• Ben Widawsky's avatar
    drm/i915/bdw: GEN8 backlight support · f8e10062
    Ben Widawsky authored
    Prior to Haswell the CPU control register for backlight
    (BLC_PWM_CPU_CTL) toggled the PCH baclight pin for us. This made some
    sense as there was no pin on the CPU. With Haswell came the introduction
    of a CPU backlight pin, but the interface was still controlled by
    software with the same mechnism. Behind the scenes, hardware did all the
    dirty work for us.
    
    Broadwell no longer provides this for free. If we want to use the PCH
    backlight pin [1] then we have to set the override bit BLC_PWM_PCH_CTL1
    and program BLC_PWM_PCH_CTL2 for the PWM values.
    
    This patch implements that. This patch is compile tested only, and given
    that I rarely if ever touch this code, careful review is welcome.
    
    [1] According to Art, we know of no devices that exist which use the CPU
    pin (and remember it has existed already on HSW). If such a device does
    exist, we'll have to handle it properly - this is left as TODO until
    then.
    
    v2: Drop the abstraction prep patch, as a bigger backlight overhaul is
        in the works, and do just the mimimal bdw enabling now. (by Jani)
    
    CC: Art Runyan <arthur.j.runyan@intel.com>
    Signed-off-by: default avatarBen Widawsky <ben@bwidawsk.net>
    Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
    Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
    f8e10062
intel_panel.c 24.4 KB