {
??.owner???= THIS_MODULE,
??.driver_name??= "serial",
??.dev_name??= "ttyS",
??.major???= TTY_MAJOR,//主設備號是4
??.minor???= 64,
??.cons???= SERIAL8250_CONSOLE,//終端
?};
?
?#define SERIAL8250_CONSOLE?&serial8250_console
?
?static struct console serial8250_console = {
??.name??= "ttyS",
??.write??= serial8250_console_write,
??.device??= uart_console_device,
??.setup??= serial8250_console_setup,//設置串口波特率，也就是設置串口。很重要，里面涉及到平臺特性，波特率相關。
??.early_setup?= serial8250_console_early_setup,
??.flags??= CON_PRINTBUFFER | CON_ANYTIME,
??.index??= -1,
??.data??= &serial8250_reg,
?};
?*/
?//函數定義在serial_core.c中
?//注冊uart串口驅動，完善uart_driver結構serial8250_reg的uart_state成員及tty_driver成員，并注冊tty驅動
?ret = uart_register_driver(&serial8250_reg);
#endif
?if (ret)
??goto out;
?
?//創建一個platform_device結構：serial8250_isa_devs
?serial8250_isa_devs = platform_device_alloc("serial8250",PLAT8250_DEV_LEGACY);
?if (!serial8250_isa_devs) {
??ret = -ENOMEM;
??goto unreg_uart_drv;
?}
?
? //將該結構serial8250_isa_devs注冊到總線上
?ret = platform_device_add(serial8250_isa_devs);
?if (ret)
??goto put_dev;
??
?//對uart_8250_port結構serial8250_reg[]初始化,即對3個串口的uart_port結構初始化，并添加端口
?serial8250_register_ports(&serial8250_reg, &serial8250_isa_devs->dev);
?
?/*
?static struct platform_driver serial8250_isa_driver = {
??.probe??= serial8250_probe,
??.remove??= __devexit_p(serial8250_remove),
??.suspend?= serial8250_suspend,
??.resume??= serial8250_resume,
??.driver??= {
???.name?= "serial8250",
???.owner?= THIS_MODULE,
??},
?};
?*/
?//注冊設備,會調用serial8250_probe()。怎樣調用的serial8250_probe？？？？？？？
?ret = platform_driver_register(&serial8250_isa_driver);
?if (ret == 0)
??goto out;

?platform_device_del(serial8250_isa_devs);
put_dev:
?platform_device_put(serial8250_isa_devs);
unreg_uart_drv:
#ifdef CONFIG_SPARC
?sunserial_unregister_minors(&serial8250_reg, UART_NR);
#else
?uart_unregister_driver(&serial8250_reg);
#endif
out:
?return ret;
}

//注冊串口驅動
int uart_register_driver(struct uart_driver *drv)
{
?struct tty_driver *normal;
?int i, retval;

?BUG_ON(drv->state);

?//為串口的uart_driver結構分配要指向的uart_state結構的空間*串口數量
?drv->state = kzalloc(sizeof(struct uart_state) * drv->nr, GFP_KERNEL);
?if (!drv->state)
??goto out;
?
?//為uart_driver結構分配要指向的tty_driver結構的空間
?/*struct tty_driver *alloc_tty_driver(int lines)
?{
??struct tty_driver *driver;
?
??driver = kzalloc(sizeof(struct tty_driver), GFP_KERNEL);//分配空間
??if (driver) {
???kref_init(&driver->kref);
???driver->magic = TTY_DRIVER_MAGIC;//tty_driver的魔數
???driver->num = lines;//串口數量3個
??}
??return driver;
?}*/
?normal = alloc_tty_driver(drv->nr);
?if (!normal)
??goto out_kfree;

?drv->tty_driver = normal;//賦值給uart_driver結構的tty_driver成員
?//對tty_driver成員指向的結構初始化
?normal->owner??= drv->owner;//THIS_MODULE
?normal->driver_name?= drv->driver_name;//"serial"
?normal->name??= drv->dev_name;//"ttyS"
?normal->major??= drv->major;//主設備號：TTY_MAJOR=4
?normal->minor_start?= drv->minor;//次設備號：64
?normal->type??= TTY_DRIVER_TYPE_SERIAL;//#define TTY_DRIVER_TYPE_SERIAL 0x0003
?normal->subtype??= SERIAL_TYPE_NORMAL;//#define SERIAL_TYPE_NORMAL? 1(定義在include/linux/tty_driver.h)
?normal->init_termios?= tty_std_termios;//終端的標準配置（drivers/tty/tty_io.c）
?normal->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL;//配置c_cflag
?normal->init_termios.c_ispeed = normal->init_termios.c_ospeed = 9600;//波特率設為9600
?normal->flags??= TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
?normal->driver_state??? = drv;//指向相應的uart_driver
?tty_set_operations(normal, &uart_ops);//將tty_driver結構的normal操作指向uart_ops
?/*void tty_set_operations(struct tty_driver *driver,const struct tty_operations *op)
?{
??driver->ops = op;
?};
?static const struct tty_operations uart_ops = {
??.open??= uart_open,
??.close??= uart_close,
??.write??= uart_write,
??.put_char?= uart_put_char,
??.flush_chars?= uart_flush_chars,
??.write_room?= uart_write_room,
??.chars_in_buffer= uart_chars_in_buffer,
??.flush_buffer?= uart_flush_buffer,
??.ioctl??= uart_ioctl,
??.throttle?= uart_throttle,
??.unthrottle?= uart_unthrottle,
??.send_xchar?= uart_send_xchar,
??.set_termios?= uart_set_termios,
??.set_ldisc?= uart_set_ldisc,
??.stop??= uart_stop,
??.start??= uart_start,
??.hangup??= uart_hangup,
??.break_ctl?= uart_break_ctl,
??.wait_until_sent= uart_wait_until_sent,
?#ifdef CONFIG_PROC_FS
??.proc_fops?= &uart_proc_fops,
?#endif
??.tiocmget?= uart_tiocmget,
??.tiocmset?= uart_tiocmset,
??.get_icount?= uart_get_icount,
?#ifdef CONFIG_CONSOLE_POLL
??.poll_init?= uart_poll_init,
??.poll_get_char?= uart_poll_get_char,
??.poll_put_char?= uart_poll_put_char,
?#endif
?};
?*/

