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

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#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:  kernel    |     Version:  not specified      
         Resolution:            |    Keywords:  viafb              
        Next_action:  diagnose  |    Verified:  0                  
Deployment_affected:            |   Blockedby:                     
           Blocking:            |  
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Changes (by jon.nettleton):

  * keywords:  => viafb
  * component:  x window system => kernel


Comment:

 This problem is caused by the CR00-CR05 not being preserved across suspend
 resume.  After talking with Mitch we think that the viafb suspend/resume
 cycles should be responsible for storing and restoring the Control and
 Sequence registers instead of doing this in OFW.

 For performance reasons Mitch suggested the registers be accessed through
 MMIO space.

 <Mitch_Bradley> I believe that it is possible to access the CRT and SEQ
 registers through MMIO space, using offets 0x83cX and 0x83dX, instead of
 through I/O ports 3cX and 3dX, thus (probably) making it go faster I/O
 port accesses are inherently quite slow, to the tune of nearly 1 uS per
 access, thus costing a total of 4 uS for every such register you want to
 save/restore

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Ticket URL: <http://dev.laptop.org/ticket/10068#comment:12>
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