[Intel-gfx] Regression: Backlight not coming on after resume.

[James Courtier-Dutton]

Bisect done on tree:
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
Worked on 3.7.
Broken on 3.8

Problem: "Backlight not coming on after resume."
git finally bisected  for my Samsung Serial 7 Laptop.
Bisecting: 0 revisions left to test after this (roughly 0 steps)
[cf0a6584aa6d382f802f2c3cacac23ccbccde0cd] drm/i915: write backlight
harder     <- This is the problem commit. Seems that fixing some
machines breaks others, based on the existing comments on that patch.

git bisect log
git bisect start
# bad: [09884964335e85e897876d17783c2ad33cf8a2e0] mm: do not grow the
stack vma just because of an overrun on preceding vma
git bisect bad 09884964335e85e897876d17783c2ad33cf8a2e0
# good: [6c5096e5538b455bc3bea2b02588c380f070d8c6] Merge tag 'boards'
of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc
git bisect good 6c5096e5538b455bc3bea2b02588c380f070d8c6
# good: [21fbd5809ad126b949206d78e0a0e07ec872ea11] Merge branch
'v4l_for_linus' of
git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
git bisect good 21fbd5809ad126b949206d78e0a0e07ec872ea11
# bad: [fffddfd6c8e0c10c42c6e2cc54ba880fcc36ebbb] Merge branch
'drm-next' of git://people.freedesktop.org/~airlied/linux
git bisect bad fffddfd6c8e0c10c42c6e2cc54ba880fcc36ebbb
# bad: [b81e059ec5a7128622ab5d74d78e9b4f361b54ae] Merge branch
'drm-intel-fixes' of git://people.freedesktop.org/~danvet/drm-intel
into drm-next
git bisect bad b81e059ec5a7128622ab5d74d78e9b4f361b54ae
# good: [d6dd9eb1d96d2b7345fe4664066c2b7ed86da898] drm/i915: dynamic
Haswell display power well support
git bisect good d6dd9eb1d96d2b7345fe4664066c2b7ed86da898
# good: [73ccd6962fff19e53a7d4baaa17cf9311284ac9c] Merge branch
'drm-next-3.9' of git://people.freedesktop.org/~agd5f/linux into
drm-next
git bisect good 73ccd6962fff19e53a7d4baaa17cf9311284ac9c
# good: [a4462f246c8821f625f45bce52c7ca7e0207dffe] staging/omapdrm:
Use kmemdup rather than duplicating its implementation
git bisect good a4462f246c8821f625f45bce52c7ca7e0207dffe
# bad: [d84f031bd230fdf9c3b7734940c859bf28b90219] drm: Use C8 instead
of RGB332 when determining the format from depth/bpp
git bisect bad d84f031bd230fdf9c3b7734940c859bf28b90219
# bad: [f73f760725636b9d0c3786273e185b053516d1eb] drm/i915/ctx: Remove
bad invariant
git bisect bad f73f760725636b9d0c3786273e185b053516d1eb
# bad: [26739f12cf210cb8df35969258a1f064e8e12b63] drm/i915: unify
HDMI/DP hpd definitions
git bisect bad 26739f12cf210cb8df35969258a1f064e8e12b63
# good: [b8efb17b3d687695b81485f606fc4e6c35a50f9a] i915: ignore lid
open event when resuming
git bisect good b8efb17b3d687695b81485f606fc4e6c35a50f9a
# bad: [07ea0d85ac8adb87b817913d9720e3c76171b1f6] drm/i915: Clarify HW
context size logic
git bisect bad 07ea0d85ac8adb87b817913d9720e3c76171b1f6