?for (i = 0; i < drv->nr; i++) {//根據串口數量依次掃描drv->nr=3
??struct uart_state *state = drv->state + i;//找到每個串口的uart_state地址
??struct tty_port *port = &state->port;//每個串口有一個tty_port結構
??
??//初始化每個串口的tty_port結構
??tty_port_init(port);
??port->ops = &uart_port_ops;
??port->close_delay???? = 500;?/* .5 seconds */
??port->closing_wait??? = 30000;?/* 30 seconds */
??tasklet_init(&state->tlet, uart_tasklet_action,(unsigned long)state);
?}
?
?//注冊tty驅動
?retval = tty_register_driver(normal);
?if (retval >= 0)
??return retval;

?put_tty_driver(normal);
out_kfree:
?kfree(drv->state);
out:
?return -ENOMEM;
}

//初始化串口的uart_port結構
static void __init serial8250_register_ports(struct uart_driver *drv, struct device *dev)
{
?int i;
?
?//對uart_8250_port結構的serial8250_ports進行初始化
?for (i = 0; i < nr_uarts; i++) {//共3個串口
??struct uart_8250_port *up = &serial8250_ports[i];
??up->cur_iotype = 0xFF;//先初始化為0xFF，在set_io_from_upio（）會賦值成uart_port->iotype（即UPIO_MEM=2）
?}
?
?//對uart_8250_port結構的serial8250_ports[]接著進行初始化,主要是設置uart_port字段ops的操作
?//由于此函數在初始化console時被調用過，所以現在調用的話會直接返回。即串口的uart_port的ops字段已經賦過值了
?serial8250_isa_init_ports();

?for (i = 0; i < nr_uarts; i++) {//共3個串口
??struct uart_8250_port *up = &serial8250_ports[i];

??up->port.dev = dev;//指向相應的struct device結構

??if (up->port.flags & UPF_FIXED_TYPE)//因為未進行serial8250_probe(),所以此標志未設置，不進入下邊函數
???serial8250_init_fixed_type_port(up, up->port.type);//設置串口type=PORT_AR7，即18
??
??//向設備添加端口,是在uart_driver增加一個port，在未進行serial8250_probe()之前，這個函數的串口配置操作會失敗
??//進行過serial8250_probe()后，還會再調用此函數，那時就可以配置好串口。
??uart_add_one_port(drv, &up->port);
?}
}

static void __init serial8250_isa_init_ports(void)
{
?struct uart_8250_port *up;
?static int first = 1;
?int i, irqflag = 0;

?if (!first)//靜態變量，serial8250_console_init（）第一次進入這個函數，之后serial8250_init()再進入這個函數就會直接返回
??return;
?first = 0;
?
?//對三個串口的uart_8250_port結構serial8250_ports結構體進行初始化
?for (i = 0; i < nr_uarts; i++) {
??struct uart_8250_port *up = &serial8250_ports[i];

??up->port.line = i;//0代表串口0,1代表串口1
??spin_lock_init(&up->port.lock);

??init_timer(&up->timer);//初始化定時器
??up->timer.function = serial8250_timeout;//初始化定時器的超時函數

??//ALPHA_KLUDGE_MCR needs to be killed.
??up->mcr_mask = ~ALPHA_KLUDGE_MCR;
??up->mcr_force = ALPHA_KLUDGE_MCR;
??
??//初始化uart_8250_port指向的uart_port字段port的操作
??up->port.ops = &serial8250_pops;
??/*
??static struct uart_ops serial8250_pops = {
???.tx_empty?= serial8250_tx_empty,
???.set_mctrl?= serial8250_set_mctrl,
???.get_mctrl?= serial8250_get_mctrl,
???.stop_tx?= serial8250_stop_tx,
???.start_tx?= serial8250_start_tx,
???.stop_rx?= serial8250_stop_rx,
???.enable_ms?= serial8250_enable_ms,
???.break_ctl?= serial8250_break_ctl,
???.startup?= serial8250_startup,
???.shutdown?= serial8250_shutdown,
???.set_termios?= serial8250_set_termios,
???.set_ldisc?= serial8250_set_ldisc,
???.pm??= serial8250_pm,
???.type??= serial8250_type,
???.release_port?= serial8250_release_port,
???.request_port?= serial8250_request_port,
???.config_port?= serial8250_config_port,
???.verify_port?= serial8250_verify_port,
??#ifdef CONFIG_CONSOLE_POLL
???.poll_get_char = serial8250_get_poll_char,
???.poll_put_char = serial8250_put_poll_char,
??#endif
??};
??*/
?}

