[Bug 54661] Backlight doesn't turn on after suspend on Acer 1830T with Ironlake chip running 3.8.1

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=54661





--- Comment #1 from Ilya Tumaykin <itumaykin at gmail.com>  2013-03-02 19:13:29 ---
I've done `git bisect` against 3.8.0 and the result is:

719429a54d9c8fd32d457c7d564d1272d9003282 is the first bad commit
commit 719429a54d9c8fd32d457c7d564d1272d9003282
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Wed Feb 6 11:24:41 2013 +0100

    drm/i915: write backlight harder

    commit cf0a6584aa6d382f802f2c3cacac23ccbccde0cd upstream.

    770c12312ad617172b1a65b911d3e6564fc5aca8 is the first bad commit
    commit 770c12312ad617172b1a65b911d3e6564fc5aca8
    Author: Takashi Iwai <tiwai at suse.de>
    Date:   Sat Aug 11 08:56:42 2012 +0200

        drm/i915: Fix blank panel at reopening lid

    changed the register write sequence for restoring the backlight, which
    helped prevent non-working backlights on some machines. Turns out that
    the original sequence was the right thing to do for a different set of
    machines. Worse, setting the backlight level _after_ enabling it seems
    to reset it somehow. So we need to make that one conditional upon the
    backlight having been reset to zero, and add the old one back.

    Cargo-culting at it's best, but it seems to work.

    Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=47941
    Cc: Takashi Iwai <tiwai at suse.de>
    Reviewed-by: Jani Nikula <jani.nikula at intel.com>
    Acked-by: Takashi Iwai <tiwai at suse.de>
    Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
    Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>

:040000 040000 5ec4d4ca970fb18ac9979a330017ee1a1fb34223
18e15a8e31b41165605c65eba325052a352ec587 M      drivers

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