从零开始之驱动发开、linux驱动（六十五、内核调试篇--串口驱动）

上一节我们分析了bootoader中传过来的cmdline中的命令是如何解析并执行的。

同时也是对bootloader中传过来的console进行了记录。

console也就是我们所说的控制台，可以是任何常见的输出设备，比如serial，比如framebuffer，比如网口。

 

本节主要以最常见的串口为例说明。

如果有搜索过内核代码，可以看到绝大多数的console都是串口设备。

所以内核对用作串口程序进行了进一步的封装，抽象出的serial_core.c文件中，对console的注册留有了接口。

console的注册函数是register_console，这个函数我们后面说。

void register_console(struct console *newcon)

 

这里我们先简单看一下串口驱动。

这里以三星的为例，这里不会详细分析代码，只会说一下串口驱动的架构。

 

串口驱动主要由下面这个来表示

struct uart_driver {
	struct module		*owner;
	const char		*driver_name;
	const char		*dev_name;
	int			 major;
	int			 minor;
	int			 nr;
	struct console		*cons;

	/*
	 * these are private; the low level driver should not
	 * touch these; they should be initialised to NULL
	 */
	struct uart_state	*state;
	struct tty_driver	*tty_driver;
};

三星的实现如下，这里的console是console使用的

static struct uart_driver s3c24xx_uart_drv = {
	.owner		= THIS_MODULE,
	.driver_name	= "s3c2410_serial",
	.nr		= CONFIG_SERIAL_SAMSUNG_UARTS,
	.cons		= S3C24XX_SERIAL_CONSOLE,
	.dev_name	= S3C24XX_SERIAL_NAME,
	.major		= S3C24XX_SERIAL_MAJOR,
	.minor		= S3C24XX_SERIAL_MINOR,
};


static struct console s3c24xx_serial_console = {
	.name		= S3C24XX_SERIAL_NAME,
	.device		= uart_console_device,
	.flags		= CON_PRINTBUFFER,
	.index		= -1,
	.write		= s3c24xx_serial_console_write,
	.setup		= s3c24xx_serial_console_setup,
	.data		= &s3c24xx_uart_drv,
};

#define S3C24XX_SERIAL_NAME	"ttySAC"
#define S3C24XX_SERIAL_MAJOR	204
#define S3C24XX_SERIAL_MINOR	64

/* 串口设备数量由具体的CPU决定 */
CONFIG_SERIAL_SAMSUNG_UARTS

这里我们只关注名字为"ttySAC"，所以我们uboot的传参就是console = "ttySACx"

后面的这个x，内核解析为了index。

 

 

接下来再看一下一个uart端口是如何描述

内核抽象出了公共的部分。

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);
	void			(*set_ldisc)(struct uart_port *,
					     struct ktermios *);
	unsigned int		(*get_mctrl)(struct uart_port *);
	void			(*set_mctrl)(struct uart_port *, unsigned int);
	unsigned int		(*get_divisor)(struct uart_port *,
					       unsigned int baud,
					       unsigned int *frac);
	void			(*set_divisor)(struct uart_port *,
					       unsigned int baud,
					       unsigned int quot,
					       unsigned int quot_frac);
	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 *);
	int			(*rs485_config)(struct uart_port *,
						struct serial_rs485 *rs485);
	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		quirks;			/* internal quirks */

#define UPIO_PORT		(SERIAL_IO_PORT)	/* 8b I/O port access */
#define UPIO_HUB6		(SERIAL_IO_HUB6)	/* Hub6 ISA card */
#define UPIO_MEM		(SERIAL_IO_MEM)		/* driver-specific */
#define UPIO_MEM32		(SERIAL_IO_MEM32)	/* 32b little endian */
#define UPIO_AU			(SERIAL_IO_AU)		/* Au1x00 and RT288x type IO */
#define UPIO_TSI		(SERIAL_IO_TSI)		/* Tsi108/109 type IO */
#define UPIO_MEM32BE		(SERIAL_IO_MEM32BE)	/* 32b big endian */
#define UPIO_MEM16		(SERIAL_IO_MEM16)	/* 16b little endian */

	/* quirks must be updated while holding port mutex */
#define UPQ_NO_TXEN_TEST	BIT(0)

	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;

	/*
	 * These flags must be equivalent to the flags defined in
	 * include/uapi/linux/tty_flags.h which are the userspace definitions
	 * assigned from the serial_struct flags in uart_set_info()
	 * [for bit definitions in the UPF_CHANGE_MASK]
	 *
	 * Bits [0..UPF_LAST_USER] are userspace defined/visible/changeable
	 * The remaining bits are serial-core specific and not modifiable by
	 * userspace.
	 */
#define UPF_FOURPORT		((__force upf_t) ASYNC_FOURPORT       /* 1  */ )
#define UPF_SAK			((__force upf_t) ASYNC_SAK            /* 2  */ )
#define UPF_SPD_HI		((__force upf_t) ASYNC_SPD_HI         /* 4  */ )
#define UPF_SPD_VHI		((__force upf_t) ASYNC_SPD_VHI        /* 5  */ )
#define UPF_SPD_CUST		((__force upf_t) ASYNC_SPD_CUST   /* 0x0030 */ )
#define UPF_SPD_WARP		((__force upf_t) ASYNC_SPD_WARP   /* 0x1010 */ )
#define UPF_SPD_MASK		((__force upf_t) ASYNC_SPD_MASK   /* 0x1030 */ )
#define UPF_SKIP_TEST		((__force upf_t) ASYNC_SKIP_TEST      /* 6  */ )
#define UPF_AUTO_IRQ		((__force upf_t) ASYNC_AUTO_IRQ       /* 7  */ )
#define UPF_HARDPPS_CD		((__force upf_t) ASYNC_HARDPPS_CD     /* 11 */ )
#define UPF_SPD_SHI		((__force upf_t) ASYNC_SPD_SHI        /* 12 */ )
#define UPF_LOW_LATENCY		((__force upf_t) ASYNC_LOW_LATENCY    /* 13 */ )
#define UPF_BUGGY_UART		((__force upf_t) ASYNC_BUGGY_UART     /* 14 */ )
#define UPF_MAGIC_MULTIPLIER	((__force upf_t) ASYNC_MAGIC_MULTIPLIER /* 16 */ )

#define UPF_NO_THRE_TEST	((__force upf_t) (1 << 19))
/* Port has hardware-assisted h/w flow control */
#define UPF_AUTO_CTS		((__force upf_t) (1 << 20))
#define UPF_AUTO_RTS		((__force upf_t) (1 << 21))
#define UPF_HARD_FLOW		((__force upf_t) (UPF_AUTO_CTS | UPF_AUTO_RTS))
/* 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	0x17fff
#define UPF_CHANGE_MASK		((__force upf_t) __UPF_CHANGE_MASK)
#define UPF_USR_MASK		((__force upf_t) (UPF_SPD_MASK|UPF_LOW_LATENCY))

#if __UPF_CHANGE_MASK > ASYNC_FLAGS
#error Change mask not equivalent to userspace-visible bit defines
#endif

	/*
	 * Must hold termios_rwsem, port mutex and port lock to change;
	 * can hold any one lock to read.
	 */
	upstat_t		status;

#define UPSTAT_CTS_ENABLE	((__force upstat_t) (1 << 0))
#define UPSTAT_DCD_ENABLE	((__force upstat_t) (1 << 1))
#define UPSTAT_AUTORTS		((__force upstat_t) (1 << 2))
#define UPSTAT_AUTOCTS		((__force upstat_t) (1 << 3))
#define UPSTAT_AUTOXOFF		((__force upstat_t) (1 << 4))
#define UPSTAT_SYNC_FIFO	((__force upstat_t) (1 << 5))