?if (share_irqs)//中斷是否共享（這里設置成不共享）
??irqflag = IRQF_SHARED;
?
?//條件不滿足，不會進來初始化
?for (i = 0, up = serial8250_ports;i < ARRAY_SIZE(old_serial_port) && i < nr_uarts;i++, up++) {
/*?up->port.iobase?? = old_serial_port[i].port;
??up->port.irq????? = irq_canonicalize(old_serial_port[i].irq);
??up->port.irqflags = old_serial_port[i].irqflags;
??up->port.uartclk? = old_serial_port[i].baud_base * 16;
??up->port.flags??? = old_serial_port[i].flags;
??up->port.hub6???? = old_serial_port[i].hub6;
??up->port.membase? = old_serial_port[i].iomem_base;
??up->port.iotype?? = old_serial_port[i].io_type;
??up->port.regshift = old_serial_port[i].iomem_reg_shift;
??set_io_from_upio(&up->port);
??up->port.irqflags |= irqflag;
??if (serial8250_isa_config != NULL)
???serial8250_isa_config(i, &up->port, &up->capabilities);
*/
?}
}

int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
{
?struct uart_state *state;
?struct tty_port *port;
?int ret = 0;
?struct device *tty_dev;

?BUG_ON(in_interrupt());//不能在中斷中調用
?
?//Uart_port->line就是對uart設備文件序號.它對應的也就是uart_driver->state數組中的uart_port->line項.
?if (uport->line >= drv->nr)//在serial8250_isa_init_ports()已經初始化過，代表端口號，0代表串口0。
??return -EINVAL;
?
?//根據串口號找到每個串口對應的uart_state結構
?state = drv->state + uport->line;
?port = &state->port;//通過uart_state結構找到每個串口的tty_port結構

?mutex_lock(&port_mutex);
?mutex_lock(&port->mutex);
?if (state->uart_port) {
??ret = -EINVAL;
??goto out;
?}
?
?//將uart_state和uart_port結構相關聯起來
?state->uart_port = uport;?
?state->pm_state = -1;

?uport->cons = drv->cons;//將uart_driver的serial8250_console成員賦值給uart_port成員
?uport->state = state;//uart_port的state成員指向相應的uart_state

? //If this port is a console, then the spinlock is already initialised.
? //檢查這個串口是否就是終端，并且此終端是否已經注冊完畢
?if (!(uart_console(uport) && (uport->cons->flags & CON_ENABLED))) {
??spin_lock_init(&uport->lock);
??lockdep_set_class(&uport->lock, &port_lock_key);
?}
?
?//進行port的自動配置，在未進行serial8250_probe()，串口的port->iobase、port->mapbase、port->membase都為空，所以函數進去會立即返回，即未配置成功。
?//當進行完serial8250_probe()函數時，還會調用uart_add_one_port()，再到這個函數配置時就會配置成功
?uart_configure_port(drv, state, uport);

? //然后注冊tty_device.如果用戶空間運行了udev或者已經配置好了hotplug.就會在/dev下自動生成設備文件了.
?tty_dev = tty_register_device(drv->tty_driver, uport->line, uport->dev);
?if (likely(!IS_ERR(tty_dev))) {//設置設備的喚醒狀態
??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",uport->line);

? //Ensure UPF_DEAD is not set.
?uport->flags &= ~UPF_DEAD;

?out:
?mutex_unlock(&port->mutex);
?mutex_unlock(&port_mutex);

?return ret;
}

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

?if (!port->iobase && !port->mapbase && !port->membase)//未調用serial8250_probe()之前，會從這里直接返回。
??return;
?
?//調用serial8250_probe()之后，會接著往下進行
?flags = 0;
?if (port->flags & UPF_AUTO_IRQ)//未設置此標志
??flags |= UART_CONFIG_IRQ;
??
?if (port->flags & UPF_BOOT_AUTOCONF) {//經過probe()函數，此標志已配置
??if (!(port->flags & UPF_FIXED_TYPE)) {//已設置該標志，下邊的不會進入
???port->type = PORT_UNKNOWN;//不會進入
???flags |= UART_CONFIG_TYPE;
??}
??port->ops->config_port(port, flags);//調用設備的自動配置函數，即serial8250_config_port()
?}

?if (port->type != PORT_UNKNOWN) {
??unsigned long flags;
??
??//打印串口的信息
??uart_report_port(drv, port);

??/* Power up port for set_mctrl() */
??uart_change_pm(state, 0);改變端口的電源狀態，上電

??spin_lock_irqsave(&port->lock, flags);
??port->ops->set_mctrl(port, port->mctrl & TIOCM_DTR);設置串口modem控制，調用serial8250_set_mctrl()
??spin_unlock_irqrestore(&port->lock, flags);

?? //注冊終端,配置終端的信息，若此端口有cons字段，并且console的注冊不成功。注冊成功CON_ENABLED標志為1
??if (port->cons && !(port->cons->flags & CON_ENABLED))
??{
???/*serial8250_console_init()函數會比serial8250_probe()先調用,所以調用register_console的時候,port還沒有初始化,所以當
????register_console調用serial8250_console_setup()設置buad,parity bits的時候,
????serial8250_console_setup()會檢測port->iobase和port->membase是否是有效值,如果不是就返回,
????放棄初始化console,所以實際上,console不是在serial8250_console_init()里邊初始化。
????
????當serial8250_probe()調用uart_add_one_port->uart_configure_port:又會調用register_console()，
????在這里會將真正的console注冊掉。
????該函數會檢查console有沒有初始化,如果沒有初始化,則調用register_console來初始化.
????所以console放在這里初始化也是比較好一些.
???*/
???register_console(port->cons);//將該console注冊到console_drivers鏈表上,最后調用release_console_sem,將printk緩沖的數據打印到ttyS2上
??}

??//檢查此串口是否是終端，除了我們使用作為console的串口，其余的進行斷電
??if (!uart_console(port))//#define uart_console(port)?((port)->cons && (port)->cons->index == (port)->line)
???uart_change_pm(state, 3);//除了我們使用的console，其余的進行斷電
?}
}

//注冊設備serial8250_isa_driver時，會調用此函數
static int __devinit serial8250_probe(struct platform_device *dev)
{
?//傳入的參數就是da8xx_serial_device
?/*struct platform_device da8xx_serial_device = {//platform_device就描述了設備對象。
??.name?= "serial8250",
??.id?= PLAT8250_DEV_PLATFORM,
??.dev?= {
???.platform_data?= da8xx_serial_pdata,//這個platform_device對象的私有數據指成員向一個plat_serial8250_port類型的數組。在這里該數組描述了三個串口接口的基本信息。
?????????????????????//當8250驅動檢測到這個platform_device對象后，就分析該對象的私有數據成員指向的那個plat_serial8250_port類型的數組。
?????????????????????//然后根據該數組的每個成員描述的信息生成一個串口對象設備。
??},
?};
?
?static struct plat_serial8250_port da8xx_serial_pdata[] = {
??{
???.mapbase?= DA8XX_UART0_BASE,//串口接口寄存器物理地址的基地址,#define DAVINCI_UART0_BASE?(IO_PHYS + 0x20000)（見/arch/arm/mach-davinci/include/mach/serial.h）
???.irq??= IRQ_DA8XX_UARTINT0,//該串口接口使用的中斷號, #define IRQ_DA8XX_UARTINT0? 25,（在/arch/arm/mach-davinci/include/mach/irqs.h）
???.flags??= UPF_BOOT_AUTOCONF | UPF_SKIP_TEST | UPF_IOREMAP | UPF_FIXED_TYPE,
???.type??= PORT_AR7,//串口0類型
???.iotype??= UPIO_MEM,//成員表示該串口接口寄存器的地址類型，8位的內存地址?
???.regshift?= 2,//在訪問該串口接口的某個寄存器時，需把該寄存器的號左移多少位然后加基地址（不管是物理或虛擬地址）才能得能到這個寄存器的址址
??},
??{
???.mapbase?= DA8XX_UART1_BASE, //DAVINCI_UART1_BASE?(IO_PHYS + 0x20400)
???.irq??= IRQ_DA8XX_UARTINT1, //中斷號是53
???.flags??= UPF_BOOT_AUTOCONF | UPF_SKIP_TEST |UPF_IOREMAP | UPF_FIXED_TYPE,
???.type??= PORT_AR7,
???.iotype??= UPIO_MEM,
???.regshift?= 2,
??},
??{
???.mapbase?= DA8XX_UART2_BASE, //#define DAVINCI_UART2_BASE?(IO_PHYS + 0x20800)
???.irq??= IRQ_DA8XX_UARTINT2, //中斷號是61
???.flags??= UPF_BOOT_AUTOCONF | UPF_SKIP_TEST |UPF_IOREMAP | UPF_FIXED_TYPE,
???.type??= PORT_AR7,
???.iotype??= UPIO_MEM,
???.regshift?= 2,
??},
??{
???.flags?= 0,
??},
?};*/
?struct plat_serial8250_port *p = dev->dev.platform_data;
?struct uart_port port;
?int ret, i, irqflag = 0;

?memset(&port, 0, sizeof(struct uart_port));

