linux-kernel - Re: [Intel-gfx] [PATCH 1/2] drm/i915: Force explicit bpp selection for intel_dp_link

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Date:	Mon, 6 Feb 2012 12:12:16 +0000
From:	Dave Airlie <airlied@...il.com>
To:	Keith Packard <keithp@...thp.com>, intel-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	Lubos Kolouch <lubos.kolouch@...il.com>
Subject: Re: [Intel-gfx] [PATCH 1/2] drm/i915: Force explicit bpp selection
 for intel_dp_link_required

On Fri, Jan 27, 2012 at 10:30 AM, Daniel Vetter <daniel@...ll.ch> wrote:
> On Wed, Jan 25, 2012 at 08:16:25AM -0800, Keith Packard wrote:
>> It is never correct to use intel_crtc->bpp in intel_dp_link_required,
>> so instead pass an explicit bpp in to this function. This patch
>> only supports 18bpp and 24bpp modes, which means that 10bpc modes will
>> be computed incorrectly. Fixing that will require more extensive
>> changes, and so must be addressed separately from this bugfix.
>>
>> intel_dp_link_required is called from intel_dp_mode_valid and
>> intel_dp_mode_fixup.
>>
>> * intel_dp_mode_valid is called to list supported modes; in this case,
>>   the current crtc values cannot be relevant as the modes in question
>>   may never be selected. Thus, using intel_crtc->bpp is never right.
>>
>> * intel_dp_mode_fixup is called during mode setting, but it is run
>>   well before ironlake_crtc_mode_set is called to set intel_crtc->bpp,
>>   so using intel_crtc-bpp in this path can only ever get a stale
>>   value.
>>
>> Cc: Lubos Kolouch <lubos.kolouch@...il.com>
>> Cc: Adam Jackson <ajax@...hat.com>
>> Signed-off-by: Keith Packard <keithp@...thp.com>
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=42263
> Tested-by: camalot@...nicpark.org (Dell Latitude 6510)
>
> Not the original reporter and might not exactly be this bug, but likely.
> -Daniel

Tested-by: Dave Airlie <airlied@...hat.com>

Without this patch the eDP panel on my HP 2540p won't resume.

Please get this into -fixes and too me asap.

Dave.
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