From mboxrd@z Thu Jan  1 00:00:00 1970
From: Daniel Vetter <daniel@ffwll.ch>
Subject: Re: [PATCH] drm/i915: CPT/PPT pch dp transcoder
 workaround
Date: Thu, 1 Nov 2012 16:33:45 +0100
Message-ID: <20121101153345.GV5755@phenom.ffwll.local>
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To: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>, Intel Graphics Development <intel-gfx@lists.freedesktop.org>, Arthur Ranyan <arthur.j.runyan@intel.com>
List-Id: intel-gfx@lists.freedesktop.org

On Thu, Nov 01, 2012 at 07:37:36AM -0700, Jesse Barnes wrote:
> > v3: Paulo Zanoni pointed out that this workaround is also required on
> > the LPT PCH. And Arthur Ranyan confirmed that this workaround is
> > requierd for all ports on the pch, not just DP: The important part
> > is that the bit is set whenever the pch transcoder is enabled, and
> > that it is _not_ set while the fdi link is trained. It is also
> > important that the pch transcoder is fully disabled, i.e. we have to
> > wait for bit 30 to clear before clearing the w/a bit.

See above: "Paulo Zanoni pointed out that this workaround is also required
on the LPT PCH".

> > +	if (!HAS_PCH_IBX(dev)) {
> > +		/* Workaround: Set the timing override bit before enabling the
> > +		 * pch transcoder. */
> > +		reg = TRANS_CHICKEN2(pipe);
> > +		val = I915_READ(reg);
> > +		val |= TRANS_CHICKEN2_TIMING_OVERRIDE;
> > +		I915_WRITE(reg, val);
> > +	}
> 
> I'd like this better if it were HAS_PCH_CPT; we use that as a synonym
> for PPT elsehwere, and it shouldn't apply to LPT right?  I see LPT has
> the bit, but I don't know if it's needed (the changelong and summary
> are misleading if so).

Paulo's vga patch bomb will split this up, so we can use HAS_PCH_CPT
instead of !IBX. But since I've written this patch against dinq without
paulo's patches, hence HAS_CPT would be wrong. So:

What colour would please you most, Sir?

Cheers, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch