Linux串口驱动分析初始化

最新推荐文章于 2025-03-31 14:48:46 发布

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最新推荐文章于 2025-03-31 14:48:46 发布

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分类专栏： linux-驱动内核函数

linux-驱动同时被 2 个专栏收录

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本文深入分析了S3C2440串口驱动的实现原理，包括初始化过程、硬件资源获取及配置，以及驱动与硬件的关联。通过解析关键函数，展示了如何在Linux内核中实现一个完整的串口驱动。

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代码来自：http://blog.youkuaiyun.com/longwang155069/article/details/42712551
* uart分析
*
* 其实串口分析就两个重要的文件: S3c2440.c Samsung.c
*
* **/
/*1. 首先从Samsung.c的模块初始化函数看起*/
static int __init s3c24xx_serial_modinit(void)
{
int ret;
ret = uart_register_driver(&s3c24xx_uart_drv);
if (ret < 0) {
printk(KERN_ERR "failed to register UART driver\n");
return -1;
}
return 0;
}
/*参数是需要程序员自己定义 */
/** s3c2440.c **/
static struct s3c24xx_uart_info s3c2440_uart_inf = {
.name = "Samsung S3C2440 UART",
.type = PORT_S3C2440, //端口类型
.fifosize = 64, //FIFO缓冲区大小
.rx_fifomask = S3C2440_UFSTAT_RXMASK,
.rx_fifoshift = S3C2440_UFSTAT_RXSHIFT,
.rx_fifofull = S3C2440_UFSTAT_RXFULL,
.tx_fifofull = S3C2440_UFSTAT_TXFULL,
.tx_fifomask = S3C2440_UFSTAT_TXMASK,
.tx_fifoshift = S3C2440_UFSTAT_TXSHIFT,
.get_clksrc = s3c2440_serial_getsource,
.set_clksrc = s3c2440_serial_setsource,
.reset_port = s3c2440_serial_resetport,
};
/*platform 驱动定义： s3c2440_serial_driver*/
static struct platform_driver s3c2440_serial_driver = {
.probe = s3c2440_serial_probe, //匹配后设备调用
.remove = __devexit_p(s3c24xx_serial_remove),
.driver = {
.name = "s3c2440-uart", //驱动的名字
.owner = THIS_MODULE,
},
};
/*分析uart_register_driver函数*/
/* 这个函数的主要作用是初始化tty_driver结构体。其实tty_driver的主要成员都是通过传进来的参数drv赋值的
* 其次是初始化uart_driver中的uart_state成员。
*
* uart_state是一个结构体包含了tty_port和uart_port。而uart_port主要是和硬件相关。其实每一个串口都对应一个uart_port结构
* 这里只初始化了tty_port结构。而uart_port是在等设备匹配上后在设备的ops中的probe函数中初始化
*/
int uart_register_driver(struct uart_driver *drv)
{
/*
* 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);
if (!drv->state)
goto out;
normal = alloc_tty_driver(drv->nr);
if (!normal)
goto out_kfree;
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;
normal->subtype = SERIAL_TYPE_NORMAL;
normal->init_termios = tty_std_termios;
normal->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL;
normal->init_termios.c_ispeed = normal->init_termios.c_ospeed = 9600;
normal->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
normal->driver_state = drv;
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;
struct tty_port *port = &state->port;
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);
}
retval = tty_register_driver(normal);
}
/* 当设备与驱动匹配后，会调用此函数。
*
* probe函数一般就是做的硬件相关的初始化。
*
* 其实uart_port的初始化也是通过s3c24xx_uart_port来初始化的。
* */
int s3c24xx_serial_probe(struct platform_device *dev,
struct s3c24xx_uart_info *info)
{
struct s3c24xx_uart_port *ourport;
int ret;
dbg("s3c24xx_serial_probe(%p, %p) %d\n", dev, info, probe_index);
