From: Chris Wilson <chris@chris-wilson.co.uk>
To: Intel Graphics Development <intel-gfx@lists.freedesktop.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Subject: Re: [PATCH] drm/i915: rip out early dp port write for gm45/ilk
Date: Thu, 13 Sep 2012 11:10:14 +0100 [thread overview]
Message-ID: <6c3329$61f23h@orsmga002.jf.intel.com> (raw)
In-Reply-To: <1347485049-19003-1-git-send-email-daniel.vetter@ffwll.ch>
On Wed, 12 Sep 2012 23:24:09 +0200, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> It's bogus.
>
> If I've followed the history of this piece of code correctly, i.e. the
> initial register write with the following vblank wait, this goes all
> the way back to the original enabling of DP support in
>
> commit a4fc5ed69817c73e32571ad7837bb707f9890009
> Author: Keith Packard <keithp@keithp.com>
> Date: Tue Apr 7 16:16:42 2009 -0700
>
> drm/i915: Add Display Port support
>
> Unfortunately it seems to be nothing more than glorified duct-tape and
> sometimes actively harmful. Adam Jackson noticed this for CPT
> platforms with
>
> commit e85194641bec56179dcf5e1704ce5c6bf30340c6
> Author: Adam Jackson <ajax@redhat.com>
> Date: Thu Jul 21 17:48:38 2011 -0400
>
> drm/i915/dp: Don't turn CPT DP ports on too early
>
> Unfortunately this kept the code around for ilk and gm45.
>
> The specific failure case I'm seeing here is that after a dpms off/on
> cycle we have the bits from the last link training (hopefully
> successful link training) set in intel_dp->DP. This is requiered so
> that complete_link_train can enable the port with the right tuning
> values.
>
> Unfortunately writing these again to the disabled port at dpms on time
> kills the port somehow until it's disabled - dp link training fails in
> an endless loop without this patch on my mobile ilk and gm45.
>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Works for me, only time will time if I no longer get the occasional
failure in link training, but it definitely fixes the issue with dpms
off.
Tested-by: Chris Wilson <chris@chris-wilson.co.uk>
Probably https://bugs.freedesktop.org/show_bug.cgi?id=51493
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
next prev parent reply other threads:[~2012-09-13 10:10 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-12 21:24 [PATCH] drm/i915: rip out early dp port write for gm45/ilk Daniel Vetter
2012-09-13 10:10 ` Chris Wilson [this message]
2012-09-13 11:39 ` Daniel Vetter
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