On Fri, Nov 09, 2018 at 10:48:57AM +0100, Heiko Stuebner wrote:
> Commit e6bcca0890b9 ("backlight: pwm_bl: Switch to using "atomic" PWM API")
> removed the driver internal enabled tracking in favor of simply checking
> the pwm state.
>
> This can lead to issues as all of gpio-, regulator- and pwm-state are used
> to determine the initial state and the bootloader or kernel can leave them
> in an inconsistent state at boot.
>
> In my case on rk3399-kevin, the pwm backlight is build as module and the
> kernel disables the supply regulator as unused while keeping the pwm running
> thus pwm_bl calling pwm_backlight_power_off() during probe and creating an
> unmatched regulator-disable call, as it never got enabled from the pwm-bl
> before.
>
> To prevent these consistency issues, reintroduce the driver-internal
> tracking of the enabled state.
>
> Fixes: e6bcca0890b9 ("backlight: pwm_bl: Switch to using "atomic" PWM API")
> Signed-off-by: Heiko Stuebner <heiko@xxxxxxxxx>
> ---
> drivers/video/backlight/pwm_bl.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
Acked-by: Thierry Reding <thierry.reding@xxxxxxxxx>
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