- 文件夹
	- kernel/power/
		- main.c      模块入口  core_initcall
		- suspend.c   睡眠  to RAM
		- hibernate.c 休眠  to DISK
		- poweroff.c  关机
- 数据结构
	- syspend的几种模式
		- `#define PM_SUSPEND_ON       ((__force suspend_state_t) 0)`
		- `#define PM_SUSPEND_TO_IDLE  ((__force suspend_state_t) 1)`  // s2-idle sleep
		- `#define PM_SUSPEND_STANDBY  ((__force suspend_state_t) 2)`  // standby modern?
		- `#define PM_SUSPEND_MEM      ((__force suspend_state_t) 3)`  // s3 sleep
- 函数
-  pm_suspend  S2 S3(deep sleep)  CONFIG_SUSPEND_SKIP_SYNC
	- **enter_state**  //  s2idle  shallow  deep
		- **ksys_sync_helper** // 选择是否sync   CONFIG_SUSPEND_SKIP_SYNC
		- **suspend_prepare** // 主要就是冻结软件进程
			- suspend_freeze_processes
				- freeze_processes    //  冻结用户态进程
				- freeze_kernel_threads  // 冻结内核任务
		- **suspend_devices_and_enter**   // core function 
			- platform_suspend_begin
			- suspend_console // 挂起console，从此时开始console无法再输出
			- **suspend_enter**   // power/suspend.c  进入syspend模式
				- s2 和 s3的模式在这个函数中很不一样
				- S2
					- s2idle_loop  // s2本质上是一个循环
				- S3  standby
					- suspend_disable_secondary_cpus
					- **arch_suspend_disable_irqs** -> local_irq_disable 屏蔽本核I位， 但是FIQ依然可以响应
					- syscore_suspend   drivers/base/syscore.c
						- **psci_system_suspend_enter**  // arm64用的是psci进行电源管理
							- cpu_suspend  // arm64
								- cpu_suspend_enter  // arch/arm64/kernel/sleep.s
								- psci_system_suspend ？  ==> bl3
		- suspend_finish


[H    86.979381374] cs: c0 pc[c023c69a] lr[c023c689] sp[c0e5bdf0]
[H    86.985310124] c0 pc: [<0xc023c69a>] arch_spin_lock+0x1a/0x32
[H    86.991243291] c0 [<0xc047cd4b>] _raw_spin_lock_irqsave+0xd/0x10
[H    86.997429541] c0 [<0xc023b997>] down_trylock+0x9/0x1c
[H    87.2745749] c0 [<0xc023ebb3>] __down_trylock_console_sem.constprop.0+0x13/0x28
[H    87.10231208] c0 [<0xc023ebcf>] console_trylock+0x7/0x30
[H    87.15717749] c0 [<0xc023ebff>] console_trylock_spinning+0x7/0x78
[H    87.21985249] c0 [<0xc024038f>] vprintk_emit+0x6b/0x90
[H    87.27297749] c0 [<0xc02403c7>] vprintk_default+0x13/0x18
[H    87.32869624] c0 [<0xbf8cb173>] osal_printk+0x1f/0x34 [osaldrv]
[H    87.39013916] c0 [<0xbf9941ad>] vnne_suspend+0x19/0x30 [vnne]
[H    87.44949749] c0 [<0xc03983a7>] dpm_run_callback+0x17/0x30
[H    87.50613124] c0 [<0xc0398705>] __device_suspend+0x109/0x230
[H    87.56445583] c0 [<0xc0398d8d>] dpm_suspend+0x5f/0xea
[H    87.61672416] c0 [<0xc0398eeb>] dpm_suspend_start+0x2f/0x38
[H    87.67417708] c0 [<0xc023e5cd>] suspend_devices_and_enter+0x49/0xe4