	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 */
	unsigned int		minor;
	resource_size_t		mapbase;		/* for ioremap */
	resource_size_t		mapsize;
	struct device		*dev;			/* parent device */
	unsigned char		hub6;			/* this should be in the 8250 driver */
	unsigned char		suspended;
	unsigned char		unused[2];
	const char		*name;			/* port name */
	struct attribute_group	*attr_group;		/* port specific attributes */
	const struct attribute_group **tty_groups;	/* all attributes (serial core use only) */
	struct serial_rs485     rs485;
	void			*private_data;		/* generic platform data pointer */
};

 

不同厂家在内核的基础上继续封装实现自己独特的部分。

struct s3c24xx_uart_port {
	unsigned char			rx_claimed;
	unsigned char			tx_claimed;
	unsigned int			pm_level;
	unsigned long			baudclk_rate;
	unsigned int			min_dma_size;

	unsigned int			rx_irq;
	unsigned int			tx_irq;

	unsigned int			tx_in_progress;
	unsigned int			tx_mode;
	unsigned int			rx_mode;

	struct s3c24xx_uart_info	*info;
	struct clk			*clk;
	struct clk			*baudclk;
	struct uart_port		port;
	struct s3c24xx_serial_drv_data	*drv_data;

	/* reference to platform data */
	struct s3c2410_uartcfg		*cfg;

	struct s3c24xx_uart_dma		*dma;

#ifdef CONFIG_ARM_S3C24XX_CPUFREQ
	struct notifier_block		freq_transition;
#endif
};

 

三星一个SOC最多4个串口，所以这里根据配置最多定义了4个。

这里我们关注一个点，line，为串口的硬件编号，和次序一样。

#define __PORT_LOCK_UNLOCKED(i) \
	__SPIN_LOCK_UNLOCKED(s3c24xx_serial_ports[i].port.lock)
static struct s3c24xx_uart_port
s3c24xx_serial_ports[CONFIG_SERIAL_SAMSUNG_UARTS] = {
	[0] = {
		.port = {
			.lock		= __PORT_LOCK_UNLOCKED(0),
			.iotype		= UPIO_MEM,
			.uartclk	= 0,
			.fifosize	= 16,
			.ops		= &s3c24xx_serial_ops,
			.flags		= UPF_BOOT_AUTOCONF,
			.line		= 0,
		}
	},
	[1] = {
		.port = {
			.lock		= __PORT_LOCK_UNLOCKED(1),
			.iotype		= UPIO_MEM,
			.uartclk	= 0,
			.fifosize	= 16,
			.ops		= &s3c24xx_serial_ops,
			.flags		= UPF_BOOT_AUTOCONF,
			.line		= 1,
		}
	},
#if CONFIG_SERIAL_SAMSUNG_UARTS > 2

	[2] = {
		.port = {
			.lock		= __PORT_LOCK_UNLOCKED(2),
			.iotype		= UPIO_MEM,
			.uartclk	= 0,
			.fifosize	= 16,
			.ops		= &s3c24xx_serial_ops,
			.flags		= UPF_BOOT_AUTOCONF,
			.line		= 2,
		}
	},
#endif
#if CONFIG_SERIAL_SAMSUNG_UARTS > 3
	[3] = {
		.port = {
			.lock		= __PORT_LOCK_UNLOCKED(3),
			.iotype		= UPIO_MEM,
			.uartclk	= 0,
			.fifosize	= 16,
			.ops		= &s3c24xx_serial_ops,
			.flags		= UPF_BOOT_AUTOCONF,
			.line		= 3,
		}
	}
#endif
};
#undef __PORT_LOCK_UNLOCKED

其它标志之类比较常见，但其实我们都知道，重点在操作方法，也就是ops。

 

这是一个很复杂的结构，里面函数很多，但基本都是硬件操作相关的。这里就不再细看。

static struct uart_ops s3c24xx_serial_ops = {
	.pm		= s3c24xx_serial_pm,
	.tx_empty	= s3c24xx_serial_tx_empty,
	.get_mctrl	= s3c24xx_serial_get_mctrl,
	.set_mctrl	= s3c24xx_serial_set_mctrl,
	.stop_tx	= s3c24xx_serial_stop_tx,
	.start_tx	= s3c24xx_serial_start_tx,
	.stop_rx	= s3c24xx_serial_stop_rx,
	.break_ctl	= s3c24xx_serial_break_ctl,
	.startup	= s3c24xx_serial_startup,
	.shutdown	= s3c24xx_serial_shutdown,
	.set_termios	= s3c24xx_serial_set_termios,
	.type		= s3c24xx_serial_type,
	.release_port	= s3c24xx_serial_release_port,
	.request_port	= s3c24xx_serial_request_port,
	.config_port	= s3c24xx_serial_config_port,
	.verify_port	= s3c24xx_serial_verify_port,
#if defined(CONFIG_SERIAL_SAMSUNG_CONSOLE) && defined(CONFIG_CONSOLE_POLL)
	.poll_get_char = s3c24xx_serial_get_poll_char,
	.poll_put_char = s3c24xx_serial_put_poll_char,
#endif
};

 

这里我们看一下驱动入口，

static const struct platform_device_id s3c24xx_serial_driver_ids[] = {
	{
		.name		= "s3c2410-uart",
		.driver_data	= S3C2410_SERIAL_DRV_DATA,
	}, {
		.name		= "s3c2412-uart",
		.driver_data	= S3C2412_SERIAL_DRV_DATA,
	}, {
		.name		= "s3c2440-uart",
		.driver_data	= S3C2440_SERIAL_DRV_DATA,
	}, {
		.name		= "s3c6400-uart",
		.driver_data	= S3C6400_SERIAL_DRV_DATA,
	}, {
		.name		= "s5pv210-uart",
		.driver_data	= S5PV210_SERIAL_DRV_DATA,
	}, {
		.name		= "exynos4210-uart",
		.driver_data	= EXYNOS4210_SERIAL_DRV_DATA,
	}, {
		.name		= "exynos5433-uart",
		.driver_data	= EXYNOS5433_SERIAL_DRV_DATA,
	},
	{ },
};
MODULE_DEVICE_TABLE(platform, s3c24xx_serial_driver_ids);

#ifdef CONFIG_OF
static const struct of_device_id s3c24xx_uart_dt_match[] = {
	{ .compatible = "samsung,s3c2410-uart",
		.data = (void *)S3C2410_SERIAL_DRV_DATA },
	{ .compatible = "samsung,s3c2412-uart",
		.data = (void *)S3C2412_SERIAL_DRV_DATA },
	{ .compatible = "samsung,s3c2440-uart",
		.data = (void *)S3C2440_SERIAL_DRV_DATA },
	{ .compatible = "samsung,s3c6400-uart",
		.data = (void *)S3C6400_SERIAL_DRV_DATA },
	{ .compatible = "samsung,s5pv210-uart",
		.data = (void *)S5PV210_SERIAL_DRV_DATA },
	{ .compatible = "samsung,exynos4210-uart",
		.data = (void *)EXYNOS4210_SERIAL_DRV_DATA },
	{ .compatible = "samsung,exynos5433-uart",
		.data = (void *)EXYNOS5433_SERIAL_DRV_DATA },
	{},
};
MODULE_DEVICE_TABLE(of, s3c24xx_uart_dt_match);
#endif


static struct platform_driver samsung_serial_driver = {
	.probe		= s3c24xx_serial_probe,
	.remove		= s3c24xx_serial_remove,
	.id_table	= s3c24xx_serial_driver_ids,
	.driver		= {
		.name	= "samsung-uart",
		.pm	= SERIAL_SAMSUNG_PM_OPS,
		.of_match_table	= of_match_ptr(s3c24xx_uart_dt_match),
	},
};

module_platform_driver(samsung_serial_driver);

