linux-kernel - Re: [Intel-gfx] [PATCH 4/7] drm/i915: Let panel power sequencing hardware do its job

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Message-ID: <20111102092310.2177a339@jbarnes-desktop>
Date:	Wed, 2 Nov 2011 09:23:10 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Keith Packard <keithp@...thp.com>
Cc:	intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH 4/7] drm/i915: Let panel power sequencing
 hardware do its job

On Wed, 02 Nov 2011 00:31:40 -0700
Keith Packard <keithp@...thp.com> wrote:

> On Tue,  1 Nov 2011 23:20:27 -0700, Keith Packard <keithp@...thp.com> wrote:
> 
> > -static void ironlake_wait_panel_off(struct intel_dp *intel_dp)
> > +#define IDLE_ON_MASK		(PP_ON | PP_READY | PP_SEQUENCE_MASK | 0                     | PP_SEQUENCE_STATE_MASK)
> > +#define IDLE_ON_VALUE   	(PP_ON | PP_READY | PP_SEQUENCE_NONE | 0                     | PP_SEQUENCE_STATE_ON_IDLE)
> 
> A bit more testing -- looks like the MacBook Air doesn't mange to get
> PP_READY set when it's time to turn the panel on. I should look at this
> a bit more closely; there's no reason it shouldn't be set. But, nothing
> bad seems to happen if we simply ignore the PP_READY bit
> 
> +#define IDLE_ON_MASK		(PP_ON | 0      | PP_SEQUENCE_MASK | 0                     | PP_SEQUENCE_STATE_MASK)
> +#define IDLE_ON_VALUE   	(PP_ON | 0      | PP_SEQUENCE_NONE | 0                     | PP_SEQUENCE_STATE_ON_IDLE)

Note that PP_READY will incorrectly depend on some other register
values, so in some configs the panel will happily power up even if
PP_READY isn't set yet...

-- 
Jesse Barnes, Intel Open Source Technology Center

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