From mboxrd@z Thu Jan  1 00:00:00 1970
From: Daniel Vetter <daniel@ffwll.ch>
Subject: Re: [Intel-gfx] [PATCH 1/2] drm/i915: Force explicit bpp selection
 for intel_dp_link_required
Date: Mon, 6 Feb 2012 17:03:37 +0100
Message-ID: <20120206160337.GB4066@phenom.ffwll.local>
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To: Dave Airlie <airlied@gmail.com>
Cc: Keith Packard <keithp@keithp.com>, intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Lubos Kolouch <lubos.kolouch@gmail.com>
List-Id: dri-devel@lists.freedesktop.org

On Mon, Feb 06, 2012 at 12:12:16PM +0000, Dave Airlie wrote:
> On Fri, Jan 27, 2012 at 10:30 AM, Daniel Vetter <daniel@ffwll.ch> wro=
te:
> > 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_requir=
ed,
> >> 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 c=
ase,
> >> =A0 the current crtc values cannot be relevant as the modes in que=
stion
> >> =A0 may never be selected. Thus, using intel_crtc->bpp is never ri=
ght.
> >>
> >> * intel_dp_mode_fixup is called during mode setting, but it is run
> >> =A0 well before ironlake_crtc_mode_set is called to set intel_crtc=
->bpp,
> >> =A0 so using intel_crtc-bpp in this path can only ever get a stale
> >> =A0 value.
> >>
> >> Cc: Lubos Kolouch <lubos.kolouch@gmail.com>
> >> Cc: Adam Jackson <ajax@redhat.com>
> >> Signed-off-by: Keith Packard <keithp@keithp.com>
> >
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=3D42263
> > Tested-by: camalot@picnicpark.org (Dell Latitude 6510)
> >
> > Not the original reporter and might not exactly be this bug, but li=
kely.
> > -Daniel
>=20
> Tested-by: Dave Airlie <airlied@redhat.com>

Another bugzilla for this patch:

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=3D44881
Tested-by: Roland Dreier <roland@digitalvampire.org>

-Daniel
--=20
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48