Re: Problems w/Sandy Bridge & 27" monitor

Chun-Yu Shei
2012-08-27T19:30:32Z

On 08/27/2012 03:08 PM, Daniel Vetter wrote:
> 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
>

Seems to be working perfectly at 1600x900 (btw, I'm on Sandy Bridge, not
ivb).

Chun-Yu