[Bug 88325] screen brightness regression on resume

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=88325

--- Comment #9 from Daniel Nicoletti <dantti12 at gmail.com> ---
This is the commit which introduced the regression, by the description it seems
to be it:

daniel at bart:~/code/drm-intel$ git bisect good
c675949ec58ca50d5a3ae3c757892f1560f6e896 is the first bad commit
commit c675949ec58ca50d5a3ae3c757892f1560f6e896
Author: Jani Nikula <jani.nikula at intel.com>
Date:   Wed Apr 9 11:31:37 2014 +0300

    drm/i915: do not setup backlight if not available according to VBT

    Some machines use an external EC for controlling the backlight. Info
    about this is present in the VBT. Do not setup native backlight control
    if no PWM backlight is available or supported according to VBT. The
    acpi_backlight interface appears to work for the EC control.

    In most cases there has been no harm done, but it looks like there are
    machines out there that have both an EC and our PWM line connected to
    the same wire. This, obviously, does not end well.

    This should fix the regression caused by
    commit bc0bb9fd1c7810407ab810d204bbaecb255fddde
    Author: Jani Nikula <jani.nikula at intel.com>
    Date:   Thu Nov 14 12:14:29 2013 +0200

        drm/i915: remove QUIRK_NO_PCH_PWM_ENABLE

    AFAICT the quirk removed by the above commit effectively resulted in
    i915 not driving the backlight PWM output, thus not messing things up.

    Additionally this should fix the regression caused by
    commit fbc9fe1b4f222a7c575e3bd8e9defe59c6190a04
    Author: Aaron Lu <aaron.lu at intel.com>
    Date:   Fri Oct 11 21:27:45 2013 +0800

        ACPI / video: Do not register backlight if win8 and native interface
exists

    which left some machines without a functioning backlight interface.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76276                
    Reference: https://bugzilla.kernel.org/show_bug.cgi?id=47941                
    Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=62281                 
    CC: Aaron Lu <aaron.lu at intel.com>                                           
    CC: Eric Griffith <EGriffith92 at gmail.com>                                   
    CC: Kent Baxley <kent.baxley at canonical.com>                                 
    Tested-by: Kamal Mostafa <kamal at canonical.com>                              
    Tested-by: Martin <bugs at mrvanes.com>                                        
    Tested-by: jrg.otte at gmail.com
    Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
    Signed-off-by: Jani Nikula <jani.nikula at intel.com>

:040000 040000 9ed3e48521f181c53dfe780b28450e678aa4b9ea
b9a776bb2de3ba84f614087619e9e91a2bdcc960 M      drivers

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