Linux 串列埠驅動相關
Linux串列埠驅動相關主要涉及3個重要的結構體，uart_driver，uart_port，uart_ops。本文主要以msm8917平臺分析, 先貼dts相關程式碼
blsp1_uart2: [email protected]78b0000 {
compatible = "qcom,msm-lsuart-v14";
reg = <0x78b0000 0x200>;
interrupts = <0 108 0>;
status = "disabled";
clocks = <&clock_gcc clk_gcc_blsp1_uart2_apps_clk> 幾個重要結構體定義
uart_driver封裝了tty_driver，使底層uart驅動不用關心tty_driver。一個tty驅動程式必須註冊/登出 tty_driver，而uart驅動則變為註冊/登出uart_driver。使用如下介面:
int uart_register_driver(struct uart_driver *drv);
void uart_unregister_driver 實際上，uart_register_driver()和uart_unregister_driver()中分別包含了tty_register_driver()和tty_unregister_driver()的操作。
uart_driver的定義
struct uart_driver {
struct module *owner;
const char *driver_name;
const char *dev_name;
int major;
int 對應高通平臺的程式碼
static struct uart_driver msm_hsl_uart_driver = {
.owner = THIS_MODULE,
.driver_name = "msm_serial_hsl",
.dev_name = "ttyHSL",
.nr = UART_NR,
.cons = MSM_HSL_CONSOLE,
};
其中uart_driver中的uart_state比較重要,在uart_register_driver中為state分配了記憶體
/*
* This is the state information which is persistent across opens.
*/
struct uart_state {
struct tty_port port;
enum uart_pm_state pm_state;
struct circ_buf xmit;
struct uart_port *uart_port;
};
uart_port用於描述一個UART埠（直接對應於一個串列埠）的I/O埠或I/O記憶體地址、FIFO大小、埠型別等資訊。串列埠核心層提供如下函式來新增1個埠：
int uart_add_one_port(struct uart_driver *drv, struct uart_port *port);
對上述函式的呼叫應該發生在uart_register_driver()之後，uart_add_one_port()的一個最重要作用是封裝了 tty_register_device()。
uart_add_one_port()的“反函式”是uart_remove_one_port()，其中會呼叫tty_unregister_device()，原型為：
int uart_remove_one_port(struct uart_driver *drv, struct uart_port *port);
uart_port定義
struct uart_port {
spinlock_t lock; /* port lock */
unsigned long iobase; /* in/out[bwl] */
unsigned char __iomem *membase; /* read/write[bwl] */
unsigned int (*serial_in)(struct uart_port *, int);
void (*serial_out)(struct uart_port *, int, int);
void (*set_termios)(struct uart_port *,
struct ktermios *new,
struct ktermios *old);
int (*startup)(struct uart_port *port);
void (*shutdown)(struct uart_port *port);
void (*throttle)(struct uart_port *port);
void (*unthrottle)(struct uart_port *port);
int (*handle_irq)(struct uart_port *);
void (*pm)(struct uart_port *, unsigned int state,
unsigned int old);
void (*handle_break)(struct uart_port *);
unsigned int irq; /* irq number */
unsigned long irqflags; /* irq flags */
unsigned int uartclk; /* base uart clock */
unsigned int fifosize; /* tx fifo size */
unsigned char x_char; /* xon/xoff char */
unsigned char regshift; /* reg offset shift */
unsigned char iotype; /* io access style */
unsigned char unused1;
#define UPIO_PORT (0)
#define UPIO_HUB6 (1)
#define UPIO_MEM (2)
#define UPIO_MEM32 (3)
#define UPIO_AU (4) /* Au1x00 and RT288x type IO */
#define UPIO_TSI (5) /* Tsi108/109 type IO */
unsigned int read_status_mask; /* driver specific */
unsigned int ignore_status_mask; /* driver specific */
struct uart_state *state; /* pointer to parent state */
struct uart_icount icount; /* statistics */
struct console *cons; /* struct console, if any */
#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(SUPPORT_SYSRQ)
unsigned long sysrq; /* sysrq timeout */
#endif
/* flags must be updated while holding port mutex */
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_NO_TXEN_TEST ((__force upf_t) (1 << 15))
#define UPF_MAGIC_MULTIPLIER ((__force upf_t) (1 << 16))
