关于MACHINE_START

最新推荐文章于 2025-09-13 12:59:37 发布

转载最新推荐文章于 2025-09-13 12:59:37 发布 · 2.4k 阅读

文章标签：

#struct #timer #io #video #function #system

本文详细解析了ARM架构下特定硬件平台的启动配置过程，包括关键宏定义的使用及各函数调用时机，展示了如何通过这些配置实现系统的初始化。

MACHINE_START(VR1000, "Thorcom-VR1000")
/* Maintainer: Ben Dooks < ben@simtec.co.uk > */
.phys_ram = S3C2410_SDRAM_PA,
.phys_io = S3C2410_PA_UART,
.io_pg_offst = (((u32)S3C24XX_VA_UART) >> 18) & 0xfffc,
.boot_params = S3C2410_SDRAM_PA + 0x100,
.map_io = vr1000_map_io,
.init_irq = s3c24xx_init_irq,
.timer = &s3c24xx_timer,
MACHINE_END

这两个是宏定义原型为

#define MACHINE_START(_type,_name)  /
const struct machine_desc __mach_desc_##_type /
__attribute__((__section__(".arch.info.init"))) = { /
.nr  = MACH_TYPE_##_type, /
.name  = _name,

#define MACHINE_END /
};

struct machine_desc 的原型为：

struct machine_desc {
/*
* Note! The first five elements are used
* by assembler code in head-armv.S
*/
unsigned int  nr;  /* architecture number */
unsigned int  phys_ram; /* start of physical ram */
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);
};

MACH_TYPE_SMDK2410定义在arch/include/asm-arm/mach-types.h内，值为193.
/* arch/include/asm-arm/mach-types.h */
#define MACH_TYPE_SMDK2410 193
这个值是机器的类型值，编译时由arch/arm/tool/mach-types里面定义的数据生成的。
/* arch/arm/tool/mach-types */
smdk2410 ARCH_SMDK2410 SMDK2410 193

由上发现，MACHINE_START主要是定义了"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。

各个成员函数在不同时期被调用：
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。

2. init_irq在start_kernel() --> init_IRQ() --> init_arch_irq() 被调用
3. map_io 在 setup_arch() --> paging_init() --> devicemaps_init()被调用

其他主要都在 setup_arch() 中用到。