uboot-spl启动流程 u-boot-2017.01+gitAUTOINC+9fd60700db-g9fd60700db

基于ti-processor-sdk-linux-am335x-evm-04.00.00.04的uboot启动流程备忘，重点是要修改下sdram_init(),使之与板上的内存相匹配

_start  arch/arm/lib/vectors.S
        b    reset
reset      arch\arm\cpu\armv7\start.S
          bl    _main

_main    arch\arm\lib\crt0.S
        bl    board_init_f
        bl spl_relocate_stack_gd
board_init_f        arch\arm\mach-omap2\am33xx\board.c
        sdram_init();
sdram_init()        board\ti\am335x\board.c

board_init_f        common\board_f.c

save_omap_boot_params() arch\arm\mach-omap2\boot-common.c


board_init_r        common\spl\spl.c
        printf(">>spl:board_init_r()\n");

SPL阶段
1=>_start                            //arch/arm/lib/vectors.S
2==>b reset                        //jump to arch\arm\cpu\armv7\start.S:reset
3===>bl _main                //jump to arch\arm\lib\crt0.S:_main
4====>bl board_init_f        //jump to arch\arm\mach-omap2\am33xx\board.c:board_init_f
5=====>sdram_init()    //jump to board\ti\am335x\board.c:sdram_init()
4====>bl spl_relocate_stack_gd    //jump to common\board_f.c:spl_relocate_stack_gd
4====>ldr    pc, =board_init_r        //jump to common\spl\spl.c:board_init_r
5=====>spl_board_init()            //jump to arch\arm\mach-omap2\boot-common.c:spl_board_init()
6======>save_omap_boot_params() //jump to arch\arm\mach-omap2\boot-common.c:save_omap_boot_params()
5=====>boot_from_devices()            //jump to common\spl\spl.c:boot_from_devices()
6======>printf("Trying to boot from %s\n", loader->name);
6======>spl_load_image()
7=======>spl_ymodem_load_image()        //ommon\spl\spl_ymodem.c

save_boot_params            arch\arm\mach-omap2\lowlevel_init.S:save_boot_params
ENTRY(save_boot_params)
    ldr    r1, =OMAP_SRAM_SCRATCH_BOOT_PARAMS
    str    r0, [r1]
    b    save_boot_params_ret
ENDPROC(save_boot_params)

save_omap_boot_params() //arch\arm\mach-omap2\boot-common.c:save_omap_boot_params()
{
u32 boot_params = *((u32 *)OMAP_SRAM_SCRATCH_BOOT_PARAMS);
...
omap_boot_params = (struct omap_boot_parameters *)boot_params;
boot_device = omap_boot_params->boot_device;
}

SPL_LOAD_IMAGE_METHOD("UART", 0, BOOT_DEVICE_UART, spl_ymodem_load_image);//ommon\spl\spl_ymodem.c


第二阶段：
==>board_init_r()            //common\board_r.c
===>init_fnc_t init_sequence_r[] = {...,initr_net,...}    //common\board_r.c
===>initr_net()                //common\board_r.c
====>eth_initialize();        //net\eth_legacy.c
=====>board_eth_init()     //board\ti\am335x\board.c    置为MII
======>cpsw_register()         //drivers\net\cpsw.c
=======>_cpsw_register()     //drivers\net\cpsw.c
========>cpsw_mdio_init()     //drivers\net\cpsw.c
=========>cpsw_mdio_read()        //drivers\net\cpsw.c
==========>wait_for_user_access    //drivers\net\cpsw.c

//引脚配置
==>board_init_f()
===>init_fnc_t init_sequence_f[] = {...,board_early_init_f,display_options,...}
====>board_early_init_f()
=====>set_mux_conf_regs()
======>enable_board_pin_mux()
=======>configure_module_pin_mux()