[Bug 94825] LVDS blank screen on GM45

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94825

--- Comment #13 from Rob Kramer <rob at solution-space.com> ---
Some things I could try:

1) Override broken panel type via module parameter.
2) Disable VBT via module parameter, force use of existing mode.
3) Use video=.. parameter to lookup matching VBT panel.

I've tried option 1, hack panel_type to 15 in intel_bios.c, and that works:

  [    4.770027] [drm:intel_lvds_init] using mode from VBT:
  [    4.770030] [drm:drm_mode_debug_printmodeline] Modeline 0:"1920x1080" 0
148500 1920 2040 2080 2200 1080 1081 1092 1125 0x8 0xa
  [    4.770033] [drm:intel_lvds_init] detected dual-link lvds configuration

Option 2 also works (hack out VBT setting), but results in messy kernel
warnings/backtraces about pipe state mismatches, see previously attached logs.

I don't know if option 3 is too horrible to consider.

I've applied your patch to 4.5 (with minor port), but it returns too early at:

        ret = acpi_video_get_edid(acpidev, ACPI_VIDEO_DISPLAY_LCD, -1, &edid);
        if (ret < 0)
                return ret;

Could my kernel be missing some ACPI stuff? There is CONFIG_ACPI_VIDEO=m, and
the module is loaded. I didn't add a new boot log since there wasn't anything
new. If you have some ideas on how to debug this, please let me know (I know
very little about ACPI)..

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