[PATCH] backlight: pwm_bl: re-add driver internal enabled tracking

[Uwe Kleine-König]

Hello Heiko,

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 at sntech.de>

This looks right,

Acked-by: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>

Best regards
Uwe

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