#12377 LOW 4-firmw: XO-4 B1 timeout entering DCON mode

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#12377: XO-4 B1 timeout entering DCON mode
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           Reporter:  Quozl                |       Owner:  Quozl               
               Type:  defect               |      Status:  new                 
           Priority:  low                  |   Milestone:  4-firmware          
          Component:  ofw - open firmware  |     Version:  Development firmware
         Resolution:                       |    Keywords:                      
        Next_action:  diagnose             |    Verified:  0                   
Deployment_affected:                       |   Blockedby:                      
           Blocking:                       |  
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Comment(by Quozl):

 * tested DCON power cycle, ''dcon-suspend dcon-resume'' did not clear
 problem, ''dcon-suspend d# 3 ms dcon-resume'' did clear problem.
  * tested disabling the default pull-ups on DCONSTAT and DCONIRQ#, no
 effect.
  * compared DCON register values between working and non-working states,
 no difference.
  * reviewed kernel driver, could not find code that would power cycle DCON
 for this problem,
  * did find a comment that "the DCON seems to get confused if we change
 DCONLOAD too frequently", which we are doing half the time in Open
 Firmware, but adding a 25 ms delay between each change does not prevent
 problem.

 An additional observation about the symptom: the static screen shimmers
 for about ten seconds after the test-dcon-freeze-glitch is stopped by key
 press.

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Ticket URL: <http://dev.laptop.org/ticket/12377#comment:3>
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