 

这里我们看一下不同的soc都绑定了自己的硬件特有的信息，比如fifo大小等。

#ifdef CONFIG_CPU_S3C2410
static struct s3c24xx_serial_drv_data s3c2410_serial_drv_data = {
	.info = &(struct s3c24xx_uart_info) {
		.name		= "Samsung S3C2410 UART",
		.type		= PORT_S3C2410,
		.fifosize	= 16,
		.rx_fifomask	= S3C2410_UFSTAT_RXMASK,
		.rx_fifoshift	= S3C2410_UFSTAT_RXSHIFT,
		.rx_fifofull	= S3C2410_UFSTAT_RXFULL,
		.tx_fifofull	= S3C2410_UFSTAT_TXFULL,
		.tx_fifomask	= S3C2410_UFSTAT_TXMASK,
		.tx_fifoshift	= S3C2410_UFSTAT_TXSHIFT,
		.def_clk_sel	= S3C2410_UCON_CLKSEL0,
		.num_clks	= 2,
		.clksel_mask	= S3C2410_UCON_CLKMASK,
		.clksel_shift	= S3C2410_UCON_CLKSHIFT,
	},
	.def_cfg = &(struct s3c2410_uartcfg) {
		.ucon		= S3C2410_UCON_DEFAULT,
		.ufcon		= S3C2410_UFCON_DEFAULT,
	},
};
#define S3C2410_SERIAL_DRV_DATA ((kernel_ulong_t)&s3c2410_serial_drv_data)
#else
#define S3C2410_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#endif

#ifdef CONFIG_CPU_S3C2412
static struct s3c24xx_serial_drv_data s3c2412_serial_drv_data = {
	.info = &(struct s3c24xx_uart_info) {
		.name		= "Samsung S3C2412 UART",
		.type		= PORT_S3C2412,
		.fifosize	= 64,
		.has_divslot	= 1,
		.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,
		.def_clk_sel	= S3C2410_UCON_CLKSEL2,
		.num_clks	= 4,
		.clksel_mask	= S3C2412_UCON_CLKMASK,
		.clksel_shift	= S3C2412_UCON_CLKSHIFT,
	},
	.def_cfg = &(struct s3c2410_uartcfg) {
		.ucon		= S3C2410_UCON_DEFAULT,
		.ufcon		= S3C2410_UFCON_DEFAULT,
	},
};
#define S3C2412_SERIAL_DRV_DATA ((kernel_ulong_t)&s3c2412_serial_drv_data)
#else
#define S3C2412_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#endif

#if defined(CONFIG_CPU_S3C2440) || defined(CONFIG_CPU_S3C2416) || \
	defined(CONFIG_CPU_S3C2443) || defined(CONFIG_CPU_S3C2442)
static struct s3c24xx_serial_drv_data s3c2440_serial_drv_data = {
	.info = &(struct s3c24xx_uart_info) {
		.name		= "Samsung S3C2440 UART",
		.type		= PORT_S3C2440,
		.fifosize	= 64,
		.has_divslot	= 1,
		.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,
		.def_clk_sel	= S3C2410_UCON_CLKSEL2,
		.num_clks	= 4,
		.clksel_mask	= S3C2412_UCON_CLKMASK,
		.clksel_shift	= S3C2412_UCON_CLKSHIFT,
	},
	.def_cfg = &(struct s3c2410_uartcfg) {
		.ucon		= S3C2410_UCON_DEFAULT,
		.ufcon		= S3C2410_UFCON_DEFAULT,
	},
};
#define S3C2440_SERIAL_DRV_DATA ((kernel_ulong_t)&s3c2440_serial_drv_data)
#else
#define S3C2440_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#endif

#if defined(CONFIG_CPU_S3C6400) || defined(CONFIG_CPU_S3C6410)
static struct s3c24xx_serial_drv_data s3c6400_serial_drv_data = {
	.info = &(struct s3c24xx_uart_info) {
		.name		= "Samsung S3C6400 UART",
		.type		= PORT_S3C6400,
		.fifosize	= 64,
		.has_divslot	= 1,
		.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,
		.def_clk_sel	= S3C2410_UCON_CLKSEL2,
		.num_clks	= 4,
		.clksel_mask	= S3C6400_UCON_CLKMASK,
		.clksel_shift	= S3C6400_UCON_CLKSHIFT,
	},
	.def_cfg = &(struct s3c2410_uartcfg) {
		.ucon		= S3C2410_UCON_DEFAULT,
		.ufcon		= S3C2410_UFCON_DEFAULT,
	},
};
#define S3C6400_SERIAL_DRV_DATA ((kernel_ulong_t)&s3c6400_serial_drv_data)
#else
#define S3C6400_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#endif

#ifdef CONFIG_CPU_S5PV210
static struct s3c24xx_serial_drv_data s5pv210_serial_drv_data = {
	.info = &(struct s3c24xx_uart_info) {
		.name		= "Samsung S5PV210 UART",
		.type		= PORT_S3C6400,
		.has_divslot	= 1,
		.rx_fifomask	= S5PV210_UFSTAT_RXMASK,
		.rx_fifoshift	= S5PV210_UFSTAT_RXSHIFT,
		.rx_fifofull	= S5PV210_UFSTAT_RXFULL,
		.tx_fifofull	= S5PV210_UFSTAT_TXFULL,
		.tx_fifomask	= S5PV210_UFSTAT_TXMASK,
		.tx_fifoshift	= S5PV210_UFSTAT_TXSHIFT,
		.def_clk_sel	= S3C2410_UCON_CLKSEL0,
		.num_clks	= 2,
		.clksel_mask	= S5PV210_UCON_CLKMASK,
		.clksel_shift	= S5PV210_UCON_CLKSHIFT,
	},
	.def_cfg = &(struct s3c2410_uartcfg) {
		.ucon		= S5PV210_UCON_DEFAULT,
		.ufcon		= S5PV210_UFCON_DEFAULT,
	},
	.fifosize = { 256, 64, 16, 16 },
};
#define S5PV210_SERIAL_DRV_DATA ((kernel_ulong_t)&s5pv210_serial_drv_data)
#else
#define S5PV210_SERIAL_DRV_DATA	(kernel_ulong_t)NULL
#endif

#if defined(CONFIG_ARCH_EXYNOS)
#define EXYNOS_COMMON_SERIAL_DRV_DATA				\
	.info = &(struct s3c24xx_uart_info) {			\
		.name		= "Samsung Exynos UART",	\
		.type		= PORT_S3C6400,			\
		.has_divslot	= 1,				\
		.rx_fifomask	= S5PV210_UFSTAT_RXMASK,	\
		.rx_fifoshift	= S5PV210_UFSTAT_RXSHIFT,	\
		.rx_fifofull	= S5PV210_UFSTAT_RXFULL,	\
		.tx_fifofull	= S5PV210_UFSTAT_TXFULL,	\
		.tx_fifomask	= S5PV210_UFSTAT_TXMASK,	\
		.tx_fifoshift	= S5PV210_UFSTAT_TXSHIFT,	\
		.def_clk_sel	= S3C2410_UCON_CLKSEL0,		\
		.num_clks	= 1,				\
		.clksel_mask	= 0,				\
		.clksel_shift	= 0,				\
	},							\
	.def_cfg = &(struct s3c2410_uartcfg) {			\
		.ucon		= S5PV210_UCON_DEFAULT,		\
		.ufcon		= S5PV210_UFCON_DEFAULT,	\
		.has_fracval	= 1,				\
	}							\

static struct s3c24xx_serial_drv_data exynos4210_serial_drv_data = {
	EXYNOS_COMMON_SERIAL_DRV_DATA,
	.fifosize = { 256, 64, 16, 16 },
};

static struct s3c24xx_serial_drv_data exynos5433_serial_drv_data = {
	EXYNOS_COMMON_SERIAL_DRV_DATA,
	.fifosize = { 64, 256, 16, 256 },
};

