#9869 HIGH 1.5-sof: XO-1.5 screen glitches on resume

[Zarro Boogs per Child]

#9869: XO-1.5 screen glitches on resume
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           Reporter:  wad              |       Owner:  cjb                              
               Type:  defect           |      Status:  new                              
           Priority:  high             |   Milestone:  1.5-software-later               
          Component:  x window system  |     Version:  Development build as of this date
         Resolution:                   |    Keywords:  DCON XO-1.5                      
        Next_action:  code             |    Verified:  0                                
Deployment_affected:                   |   Blockedby:                                   
           Blocking:                   |  
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Comment(by pgf):

 because it came up the other night on IRC, i'll address this, too:
 driving the dcon freeze/unfreeze too fast can cause erratic behavior.
 quozl saw a lockup with this loop:
 {{{
 for x in $(seq 100)
 do
   sleep 0.01
   echo 1 > freeze
   sleep 0.01
   echo 0 > freeze
   echo -n .
 done
 }}}

 and even after switching to a synchronous dcon freeze, this loop:
 {{{
 while true; do
         echo 1 > /sys/devices/platform/dcon/freeze
         sleep .01
         echo 0 > /sys/devices/platform/dcon/freeze
         sleep .01
 done
 }}}
 will miss dcon interrupts during the freeze, causing a timeout and an
 error in the kernel log.  changing that loop to:
 {{{
 while true; do
         echo 1 > /sys/devices/platform/dcon/freeze
         sleep .01
         echo 0 > /sys/devices/platform/dcon/freeze
         sleep .02
 done
 }}}
 eliminates that problem.

 the scope shows the interrupt never occurring in the shorter delay case,
 presumably because the dcon has some internal state (?) that isn't yet
 ready.

 the moral?  don't stress the freeze/unfreeze mechanism so hard.

-- 
Ticket URL: <http://dev.laptop.org/ticket/9869#comment:6>
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