[Intel-gfx] [PATCH] drm/i915: prefer VBT modes for SVDO-LVDS over EDID

[Chris Wilson]

On Sun, Jun 09, 2013 at 10:58:38PM +0200, Daniel Vetter wrote:
> In
> 
> commit 53d3b4d7778daf15900867336c85d3f8dd70600c
> Author: Egbert Eich <eich at suse.de>
> Date:   Tue Jun 4 17:13:21 2013 +0200
> 
>     drm/i915/sdvo: Use &intel_sdvo->ddc instead of intel_sdvo->i2c for DDC
> 
> Ebgert Eich fixed a long-standing bug where we simply used a
> non-working i2c controller to read the EDID for SDVO-LVDS panels.
> Unfortunately some machines seem to not be able to cope with the mode
> provided in the EDID (specifically they seem to not be able to cope
> with a 4x pixel mutliplier instead of a 2x one).
> 
> Since it took forever to notice the breakage it's fairly safe to
> assume that at least for SDVO-LVDS panels the VBT contains fairly sane
> data. So just switch around the order and use VBT modes first.
> 
> Cc: Egbert Eich <eich at suse.de>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=65524
> Cc: stable at vger.kernel.org
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>

I can accept the argument that we need to prefer the VBT mode here to
paper over the apparent regression, but to not pass on the full EDID
modes seems dubious.

Even if you do choose to skip the EDID if you have a VBT mode, you could
write the function a little cleaner. ;-)
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre