linux pl011串口简述

基于nanopi m2内核3.4.39

串口驱动编译选项

nanopi m2 4418中串口驱动的选项如下：

       < > 8250/16550 and compatible serial support                                                     *** Non-8250 serial port support ***                                                     < > ARM AMBA PL010 serial port support                                                     <*> ARM AMBA PL011 serial port support                                                      [*]   Support for console on AMBA serial port                                               < > MAX3100 support                                                                        < > MAX3107 support                                                                        < > Support for timberdale UART                                                            < > Altera JTAG UART support                                                               < > Altera UART support                                                                    < > SPI protocol driver for Infineon 6x60 modem (EXPERIMENTAL)                          < > Xilinx PS UART support                                                                 < > Nexell S3C SoC serial port support                                                     [*]   Serial port 0                                                                        [ ]     Use DMA                                                                            [*]   Serial port 1                                                                        [ ]     Use DMA                                                                            [ ]   Serial port 2                                                                        [*]   Serial port 3                                                                        [*]   Serial port 4                                                                        [ ]   Serial port 5                                                                        [*] Set this to reduce resume time (PL011) 

使用ls /pro/tty/driver/可以看到所有串口驱动,相应的中断号，mmio,传输的数据字节

root@NanoPi2:~# ls /proc/tty/driver/ttyAMA  usbserialroot@NanoPi2:~# cat /proc/tty/driver/ttyAMA serinfo:1.0 driver revision:0: uart:PL011 rev3 mmio:0xC00A1000 irq:7 tx:2846 rx:133 RTS|DTR1: uart:PL011 rev3 mmio:0xC00A0000 irq:6 tx:0 rx:0 DSR|CD2: uart:PL011 rev3 mmio:0xC00A3000 irq:9 tx:0 rx:03: uart:PL011 rev3 mmio:0xC006D000 irq:10 tx:0 rx:0root@NanoPi2:~# ls /dev/ttyAMA* -lcrw------- 1 root tty     204, 64 Sep 20 04:21 /dev/ttyAMA0crw-rw---- 1 root dialout 204, 65 Sep 20 03:28 /dev/ttyAMA1crw-rw---- 1 root dialout 204, 66 Sep 20 03:28 /dev/ttyAMA2crw-rw---- 1 root dialout 204, 67 Sep 20 03:28 /dev/ttyAMA3

4418中一共有5个uart串口，使用了PL011驱动，nanopi中勾选了4 个，其中引出给我们用的有3个，ttyAMA0（调试口），ttyAMA2，ttyAMA3

驱动层次

tty层：uart_register_driver，uart_add_one_port
amba层：提供amba_driver,amba_device的注册实现，
UART层：主要涉及uart_driver，amba_driver,uart_port，uart_ops三个结构体，并调用tty层和amba层的两个函数完成amba_driver,uart_driver和uart_port端口的注册

ARM amba总线驱动

amba_device使用分析
Linux AMBA设备驱动注册过程浅析

内核中专门定义了一类amba_bustype、amba_device、amba_driver。具体定义在内核的/drivers/amba/bus.c中

源码查看

设备驱动文件位置

driver/tty/serial/amba-pl011.c

作用

向系统注册串口驱动

从module_init看起

static int __init pl011_init(void){    int ret;    ret = uart_register_driver(&amba_reg);    if (ret == 0) {        ret = amba_driver_register(&pl011_driver);        if (ret)            uart_unregister_driver(&amba_reg);    }    return ret;}static void __exit pl011_exit(void){    amba_driver_unregister(&pl011_driver);    uart_unregister_driver(&amba_reg);}

注册了一个uart_driver和一个amba_driver，两个结构的实例如下

static struct uart_driver amba_reg = {    .owner          = THIS_MODULE,    .driver_name        = "ttyAMA",/* /proc/tty/sesial/ttyAMA */    .dev_name       = "ttyAMA",   /* /dev/ttyAMA */    .major          = SERIAL_AMBA_MAJOR,  /* /dev/ttyAMAn的节点信息 */    .minor          = SERIAL_AMBA_MINOR,    .nr         = UART_NR,    .cons           = AMBA_CONSOLE,};//----------------static struct amba_id pl011_ids[] = {    {        .id = 0x00041011,        .mask   = 0x000fffff,        .data   = &vendor_arm,    },    {        .id = 0x00380802,        .mask   = 0x00ffffff,        .data   = &vendor_st,    },    { 0, 0 },};MODULE_DEVICE_TABLE(amba, pl011_ids);static struct amba_driver pl011_driver = {    .drv = {        .name   = "uart-pl011",    },    .id_table   = pl011_ids,/*用来匹配设备的,*/    .probe      = pl011_probe,/*在里面实现了uart_port的注册和uart_ops的赋值*/    .remove     = pl011_remove,};

当有设备与此驱动匹配时，就调用pl011_probe函数了，主要就是填充uart_add_one_port，并实现uart_ops

static int pl011_probe(struct amba_device *dev, const struct amba_id *id){    struct uart_amba_port *uap;    ...    uap->port.ops = &amba_pl011_pops;    ...    ret = uart_add_one_port(&amba_reg, &uap->port);    ...}

先说下匹配过程，在注册驱动时amba_driver_register函数中有下句

drv->drv.bus = &amba_bustype;//表明将该驱动注册到amba_bus总线上去,由amba_bus中的match方法匹配

同样的在注册设备时，amba_device_register–>amba_device_initialize中

dev->dev.bus = &amba_bustype;//同样将设备注册到amba_bus总线上去，由amba_bus中的match方法匹配

而且，在amba_device_register–>amba_device_add中会如果没设定会自行计算出AMBA设备的ID号

int amba_device_add(struct amba_device *dev, struct resource *parent){    ...    /* Hard-coded primecell ID instead of plug-n-play */    if (dev->periphid != 0)/*如果在添加设备时自行加了id就不再读取硬件上的ID了*/        goto skip_probe;    ...    ret = amba_get_enable_pclk(dev);    if (ret == 0) {        u32 pid, cid;        /*         * Read pid and cid based on size of resource         * they are located at end of region 在芯片资源的末区域读取ID信息         */        for (pid = 0, i = 0; i < 4; i++)            pid |= (readl(tmp + size - 0x20 + 4 * i) & 255) <<                (i * 8);        for (cid = 0, i = 0; i < 4; i++)            cid |= (readl(tmp + size - 0x10 + 4 * i) & 255) <<                (i * 8);        amba_put_disable_pclk(dev);        if (cid == AMBA_CID)            dev->periphid = pid;        if (!dev->periphid)            ret = -ENODEV;    }    ...}

那么最后就是由amba_bus总线中的match来匹配驱动和设备了。如下，table就是驱动中的amba_id 了

struct bus_type amba_bustype = {    ...    .match      = amba_match,    ...};