From mboxrd@z Thu Jan  1 00:00:00 1970
From: Daniel Vetter <daniel@ffwll.ch>
Subject: Re: [PATCH] drm/i915: enable vdd when switching off the
	eDP panel
Date: Tue, 22 May 2012 08:14:55 +0200
Message-ID: <20120522061455.GA4672@phenom.ffwll.local>
References: <1337526890-9685-1-git-send-email-daniel.vetter@ffwll.ch>
	<20120521164030.GB4970@phenom.ffwll.local>
	<86vcjphtnl.fsf@sumi.keithp.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org>
Received: from mail-we0-f177.google.com (mail-we0-f177.google.com
	[74.125.82.177])
	by gabe.freedesktop.org (Postfix) with ESMTP id C040A9E852
	for <intel-gfx@lists.freedesktop.org>;
	Mon, 21 May 2012 23:13:42 -0700 (PDT)
Received: by werc12 with SMTP id c12so4626715wer.36
	for <intel-gfx@lists.freedesktop.org>;
	Mon, 21 May 2012 23:13:41 -0700 (PDT)
Content-Disposition: inline
In-Reply-To: <86vcjphtnl.fsf@sumi.keithp.com>
List-Unsubscribe: <http://lists.freedesktop.org/mailman/options/intel-gfx>,
	<mailto:intel-gfx-request@lists.freedesktop.org?subject=unsubscribe>
List-Archive: <http://lists.freedesktop.org/archives/intel-gfx>
List-Post: <mailto:intel-gfx@lists.freedesktop.org>
List-Help: <mailto:intel-gfx-request@lists.freedesktop.org?subject=help>
List-Subscribe: <http://lists.freedesktop.org/mailman/listinfo/intel-gfx>,
	<mailto:intel-gfx-request@lists.freedesktop.org?subject=subscribe>
Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org
Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org
To: Keith Packard <keithp@keithp.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>, Intel Graphics Development <intel-gfx@lists.freedesktop.org>, stable@kernel.org
List-Id: intel-gfx@lists.freedesktop.org

On Mon, May 21, 2012 at 06:49:18PM -0700, Keith Packard wrote:
> Daniel Vetter <daniel@ffwll.ch> writes:
> 
> >> --- a/drivers/gpu/drm/i915/intel_dp.c
> >> +++ b/drivers/gpu/drm/i915/intel_dp.c
> >> @@ -1154,11 +1154,10 @@ static void ironlake_edp_panel_off(struct intel_dp *intel_dp)
> >>  
> >>  	DRM_DEBUG_KMS("Turn eDP power off\n");
> >>  
> >> -	WARN(intel_dp->want_panel_vdd, "Cannot turn power off while VDD is on\n");
> >> -	ironlake_panel_vdd_off_sync(intel_dp); /* finish any pending work */
> >> +	WARN(!intel_dp->want_panel_vdd, "Need VDD to turn off panel\n");
> >>  
> >>  	pp = ironlake_get_pp_control(dev_priv);
> >> -	pp &= ~(POWER_TARGET_ON | EDP_FORCE_VDD | PANEL_POWER_RESET | EDP_BLC_ENABLE);
> >> +	pp &= ~(POWER_TARGET_ON | PANEL_POWER_RESET | EDP_BLC_ENABLE);
> 
> Can you explain where the panel is getting turned off here?

Well, before this change the edp power off sequence was:
- switch vdd off (or more precise: ensure it's off)
- switch backlight off
- switch panel power off (i.e. the above function)

Now the new sequence is (always with the right amounts of delays,
obviously):
- switch vdd on
- switch backlight off
- switch panel off
- switch vdd off

That's why I've had to remove the EDP_FORCE_VDD bit from the above
bitfrobbing, because we now want vdd to stay on while we do the power
sequence above.

The reason is that we have a callchain (in intel_dp_prepare) where we do
some aux channel communication after having switched off the panel. And
that needs vdd, but because edp_panel_off killed that, things got
confused.
-Daniel
-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48