android restart reason机制

转载：http://blog.csdn.net/linux_devices_driver/article/details/17928663

 

Reboot传递参数,使得开机进入参数固定的模式（通常有我们熟悉的bootloader和recovery等），本质是在kernel shutdown时会调用到restart，

将模式数值写到share memory中，那么在开机bootloader阶段，再去读取这块内存，boot进入指定的模式，要是匹配不起来就正常boot,以下是贴出的代码；

restart 2种方式：

a: android_reboot(ANDROID_RB_RESTART2, 0, "rtcalarm");//进入rtc alarm模式

b: adb reboot bootloader,adb reboot recovery;        //进入我们熟悉的bootloader和recorevy模式

 

Restar.c:

void *restart_reason;

/*函数将被赋值给machine restart指针*/

void msm_restart(char mode, const char *cmd)

{

#ifdef CONFIG_MSM_DLOAD_MODE

 /* This looks like a normal reboot at this point. */

 set_dload_mode(0);

 /* Write download mode flags if we're panic'ing */

 set_dload_mode(in_panic);

 /* Write download mode flags if restart_mode says so */

 if (restart_mode == RESTART_DLOAD) {

  set_dload_mode(1);

#ifdef CONFIG_LGE_CRASH_HANDLER

  writel(0x6d63c421, restart_reason);

  goto reset;

#endif

 }

 /* Kill download mode if master-kill switch is set */

 if (!download_mode)

  set_dload_mode(0);

#endif

 printk(KERN_NOTICE "Going down for restart now\n");

 pm8xxx_reset_pwr_off(1);

 if (cmd != NULL) {

  if (!strncmp(cmd, "bootloader", 10)) {

   __raw_writel(0x77665500, restart_reason);

  } else if (!strncmp(cmd, "recovery", 8)) {

   __raw_writel(0x77665502, restart_reason);

  } else if (!strncmp(cmd, "oem-", 4)) {

   unsigned long code;

   code = simple_strtoul(cmd + 4, NULL, 16) & 0xff;

   __raw_writel(0x6f656d00 | code, restart_reason);

  } else {

   __raw_writel(0x77665501, restart_reason);

  }

 } else {

  __raw_writel(0x77665501, restart_reason);

 }

#ifdef CONFIG_LGE_CRASH_HANDLER

 if (in_panic == 1)

  set_kernel_crash_magic_number();

reset:

#endif /* CONFIG_LGE_CRASH_HANDLER */

 __raw_writel(0, msm_tmr0_base + WDT0_EN);

 if (!(machine_is_msm8x60_fusion() || machine_is_msm8x60_fusn_ffa())) {

  mb();

  __raw_writel(0, PSHOLD_CTL_SU); /* Actually reset the chip */

  mdelay(5000);

  pr_notice("PS_HOLD didn't work, falling back to watchdog\n");

 }

 __raw_writel(1, msm_tmr0_base + WDT0_RST);

 __raw_writel(5*0x31F3, msm_tmr0_base + WDT0_BARK_TIME);

 __raw_writel(0x31F3, msm_tmr0_base + WDT0_BITE_TIME);

 __raw_writel(1, msm_tmr0_base + WDT0_EN);

 mdelay(10000);

 printk(KERN_ERR "Restarting has failed\n");

}

static int __init msm_restart_init(void)

{

#ifdef CONFIG_MSM_DLOAD_MODE

 atomic_notifier_chain_register(&panic_notifier_list, &panic_blk);

 dload_mode_addr = MSM_IMEM_BASE + DLOAD_MODE_ADDR;

#ifdef CONFIG_LGE_CRASH_HANDLER

 lge_error_handler_cookie_addr = MSM_IMEM_BASE +

  LGE_ERROR_HANDLER_MAGIC_ADDR;

#endif

 set_dload_mode(download_mode);

#endif

 msm_tmr0_base = msm_timer_get_timer0_base();

 restart_reason = MSM_IMEM_BASE + RESTART_REASON_ADDR;// restart_reason被赋值内存地址

 pm_power_off = msm_power_off;

 return 0;

}

 

lk:init.c

/*lk里面读出kernel写入的restart数值*/

unsigned check_reboot_mode(void)

{

 unsigned restart_reason = 0;

 void *restart_reason_addr = (void *)0x2A05F65C;

 /* Read reboot reason and scrub it */

 restart_reason = readl(restart_reason_addr);

 writel(0x00, restart_reason_addr);

 return restart_reason;

}

#define RECOVERY_MODE   0x77665502

#define FASTBOOT_MODE   0x77665500

#define ADB_REBOOT_MODE 0x77665501

/*check reboot mode*/

reboot_mode = check_reboot_mode();

 #if CONFIG_CHARING_WHILE_MECHINE_TRUN_OFF

 {

  extern unsigned int custom_power_on_charger(void);

  if(custom_power_on_charger() && reboot_mode && (reboot_mode!=FASTBOOT_MODE) && (reboot_mode != ADB_REBOOT_MODE))

   boot_into_recovery=1;

  dprintf(0, "[charger] %s() custom_power_on_charger()=%x check_reboot_mode()=%0x\n", __func__, custom_power_on_charger(), reboot_mode);

 }

 #endif

 

 if (reboot_mode == RECOVERY_MODE) {

  boot_into_recovery = 1;

 } else if(reboot_mode == FASTBOOT_MODE) {

  goto fastboot;

 }

 

 那么熟悉这套机制，我们就可以添加自己的模式了，比如闹钟模式，工厂模式等等；