linux-kernel - Re: i915 wakes from suspend to RAM with blank screen after commit cd9dde44f47501394b9f0715b6a36a92aa74c0d0

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Message-ID: <20120123063313.GA2113@nbgentoo>
Date:	Mon, 23 Jan 2012 07:33:14 +0100
From:	Lubos Kolouch <lubos.kolouch@...il.com>
To:	Keith Packard <keithp@...thp.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: i915 wakes from suspend to RAM with blank screen after commit
 cd9dde44f47501394b9f0715b6a36a92aa74c0d0

On Sun, Jan 22, 2012, 20:00:18, Keith Packard wrote:
> On Sun, 22 Jan 2012 11:29:12 +0100, Lubos Kolouch <lubos.kolouch@...il.com> wrote:
> 
> > Thanks, here you go:
> > dmesg after boot - http://paste.pocoo.org/show/538625/
> > dmesg after failed resume - http://paste.pocoo.org/show/538626/
> 
> Ok, looks like my theory is correct. We're fitting a 24bpp mode to an
> 18bpp data rate, which doesn't work.
> 
> I'm in the middle of bisecting a bluetooth failure in 3.3-rc1, so I
> don't have a working kernel at present, but here's a section of
> intel_dp.c in the intel_dp_mode_fixup function:
> 
>   	int max_clock = intel_dp_max_link_bw(intel_dp) == DP_LINK_BW_2_7 ? 1 : 0;
> -	int bpp = mode->private_flags & INTEL_MODE_DP_FORCE_6BPC ? 18 : 0;
> +	int bpp = mode->private_flags & INTEL_MODE_DP_FORCE_6BPC ? 18 : 24;
>  	static int bws[2] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7 };
> 
> (this is completely hand-generated, so 'patch' will almost certainly not work)
> 
> This will force it to use the correct bpp when computing the bandwidth
> used by the new mode. This should fix your problem. If so, I'll have a
> larger patch which stops the underlying function from (almost always
> incorrectly) using the current bpp when computing bandwidth.
> 
> -- 
> keith.packard@...el.com
Thanks, I applied it and it seems to solve the issue!

dmesg after boot - http://paste.pocoo.org/show/539115/
dmesg after OK resume - http://paste.pocoo.org/show/539117/

Lubos
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