linux-kernel - Re: [Intel-gfx] [PATCH 05/21] drm/i915: Check eDP power when doing aux channel communications

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Message-Id: <c55c5d$l6fkn@AZSMGA002.ch.intel.com>
Date:	Fri, 30 Sep 2011 19:23:44 +0100
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	Keith Packard <keithp@...thp.com>, Daniel Vetter <daniel@...ll.ch>
Cc:	Dave Airlie <airlied@...hat.com>, intel-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH 05/21] drm/i915: Check eDP power when doing aux channel communications

On Fri, 30 Sep 2011 11:01:06 -0700, Keith Packard <keithp@...thp.com> wrote:
Non-text part: multipart/signed
> On Fri, 30 Sep 2011 19:02:42 +0200, Daniel Vetter <daniel@...ll.ch> wrote:
> 
> > Use pp_control instead of re-reading?
> 
> Could, but you'll note a later patch eliminates both pp_status and
> pp_control local variables, so I didn't bother to clean this up when
> refactoring.
> 
> > dp_aux_ch does the low-level io for the below, so either this one or the
> > below three hunks look a bit redundant.
> 
> Yeah, probably not necessary. I just added checks everywhere I could
> think of to try and figure out where power was not being applied when
> needed.
> 
> Should I bother to include this patch in the series at all? It's purely
> for diagnostics to make sure the panel is powered during all aux channel
> transactions.

Yes, adding the extra checks made my day. :)

Modesetting bugs are the hardest to reproduce so every additional check
(with a reasonable false positive rate) is worth their weight in gold when
it comes to diagnosing misbehaving hardware. And the checks improve the
maintainability of the code.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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