Will iMX6 SNVS_LP alarm enabled wake up PMIC to turn on even in power down state?

[raymondwang]

Dear All,

    my board design is based on SabreSD . There is a strange issue that board will auto turn on automatically even whole system is turned off (battery always mount).

I have double check the snvs_lp part which is alarm source to generate wake up to linux/android kernel.

   My kernel is 3.0.35, android release is android_jb_4.2.2_1.1.0. Does anyone ever encounter issue like that?

[raymondwang]

Anyway,thanks for your reply.

[SKWoon]

Just to further add some point as I realize that if the suspend period is short, issue may not appear; I have tested 5 mins suspend seems to cause the issue to appear consistently - point 2. "alrm_time" may be zero value initially, suspend the board for at least 5 mins & then resume the board, the "alrm_time" will become non-zero value.  So to list the steps again:

1. After booting up Android, type command root@sabresd_6dq:/ # cat /proc/driver/rtc to see "alrm_time".
2. "alrm_time" may be zero value initially, suspend the board for at least 5 mins & then resume the board, the "alrm_time" will become non-zero value           
3. Change the Android system time around 2 mins before "alrm_time", e.g. if "alrm_time" is now "00:13:00", then set Android system time to "12:11 am" (which is 00:11:00 hrs).
4. Power down the board by long pressing the "POWER SW1" button.
5. Board should not wake up since it has been powered down; but when Android system time reaches 00:13:00 hrs (12:13 am), the SDP board will automatically power up.

[SKWoon]

Hi Peter,

Thanks for your advice.  Issue can be reproduced on both our android_jb4.3_1.1.0-ga & android_kk4.4.2_1.0.0 images running on Freescale Rev C4 SDP board.  Customer reported this issue on their Rev B3 SDP running android_jb4.3_1.1.0-ga.  Steps to reproduce:

1. After booting up Android, type command root@sabresd_6dq:/ # cat /proc/driver/rtc to see "alrm_time".
2. "alrm_time" may be zero value initially, suspend & resume the board a few times & "alrm_time" will become non-zero value.            
3. Change the Android system time around 2 mins before "alrm_time", e.g. if "alrm_time" is now "2:38:00", then set Android system time to "2:36".
4. Power down the board by long pressing the "POWER SW1" button.
5. Board should not wake up since it has been powered down; but when Android system time reaches "2:38", the SDP board will automatically power up.

There is no need to set the Android system alarm for the issue to occur, instead dependency is on the "alrm_time" read out by the command root@sabresd_6dq:/ # cat /proc/driver/rtc .  "alrm_time" is initially zero when the image is freshly loaded,  but it will automatically be filled up with some value after some suspend & resume.

Best regards

Sock Keng

[raymondwang]

Well, I add code to clear LPTA_EN bit while system is powered off. Hope this is really what annoyed me.

[jh_zhao]

Hi Raymond, we have the problem too. After you clear LPTA_EN, is the problem solved?

[raymondwang]

I think so.but I use another method. You can search it in github with xhteam . My board name is qpad.