s3c2410 linux板级文件设备的初始化过程

/*linux板级设备的初始化过程

start_kernel() -> setup_arch(&command_line) -> mdesc = setup_machine(machine_arch_type) -> list = lookup_machine_type(nr) -> return struct machine_desc.

内核在启动的时候就是最先运行start_kernel() , 然后她就会调用体系结构相关的setup_arch(&command_line), 如arm体系结构的在arch/arm/kernel/setup.c中,

进一步, 她就要初始化板级相关的设备, 但在此之前, 她必须找到这块目标板的描述结构, 所以她就先通过lookup_machine_type(nr)来查找这个结构,

传入的参数是又uboot传过来的, 存储在r2中. 如假设她传入的是'SMDK2410' 的nr, lookup_machine_type(nr) 就会找到如下的machine_desc.

这个结构在一个专门描述sddk2410的文件中--arch/arm/mach-s3c2410/mach-smdk2410.c

*/

MACHINE_START(SMDK2410, "SMDK2410") /* @TODO: request a new identifier and switch

* to SMDK2410 */

/* Maintainer: Jonas Dietsche */

.phys_io = S3C2410_PA_UART,

.io_pg_offst = (((u32)S3C24XX_VA_UART) >> 18) & 0xfffc,

.boot_params = S3C2410_SDRAM_PA + 0x100,

//重要的板级初始化函数

.map_io = smdk2410_map_io,

.init_irq = s3c24xx_init_irq,

.init_machine = smdk2410_init,

.timer = &s3c24xx_timer,

MACHINE_END

/*

MACHINE_START的第一个参数是用来构造机器的类型的, 如这里的SMDK2410 ,

又下面的定义

.nr = MACH_TYPE_##_type

有 nr = MACH_TYPE_SMDK2410

而 MACH_TYPE_SMDK2410这些机器类型则在/include/asm-arm/mach-types.h中定义:

#define MACH_TYPE_SMDK2410 193

完整的结构描述如下:

*/

struct machine_desc {

/*

* Note! The first four elements are used

* by assembler code in head-armv.S

*/

unsigned int nr; /* architecture number */

unsigned int phys_io; /* start of physical io */

unsigned int io_pg_offst; /* byte offset for io

* page tabe entry */

const char *name; /* architecture name */

unsigned long boot_params; /* tagged list */

unsigned int video_start; /* start of video RAM */

unsigned int video_end; /* end of video RAM */

unsigned int reserve_lp0 :1; /* never has lp0 */

unsigned int reserve_lp1 :1; /* never has lp1 */

unsigned int reserve_lp2 :1; /* never has lp2 */

unsigned int soft_reboot :1; /* soft reboot */

void (*fixup)(struct machine_desc *,

struct tag *, char **,

struct meminfo *);

void (*map_io)(void);/* IO mapping function */

void (*init_irq)(void);

struct sys_timer *timer; /* system tick timer */

void (*init_machine)(void);

};

/*

* Set of macros to define architecture features. This is built into

* a table by the linker.

*/

#define MACHINE_START(_type,_name) \

static const struct machine_desc __mach_desc_##_type \

__used \

__attribute__((__section__(".arch.info.init"))) = { \

.nr = MACH_TYPE_##_type, \

.name = _name,

#define MACHINE_END \

};

/*

在arch/arm/mach-s3c2410/mach-smdk2410.c 定义了以下两个函数实现:

*/

static struct map_desc smdk2410_iodesc[] __initdata = {

/* nothing here yet */

};

static struct platform_device *smdk2410_devices[] __initdata = {

&s3c_device_usb,

&s3c_device_lcd,

&s3c_device_wdt,

&s3c_device_i2c,

&s3c_device_iis,

};

static void __init smdk2410_map_io(void)

{

//主要是做外围设备的物理地址到虚拟地址的映射

s3c24xx_init_io(smdk2410_iodesc, ARRAY_SIZE(smdk2410_iodesc));

//频率的初始化

s3c24xx_init_clocks(0);

//串口的初始化

s3c24xx_init_uarts(smdk2410_uartcfgs, ARRAY_SIZE(smdk2410_uartcfgs));

}

static void __init smdk2410_init(void)

{

//注册smdk2410特有的设备

platform_add_devices(smdk2410_devices, ARRAY_SIZE(smdk2410_devices));

//smdk系列的初始化, 我们知道smdk有2410, 2412, 2440等等, 所以这里她又抽象出了一些共有的相同的部分, 都使用下面的函数做初始化工作.

smdk_machine_init();

}

/* devices we initialise */

static struct platform_device __initdata *smdk_devs[] = {

&s3c_device_nand,

&smdk_led4,

&smdk_led5,

&smdk_led6,

&smdk_led7,

};

void __init smdk_machine_init(void)

{

/* Configure the LEDs (even if we have no LED support)*/

s3c2410_gpio_cfgpin(S3C2410_GPF4, S3C2410_GPF4_OUTP);

s3c2410_gpio_cfgpin(S3C2410_GPF5, S3C2410_GPF5_OUTP);

s3c2410_gpio_cfgpin(S3C2410_GPF6, S3C2410_GPF6_OUTP);

s3c2410_gpio_cfgpin(S3C2410_GPF7, S3C2410_GPF7_OUTP);

s3c2410_gpio_setpin(S3C2410_GPF4, 1);

s3c2410_gpio_setpin(S3C2410_GPF5, 1);

s3c2410_gpio_setpin(S3C2410_GPF6, 1);

s3c2410_gpio_setpin(S3C2410_GPF7, 1);

if (machine_is_smdk2443())

smdk_nand_info.twrph0 = 50;

//注意这一行, 注册了nand flash的分区信息

s3c_device_nand.dev.platform_data = &smdk_nand_info;

//再一次注册设备, 但这一次是smdk共有的. 如nand flash等等

platform_add_devices(smdk_devs, ARRAY_SIZE(smdk_devs));

//电源管理的初始化

s3c2410_pm_init();

}