?if (share_irqs)
??irqflag = IRQF_SHARED;
??
?// 會 將 dev->dev.platform_data 所代表的 port 添加到 uart_driver 中
?for (i = 0; p && p->flags != 0; p++, i++) {//遍歷三個串口
??port.iobase??= p->iobase;
??port.membase??= p->membase;
??port.irq??= p->irq;//中斷號
??port.irqflags??= p->irqflags;
??port.uartclk??= p->uartclk;//時鐘
??port.regshift??= p->regshift;//寄存器偏移量 2
??port.iotype??= p->iotype;//IO類型
??port.flags??= p->flags;//標志
??port.mapbase??= p->mapbase;//串口接口寄存器物理地址的基地址
??port.hub6??= p->hub6;
??port.private_data?= p->private_data;
??port.type??= p->type;//PORT_AR7,串口類型
??port.serial_in??= p->serial_in;
??port.serial_out??= p->serial_out;
??port.set_termios?= p->set_termios;
??port.pm???= p->pm;
??port.dev??= &dev->dev;
??port.irqflags??|= irqflag;
??if (p->clk)
???serial8250_ports[i].clk = p->clk;
??
??//再重新注冊串口
??ret = serial8250_register_port(&port);
??if (ret < 0) {
???dev_err(&dev->dev, "unable to register port at index %d ""(IO%lx MEM%llx IRQ%d): %d\n", i,p->iobase, (unsigned long long)p->mapbase,p->irq, ret);
??}
?}
?return 0;//到這里串口的初始化就結束!!!!
}

int serial8250_register_port(struct uart_port *port)
{
?struct uart_8250_port *uart;
?int ret = -ENOSPC;

?if (port->uartclk == 0)
??return -EINVAL;

?mutex_lock(&serial_mutex);
?
?//查找在serial8250_ports[]數組中是否已有記錄
?uart = serial8250_find_match_or_unused(port);
?if (uart) {//都會查到有記錄
??uart_remove_one_port(&serial8250_reg, &uart->port);//把原來的串口移除掉，再重新添加
??
??//串口的uart_port再賦值
??uart->port.iobase?????? = port->iobase;
??uart->port.membase????? = port->membase;
??uart->port.irq????????? = port->irq;
??uart->port.irqflags???? = port->irqflags;
??uart->port.uartclk????? = port->uartclk;
??uart->port.fifosize???? = port->fifosize;
??uart->port.regshift???? = port->regshift;
??uart->port.iotype?????? = port->iotype;
??uart->port.flags??????? = port->flags | UPF_BOOT_AUTOCONF;
??uart->port.mapbase????? = port->mapbase;
??uart->port.private_data = port->private_data;
??if (port->dev)
???uart->port.dev = port->dev;

??if (port->flags & UPF_FIXED_TYPE)//probe()進行時，此標志已設置
???serial8250_init_fixed_type_port(uart, port->type);//設置串口type=PORT_AR7，即18

??set_io_from_upio(&uart->port);//設置串口的讀寫函數
??
??//如果傳進來的參數此成員有值，用原來的。實際時原來此成員變量為空，da8xx_serial_pdata變量中未賦值
??if (port->serial_in)
???uart->port.serial_in = port->serial_in;
??if (port->serial_out)
???uart->port.serial_out = port->serial_out;
??if (port->set_termios)
???uart->port.set_termios = port->set_termios;
??if (port->pm)
???uart->port.pm = port->pm;

??if (serial8250_isa_config != NULL)
???serial8250_isa_config(0, &uart->port,&uart->capabilities);
??
??//再重新添加串口，這時配置串口就能成功
??ret = uart_add_one_port(&serial8250_reg, &uart->port);
??if (ret == 0)
???ret = uart->port.line;

??ret = serial8250_cpufreq_register(uart);
??if (ret < 0)
???printk(KERN_ERR "Failed to add cpufreq notifier\n");
?}
?mutex_unlock(&serial_mutex);

?return ret;
}

static void serial8250_config_port(struct uart_port *port, int flags)
{
?struct uart_8250_port *up = (struct uart_8250_port *)port;
?int probeflags = PROBE_ANY;
?int ret;

?if (cpu_is_davinci_da850())//是否為達芬奇平臺
??up->bugs |= UART_BUG_NOMSR;

?ret = serial8250_request_std_resource(up);//分配內存資源,IO資源
?if (ret < 0)
??return;

?ret = serial8250_request_rsa_resource(up);//會返回失敗
?if (ret < 0)
??probeflags &= ~PROBE_RSA;//清除PROBE_RSA標志
?
?//up->cur_iotype在serial8250_register_ports（）設置成0xFF，
?//而up->port.iotype在serial8250_isa_init_ports()被設置為UPIO_MEM，即2
?if (up->port.iotype != up->cur_iotype)
??set_io_from_upio(port);//設置uart_port結構的serial_in函數和serial_out函數

?if (flags & UART_CONFIG_TYPE)//此標志沒有被設置
??autoconfig(up, probeflags);//不會調用

?if (up->port.type == PORT_16550A && up->port.iotype == UPIO_AU)
??up->bugs |= UART_BUG_NOMSR;