/* Port has hardware-assisted h/w flow control (iow, auto-RTS *not* auto-CTS) */
#define UPF_HARD_FLOW ((__force upf_t) (1 << 21))
/* Port has hardware-assisted s/w flow control */
#define UPF_SOFT_FLOW ((__force upf_t) (1 << 22))
#define UPF_CONS_FLOW ((__force upf_t) (1 << 23))
#define UPF_SHARE_IRQ ((__force upf_t) (1 << 24))
#define UPF_EXAR_EFR ((__force upf_t) (1 << 25))
#define UPF_BUG_THRE ((__force upf_t) (1 << 26))
/* The exact UART type is known and should not be probed. */
#define UPF_FIXED_TYPE ((__force upf_t) (1 << 27))
#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))
/* status must be updated while holding port lock */
upstat_t status;
#define UPSTAT_CTS_ENABLE ((__force upstat_t) (1 << 0))
#define UPSTAT_DCD_ENABLE ((__force upstat_t) (1 << 1))
int hw_stopped; /* sw-assisted CTS flow state */
unsigned int mctrl; /* current modem ctrl settings */
unsigned int timeout; /* character-based timeout */
unsigned int type; /* port type */
const struct uart_ops *ops;
unsigned int custom_divisor;
unsigned int line; /* port index */
resource_size_t mapbase; /* for ioremap */
struct device *dev; /* parent device */
unsigned char hub6; /* this should be in the 8250 driver */
unsigned char suspended;
unsigned char irq_wake;
unsigned char unused[2];
struct attribute_group *attr_group; /* port specific attributes */
const struct attribute_group **tty_groups; /* all attributes (serial core use only) */
void *private_data; /* generic platform data pointer */
};
對應高通平臺的程式碼
struct msm_hsl_port {
struct uart_port uart;
char name[16];
struct clk *clk;
struct clk *pclk;
struct dentry *loopback_dir;
unsigned int imr;
unsigned int *uart_csr_code;
unsigned int *gsbi_mapbase;
unsigned int *mapped_gsbi;
unsigned int old_snap_state;
unsigned long ver_id;
int tx_timeout;
struct mutex clk_mutex;
enum uart_core_type uart_type;
enum uart_func_mode func_mode;
struct wakeup_source port_open_ws;
int clk_enable_count;
u32 bus_perf_client;
/* BLSP UART required BUS Scaling data */
struct msm_bus_scale_pdata *bus_scale_table;
};
msm_hsl_port 對uart_port做了一個封裝
static struct msm_hsl_port msm_hsl_uart_ports[] = {
{
.uart = {
.iotype = UPIO_MEM,
.ops = &msm_hsl_uart_pops,
.flags = UPF_BOOT_AUTOCONF,
.fifosize = 64,
.line = 0,
},
},
{
.uart = {
.iotype = UPIO_MEM,
.ops = &msm_hsl_uart_pops,
.flags = UPF_BOOT_AUTOCONF,
.fifosize = 64,
.line = 1,
},
},
{
.uart = {
.iotype = UPIO_MEM,
.ops = &msm_hsl_uart_pops,
.flags = UPF_BOOT_AUTOCONF,
.fifosize = 64,
.line = 2,
},
},
};
uart_ops
/*
* This structure describes all the operations that can be done on the
* physical hardware. See Documentation/serial/driver for details.
*/
struct uart_ops {
unsigned int (*tx_empty)(struct uart_port *);
void (*set_mctrl)(struct uart_port *, unsigned int mctrl);
unsigned int (*get_mctrl)(struct uart_port *);
void (*stop_tx)(struct uart_port *);
void (*start_tx)(struct uart_port *);
void (*throttle)(struct uart_port *);
void (*unthrottle)(struct uart_port *);
void (*send_xchar)(struct uart_port *, char ch);
void (*stop_rx)(struct uart_port *);
void (*enable_ms)(struct uart_port *);
void (*break_ctl)(struct uart_port *, int ctl);
int (*startup)(struct uart_port *);
void (*shutdown)(struct uart_port *);
void (*flush_buffer)(struct uart_port *);
void (*set_termios)(struct uart_port *, struct ktermios *new,
