[Bugme-new] [Bug 24982] New: Inconsistent DPMS handling with 2.6.37 DRM

bugzilla-daemon at bugzilla.kernel.org bugzilla-daemon at bugzilla.kernel.org
Thu Dec 16 08:32:17 PST 2010


https://bugzilla.kernel.org/show_bug.cgi?id=24982

           Summary: Inconsistent DPMS handling with 2.6.37 DRM
           Product: Drivers
           Version: 2.5
    Kernel Version: 2.6.37-rc6
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - Intel)
        AssignedTo: drivers_video-dri-intel at kernel-bugs.osdl.org
        ReportedBy: tiwai at suse.de
                CC: keithp at keithp.com, eric at anholt.net,
                    chris at chris-wilson.co.uk, sndirsch at suse.de
        Regression: Yes


When the output is turned off via XRandr and turned on again with the same mode
while another output is a clone mode, the first output won't be recovered but
remains blank.  In short,

    % xrandr --output LVDS1 --mode 1024x768
    % xrandr --output VGA1 --mode 1024x768

where both shown correctly,

    % xrandr --output LVDS1 --off
    % xrandr --output LVDS1 --mode 1024x768

where LVDS1 is still blank although xrandr reports it's on.

The issue can be reproduced on IronLake and SandyBridge with 2.6.37-rc6. 
Untested on other platforms.

Looking down the problem, it seems related with DPMS.  The DPMS is declared as
ON in drm_crtc_helper_set_config() by the patch in commit
bf9dc102e284a5aa78c73fc9d72e11d5ccd8669f, but it wasn't actaully turned on the
device.

Also, the sysfs entries of dpms are totally bogus.  LVDS1 shows always Off, and
once doing after on and off, VGA1 can be also Off forever.

A temporary fix patch is attached below.

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