#define EXYNOS4210_SERIAL_DRV_DATA ((kernel_ulong_t)&exynos4210_serial_drv_data)
#define EXYNOS5433_SERIAL_DRV_DATA ((kernel_ulong_t)&exynos5433_serial_drv_data)
#else
#define EXYNOS4210_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#define EXYNOS5433_SERIAL_DRV_DATA (kernel_ulong_t)NULL
#endif

 

这里我们分析的4.19内核，设备树也是必须看的。

		uart0: serial@e2900000 {
			compatible = "samsung,s5pv210-uart";
			reg = <0xe2900000 0x400>;
			interrupt-parent = <&vic1>;
			interrupts = <10>;
			clock-names = "uart", "clk_uart_baud0",
					"clk_uart_baud1";
			clocks = <&clocks CLK_UART0>, <&clocks CLK_UART0>,
					<&clocks SCLK_UART0>;
			status = "disabled";
		};

		uart1: serial@e2900400 {
			compatible = "samsung,s5pv210-uart";
			reg = <0xe2900400 0x400>;
			interrupt-parent = <&vic1>;
			interrupts = <11>;
			clock-names = "uart", "clk_uart_baud0",
					"clk_uart_baud1";
			clocks = <&clocks CLK_UART1>, <&clocks CLK_UART1>,
					<&clocks SCLK_UART1>;
			status = "disabled";
		};

		uart2: serial@e2900800 {
			compatible = "samsung,s5pv210-uart";
			reg = <0xe2900800 0x400>;
			interrupt-parent = <&vic1>;
			interrupts = <12>;
			clock-names = "uart", "clk_uart_baud0",
					"clk_uart_baud1";
			clocks = <&clocks CLK_UART2>, <&clocks CLK_UART2>,
					<&clocks SCLK_UART2>;
			status = "disabled";
		};

		uart3: serial@e2900c00 {
			compatible = "samsung,s5pv210-uart";
			reg = <0xe2900c00 0x400>;
			interrupt-parent = <&vic1>;
			interrupts = <13>;
			clock-names = "uart", "clk_uart_baud0",
					"clk_uart_baud1";
			clocks = <&clocks CLK_UART3>, <&clocks CLK_UART3>,
					<&clocks SCLK_UART3>;
			status = "disabled";
		};

 

接下来这里就直接看probe

static int s3c24xx_serial_probe(struct platform_device *pdev)
{
	struct device_node *np = pdev->dev.of_node;
	struct s3c24xx_uart_port *ourport;
	int index = probe_index;
	int ret;

	if (np) {
		ret = of_alias_get_id(np, "serial");
		if (ret >= 0)
			index = ret;
	}

	dbg("s3c24xx_serial_probe(%p) %d\n", pdev, index);

	if (index >= ARRAY_SIZE(s3c24xx_serial_ports)) {
		dev_err(&pdev->dev, "serial%d out of range\n", index);
		return -EINVAL;
	}
	ourport = &s3c24xx_serial_ports[index];

	ourport->drv_data = s3c24xx_get_driver_data(pdev);
	if (!ourport->drv_data) {
		dev_err(&pdev->dev, "could not find driver data\n");
		return -ENODEV;
	}

	ourport->baudclk = ERR_PTR(-EINVAL);
	ourport->info = ourport->drv_data->info;
	ourport->cfg = (dev_get_platdata(&pdev->dev)) ?
			dev_get_platdata(&pdev->dev) :
			ourport->drv_data->def_cfg;

	if (np)
		of_property_read_u32(np,
			"samsung,uart-fifosize", &ourport->port.fifosize);

	if (ourport->drv_data->fifosize[index])
		ourport->port.fifosize = ourport->drv_data->fifosize[index];
	else if (ourport->info->fifosize)
		ourport->port.fifosize = ourport->info->fifosize;

	/*
	 * DMA transfers must be aligned at least to cache line size,
	 * so find minimal transfer size suitable for DMA mode
	 */
	ourport->min_dma_size = max_t(int, ourport->port.fifosize,
				    dma_get_cache_alignment());

	dbg("%s: initialising port %p...\n", __func__, ourport);

	ret = s3c24xx_serial_init_port(ourport, pdev);
	if (ret < 0)
		return ret;

	if (!s3c24xx_uart_drv.state) {
		ret = uart_register_driver(&s3c24xx_uart_drv);
		if (ret < 0) {
			pr_err("Failed to register Samsung UART driver\n");
			return ret;
		}
	}

	dbg("%s: adding port\n", __func__);
	uart_add_one_port(&s3c24xx_uart_drv, &ourport->port);
	platform_set_drvdata(pdev, &ourport->port);

	/*
	 * Deactivate the clock enabled in s3c24xx_serial_init_port here,
	 * so that a potential re-enablement through the pm-callback overlaps
	 * and keeps the clock enabled in this case.
	 */
	clk_disable_unprepare(ourport->clk);

	ret = s3c24xx_serial_cpufreq_register(ourport);
	if (ret < 0)
		dev_err(&pdev->dev, "failed to add cpufreq notifier\n");

	probe_index++;

	return 0;
}

上面函数我们主要看四点。

 

1.序号，设备树有定义别名，优先使用设备树里面的，如何没有，则按注册时序编号。

static int s3c24xx_serial_probe(struct platform_device *pdev)
{
	int index = probe_index;
	int ret;

	if (np) {
		ret = of_alias_get_id(np, "serial");
		if (ret >= 0)
			index = ret;
	}

        .....

	probe_index++;

	return 0;
}

设备树定义别名我们之前有过，三星默认是没定义的，定义的话也很简单serial0 = &uart0; serial1 = &uart1;  ......

	aliases {
		csis0 = &csis0;
		fimc0 = &fimc0;
		fimc1 = &fimc1;
		fimc2 = &fimc2;
		i2c0 = &i2c0;
		i2c1 = &i2c1;
		i2c2 = &i2c2;
		i2s0 = &i2s0;
		i2s1 = &i2s1;
		i2s2 = &i2s2;
		pinctrl0 = &pinctrl0;
		spi0 = &spi0;
		spi1 = &spi1;
	};

 

2.接下来就是去除设端口，根据设备获取对应的特有数据，初始化一些参数，进而进行硬件的初始化，中断申请，寄存器映射等。

	ourport = &s3c24xx_serial_ports[index];

	ourport->drv_data = s3c24xx_get_driver_data(pdev);
	if (!ourport->drv_data) {
		dev_err(&pdev->dev, "could not find driver data\n");
		return -ENODEV;
	}

	ourport->baudclk = ERR_PTR(-EINVAL);
	ourport->info = ourport->drv_data->info;
	ourport->cfg = (dev_get_platdata(&pdev->dev)) ?
			dev_get_platdata(&pdev->dev) :
			ourport->drv_data->def_cfg;

	if (np)
		of_property_read_u32(np,
			"samsung,uart-fifosize", &ourport->port.fifosize);

	if (ourport->drv_data->fifosize[index])
		ourport->port.fifosize = ourport->drv_data->fifosize[index];
	else if (ourport->info->fifosize)
		ourport->port.fifosize = ourport->info->fifosize;