struct ktermios *old);
void (*set_ldisc)(struct uart_port *, int new);
void (*pm)(struct uart_port *, unsigned int state,
unsigned int oldstate);
void (*wake_peer)(struct uart_port *);
/*
* 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);
int (*verify_port)(struct uart_port *, struct serial_struct *);
int (*ioctl)(struct uart_port *, unsigned int, unsigned long);
#ifdef CONFIG_CONSOLE_POLL
int (*poll_init)(struct uart_port *);
void (*poll_put_char)(struct uart_port *, unsigned char);
int (*poll_get_char)(struct uart_port *);
#endif
};
高通平臺對應程式碼
static struct uart_ops msm_hsl_uart_pops = {
.tx_empty = msm_hsl_tx_empty,
.set_mctrl = msm_hsl_set_mctrl,
.get_mctrl = msm_hsl_get_mctrl,
.stop_tx = msm_hsl_stop_tx,
.start_tx = msm_hsl_start_tx,
.stop_rx = msm_hsl_stop_rx,
.enable_ms = msm_hsl_enable_ms,
.break_ctl = msm_hsl_break_ctl,
.startup = msm_hsl_startup,
.shutdown = msm_hsl_shutdown,
.set_termios = msm_hsl_set_termios,
.type = msm_hsl_type,
.release_port = msm_hsl_release_port,
.request_port = msm_hsl_request_port,
.config_port = msm_hsl_config_port,
.verify_port = msm_hsl_verify_port,
.pm = msm_hsl_power,
};
驅動註冊流程
在使用串列埠核心層這個通用串列埠tty驅動層的介面後，一個串列埠驅動要完成的主要工作將包括：
- 定義uart_driver、uart_ops、uart_port等結構體的例項並在適當的地方根據具體硬體和驅動的情況初始化它們，當然具體裝置 xxx的驅動可以將這些結構套在新定義的xxx_uart_driver、xxx_uart_ops、xxx_uart_port之內。
- 在模組初始化時呼叫uart_register_driver()和uart_add_one_port()以註冊UART驅動並新增埠，在模組解除安裝時呼叫uart_unregister_driver()和uart_remove_one_port()以登出UART驅動並移除埠。
- 根據具體硬體的datasheet實現uart_ops中的成員函式，這些函式的實現成為UART驅動的主體工作。
串列埠驅動初始化過程
在高通串列埠驅動的模組載入函式(msm_serial_hsl_init)中會呼叫uart_register_driver()註冊msm_hsl_uart_driver這個uart_driver(對應driver)
同時經過msm_serial_hsl_init()–>platform_driver_register(&msm_hsl_platform_driver);–>msm_serial_hsl_probe–>初始化UART埠並呼叫uart_add_one_port()新增埠。(對應device)
下面開始具體分析，從uart_register_driver開始，對應程式碼在serial_core.c中
/**
* 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;
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);
if (!drv->state)
goto out;
normal = alloc_tty_driver(drv->nr);
if (!normal)
goto out_kfree;
drv->tty_driver = normal;
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); //會呼叫到此ops中有uart_open等
/*
* 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 = HZ / 2; /* .5 seconds */
port->closing_wait = 30 * HZ;/* 30 seconds */
}
retval = tty_register_driver(normal);
if (retval >= 0)
return retval;
for (i = 0; i < drv->nr; i++)
tty_port_destroy(&drv->state[i].port);
put_tty_driver(normal);
out_kfree:
kfree(drv->state);
out:
return -ENOMEM;
}
貼兩個ops
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
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Linux串列埠程式設計教程（三）——串列埠程式設計詳（原始碼）解：http://blog.csdn.net/u011192270/article/details/48174353
Linux下的串列埠程式設計(二）----（圖文並茂，講解深刻）http://blog.csdn.ne
Linux串列埠程式設計
串列埠通訊是指一次只傳送一個數據位。雖然在通訊的時候串列埠有 8 位或者 9 位等，但是在物理層面傳輸的時候，它仍然是以單個 bit 的方式傳輸的
一般特指 RS232 標準的介面
在 linux 下串列埠程式設計流程如下：
開啟串列埠
核心是用op
MTK串列埠驅動開發
MTK串列埠驅動開發
由於最近在工作中需要使用MTK的MT6261進行移動嵌入式裝置的開發，所以將MTK串列埠驅動開發流程貼出來分享給大家。
1.使用串列埠工具配置UART管腳，此處配置的是UART2開啟原始碼目錄下的\custom\drv\Drv_Tool\DrvGen.exe
ubuntu安裝USB轉串列埠驅動（PL2303）
在Ubuntu下利用minicom進行嵌入式開發時可能會用到USB轉串列埠，這時就會用到USB轉串列埠驅動，以前的Ubuntu是直接將此驅動編譯進核心，但不知道從哪個版本開始Ubuntu將其從核心去掉了，所以要用到Ubuntu的minicom時只能由我們自己安裝USB轉串列埠驅動，方法如下：
ITOP4412裸機程式設計-串列埠驅動
文章目錄
前言：
原理分析：
原始碼：
修改main.S
修改exynos4412.h