#10068 NORM 1.5-sof: Black Xv overlay when starting Record

[Zarro Boogs per Child]

#10068: Black Xv overlay when starting Record
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           Reporter:  cjb              |       Owner:  jon.nettleton      
               Type:  defect           |      Status:  new                
           Priority:  normal           |   Milestone:  1.5-software-update
          Component:  x window system  |     Version:  not specified      
         Resolution:                   |    Keywords:                     
        Next_action:  never set        |    Verified:  0                  
Deployment_affected:                   |   Blockedby:                     
           Blocking:                   |  
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Comment(by wmb at firmworks.com):

 OFW does indeed establish the values of quite a few display-related
 registers on resume - but for the most part it sets them to known-good
 values instead of trying to do the save/restore dance.

 Results of analyzing register diffs between LeaveVT-sleep and EnterVT-
 sleep:

 a) Some registers should only matter when using a legacy VGA display mode
 - i.e. irrelevant in a frame buffer mode:  SR04,15,16,1a,1c,1d
 CR00-0A,10-18,33,35 GR05,06,07 AR10-13  Misc bit 5

 b) Some registers apply to the primary display controller, unused for the
 XO: SR 44,45,46

 c) OFW uses slightly different timing (56.2 MHz) than the Linux driver
 (56.8 MHz): SR4a,4b,4c CR56,57m5em5f

 d) Others: CR36 affects nonexistent external CRT.  CR6a is for indexed
 color mode.

 e) Read-only registers: SR3d,3e,5b,5c CR60,61

 f) LVDS stuff and LCD power sequencing that is irrelevant for OLPC:
 CR88,8a-90,99

 g) Performance tuning:  SR58,59 CR68,94,95

 Misc bit 7 - vertical sync polarity - might possibly be a problem.

 The value of CR9B (0x00) in EnterVT-sleep seems blatantly wrong.  When I
 set that register to 0 in OFW, I lose the raster entirely.  The correct
 value 0x1b selects the secondary display engine as the data source to feed
 to the DCON.

-- 
Ticket URL: <http://dev.laptop.org/ticket/10068#comment:8>
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