	/*
	 * DMA transfers must be aligned at least to cache line size,
	 * so find minimal transfer size suitable for DMA mode
	 */
	ourport->min_dma_size = max_t(int, ourport->port.fifosize,
				    dma_get_cache_alignment());

	dbg("%s: initialising port %p...\n", __func__, ourport);

	ret = s3c24xx_serial_init_port(ourport, pdev);
	if (ret < 0)
		return ret;

	if (!s3c24xx_uart_drv.state) {
		ret = uart_register_driver(&s3c24xx_uart_drv);
		if (ret < 0) {
			pr_err("Failed to register Samsung UART driver\n");
			return ret;
		}
	}

 

当然这里我们就看一下资源串口初始化和资源申请，寄存器映射，当然中断这里申请了，在别的地方初始化的。

/* s3c24xx_serial_init_port
 *
 * initialise a single serial port from the platform device given
 */

static int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,
				    struct platform_device *platdev)
{
	struct uart_port *port = &ourport->port;
	struct s3c2410_uartcfg *cfg = ourport->cfg;
	struct resource *res;
	int ret;

	dbg("s3c24xx_serial_init_port: port=%p, platdev=%p\n", port, platdev);

	if (platdev == NULL)
		return -ENODEV;

	if (port->mapbase != 0)
		return -EINVAL;

	/* setup info for port */
	port->dev	= &platdev->dev;

	/* Startup sequence is different for s3c64xx and higher SoC's */
	if (s3c24xx_serial_has_interrupt_mask(port))
		s3c24xx_serial_ops.startup = s3c64xx_serial_startup;

	port->uartclk = 1;

	if (cfg->uart_flags & UPF_CONS_FLOW) {
		dbg("s3c24xx_serial_init_port: enabling flow control\n");
		port->flags |= UPF_CONS_FLOW;
	}

	/* sort our the physical and virtual addresses for each UART */

	res = platform_get_resource(platdev, IORESOURCE_MEM, 0);
	if (res == NULL) {
		dev_err(port->dev, "failed to find memory resource for uart\n");
		return -EINVAL;
	}

	dbg("resource %pR)\n", res);

	port->membase = devm_ioremap(port->dev, res->start, resource_size(res));
	if (!port->membase) {
		dev_err(port->dev, "failed to remap controller address\n");
		return -EBUSY;
	}

	port->mapbase = res->start;
	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;
	/*
	 * DMA is currently supported only on DT platforms, if DMA properties
	 * are specified.
	 */
	if (platdev->dev.of_node && of_find_property(platdev->dev.of_node,
						     "dmas", NULL)) {
		ourport->dma = devm_kzalloc(port->dev,
					    sizeof(*ourport->dma),
					    GFP_KERNEL);
		if (!ourport->dma) {
			ret = -ENOMEM;
			goto err;
		}
	}

	ourport->clk	= clk_get(&platdev->dev, "uart");
	if (IS_ERR(ourport->clk)) {
		pr_err("%s: Controller clock not found\n",
				dev_name(&platdev->dev));
		ret = PTR_ERR(ourport->clk);
		goto err;
	}

	ret = clk_prepare_enable(ourport->clk);
	if (ret) {
		pr_err("uart: clock failed to prepare+enable: %d\n", ret);
		clk_put(ourport->clk);
		goto err;
	}

	/* Keep all interrupts masked and cleared */
	if (s3c24xx_serial_has_interrupt_mask(port)) {
		wr_regl(port, S3C64XX_UINTM, 0xf);
		wr_regl(port, S3C64XX_UINTP, 0xf);
		wr_regl(port, S3C64XX_UINTSP, 0xf);
	}

	dbg("port: map=%pa, mem=%p, irq=%d (%d,%d), clock=%u\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;

err:
	port->mapbase = 0;
	return ret;
}

 

这里我们看一下串口的中断申请在那个函数里。

static struct uart_ops s3c24xx_serial_ops = {
	.pm		= s3c24xx_serial_pm,
	.tx_empty	= s3c24xx_serial_tx_empty,
	.get_mctrl	= s3c24xx_serial_get_mctrl,
	.set_mctrl	= s3c24xx_serial_set_mctrl,
	.stop_tx	= s3c24xx_serial_stop_tx,
	.start_tx	= s3c24xx_serial_start_tx,
	.stop_rx	= s3c24xx_serial_stop_rx,
	.break_ctl	= s3c24xx_serial_break_ctl,
	.startup	= s3c24xx_serial_startup,
	.shutdown	= s3c24xx_serial_shutdown,
	.set_termios	= s3c24xx_serial_set_termios,
	.type		= s3c24xx_serial_type,
	.release_port	= s3c24xx_serial_release_port,
	.request_port	= s3c24xx_serial_request_port,
	.config_port	= s3c24xx_serial_config_port,
	.verify_port	= s3c24xx_serial_verify_port,
#if defined(CONFIG_SERIAL_SAMSUNG_CONSOLE) && defined(CONFIG_CONSOLE_POLL)
	.poll_get_char = s3c24xx_serial_get_poll_char,
	.poll_put_char = s3c24xx_serial_put_poll_char,
#endif
};



static int s3c24xx_serial_startup(struct uart_port *port)
{
	struct s3c24xx_uart_port *ourport = to_ourport(port);
	int ret;

	dbg("s3c24xx_serial_startup: port=%p (%08llx,%p)\n",
	    port, (unsigned long long)port->mapbase, port->membase);

	rx_enabled(port) = 1;

	ret = request_irq(ourport->rx_irq, s3c24xx_serial_rx_chars, 0,
			  s3c24xx_serial_portname(port), ourport);

	if (ret != 0) {
		dev_err(port->dev, "cannot get irq %d\n", ourport->rx_irq);
		return ret;
	}

	ourport->rx_claimed = 1;

	dbg("requesting tx irq...\n");

	tx_enabled(port) = 1;

	ret = request_irq(ourport->tx_irq, s3c24xx_serial_tx_chars, 0,
			  s3c24xx_serial_portname(port), ourport);

	if (ret) {
		dev_err(port->dev, "cannot get irq %d\n", ourport->tx_irq);
		goto err;
	}

	ourport->tx_claimed = 1;

	dbg("s3c24xx_serial_startup ok\n");

	/* the port reset code should have done the correct
	 * register setup for the port controls */

	return ret;

err:
	s3c24xx_serial_shutdown(port);
	return ret;
}

上面我们已经看到了发生和中断接收函数了，具体的细节就不再描述。

 

三、串口驱动的注册

	if (!s3c24xx_uart_drv.state) {
		ret = uart_register_driver(&s3c24xx_uart_drv);
		if (ret < 0) {
			pr_err("Failed to register Samsung UART driver\n");
			return ret;
		}
	}

串口在linux系统中属于tty设备，tty设备是从古老的纸带打印机流传下来的。当时的输入，输出都是依靠纸带来传输。

后面有了串口之后，输入输出就都通过串口来传输。当然后面又有了新的显示器，键盘之类作为新的输入输出设备。

/**
 *	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 = kcalloc(drv->nr, sizeof(struct uart_state), 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);

	/*
	 * 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;
	}

	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;
}

这个函数是通过serial_core来内核帮我们定义好的，可以看到，主要做三件事，申请tty设备，初始化tty设备，注册tty设备。

这里不详细说了，后面驱动高级专题中，会和usb，tty，tcp/ip之类再详细开专题分析。

 

四、串口增加端口，其实就是注册console驱动。

	dbg("%s: adding port\n", __func__);
	uart_add_one_port(&s3c24xx_uart_drv, &ourport->port);
	platform_set_drvdata(pdev, &ourport->port);

 

