[Bug 68355] New: [HSW ULT] eDP backlight regression at 1920x1080

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=68355

          Priority: medium
            Bug ID: 68355
          Assignee: intel-gfx-bugs at lists.freedesktop.org
           Summary: [HSW ULT] eDP backlight regression at 1920x1080
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
          Severity: normal
    Classification: Unclassified
                OS: All
          Reporter: enabfluw at gmail.com
          Hardware: Other
            Status: NEW
           Version: XOrg CVS
         Component: DRM/Intel
           Product: DRI

Created attachment 84358
  --> https://bugs.freedesktop.org/attachment.cgi?id=84358&action=edit
dmesg for failing rc1 kernel with drm.debug=6

System environment:
-- chipset: HSW ULT
-- system architecture: 64-bit
-- xf86-video-intel:
-- xserver:
-- mesa:
-- libdrm:
-- kernel: 3.11.0-031100rc2-generic
-- Linux distribution: Linux Mint 15 Olivia
-- Machine or mobo model: Acer Aspire S3-392-9460
-- Display connector: eDP1

Reproducing steps:
1. Install 3.11.0-rc1, reboot, watch it work
2. Install 3.11.0-rc2, reboot, watch it fail
3. Install 3.11.0-996.201308070456, reboot, watch it work
4. Install 3.11.0-996.201308080456 (notice the date is just the next day),
reboot, watch it fail
5. Install any kernel after rc1 or the 996.20130807, reboot, watch it fail.

Additional info:
GRUB_CMDLINE_LINUX="drm.debug=6 acpi_backlight=vendor"

I can get native 1920x1080 resolution to work on a "failing" kernel by doing
the following:
1. Boot any "failing" kernel
2. Watch everything go black
3. Blindly log into X and open a terminal
4. xrandr -s 800x600 (or some other lower resolution than 1920x1080)
5. Watch the screen flash for a millisecond and then remain black
6. Ctrl+Alt+F7 to a tty, see it switch to 1920x1080
7. Ctrl+Alt+F8 to get back to X, see it switch to the xrandr'd resolution
8. xrandr -s 1920x1080 and watch it work correctly!

More logs to come...

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