linux中MACHINE_START&END在9g10ek上实现

在linux的板卡初始化文件中有machine的相关定义

//arch/arm/mach-at91/board-sam9261ek.c

MACHINE_START(AT91SAM9G10EK, "Atmel AT91SAM9G10-EK")

/* Maintainer: Atmel */

.phys_io = AT91_BASE_SYS,

.io_pg_offst = (AT91_VA_BASE_SYS >> 18) & 0xfffc,

.boot_params = AT91_SDRAM_BASE + 0x100,

.timer = &at91sam926x_timer,

.map_io = ek_map_io,

.init_irq = ek_init_irq,

.init_machine = ek_board_init,

MACHINE_END

其中MACHINE_START和MACHINE_END为宏定义，定义于文件

//arch/arm/include/asm/arch.h

#ifndef __ASSEMBLY__

struct tag;

struct meminfo;

struct sys_timer;

struct machine_desc {

/*

* Note! The first four elements are used

* by assembler code in head.S, head-common.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 \

};

#endif

MACH_TYPE_ AT91SAM9G10EK是9G10ek开发板在linux中的机器号。

“Atmel AT91SAM9G10-EK”是开发板信息，在终端输入cat /proc/cpuinfo可以查看。

在内核文件中arch/arm/tools/mach-types定义目前内核支持的板卡、芯片等：

##machine_is_xxx CONFIG_xxxx MACH_TYPE_xxx number

at91sam9g10ek MACH_AT91sam9G10EK AT91SAM9G10EK 2159

MACHINE_START主要定义了“struct machine_desc”的类型，放在section（“.arch.info.init”），是初始化数据，kernel起来之后将被丢弃。

其余各个成员函数在setup_arch()中被赋值到内核结构体，在不同时期被调用：

1. .init_machine 在 arch/arm/kernel/setup.c 中被 customize_machine 调用，放在 arch_initcall() 段里面，会自动按顺序被调用。

arch_initcall(customize_machine);

customize_machine()[setup.c#692] -> init_machine();

2. .init_irq在start_kernel()(文件init/main.c)--> init_IRQ() (在文件arch/arm/kernel/Irq.c)--> init_arch_irq()中被调用

3. .map_io 在 start_kernel()(文件init/main.c)-->setup_arch(&command_line) (在文件arch/arm/kernel/setup.c)-->
paging_init()(在文件arch/arm/kernel/mm/Mmu.c)
--> devicemaps_init()(在文件arch/arm/kernel/mm/Mmu.c)中被调用

4. .timer是定义系统时钟，定义TIMER4为系统时钟，在arch/arm/plat-s3c/time.c中体现。在start_kernel() --> time_init()(在文件arch/arm/kernel/Time.c)-->system_time->init()中调用。

5. .boot_params是bootloader向内核传递的参数的位置，这要和bootloader中参数的定义要一致。

从它们在start_kernel()中被调用的顺序，可知它们执行的先后为：map_io; init_irq; timer->time_init; init_machine。

参考：

1. http://blog.sina.com.cn/s/blog_753fd0b00100t8js.html

2. http://blog.csdn.net/thl789/article/details/6699259