/*取得相应的端口*/
ourport = &s3c24xx_serial_ports[probe_index];
probe_index++;
dbg("%s: initialising port %p...\n", __func__, ourport);
/*初始化端口*/
ret = s3c24xx_serial_init_port(ourport, info, dev);
if (ret < 0)
goto probe_err;
dbg("%s: adding port\n", __func__);
/*这个函数的主要作用是：将uart_port和uart_driver关联起来*/
uart_add_one_port(&s3c24xx_uart_drv, &ourport->port);
platform_set_drvdata(dev, &ourport->port);
ret = device_create_file(&dev->dev, &dev_attr_clock_source);
if (ret < 0)
printk(KERN_ERR "%s: failed to add clksrc attr.\n", __func__);
ret = s3c24xx_serial_cpufreq_register(ourport);
if (ret < 0)
dev_err(&dev->dev, "failed to add cpufreq notifier\n");
return 0;
probe_err:
return ret;
}
/*
* 端口初始化函数
* */
static int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,
struct s3c24xx_uart_info *info,
struct platform_device *platdev)
{
struct uart_port *port = &ourport->port;
struct s3c2410_uartcfg *cfg;
struct resource *res;
int ret;
dbg("s3c24xx_serial_init_port: port=%p, platdev=%p\n", port, platdev);
if (platdev == NULL)
return -ENODEV;
/*获取设备的资源，详细解析见下面*/
cfg = s3c24xx_dev_to_cfg(&platdev->dev);
if (port->mapbase != 0)
return 0;
/*判断是否大于总数4个*/
if (cfg->hwport > CONFIG_SERIAL_SAMSUNG_UARTS) {
printk(KERN_ERR "%s: port %d bigger than %d\n", __func__,
cfg->hwport, CONFIG_SERIAL_SAMSUNG_UARTS);
return -ERANGE;
}
port->dev = &platdev->dev;
ourport->info = info;
/*初始化port的大小 = 64*/
ourport->port.fifosize = info->fifosize;
dbg("s3c24xx_serial_init_port: %p (hw %d)...\n", port, cfg->hwport);
port->uartclk = 1;
/*判断是否开启流控*/
if (cfg->uart_flags & UPF_CONS_FLOW) {
dbg("s3c24xx_serial_init_port: enabling flow control\n");
port->flags |= UPF_CONS_FLOW;
}
/*获取uart资源*/
res = platform_get_resource(platdev, IORESOURCE_MEM, 0);
if (res == NULL) {
printk(KERN_ERR "failed to find memory resource for uart\n");
return -EINVAL;
}
dbg("resource %p (%lx..%lx)\n", res, res->start, res->end);
/*初始化基地址等*/
port->mapbase = res->start;
port->membase = S3C_VA_UART + (res->start & 0xfffff);
ret = platform_get_irq(platdev, 0);
if (ret < 0)
port->irq = 0;
else {
port->irq = ret;
ourport->rx_irq = ret;
ourport->tx_irq = ret + 1;
}
ret = platform_get_irq(platdev, 1);
if (ret > 0)
ourport->tx_irq = ret;
/*获取时钟*/
ourport->clk = clk_get(&platdev->dev, "uart");
dbg("port: map=%08x, mem=%08x, irq=%d (%d,%d), clock=%ld\n",
port->mapbase, port->membase, port->irq,
ourport->rx_irq, ourport->tx_irq, port->uartclk);
/* reset the fifos (and setup the uart) */
s3c24xx_serial_resetport(port, cfg);
return 0;
}
#define s3c24xx_dev_to_cfg(__dev) (struct s3c2410_uartcfg *)((__dev)->platform_data)
/*
* cfg = s3c24xx_dev_to_cfg(&platdev->dev)
*
* 那么cfg到底是如何获得?
*
* 搜索s3c2410_uartcfg得到：
*/
#define UCON S3C2410_UCON_DEFAULT | S3C2410_UCON_UCLK
#define ULCON S3C2410_LCON_CS8 | S3C2410_LCON_PNONE | S3C2410_LCON_STOPB
#define UFCON S3C2410_UFCON_RXTRIG8 | S3C2410_UFCON_FIFOMODE