?if (up->port.type != PORT_UNKNOWN && flags & UART_CONFIG_IRQ)//此標志UART_CONFIG_IRQ未設置
??autoconfig_irq(up);//不會調用
?
?//以下不會調用
?if (up->port.type != PORT_RSA && probeflags & PROBE_RSA)
??serial8250_release_rsa_resource(up);
?if (up->port.type == PORT_UNKNOWN)
??serial8250_release_std_resource(up);
}

static int serial8250_request_std_resource(struct uart_8250_port *up)
{
?unsigned int size = serial8250_port_size(up);
?int ret = 0;

?switch (up->port.iotype) {//up->port.iotype == UPIO_MEM
?case UPIO_AU:
?case UPIO_TSI:
?case UPIO_MEM32:
?case UPIO_MEM:
?case UPIO_DWAPB:
??if (!up->port.mapbase)
???break;

??if (!request_mem_region(up->port.mapbase, size, "serial")) {
???ret = -EBUSY;
???break;
??}

??if (up->port.flags & UPF_IOREMAP) {//如果前邊映射過了，UPF_IOREMAP被清零了，這里就不需再映射了
???up->port.membase = ioremap_nocache(up->port.mapbase,size);
???if (!up->port.membase) {
????release_mem_region(up->port.mapbase, size);
????ret = -ENOMEM;
???}
??}
??break;

?case UPIO_HUB6:
?case UPIO_PORT:
??if (!request_region(up->port.iobase, size, "serial"))
???ret = -EBUSY;
??break;
?}
?return ret;
}

static void set_io_from_upio(struct uart_port *p)
{
?struct uart_8250_port *up = (struct uart_8250_port *)p;
?switch (p->iotype) {
?case UPIO_HUB6:
??p->serial_in = hub6_serial_in;
??p->serial_out = hub6_serial_out;
??break;

?case UPIO_MEM://p->iotype=2，采用這里的讀寫函數
??p->serial_in = mem_serial_in;
??p->serial_out = mem_serial_out;
??break;

?case UPIO_RM9000:
?case UPIO_MEM32:
??p->serial_in = mem32_serial_in;
??p->serial_out = mem32_serial_out;
??break;

?case UPIO_AU:
??p->serial_in = au_serial_in;
??p->serial_out = au_serial_out;
??break;

?case UPIO_TSI:
??p->serial_in = tsi_serial_in;
??p->serial_out = tsi_serial_out;
??break;

?case UPIO_DWAPB:
??p->serial_in = mem_serial_in;
??p->serial_out = dwapb_serial_out;
??break;

?default:
??p->serial_in = io_serial_in;
??p->serial_out = io_serial_out;
??break;
?}
?/* Remember loaded iotype */
?up->cur_iotype = p->iotype;//注意要賦值
}

static inline void uart_report_port(struct uart_driver *drv, struct uart_port *port)
{
?char address[64];

?switch (port->iotype) {//port->iotype == UPIO_MEM
?case UPIO_PORT:
??snprintf(address, sizeof(address), "I/O 0x%lx", port->iobase);
??break;
?case UPIO_HUB6:
??snprintf(address, sizeof(address),"I/O 0x%lx offset 0x%x", port->iobase, port->hub6);
??break;
?case UPIO_MEM:
?case UPIO_MEM32:
?case UPIO_AU:
?case UPIO_TSI:
?case UPIO_DWAPB:
??snprintf(address, sizeof(address), "MMIO 0x%llx", (unsigned long long)port->mapbase);
??break;
?default:
??strlcpy(address, "*unknown*", sizeof(address));
??break;
?}
?/*打印出的信息如下：
?serial8250.0: ttyS0 at MMIO 0x1c42000 (irq = 25) is a AR7
?serial8250.0: ttyS1 at MMIO 0x1d0c000 (irq = 53) is a AR7
?serial8250.0: ttyS2 at MMIO 0x1d0d000 (irq = 61) is a AR7
?*/
?printk(KERN_INFO "%s%s%s%d at %s (irq = %d) is a %s\n",
??????? port->dev ? dev_name(port->dev) : "",
??????? port->dev ? ": " : "",
??????? drv->dev_name,
??????? drv->tty_driver->name_base + port->line,
??????? address, port->irq, uart_type(port));
}

//下邊再次調用register_console()注冊serial8250_console真正的console終端
void register_console(struct console *newcon)
{
?int i;
?unsigned long flags;
?struct console *bcon = NULL;
?/*
?現在是注冊一個serial8250_console，即
?static struct console serial8250_console = {
??.name??= "ttyS",
??.write??= serial8250_console_write,//寫方法
??.device??= uart_console_device,//tty驅動
??.setup??= serial8250_console_setup,//設置串口波特率，也就是設置串口。很重要，里面涉及到平臺特性，波特率相關。
??.early_setup?= serial8250_console_early_setup,
??.flags??= CON_PRINTBUFFER | CON_ANYTIME,
??.index??= -1,
??.data??= &serial8250_reg,
?};
?*/
?if (console_drivers && newcon->flags & CON_BOOT) {//注冊的是serial8250_console，CON_BOOT沒有置位，不是引導控制臺。下邊不會進去遍歷
??for_each_console(bcon) {遍歷全局console_drivers數組???
???if (!(bcon->flags & CON_BOOT)) {//判斷是否已經有引導控制臺了,有了的話就直接退出
????printk(KERN_INFO "Too late to register bootconsole %s%d\n",newcon->name, newcon->index);
????return;
???}
??}
?}
?
?if (console_drivers && console_drivers->flags & CON_BOOT)//如果注冊的是引導控制臺，serial8250_console不是引導控制臺
??bcon = console_drivers;//這里不執行

