一、suspending consoles打印
代码位置：Kernel/power/suspend.c
函数调用流程：devices_and_enter(suspend_state_t state) --> suspend_console();
void suspend_console(void)
{
if (!console_suspend_enabled) 注释这一行，可以看到休眠后printk的打印
return;
printk("Suspending console(s) (use no_console_suspend to debug)\n");
console_lock();
console_suspended = 1;
up(&console_sem);
}
二、打印linux 内核 bus总线休眠唤醒流程
代码位置：Kernel/drivers/base/power/main.c
dpm_suspend() --> device_suspend() --> __device_suspend()
修改位置：
static void pm_dev_dbg(struct device *dev, pm_message_t state, char *info)
{
dev_printk(KERN_ERR,dev, "%s%s%s\n", info, pm_verb(state.event),
((state.event & PM_EVENT_SLEEP) && device_may_wakeup(dev)) ?
", may wakeup" : "");
}内核 log如下：
bus suspend:
329.576315 reg-fixed-voltage soc:emac_lan_vreg: bus suspend
329.581997 reg-fixed-voltage soc:rome_vreg: bus suspend
329.587245 reg-fixed-voltage soc:sdcard_ext_vreg: bus suspend
329.593177 qcom,mem-acc-regulator 1942131.regulator: bus suspend
329.599144 pps-gpio soc:pps: bus suspend
329.603183 platform 7c50000.qcom,emac: bus suspend
bus resume:
331.355074 msm_serial_hs 98b1000.uart: noirq driver resume
331.361022 PM: noirq resume of devices complete after 17.017 msecs
331.367635 PM: early resume of devices complete after 0.543 msecs
331.372985 reg-dummy reg-dummy: bus resume
三、设备休眠唤醒流程打印
代码位置：driver/base/platform.c
3.1 linux设备休眠流程：
int platform_pm_suspend(struct device *dev)
{
struct device_driver *drv = dev->driver;
int ret = 0;
...
...
if (drv->pm) {
if (drv->pm->suspend)
ret = drv->pm->suspend(dev);
+pr_info("%s called name = %s\n", __func__, drv->name); //此处添加suspend 设备调试打印
} else {
ret = platform_legacy_suspend(dev, PMSG_SUSPEND);
}3.2 linux设备唤醒流程
int platform_pm_resume(struct device *dev)
{
struct device_driver *drv = dev->driver;
int ret = 0;
...
...
if (drv->pm) {
if (drv->pm->resume)
ret = drv->pm->resume(dev);
pr_info("%s called name = %s\n", __func__, drv->name);//此处添加设备resume打印
} else {
ret = platform_legacy_resume(dev);
}四、linux内核线程和进程休眠过程打印
函数调用流程：
enter_state(suspend.c)--->suspend_prepare--->suspend_freeze_processes()--->freeze_processes(--->try_to_freeze_tasks--->freeze_task)--->freeze_kernel_processes
可以在kernel/power/process.c中添加如下打印：
for_each_process_thread(g,p)
...
pr_info("userspace pid %d, %d\n", p->pid, current->pid);
...打印效果如下：
327.812216 PM: suspend entry 2018-09-18 11:53:17.879150194 UTC
327.817117 PM: Syncing filesystems ... done.
327.823632 Freezing user space processes ... userspace pid 1
327.828524 userspace pid 6
327.831545 userspace pid 124
327.834264 userspace pid 1345
327.837216 userspace pid 2150
对于内核线程休眠的打印可以参考上面在freeze_kernel_processes中添加打印。
五、late_resume和earlysuspend.c加打印
在部分内核版本中可以添加如下log分析问题：
late_resume函数中：
list_for_each_entry_reverse(pos, &early_suspend_handlers, link)
if (pos->resume != NULL) {
pos->resume(pos);
+pr_info("late_resume: func %p\n",pos->resume);
}
early_suspend late_resume添加log
在earlysuspend.c中
static int debug_mask = DEBUG_USER_STATE;
->
static int debug_mask = DEBUG_USER_STATE | DEBUG_SUSPEND |
DEBUG_VERBOSE;
六、休眠唤醒时间长问题排查
参见之前调试文档说明，链接如下：