linux pl011串口简述
基于nanopi m2内核3.4.39
串口驱动编译选项
Created with Raphaël 2.1.0 linux Kernel Configuration make menuconfig device drivers character devices serial drivers
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 usbserial
root@NanoPi2:~# cat /proc/tty/driver/ttyAMA
serinfo:1.0 driver revision:
0: uart:PL011 rev3 mmio:0xC00A1000 irq:7 tx:2846 rx:133 RTS|DTR
1: uart:PL011 rev3 mmio:0xC00A0000 irq:6 tx:0 rx:0 DSR|CD
2: uart:PL011 rev3 mmio:0xC00A3000 irq:9 tx:0 rx:0
3: uart:PL011 rev3 mmio:0xC006D000 irq:10 tx:0 rx:0
root@NanoPi2:~# ls /dev/ttyAMA* -l
crw------- 1 root tty 204, 64 Sep 20 04:21 /dev/ttyAMA0
crw-rw---- 1 root dialout 204, 65 Sep 20 03:28 /dev/ttyAMA1
crw-rw---- 1 root dialout 204, 66 Sep 20 03:28 /dev/ttyAMA2
crw-rw---- 1 root dialout 204, 67 Sep 20 03:28 /dev/ttyAMA34418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,
...
};
Created with Raphaël 2.1.0 amba_driver amba_driver amba_bus amba_bus amba_device amba_device amba_driver_register() amba_device_register() 通过ID (dev->periphid & table->mask) == table->id