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

Zarro Boogs per Child bugtracker at laptop.org
Fri Dec 11 08:50:36 EST 2009


#9869: XO-1.5 screen glitches on resume
-----------------------------+----------------------------------------------
 Reporter:  wad              |                 Owner:  cjb                              
     Type:  defect           |                Status:  new                              
 Priority:  high             |             Milestone:  1.5-software-update              
Component:  x window system  |               Version:  Development build as of this date
 Keywords:  DCON XO-1.5      |           Next_action:  code                             
 Verified:  0                |   Deployment_affected:                                   
Blockedby:                   |              Blocking:                                   
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 On an XO-1.5 laptop, running a recent OS which supports suspend/resume,
 the screen occasionally glitches (jumps) when resuming.

 This is due to a lack of frame synchronization between the VX855 video
 output and the DCON at the time which the DCON is told to revert to pass-
 through mode.

 A description of the problem, along with suggestions for fixing future
 implementations of the DCON silicon, is found in #1671.  XO-1.5 uses the
 same DCON silicon as XO-1.

 In the case of XO-1.5, there are three software systems which might reinit
 the video output on resume: OFW, LinuxFB, and X.  It is important that X
 properly time the initialization of the video output such that the video
 is roughly synchronized with the DCON video retrace, before the DCON
 driver restores pass-through video.

 Checking with an oscilloscope indicates that currently there is no attempt
 to do so.  The DCON vertical sync signal is STV, accessible at either end
 of R28 (top side).  The VSYNC signal is accessible at either end of R200
 (top side), and the DCONIRQ signal is accessible at R263/R264 (bottom
 side).

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