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2153bbc12f
According to the datasheet the update bit must be set if the on-time-div or the base-unit changes. Now that we properly order device resume on Cherry Trail so that the GFX0 _PS0 method no longer exits with an error, we end up with a sequence of events where we are writing the same values twice in a row. First the _PS0 method restores the duty cycle of 0% the GPU driver set on suspend and then the GPU driver first updates just the enabled bit in the pwm_state from 0 to 1, causing us to write the same values again, before restoring the pre-suspend duty-cycle in a separate pwm_apply call. When writing the update bit the second time, without changing any of the values the update bit clears immediately / instantly, instead of staying 1 for a while as usual. After this the next setting of the update bit seems to be ignored, causing the restoring of the pre-suspend duty-cycle to not get applied. This makes the backlight come up with a 0% dutycycle after suspend/resume. Any further brightness changes after this do work. This commit moves the setting of the update bit into pwm_lpss_prepare() and only sets the bit if we have actually changed any of the values. This avoids the setting of the update bit the second time we configure the PWM to 0% dutycycle, this fixes the backlight coming up with 0% duty-cycle after a suspend/resume. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>