Re: Problems w/Sandy Bridge & 27" monitor

Daniel Vetter
2012-08-27T19:07:49Z

On Mon, Aug 27, 2012 at 02:47:58PM -0400, Chun-Yu Shei wrote:
> On 8/15/2012 6:47 PM, Daniel Vetter wrote:
> >On Wed, Aug 15, 2012 at 06:38:10PM -0400, Chun-Yu Shei wrote:
> >>Hi,
> >>
> >>I recently upgraded to a 27" monitor (2560x1440) from a 23" one
> >>(1920x1080), and had to switch to Windows because the new monitor is
> >>unusable in Linux. Today, about a month later, I decided to give
> >>Linux another try, since there have been several updates to the
> >>Intel graphics driver since then.
> >>
> >>Unfortunately, it seems that it's still unusable with
> >>xf86-video-intel 2.20.3 -- after a little while, the video signal to
> >>the 27" monitor completely stops, and it goes into power saving
> >>mode. I'm running dual monitors with the old 23", and that one
> >>continues running fine when this happens. This happens on my
> >>ThinkPad X220 (i5-2540M). The 27" is connected via DisplayPort, and
> >>the 23" via DVI. SNA is enabled, if it makes any difference (I
> >>haven't tried turning it off, but I probably should). This is the
> >>biggest problem I'm facing when it comes to Linux support.
> >>
> >>I also gave the new "TearFree" option a try, and while it does a
> >>great job of eliminating tearing, it makes the two monitors become
> >>mirrors of each other for some reason. If I take a screenshot with
> >>the GNOME tool, the screenshot comes out as expected (unmirrored),
> >>but the video output on the two monitors is mirrored in reality.
> >>Disabling "TearFree" fixes this.
> >>
> >>Also, when I'm using the ThinkPad's built-in display, it sometimes
> >>turns off for no apparent reason, although it's not too big of a
> >>deal since a suspend/resume cycle seems to fix things (and I haven't
> >>used 2.20.3 long enough to experience this yet).
> >>
> >>Any ideas/things I can do to help track these issues down?
> >
> >For the screen blanking issues, the kernel is the important part. Please
> >boot with drm.debug=0xe added to your kernel bootline and grab the full
> >dmesg.
> >-Daniel
> >
>
> OK, I finally got around to doing this... I just upgraded to the
> 3.5.3 kernel and xf86-video-intel 2.20.5 as well.
>
> Here's the initial dmesg upon bootup: http://pastebin.com/41F2AA0f
>
> And here's the dmesg right after the 27" goes blank:
> http://pastebin.com/3CTRETQ4 (not completely blank, though... there
> are a few lines at the very left & top edge of the display)
>
> A few seconds later, the display came back, and here's the dmesg
> right after that: http://pastebin.com/9mdfY5P1

Hm, there's nothing really interesting with that screen going on ... Also,
3.5.3 is up-to-date with all recent DP fixes. One thing that could be is
that this is another version of our fdi link training woes on ivb.

To check for that, can you please run your 27" screen at a much lower
resolution? If it still blanks out, it's a different issue.

Thanks, Daniel
--
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48