/**
 *	uart_add_one_port - attach a driver-defined port structure
 *	@drv: pointer to the uart low level driver structure for this port
 *	@uport: uart port structure to use for this port.
 *
 *	This allows the driver to register its own uart_port structure
 *	with the core driver.  The main purpose is to allow the low
 *	level uart drivers to expand uart_port, rather than having yet
 *	more levels of structures.
 */
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;
	int num_groups;

	BUG_ON(in_interrupt());

	if (uport->line >= drv->nr)
		return -EINVAL;

	state = drv->state + uport->line;
	port = &state->port;

	mutex_lock(&port_mutex);
	mutex_lock(&port->mutex);
	if (state->uart_port) {
		ret = -EINVAL;
		goto out;
	}

	/* Link the port to the driver state table and vice versa */
	atomic_set(&state->refcount, 1);
	init_waitqueue_head(&state->remove_wait);
	state->uart_port = uport;
	uport->state = state;

	state->pm_state = UART_PM_STATE_UNDEFINED;
	uport->cons = drv->cons;
	uport->minor = drv->tty_driver->minor_start + uport->line;
	uport->name = kasprintf(GFP_KERNEL, "%s%d", drv->dev_name,
				drv->tty_driver->name_base + uport->line);
	if (!uport->name) {
		ret = -ENOMEM;
		goto out;
	}

	/*
	 * If this port is a console, then the spinlock is already
	 * initialised.
	 */
	if (!(uart_console(uport) && (uport->cons->flags & CON_ENABLED))) {
		spin_lock_init(&uport->lock);
		lockdep_set_class(&uport->lock, &port_lock_key);
	}
	if (uport->cons && uport->dev)
		of_console_check(uport->dev->of_node, uport->cons->name, uport->line);

	uart_configure_port(drv, state, uport);

	port->console = uart_console(uport);

	num_groups = 2;
	if (uport->attr_group)
		num_groups++;

	uport->tty_groups = kcalloc(num_groups, sizeof(*uport->tty_groups),
				    GFP_KERNEL);
	if (!uport->tty_groups) {
		ret = -ENOMEM;
		goto out;
	}
	uport->tty_groups[0] = &tty_dev_attr_group;
	if (uport->attr_group)
		uport->tty_groups[1] = uport->attr_group;

	/*
	 * Register the port whether it's detected or not.  This allows
	 * setserial to be used to alter this port's parameters.
	 */
	tty_dev = tty_port_register_device_attr_serdev(port, drv->tty_driver,
			uport->line, uport->dev, port, uport->tty_groups);
	if (likely(!IS_ERR(tty_dev))) {
		device_set_wakeup_capable(tty_dev, 1);
	} else {
		dev_err(uport->dev, "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;
}

上面就是注册端口了，这里要注意，端口是在uart_register_driver申请和创建的，地址在status里面。

接下来就是调用这个串口配置这个端口了

	uart_configure_port(drv, state, uport);

 

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

	/*
	 * If there isn't a port here, don't do anything further.
	 */
	if (!port->iobase && !port->mapbase && !port->membase)
		return;

	/*
	 * Now do the auto configuration stuff.  Note that config_port
	 * is expected to claim the resources and map the port for us.
	 */
	flags = 0;
	if (port->flags & UPF_AUTO_IRQ)
		flags |= UART_CONFIG_IRQ;
	if (port->flags & UPF_BOOT_AUTOCONF) {
		if (!(port->flags & UPF_FIXED_TYPE)) {
			port->type = PORT_UNKNOWN;
			flags |= UART_CONFIG_TYPE;
		}
		port->ops->config_port(port, flags);
	}

	if (port->type != PORT_UNKNOWN) {
		unsigned long flags;

		uart_report_port(drv, port);

		/* Power up port for set_mctrl() */
		uart_change_pm(state, UART_PM_STATE_ON);

		/*
		 * Ensure that the modem control lines are de-activated.
		 * keep the DTR setting that is set in uart_set_options()
		 * We probably don't need a spinlock around this, but
		 */
		spin_lock_irqsave(&port->lock, flags);
		port->ops->set_mctrl(port, port->mctrl & TIOCM_DTR);
		spin_unlock_irqrestore(&port->lock, flags);

		/*
		 * If this driver supports console, and it hasn't been
		 * successfully registered yet, try to re-register it.
		 * It may be that the port was not available.
		 */
		if (port->cons && !(port->cons->flags & CON_ENABLED))
			register_console(port->cons);

		/*
		 * Power down all ports by default, except the
		 * console if we have one.
		 */
		if (!uart_console(port))
			uart_change_pm(state, UART_PM_STATE_OFF);
	}
}

配置端口主要还是注册console

register_console(port->cons);

上面我们注意下面这个函数，会打印一些调试信息

uart_report_port(drv, port);

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

	switch (port->iotype) {
	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_MEM16:
	case UPIO_MEM32:
	case UPIO_MEM32BE:
	case UPIO_AU:
	case UPIO_TSI:
		snprintf(address, sizeof(address),
			 "MMIO 0x%llx", (unsigned long long)port->mapbase);
		break;
	default:
		strlcpy(address, "*unknown*", sizeof(address));
		break;
	}

	pr_info("%s%s%s at %s (irq = %d, base_baud = %d) is a %s\n",
	       port->dev ? dev_name(port->dev) : "",
	       port->dev ? ": " : "",
	       port->name,
	       address, port->irq, port->uartclk / 16, uart_type(port));
}

具体的如下，可以对比着看

 

/*
 * The console driver calls this routine during kernel initialization
 * to register the console printing procedure with printk() and to
 * print any messages that were printed by the kernel before the
 * console driver was initialized.
 *
 * This can happen pretty early during the boot process (because of
 * early_printk) - sometimes before setup_arch() completes - be careful
 * of what kernel features are used - they may not be initialised yet.
 *
 * There are two types of consoles - bootconsoles (early_printk) and
 * "real" consoles (everything which is not a bootconsole) which are
 * handled differently.
 *  - Any number of bootconsoles can be registered at any time.
 *  - As soon as a "real" console is registered, all bootconsoles
 *    will be unregistered automatically.
 *  - Once a "real" console is registered, any attempt to register a
 *    bootconsoles will be rejected
 */
void register_console(struct console *newcon)
{
	int i;
	unsigned long flags;
	struct console *bcon = NULL;
	struct console_cmdline *c;
	static bool has_preferred;

	if (console_drivers)
		for_each_console(bcon)
			if (WARN(bcon == newcon,
					"console '%s%d' already registered\n",
					bcon->name, bcon->index))
				return;

	/*
	 * before we register a new CON_BOOT console, make sure we don't
	 * already have a valid console
	 */
	if (console_drivers && newcon->flags & CON_BOOT) {
		/* find the last or real console */
		for_each_console(bcon) {
			if (!(bcon->flags & CON_BOOT)) {
				pr_info("Too late to register bootconsole %s%d\n",
					newcon->name, newcon->index);
				return;
			}
		}
	}

	if (console_drivers && console_drivers->flags & CON_BOOT)
		bcon = console_drivers;

	if (!has_preferred || bcon || !console_drivers)
		has_preferred = preferred_console >= 0;

	/*
	 *	See if we want to use this console driver. If we
	 *	didn't select a console we take the first one
	 *	that registers here.
	 */
	if (!has_preferred) {
		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;
				has_preferred = true;
			}
		}
	}

