Openmoko Bug #1841: white screen of death (WSOD) after resume

[Openmoko Public Trac]

#1841: white screen of death (WSOD) after resume
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    Reporter:  Rorschach    |        Owner:  openmoko-devel
        Type:  defect       |       Status:  new           
    Priority:  highest      |    Milestone:                
   Component:  unknown      |      Version:  GTA02v5       
    Severity:  critical     |   Resolution:                
    Keywords:  wsod,resume  |    Blockedby:                
Reproducible:  always       |     Blocking:                
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Comment(by andy):

 It's hard to know what goes on for you at the moment.  Here is some more
 information about the issue.

 The "white screen" thing is what we see with no video data coming OR the
 LCM ASIC is unconfigured.

 Glamo stops sending video data at suspend because we put it in very low
 power state with no PLLs running.  So, it's normal in early resume in fact
 the LCM would show WSOD -- but the backlight is down at that time.  And it
 is also normal that after some short time first Glamo LCD controller is
 resumed and then we reinitialize LCM ASIC.  Then we bring up backlight so
 you should never see any white display.

 I have seen two behaviours that give WSOD despite the happy story above --
 first is during resume, the Glamo's Reset pin is falsely activated by a
 spike.  Because we assume most Glamo registers survive suspend, this kills
 us dead and the partial resume action we do on the registers does not
 succeed to issue any video.  So with that problem you get a sticky WSOD
 until you reboot.

 The second behaviour is that somehow resume is delayed by another driver
 (?) sometimes, then the normal sequencing does happen but delayed.  During
 the delayed portion, the backlight came up normally but LCM ASIC reinit
 did not happen, so you see the WSOD until that completes.

-- 
Ticket URL: <https://docs.openmoko.org/trac/ticket/1841#comment:5>
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