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Code Issues Releases Wiki Activity

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
This commit is contained in:
Uwe Kleine-König 2023-01-20 13:00:17 +01:00 committed by Lee Jones
parent 744fc2dada
commit 00e7e698bf
1 changed files with 10 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
drivers/video/backlight/pwm_bl.c
View File

@ -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)