linux-kernel - Re: [3.4 regression] [bisected] DisplayPort fails to come on

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Message-ID: <4FD9F9B0.9030204@cwi.nl>
Date:	Thu, 14 Jun 2012 15:48:16 +0100
From:	"Wouter M. Koolen" <W.M.Koolen-Wijkstra@....nl>
To:	Daniel Vetter <daniel.vetter@...ll.ch>
CC:	Dave Airlie <airlied@...il.com>,
	"Wouter M. Koolen" <W.M.Koolen-Wijkstra@....nl>,
	intergalactic.anonymous@...il.com, len.brown@...el.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	"Barnes, Jesse" <jbarnes@...tuousgeek.org>,
	"Wilson, Chris" <chris.wilson@...el.com>
Subject: Re: [3.4 regression] [bisected] DisplayPort fails to come on

On 06/14/2012 03:05 PM, Daniel Vetter wrote:
> Can you please boot with drm.debug=0xe added to your kernel
> cmdline and attach the full dmesg, so we know a bit what your display
> hw looks like?
Please find attached dmesg output with drm.debug=0xe.

3.3.8 is the baseline, on which the display port monitor works fine.
3.4.2.cold is a cold boot into 3.4.2. The monitor on the display port 
remains blank. That is, it displays "No Signal Input" and then enters 
power saving mode.
3.4.2 is a reboot after running 3.3.8 first. Now the monitor attached to 
the display port works too.

The main difference between 3.4.2 and 3.4.2.cold seems to be that a warm 
boot reports "clock recovery OK", whereas a cold boot fails trying to 
train the link.

I did have a look at the (many) differences between 3.3.8 and 3.4.2, but 
I can't see anything that looks important. I will happily leave further 
interpretation to you.

I hope this will give someone an idea. In the mean while I will redo the 
bisect.

With kind regards,

Wouter

View attachment "3.3.8" of type "text/plain" (83503 bytes)

View attachment "3.4.2" of type "text/plain" (111506 bytes)

View attachment "3.4.2.cold" of type "text/plain" (125239 bytes)