PM 底电流调试工作总结

 高通7x27a平台目前遇到几个底电流调试问题，发表以下见解

  1：首先个人在调试不睡眠中遇见2次由于串口睡眠模式配置不对导致系统无法睡眠的问题，要是串口连接其他模块比如BT和modem，我们在sleep模式不可以配置成普通gpio功能，这样很容易导致睡眠时无法与设备通讯导致无法睡眠,modem有radio lock 。

  2：在系统可以睡下，底电流在20mA以下但是大于2mA的情况下，很可能是设备漏电造成或者开了一些clk，特别是clk对底电流影响很大。我自己有遇见过wifi芯片gpio倒灌漏电，CTP漏电。只要发现是哪个设备漏电，解决起来应该不难。遇见过一次camera clk导致sleep底电流偏大，普通外设需要的CLK我们睡眠时应该关闭。

 3：只要系统可以睡下，我们在kenel config里使用小点的配置来逐一排查哪些设备漏电，逐一检测,睡眠模式通常gpio配置成pull_in pull_down。只要发现问题就好办了。

 4：关于系统不睡的调试，我们可以在kernel CMD中填入no_console_suspend来使睡眠时串口输出log，还有可以打开PM_DEBUG。具体方法有篇文章有介绍。

目前认为做的最有成就感的2件事，一是将无法睡下的手机调到可以sleep底电流到5mA，再排查出漏电问题底电流降到1.几mA，二是决解一款芯片漏电降低底电流致该方案成功上市。

For the current optimization, you could check with below:

1. external device, you could remove one by one to check.

2. check power supply with each LDO, please disable them if not used,

and enter LPM if needed.             --when sleep the current will add 0.1mA once you used a ldo to supply voltage known by experience.

3. check each GPIO setting

sleep log 在all devices sleep后会return 0

<6>[  448.699493] request_suspend_state: sleep (0->3) at 448701111334

(2012-04-27 08:40:12.760188648 UTC)

<7>[  448.699798] msm_batt_early_suspend: enter

<4>[  448.703643] [MSM_BATT] msm_batt_set_compensation:

batt_compensation=0

<7>[  448.703857] msm_batt_early_suspend: exit

<4>[  448.704193] [TP]---call ft5x06_hw_suspend---

<4>[  448.706634] [ELAN epl6801] elan_epl6801_early_suspend

<6>[  448.707916] PM: Syncing filesystems...

<6>[  448.719879] active wake lock PowerManagerService

<6>[  448.742767] sync done.

<6>[  449.266815] suspend: enter suspend

<4>[  449.267395] Freezing user space processes ...

<6>[  449.268920] PM: Syncing filesystems...

<6>[  449.273162] sync done.

<4>[  449.288574] (elapsed 0.02 seconds) done.

<4>[  449.288696] Freezing remaining freezable tasks ... (elapsed 0.01

seconds) done.

<4>[  449.308563] Suspending console(s) (use no_console_suspend to

debug)

<6>[  449.309509] radio-tavaruatavarua_suspend: radio suspend

<6>[  449.309539]

<6>[  449.417022] PM: suspend of devices complete after 107.513 msecs

<6>[  449.417388] power_suspend_late return 0 

<6>[  449.417419] PM: late suspend of devices complete after 0.396 msecs