[Trac #1169] dcon source switch sometimes times out

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#1169: dcon source switch sometimes times out
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 Reporter:  dilinger  |        Owner:  dilinger 
     Type:  defect    |       Status:  new      
 Priority:  normal    |    Milestone:  Untriaged
Component:  kernel    |   Resolution:           
 Keywords:            |  
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Comment (by dilinger):

 IRC is <3

 {{{
 <dilinger>   6:          0    XT-PIC-XT        DCON
  -bash-3.1#  echo 0 >  /sys//devices/platform/dcon/source
  -bash-3.1#  echo 1 >  /sys//devices/platform/dcon/source
    6:         49    XT-PIC-XT        DCON
  subsequent source switches only trigger 1 interrupt
 <CosmicPenguin> wow - pretty!
 <dilinger> something else is causing 47 extra interrupts to be triggered
 ...
 <Mitch_Bradley> dilinger: scanline interrupts!
 <Mitch_Bradley> heh
 <dilinger> and would a flock of scanline interrupts cause us to timeout
 waiting for our mode switch interrupt?
 <CosmicPenguin> and that code is buggy
  the global flag containing the mode is changed before we attempt to
 switch
 ...
 <CosmicPenguin> dilinger: but line 192 is evil
 <CosmicPenguin> you'll want to zap that - that way the source won't change
 if the DCON times out
 }}}

 Other cleanups; return values need to be checked in various places,
 locking needs to be thought about, change some values to atomic values,
 etc.

-- 
Ticket URL: <http://dev.laptop.org/ticket/1169#comment:2>
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