• Hans de Goede's avatar
    sunxi: display: Use PWM to drive backlight where applicable · 421c98d7
    Hans de Goede authored
    When the backlight's pwm input is connected to a pwm output of the SoC,
    actually use pwm to drive the backlight.
    
    The mean reason for doing this is to fix the backlight turning off
    for aprox. 1 second while the kernel is booting. This is caused by
    the kernel actually using pwm to drive the backlight, so that it
    can dim the backlight. First the pwm driver loads and switches the
    pinmux for the pin driving the backlight's pwm input to the pwm
    controller. Then about 1s later the actual backlight driver loads
    and tells the pwm driver to actually update the pwm settings, which
    have a power-on-reset value of "off".
    
    An additional advantage is that this allows us to initatiate the
    backlight at 80%, which is the kernel default, avoiding a brightness
    change while the kernel loads.
    Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
    Reviewed by: Peter Korsgaard <peter@korsgaard.com>
    421c98d7
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