[Bug 73567] New: [915 Haswell ULT Asus UX302LA/LG] eDP bpp clamping results in blank screen

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=73567

          Priority: medium
            Bug ID: 73567
                CC: intel-gfx-bugs at lists.freedesktop.org
          Assignee: intel-gfx-bugs at lists.freedesktop.org
           Summary: [915 Haswell ULT Asus UX302LA/LG] eDP bpp clamping
                    results in blank screen
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
          Severity: normal
    Classification: Unclassified
                OS: Linux (All)
          Reporter: albaguirre at gmail.com
          Hardware: x86-64 (AMD64)
            Status: NEW
           Version: unspecified
         Component: DRM/Intel
           Product: DRI

Created attachment 91970
  --> https://bugs.freedesktop.org/attachment.cgi?id=91970&action=edit
Test ignoring bpp clamping

I have an ASUS UX302LA laptop running Ubuntu 14.04 daily build. I've switched
the kernel to the latest drm-intel-nightly from here:

    http://kernel.ubuntu.com/~kernel-ppa/mainline/drm-intel-nightly/current/)

Any sequence that turns off/on the panel (suspend/resume, modesetting) results
in a blank screen.

I narrowed it down to the clamping code in intel_dp.c after going through this
old bug thread (see attached patch)

   https://bugzilla.kernel.org/show_bug.cgi?id=59841

When ignoring the clamping - no blank screen issues occur.

The hack implemented in intel_dp.c:

   commit c6cd2ee2d59111a07cd9199564c9bdcb2d11e5cf
   Author: Jani Nikula <jani.nikula at intel.com>
   Date:   Mon Oct 21 10:52:07 2013 +0300W

       drm/i915/dp: workaround BIOS eDP bpp clamping issue


Is not effective on the UX302LA/LG - from logs it looks like
intel_dp_get_config is never called - any idea why?

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