	/*
	 *	See if this console matches one we selected on
	 *	the command line.
	 */
	for (i = 0, c = console_cmdline;
	     i < MAX_CMDLINECONSOLES && c->name[0];
	     i++, c++) {
		if (!newcon->match ||
		    newcon->match(newcon, c->name, c->index, c->options) != 0) {
			/* default matching */
			BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
			if (strcmp(c->name, newcon->name) != 0)
				continue;
			if (newcon->index >= 0 &&
			    newcon->index != c->index)
				continue;
			if (newcon->index < 0)
				newcon->index = c->index;

			if (_braille_register_console(newcon, c))
				return;

			if (newcon->setup &&
			    newcon->setup(newcon, c->options) != 0)
				break;
		}

		newcon->flags |= CON_ENABLED;
		if (i == preferred_console) {
			newcon->flags |= CON_CONSDEV;
			has_preferred = true;
		}
		break;
	}

	if (!(newcon->flags & CON_ENABLED))
		return;

	/*
	 * If we have a bootconsole, and are switching to a real console,
	 * don't print everything out again, since when the boot console, and
	 * the real console are the same physical device, it's annoying to
	 * see the beginning boot messages twice
	 */
	if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
		newcon->flags &= ~CON_PRINTBUFFER;

	/*
	 *	Put this console in the list - keep the
	 *	preferred driver at the head of the list.
	 */
	console_lock();
	if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
		newcon->next = console_drivers;
		console_drivers = newcon;
		if (newcon->next)
			newcon->next->flags &= ~CON_CONSDEV;
	} else {
		newcon->next = console_drivers->next;
		console_drivers->next = newcon;
	}

	if (newcon->flags & CON_EXTENDED)
		if (!nr_ext_console_drivers++)
			pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");

	if (newcon->flags & CON_PRINTBUFFER) {
		/*
		 * console_unlock(); will print out the buffered messages
		 * for us.
		 */
		logbuf_lock_irqsave(flags);
		console_seq = syslog_seq;
		console_idx = syslog_idx;
		logbuf_unlock_irqrestore(flags);
		/*
		 * We're about to replay the log buffer.  Only do this to the
		 * just-registered console to avoid excessive message spam to
		 * the already-registered consoles.
		 */
		exclusive_console = newcon;
	}
	console_unlock();
	console_sysfs_notify();

	/*
	 * By unregistering the bootconsoles after we enable the real console
	 * we get the "console xxx enabled" message on all the consoles -
	 * boot consoles, real consoles, etc - this is to ensure that end
	 * users know there might be something in the kernel's log buffer that
	 * went to the bootconsole (that they do not see on the real console)
	 */
	pr_info("%sconsole [%s%d] enabled\n",
		(newcon->flags & CON_BOOT) ? "boot" : "" ,
		newcon->name, newcon->index);
	if (bcon &&
	    ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
	    !keep_bootcon) {
		/* We need to iterate through all boot consoles, to make
		 * sure we print everything out, before we unregister them.
		 */
		for_each_console(bcon)
			if (bcon->flags & CON_BOOT)
				unregister_console(bcon);
	}
}

注册console，其实就是把console使用链表方式next连接起来。

 

 

这就回到我们上一节的了，把注册的这个console和上节，uboot通过cmdline传过来的那些console和串口注册的做比较，如果名字和index都相同的话，则把这个串口表示使能CON_ENABLED，后面使用printk或printf的时候，就会调用使能的console打印信息。

#define MAX_CMDLINECONSOLES 8

static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];

 

这里我们看一下细节，

在串口配置之前是要执行上面这个函数的，因为我们就是设备树传参的

	if (uport->cons && uport->dev)
		of_console_check(uport->dev->of_node, uport->cons->name, uport->line);

	uart_configure_port(drv, state, uport);

 

/**
 * of_console_check() - Test and setup console for DT setup
 * @dn - Pointer to device node
 * @name - Name to use for preferred console without index. ex. "ttyS"
 * @index - Index to use for preferred console.
 *
 * Check if the given device node matches the stdout-path property in the
 * /chosen node. If it does then register it as the preferred console and return
 * TRUE. Otherwise return FALSE.
 */
bool of_console_check(struct device_node *dn, char *name, int index)
{
	if (!dn || dn != of_stdout || console_set_on_cmdline)
		return false;

	/*
	 * XXX: cast `options' to char pointer to suppress complication
	 * warnings: printk, UART and console drivers expect char pointer.
	 */
	return !add_preferred_console(name, index, (char *)of_stdout_options);
}




/**
 * add_preferred_console - add a device to the list of preferred consoles.
 * @name: device name
 * @idx: device index
 * @options: options for this console
 *
 * The last preferred console added will be used for kernel messages
 * and stdin/out/err for init.  Normally this is used by console_setup
 * above to handle user-supplied console arguments; however it can also
 * be used by arch-specific code either to override the user or more
 * commonly to provide a default console (ie from PROM variables) when
 * the user has not supplied one.
 */
int add_preferred_console(char *name, int idx, char *options)
{
	return __add_preferred_console(name, idx, options, NULL);
}

static int preferred_console = -1;

static int __add_preferred_console(char *name, int idx, char *options,
				   char *brl_options)
{
	struct console_cmdline *c;
	int i;

	/*
	 *	See if this tty is not yet registered, and
	 *	if we have a slot free.
	 */
	for (i = 0, c = console_cmdline;
	     i < MAX_CMDLINECONSOLES && c->name[0];
	     i++, c++) {
		if (strcmp(c->name, name) == 0 && c->index == idx) {
			if (!brl_options)
				preferred_console = i;
			return 0;
		}
	}
	if (i == MAX_CMDLINECONSOLES)
		return -E2BIG;
	if (!brl_options)
		preferred_console = i;
	strlcpy(c->name, name, sizeof(c->name));
	c->options = options;
	braille_set_options(c, brl_options);

	c->index = idx;
	return 0;
}

 

可以看到这里是要判断的，只有名字以及port->line和console_cmdline[x].index匹配上，preferred_console 不为-1，而是和console_cmdline匹配上的下标值

比如我们uboot传的值是"console = ttySAC2"，所以ttySAC0匹配不成功，ttySAC2才能成功。

 

这里我们主要分析下面这个

void register_console(struct console *newcon)
{


    ......
    


	if (!has_preferred || bcon || !console_drivers)
		has_preferred = preferred_console >= 0;

	/*
	 *	See if we want to use this console driver. If we
	 *	didn't select a console we take the first one
	 *	that registers here. 
	 */
	if (!has_preferred) {
		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;
				has_preferred = true;
			}
		}
	}

	/*
	 *	See if this console matches one we selected on
	 *	the command line.
	 */
	for (i = 0, c = console_cmdline;
	     i < MAX_CMDLINECONSOLES && c->name[0];
	     i++, c++) {
		if (!newcon->match ||
		    newcon->match(newcon, c->name, c->index, c->options) != 0) {
			/* default matching */
			BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
			if (strcmp(c->name, newcon->name) != 0)
				continue;
			if (newcon->index >= 0 &&
			    newcon->index != c->index)
				continue;
			if (newcon->index < 0)
				newcon->index = c->index;

			if (_braille_register_console(newcon, c))
				return;

			if (newcon->setup &&
			    newcon->setup(newcon, c->options) != 0)
				break;
		}

		newcon->flags |= CON_ENABLED;
		if (i == preferred_console) {
			newcon->flags |= CON_CONSDEV;
			has_preferred = true;
		}
		break;
	}

    ......

