[Bug 78507] New: [HD-4400]No native resolution 2560x1600 on Lenovo Onelink Pro DisplayPort and X1 Carbon 2014

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=78507

          Priority: medium
            Bug ID: 78507
                CC: intel-gfx-bugs at lists.freedesktop.org
          Assignee: intel-gfx-bugs at lists.freedesktop.org
           Summary: [HD-4400]No native resolution 2560x1600 on Lenovo
                    Onelink Pro DisplayPort and X1 Carbon 2014
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
          Severity: normal
    Classification: Unclassified
                OS: Linux (All)
          Reporter: anewgene+freedesktop at gmail.com
          Hardware: x86-64 (AMD64)
            Status: NEW
           Version: XOrg CVS
         Component: DRM/Intel
           Product: DRI

Created attachment 98791
  --> https://bugs.freedesktop.org/attachment.cgi?id=98791&action=edit
dmesg_debug_DP2.txt

Previous drm-intel-nightly kernel
(http://kernel.ubuntu.com/~kernel-ppa/mainline/drm-intel-nightly/2014-04-17-trusty/)
solves the native resolution issue, but caused blank screen on built-in laptop
display. See bug 77660.

The latest drm-intel-nightly kernel (3.15.0-994_3.15.0-994.201405080316) solves
the blank screen issue now, but I lose the native resolution 2560x1600 on
external display. It only support generic 1024x768 and 800x600 modes. 

I can see many errors like this in dmesg log:

[    6.433670] [drm:drm_dp_i2c_do_msg] I2C defer
[    6.434177] [drm:drm_dp_i2c_do_msg] too many retries, giving up

I attached full dmesg log with drm.debug=0xe.

It's very tricky that, occasionally, it does work fine, but most of time, it's
not. I tried booting into Windows 8, it never had the issue.


System environment:
-- chipset: intel i7-4600U (HD-4400)
-- system architecture: 64-bit
-- kernel: drm-intel-nightly kernel (3.15.0-994_3.15.0-994.201405080316)
-- Linux distribution: Ubuntu 14.04
-- xserver: 1.15.1
-- xserver-xorg-video-intel: 2:2.99.910-0ubuntu1 
-- Machine or mobo model: Lenovo X1 Carbon 2014 (20A7CTO1WW)
-- Display connector: DisplayPort on OneLink Pro dock
-- Monitor: Dell U3011

Reproducing steps:
* install latest drm-intel-nightly upstream kernel
* boot with this kernel

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