?if (preferred_console < 0 || bcon || !console_drivers)
??preferred_console = selected_console;//設置preferred_console為uboot命令選擇的selected_console(即在Uboot傳入的參數“console=ttyS2,115200n8”在console_cmdline[]數組中的索引)???
???????????????????? //這里preferred_console =0
?if (newcon->early_setup)//serial8250_console初始化early_setup字段
??newcon->early_setup();//調用serial8250_console_early_setup()

?if (preferred_console < 0) {//由于preferred_console =0，不會進入下邊
??if (newcon->index < 0)
???newcon->index = 0;
??if (newcon->setup == NULL ||newcon->setup(newcon, NULL) == 0) {
???newcon->flags |= CON_ENABLED;
???if (newcon->device) {
????newcon->flags |= CON_CONSDEV;
????preferred_console = 0;
???}
??}
?}

? //傳給內核參數:
? //Kernel command line: console=ttyS2,115200n8 rw root=/dev/ram0 initrd=0xc2000000,20M mem=128M ip=192.168.1.220::192.168.1.1:255.255.255.0::eth0:off
? //所以這里將根據傳參console=ttyS2,115200來配置作為console的ttyS2串口
?for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];i++) {//遍歷全局console_cmdline找到匹配的，i=0就是匹配的“ttyS2”
??if (strcmp(console_cmdline[i].name, newcon->name) != 0)//比較終端名稱“ttyS”
???continue;
??if (newcon->index >= 0 &&newcon->index != console_cmdline[i].index)//console_cmdline[i].index=2。//比較次設備號??
???continue;
??if (newcon->index < 0)
???newcon->index = console_cmdline[i].index;//將終端號賦值給serial8250_console->index，這里是2
???
??//console_cmdline[i].options = "115200n8"，對于serial8250_console而言setup字段已初始化
??if (newcon->setup && newcon->setup(newcon, console_cmdline[i].options) != 0)//調用serial8250_console_setup()對終端進行配置，未probe()前調用不成功，probe()后調用成功。
???break;
??//在這里注冊serial8250_console時，調用serial8250_console_setup()由于port->iobase和port->membase不是有效值，
??//故返回錯誤，這樣下邊的操作不會執行，直接break跳出，從flag1出跳出函數。即在這里serial8250_console沒有注冊成功
??//由于內核在下邊的操作隊串口進行初始化時，還會調用register_console（）來注冊serial8250_console，在那時注冊就會成功
??
??newcon->flags |= CON_ENABLED; //設置標志為CON_ENABLE,表示console使能(這個在printk調用中使用到)?
??newcon->index = console_cmdline[i].index;//設置索引號???
??if (i == selected_console) { //索引號和uboot指定的console的一樣?
???newcon->flags |= CON_CONSDEV;//設置標志CON_CONSDEV(全局console_drivers鏈表中靠前)?
???preferred_console = selected_console;
??}
??break;
?}//for循環作用大致是查看注冊的console是否是uboot知道的引導console，是則設置相關標志和preferred_console

? //flag1：
?if (!(newcon->flags & CON_ENABLED))//若前邊沒有設置CON_ENABLED標志，就退出。若進行過probe（）,CON_ENABLED置位，這里就往下接著注冊console
??return;

?if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))//防止重復打印???
??newcon->flags &= ~CON_PRINTBUFFER;

?acquire_console_sem();
?if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {//如果是preferred控制臺，此標志CON_CONSDEV在前邊已設置過
??newcon->next = console_drivers;
??console_drivers = newcon;//添加進全局console_drivers鏈表前面位置（printk中會遍歷該表調用合適的console的write方法打印信息）
??if (newcon->next)
???newcon->next->flags &= ~CON_CONSDEV;
?} else {//如果不是preferred控制臺?
??newcon->next = console_drivers->next;
??console_drivers->next = newcon; //添加進全局console_drivers鏈表后面位置
?}
?
?//主冊console主要是刷選preferred_console放置在全局console_drivers鏈表前面,剩下的console放置鏈表靠后的位置,并設置相應的flags,
?//console_drivers最終會在printk函數的層層調用中遍歷到,并調用console的write方法將信息打印出來

?if (newcon->flags & CON_PRINTBUFFER) {
??spin_lock_irqsave(&logbuf_lock, flags);
??con_start = log_start;
??spin_unlock_irqrestore(&logbuf_lock, flags);
?}
?release_console_sem();

?if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
??printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",newcon->name, newcon->index);
??for_each_console(bcon)
???if (bcon->flags & CON_BOOT)
????unregister_console(bcon);
?} else {//調用這里
??printk(KERN_INFO "%sconsole [%s%d] enabled\n",(newcon->flags & CON_BOOT) ? "boot" : "" ,newcon->name, newcon->index);
?}
}