static struct s3c2410_uartcfg smdk2440_uartcfgs[] __initdata = {
[0] = {
.hwport = 0,
.flags = 0,
.ucon = 0x3c5,
.ulcon = 0x03,
.ufcon = 0x51,
},
[1] = {
.hwport = 1,
.flags = 0,
.ucon = 0x3c5,
.ulcon = 0x03,
.ufcon = 0x51,
},
[2] = {
.hwport = 2,
.flags = 0,
.ucon = 0x3c5,
.ulcon = 0x43,
.ufcon = 0x51,
}
};
void __init s3c24xx_init_uarts(struct s3c2410_uartcfg *cfg, int no)
{
if (cpu == NULL)
return;
if (cpu->init_uarts == NULL) {
printk(KERN_ERR "s3c24xx_init_uarts: cpu has no uart init\n");
} else
(cpu->init_uarts)(cfg, no);
}
/*初始化系统上的串口资源*/
void __init s3c24xx_init_uartdevs(char *name,
struct s3c24xx_uart_resources *res,
struct s3c2410_uartcfg *cfg, int no)
{
struct platform_device *platdev;
struct s3c2410_uartcfg *cfgptr = uart_cfgs;
struct s3c24xx_uart_resources *resp;
int uart;
memcpy(cfgptr, cfg, sizeof(struct s3c2410_uartcfg) * no);
for (uart = 0; uart < no; uart++, cfg++, cfgptr++) {
platdev = s3c24xx_uart_src[cfgptr->hwport];
resp = res + cfgptr->hwport;
s3c24xx_uart_devs[uart] = platdev;
platdev->name = name;
platdev->resource = resp->resources;
platdev->num_resources = resp->nr_resources;
/*从这里获取platform*/
platdev->dev.platform_data = cfgptr;
}
nr_uarts = no;
}
/*uart 所对应的资源 platform_get_resourced调用**/
/* Serial port registrations */
static struct resource s3c2410_uart0_resource[] = {
[0] = {
.start = S3C2410_PA_UART0,
.end = S3C2410_PA_UART0 + 0x3fff,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = IRQ_S3CUART_RX0,
.end = IRQ_S3CUART_ERR0,
.flags = IORESOURCE_IRQ,
}
};
static struct resource s3c2410_uart1_resource[] = {
[0] = {
.start = S3C2410_PA_UART1,
.end = S3C2410_PA_UART1 + 0x3fff,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = IRQ_S3CUART_RX1,
.end = IRQ_S3CUART_ERR1,
.flags = IORESOURCE_IRQ,
}
};
static struct resource s3c2410_uart2_resource[] = {
[0] = {
.start = S3C2410_PA_UART2,
.end = S3C2410_PA_UART2 + 0x3fff,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = IRQ_S3CUART_RX2,
.end = IRQ_S3CUART_ERR2,
.flags = IORESOURCE_IRQ,
}
};
static struct resource s3c2410_uart3_resource[] = {
[0] = {
.start = S3C2443_PA_UART3,
.end = S3C2443_PA_UART3 + 0x3fff,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = IRQ_S3CUART_RX3,
.end = IRQ_S3CUART_ERR3,
.flags = IORESOURCE_IRQ,
},
};
struct s3c24xx_uart_resources s3c2410_uart_resources[] __initdata = {
[0] = {
.resources = s3c2410_uart0_resource,
.nr_resources = ARRAY_SIZE(s3c2410_uart0_resource),
},
[1] = {
.resources = s3c2410_uart1_resource,
.nr_resources = ARRAY_SIZE(s3c2410_uart1_resource),
},
[2] = {
.resources = s3c2410_uart2_resource,
.nr_resources = ARRAY_SIZE(s3c2410_uart2_resource),
},
[3] = {
.resources = s3c2410_uart3_resource,
.nr_resources = ARRAY_SIZE(s3c2410_uart3_resource),
},
};
总结：修改驱动需要设计的数据结构
1. uart_driver:用于初始化tty_driver
2. s3c24xx_uart_port: 用于初始化uart_port
3. s3c24xx_serial_ops: 硬件的操作集
4. s3c24xx_uart_info：用于初始化uart_port
其实也就是：编写S3c2440.c这个串口文件。