backlight: pwm_bl: Configure pwm only once per backlight toggle

When the function pwm_backlight_update_status() was called with
brightness > 0, pwm_get_state() was called twice (once directly and once
in compute_duty_cycle). Also pwm_apply_state() was called twice (once in
pwm_backlight_power_on() and once directly).

Optimize this to do both calls only once.

Note that with this affects the order of regulator and PWM setup. It's
not expected to have a relevant effect on hardware. The rationale for
this is that the regulator (and the GPIO) are reasonable to switch in
pwm_backlight_power_on()/pwm_backlight_power_off() but the PWM has
nothing to do with power. (The post_pwm_on_delay and pwm_off_delay are
still there though.)

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230120120018.161103-2-u.kleine-koenig@pengutronix.de

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index d0b2215..0509fec 100644 (file)
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -40,10 +40,8 @@ struct pwm_bl_data {
 
 static void pwm_backlight_power_on(struct pwm_bl_data *pb)
 {
-       struct pwm_state state;
        int err;
 
-       pwm_get_state(pb->pwm, &state);
        if (pb->enabled)
                return;
 
@@ -51,9 +49,6 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb)
        if (err < 0)
                dev_err(pb->dev, "failed to enable power supply\n");
 
-       state.enabled = true;
-       pwm_apply_state(pb->pwm, &state);
-
        if (pb->post_pwm_on_delay)
                msleep(pb->post_pwm_on_delay);
 
@@ -65,9 +60,6 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb)
 
 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
 {
-       struct pwm_state state;
-
-       pwm_get_state(pb->pwm, &state);
        if (!pb->enabled)
                return;
 
@@ -77,28 +69,21 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb)
        if (pb->pwm_off_delay)
                msleep(pb->pwm_off_delay);
 
-       state.enabled = false;
-       state.duty_cycle = 0;
-       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)
+static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness, struct pwm_state *state)
 {
        unsigned int lth = pb->lth_brightness;
-       struct pwm_state state;
        u64 duty_cycle;
 
-       pwm_get_state(pb->pwm, &state);
-
        if (pb->levels)
                duty_cycle = pb->levels[brightness];
        else
                duty_cycle = brightness;
 
-       duty_cycle *= state.period - lth;
+       duty_cycle *= state->period - lth;
        do_div(duty_cycle, pb->scale);
 
        return duty_cycle + lth;
@@ -115,11 +100,18 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
 
        if (brightness > 0) {
                pwm_get_state(pb->pwm, &state);
-               state.duty_cycle = compute_duty_cycle(pb, brightness);
+               state.duty_cycle = compute_duty_cycle(pb, brightness, &state);
+               state.enabled = true;
                pwm_apply_state(pb->pwm, &state);
+
                pwm_backlight_power_on(pb);
        } else {
                pwm_backlight_power_off(pb);
+
+               pwm_get_state(pb->pwm, &state);
+               state.enabled = false;
+               state.duty_cycle = 0;
+               pwm_apply_state(pb->pwm, &state);
        }
 
        if (pb->notify_after)