linux-kernel - Re: [Intel-gfx] [PATCH 06/21] drm/i915: Unlock PCH_PP

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Date:	Fri, 30 Sep 2011 16:14:40 -0700
From:	Keith Packard <keithp@...thp.com>
To:	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 06/21] drm/i915: Unlock PCH_PP_CONTROL always

On Fri, 30 Sep 2011 19:09:46 +0200, Daniel Vetter <daniel@...ll.ch> wrote:

> grep shows that we also write to PCH_PP_CONTROL in intel_lvds.c in the
> dpms functions - any reasons these two writes are left out?

Upon a bit of review:

  The bspec makes it clear that this write protect key only needs to
  be written for eDP on DPA -- it's a work-around for a bug where panel
  power sequencing wouldn't work right.

  The LVDS code does disable write protect in the _init function, which
  seems global enough, but misses the resume case. We shouldn't ever
  need to set this field though; it write protects registers only
  when the panel is running. We could presumably remove the
  write protect disable entirely in the LVDS code.

So, I think the patch as written is correct.

-- 
keith.packard@...el.com

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