linux-kernel - Re: [PATCH v2] drm/i915: ignore pipe select bit when checking for LVDS register initialization

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Message-ID: <20120613202600.GA3761@thinkpad-t410>
Date:	Wed, 13 Jun 2012 15:26:00 -0500
From:	Seth Forshee <seth.forshee@...onical.com>
To:	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/i915: ignore pipe select bit when checking for
 LVDS register initialization

On Wed, Jun 13, 2012 at 09:46:15PM +0200, Daniel Vetter wrote:
> On Wed, Jun 13, 2012 at 01:46:58PM -0500, Seth Forshee wrote:
> > The Lenovo Thinkpad T410 has the LVDS_PIPEB_SELECT bit set in the LVDS
> > register when booted with the lid closed, even though the LVDS hasn't
> > really been initialized. Ignore this bit so that the VBT value will be
> > used instead.
> > 
> > Signed-off-by: Seth Forshee <seth.forshee@...onical.com>
> Queued for -next, thanks for the patch. Chris had some reservations about
> the sanity of this patch, but given that it works around bios-insanity I'm
> gonna just take this chance to stab myself with lvds-machines blowing up
> left and right ;-)

Let's hope that doesn't happen ;)

I do find myself wondering though whether it might be better to prefer
the value from the VBT whenever there's one available, and only rely on
the actual register value as a fallback, since the bios can't be trusted
to initialize the register. I'm pretty ignorant about all this graphics
stuff though; I assume there's a reason it isn't done this way?

Seth

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