//serial8250_console_early_setup()-->serial8250_find_port_for_earlycon()
int serial8250_find_port_for_earlycon(void)
{
?struct early_serial8250_device *device = &early_device;//early console初始化時對early_device結構的初始化
?struct uart_port *port = &device->port;
?int line;
?int ret;

?if (!device->port.membase && !device->port.iobase)//early_device結構初始化時已經配置好
??return -ENODEV;
?//early console注冊時不會調用此函數。
?//當真正的console初始化時，會調用此函數。
?//真正的console初始化時，會查找early console注冊時用的是哪一個串口號，從serial8250_ports[]中根據uart_port->mapbase地址來比對
?line = serial8250_find_port(port);//根據uart_port結構找到串口號，比對沒有找到串口號，line返回負值
?if (line < 0)
??return -ENODEV;//從這里返回，下邊的不再執行
?
?//若找到early console用的串口號，更新當初傳入內核參數使用的console_cmdline[i]，名稱改成ttyS。。。。
?ret = update_console_cmdline("uart", 8250, "ttyS", line, device->options);
?if (ret < 0)
??ret = update_console_cmdline("uart", 0,"ttyS", line, device->options);

?return ret;
}

static int __init serial8250_console_setup(struct console *co, char *options)
{
?struct uart_port *port;
?int baud = 9600;
?int bits = 8;
?int parity = 'n';
?int flow = 'n';

?if (co->index >= nr_uarts)//console的索引，這里是2，即ttyS2
??co->index = 0;
?port = &serial8250_ports[co->index].port;//找到對應的ttyS2的uart_port結構
?
?//由于console_init在注冊serial8250_console時調用的register_console()函數調用serial8250_console_setup()
?//進入這個函數時，由于ttyS2的uart_port結構沒有初始化，port->iobase 和port->membase值都未設置，所以直接從下邊返回
?//當進行串口初始化時，還會回來注冊serial8250_console，再調用到這里，由于設置了ttyS2的uart_port結構，所以下邊的配置就會成功
?if (!port->iobase && !port->membase)//第一次注冊時，由于未設置，從這里直接返回
??return -ENODEV;

?if (options)//如果options不為空，就將options里的數值寫給baud, &parity, &bits, &flow
??uart_parse_options(options, &baud, &parity, &bits, &flow);
?//沒有配置options，則使用缺省值，否則使用傳下來的的參數options里的串口配置
?return uart_set_options(port, co, baud, parity, bits, flow);
}

void uart_parse_options(char *options, int *baud, int *parity, int *bits, int *flow)
{
?char *s = options;

?*baud = simple_strtoul(s, NULL, 10);
?while (*s >= '0' && *s <= '9')
??s++;
?if (*s)
??*parity = *s++;
?if (*s)
??*bits = *s++ - '0';
?if (*s)
??*flow = *s;
}

int uart_set_options(struct uart_port *port, struct console *co,int baud, int parity, int bits, int flow)
{
?struct ktermios termios;
?static struct ktermios dummy;
?int i;

?//Ensure that the serial console lock is initialised early.
?spin_lock_init(&port->lock);
?lockdep_set_class(&port->lock, &port_lock_key);

?memset(&termios, 0, sizeof(struct ktermios));
?termios.c_cflag = CREAD | HUPCL | CLOCAL;

?//Construct a cflag setting.
?for (i = 0; baud_rates[i].rate; i++)
??if (baud_rates[i].rate <= baud)
???break;

?termios.c_cflag |= baud_rates[i].cflag;

?if (bits == 7)
??termios.c_cflag |= CS7;
?else
??termios.c_cflag |= CS8;

?switch (parity) {
?case 'o': case 'O':
??termios.c_cflag |= PARODD;
??/*fall through*/
?case 'e': case 'E':
??termios.c_cflag |= PARENB;
??break;
?}

?if (flow == 'r')
??termios.c_cflag |= CRTSCTS;

?/*
? * some uarts on other side don't support no flow control.
? * So we set * DTR in host uart to make them happy
? */
?port->mctrl |= TIOCM_DTR;

?port->ops->set_termios(port, &termios, &dummy);//調用serial8250_set_termios()對串口進行配置

?//Allow the setting of the UART parameters with a NULL console too:
?if (co)
??co->cflag = termios.c_cflag;

?return 0;
}

struct device *tty_register_device(struct tty_driver *driver, unsigned index,struct device *device)
{
?char name[64];
?dev_t dev = MKDEV(driver->major, driver->minor_start) + index;//得到設備號

?if (index >= driver->num) {
??printk(KERN_ERR "Attempt to register invalid tty line number "" (%d).\n", index);
??return ERR_PTR(-EINVAL);
?}

?if (driver->type == TTY_DRIVER_TYPE_PTY)
??pty_line_name(driver, index, name);
?else
??tty_line_name(driver, index, name);//得到串口設備名稱ttyS0，ttyS1，ttyS2
?
?return device_create(tty_class, device, dev, NULL, name);//在/dev下創建設備文件
}

?

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