}

 

上面这个有三种情况，ttySAC0或1，ttySAC2，ttySAC3

 

第一种

从上向下走，

	if (!has_preferred || bcon || !console_drivers)
		has_preferred = preferred_console >= 0;

has_preferred 为 0

 

接下来执行下面这个，index会为0

	 */
	if (!has_preferred) {
		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;
				has_preferred = true;
			}
		}
	}

 

接下来执行下面这个，因为index为0，所以

	/*
	 *	See if this console matches one we selected on
	 *	the command line.
	 */
	for (i = 0, c = console_cmdline;
	     i < MAX_CMDLINECONSOLES && c->name[0];
	     i++, c++) {
		if (!newcon->match ||
		    newcon->match(newcon, c->name, c->index, c->options) != 0) {
			/* default matching */
			BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
			if (strcmp(c->name, newcon->name) != 0)
				continue;
			if (newcon->index >= 0 &&
			    newcon->index != c->index)
				continue;        //在这里重新遍历下一个,而因为没有下一个c-name[0]为空而跳出
			if (newcon->index < 0)
				newcon->index = c->index;

			if (_braille_register_console(newcon, c))
				return;

			if (newcon->setup &&
			    newcon->setup(newcon, c->options) != 0)
				break;
		}

		newcon->flags |= CON_ENABLED;
		if (i == preferred_console) {
			newcon->flags |= CON_CONSDEV;
			has_preferred = true;
		}
		break;
	}

最后因为没使能而跳出整个函数

	if (!(newcon->flags & CON_ENABLED))
		return;

 

第二种

对于tyySAC2，

从上向下走，因为preferred_console 不为 -1

	if (!has_preferred || bcon || !console_drivers)
		has_preferred = preferred_console >= 0;

所以has_preferred 为 1

 

接下来不会执行这个

	 */
	if (!has_preferred) {
		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;
				has_preferred = true;
			}
		}
	}

 

	/*
	 *	See if this console matches one we selected on
	 *	the command line.
	 */
	for (i = 0, c = console_cmdline;
	     i < MAX_CMDLINECONSOLES && c->name[0];
	     i++, c++) {
		if (!newcon->match ||
		    newcon->match(newcon, c->name, c->index, c->options) != 0) {
			/* default matching */
			BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
			if (strcmp(c->name, newcon->name) != 0)
				continue;
			if (newcon->index >= 0 &&
			    newcon->index != c->index)
				continue;
			if (newcon->index < 0)        //-1小于0,所以newcon->index = c->index  = 2
				newcon->index = c->index;

			if (_braille_register_console(newcon, c))
				return;

			if (newcon->setup &&
			    newcon->setup(newcon, c->options) != 0)
				break;
		}

        /* 这里会执行 */
		newcon->flags |= CON_ENABLED;
		if (i == preferred_console) {
			newcon->flags |= CON_CONSDEV;    //这里也会执行
			has_preferred = true;
		}
		break;
	}

 

最后因为这个if进不去，也就不用退出

	if (!(newcon->flags & CON_ENABLED))
		return;

加入链表，进而打印enable信息

	if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
		newcon->next = console_drivers;
		console_drivers = newcon;
		if (newcon->next)
			newcon->next->flags &= ~CON_CONSDEV;
	} else {
		newcon->next = console_drivers->next;
		console_drivers->next = newcon;
	}

    
    ......


	pr_info("%sconsole [%s%d] enabled\n",
		(newcon->flags & CON_BOOT) ? "boot" : "" ,
		newcon->name, newcon->index);

 

对于第三种情况，我们回到配置

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

	/*
	 * If there isn't a port here, don't do anything further.
	 */
	if (!port->iobase && !port->mapbase && !port->membase)
		return;

	/*
	 * Now do the auto configuration stuff.  Note that config_port
	 * is expected to claim the resources and map the port for us.
	 */
	flags = 0;
	if (port->flags & UPF_AUTO_IRQ)
		flags |= UART_CONFIG_IRQ;
	if (port->flags & UPF_BOOT_AUTOCONF) {
		if (!(port->flags & UPF_FIXED_TYPE)) {
			port->type = PORT_UNKNOWN;
			flags |= UART_CONFIG_TYPE;
		}
		port->ops->config_port(port, flags);
	}

	if (port->type != PORT_UNKNOWN) {
		unsigned long flags;

		uart_report_port(drv, port);

		/* Power up port for set_mctrl() */
		uart_change_pm(state, UART_PM_STATE_ON);

		/*
		 * Ensure that the modem control lines are de-activated.
		 * keep the DTR setting that is set in uart_set_options()
		 * We probably don't need a spinlock around this, but
		 */
		spin_lock_irqsave(&port->lock, flags);
		port->ops->set_mctrl(port, port->mctrl & TIOCM_DTR);
		spin_unlock_irqrestore(&port->lock, flags);

		/*
		 * If this driver supports console, and it hasn't been
		 * successfully registered yet, try to re-register it.
		 * It may be that the port was not available.
		 */
		if (port->cons && !(port->cons->flags & CON_ENABLED))
			register_console(port->cons);

		/*
		 * Power down all ports by default, except the
		 * console if we have one.
		 */
		if (!uart_console(port))
			uart_change_pm(state, UART_PM_STATE_OFF);
	}
}

 

虽然我们有四个串口

#define __PORT_LOCK_UNLOCKED(i) \
	__SPIN_LOCK_UNLOCKED(s3c24xx_serial_ports[i].port.lock)
static struct s3c24xx_uart_port
s3c24xx_serial_ports[CONFIG_SERIAL_SAMSUNG_UARTS] = {
	[0] = {
		.port = {
			.lock		= __PORT_LOCK_UNLOCKED(0),
			.iotype		= UPIO_MEM,
			.uartclk	= 0,
			.fifosize	= 16,
			.ops		= &s3c24xx_serial_ops,
			.flags		= UPF_BOOT_AUTOCONF,
			.line		= 0,
		}
	},
	[1] = {
		.port = {
			.lock		= __PORT_LOCK_UNLOCKED(1),
			.iotype		= UPIO_MEM,
			.uartclk	= 0,
			.fifosize	= 16,
			.ops		= &s3c24xx_serial_ops,
			.flags		= UPF_BOOT_AUTOCONF,
			.line		= 1,
		}
	},
#if CONFIG_SERIAL_SAMSUNG_UARTS > 2

	[2] = {
		.port = {
			.lock		= __PORT_LOCK_UNLOCKED(2),
			.iotype		= UPIO_MEM,
			.uartclk	= 0,
			.fifosize	= 16,
			.ops		= &s3c24xx_serial_ops,
			.flags		= UPF_BOOT_AUTOCONF,
			.line		= 2,
		}
	},
#endif
#if CONFIG_SERIAL_SAMSUNG_UARTS > 3
	[3] = {
		.port = {
			.lock		= __PORT_LOCK_UNLOCKED(3),
			.iotype		= UPIO_MEM,
			.uartclk	= 0,
			.fifosize	= 16,
			.ops		= &s3c24xx_serial_ops,
			.flags		= UPF_BOOT_AUTOCONF,
			.line		= 3,
		}
	}
#endif
};
#undef __PORT_LOCK_UNLOCKED

但只能有一个串口做console

static struct console s3c24xx_serial_console = {
	.name		= S3C24XX_SERIAL_NAME,
	.device		= uart_console_device,
	.flags		= CON_PRINTBUFFER,
	.index		= -1,
	.write		= s3c24xx_serial_console_write,
	.setup		= s3c24xx_serial_console_setup,
	.data		= &s3c24xx_uart_drv,
};

也就是在串口注册成功后，flag已经为CON_ENABLED，所以下面这个if进不去，所以串口3也是注册不了console的

​
		/*
		 * If this driver supports console, and it hasn't been
		 * successfully registered yet, try to re-register it.
		 * It may be that the port was not available.
		 */
		if (port->cons && !(port->cons->flags & CON_ENABLED))
			register_console(port->cons);
​

 

最后要说明一下，经过搜索，发现目前只有三星对串口驱动的名字叫做ttySACx

 

而其他厂家的有很多叫ttyS

 

所以设备树中，cmdline传参也是用和驱动名字一样的ttySx