linux-kernel - Re: [BUG] drm/i915 Screen corruption introduced by a00b10c360b35d6431a94cb

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Date:	Sun, 20 Feb 2011 03:20:15 +0100 (CET)
From:	"Indan Zupancic" <indan@....nu>
To:	"Indan Zupancic" <indan@....nu>,
	"Chris Wilson" <chris@...is-wilson.co.uk>,
	"LKML" <linux-kernel@...r.kernel.org>,
	dri-devel@...ts.freedesktop.org
Subject: Re: [BUG] drm/i915 Screen corruption introduced by 
     a00b10c360b35d6431a94cb

Hi,

On Sat, February 19, 2011 19:25, Daniel Vetter wrote:
> Hi Indan,
>
> Please provide the usual details about your system (especially what gpu
> this is on). Also, screenshots of what typical corruptions look like can
> help a lot in tracking down such things.

Sorry, I plainly forgot to mention that. I'm on my Thinkpad X40 with gen 2
hardware, 855GM.

I uploaded a screenshot of Firefox to:
http://img406.imageshack.us/img406/9159/31827167.png

It happens a lot when scrolling in FF on pages with images, pageup or pagedown
don't exhibit it. Text gets corrupted as well, but in a less predictable way.
It must be something that FF does that triggers it easily, I haven't managed
to get it with other programs yet, though I do see some corruption in the
window decoration too sometimes (which is Fluxbox). Scrolling horizontally
doesn't show the same behaviour. The corruptions seems to be happening on
the right side of a surface/window.

Forcing a refresh makes it go away again (e.g. switching to another window or
opening another window on top of it. Moving a window doesn't though). I get
it with and without xcompmgr running.

Okay, interesting titbit: For text corruption, the stripes are one pixel high
for the default font size, no corruption for smaller sizes than the default,
two pixel lines for 1 ctrl+ bigger than the default, 3 pixels for +2 etc.
With bigger sizes (>=5) I get less corruption to the left of the text, but
more in the text itself. The distance between the lines continues to increase,
but the stripes thickness goes back to 1 pixel.

Perhaps an off-by-one error somewhere?

> I've created two quick patches to check a few theories, please test them
> (both patches independently and both together). Patches attached.

Tried with both applied, doesn't change anything.

Greetings,

Indan

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