backlight: pwm_bl: Re-add driver internal enabled tracking

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@sntech.de>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 678b270..bcd08b4 100644 (file)
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -30,6 +30,7 @@ struct pwm_bl_data {
        struct device           *dev;
        unsigned int            lth_brightness;
        unsigned int            *levels;
+       bool                    enabled;
        struct regulator        *power_supply;
        struct gpio_desc        *enable_gpio;
        unsigned int            scale;
@@ -50,7 +51,7 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb)
        int err;
 
        pwm_get_state(pb->pwm, &state);
-       if (state.enabled)
+       if (pb->enabled)
                return;
 
        err = regulator_enable(pb->power_supply);
@@ -65,6 +66,8 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb)
 
        if (pb->enable_gpio)
                gpiod_set_value_cansleep(pb->enable_gpio, 1);
+
+       pb->enabled = true;
 }
 
 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
@@ -72,7 +75,7 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb)
        struct pwm_state state;
 
        pwm_get_state(pb->pwm, &state);
-       if (!state.enabled)
+       if (!pb->enabled)
                return;
 
        if (pb->enable_gpio)
@@ -86,6 +89,7 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb)
        pwm_apply_state(pb->pwm, &state);
 
        regulator_disable(pb->power_supply);
+       pb->enabled = false;
 }
 
 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
@@ -483,6 +487,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
        pb->check_fb = data->check_fb;
        pb->exit = data->exit;
        pb->dev = &pdev->dev;
+       pb->enabled = false;
        pb->post_pwm_on_delay = data->post_pwm_on_delay;
        pb->pwm_off_delay = data->pwm_off_delay;