pwm-backlight: Allow for non-increasing brightness levels
Currently the driver assumes that the values specified in the
brightness-levels device tree property increase as they are parsed from
left to right. But boards that invert the signal between the PWM output
and the backlight will need to specify decreasing brightness-levels.
This patch removes the assumption that the last element of the array is
the maximum value, and instead searches the array for the maximum value
and uses that in the duty cycle calculation.
Signed-off-by: Mike Dunn <mikedunn@newsguy.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index eec6c98..32e96e3 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -34,6 +34,7 @@
struct regulator *power_supply;
int enable_gpio;
unsigned long enable_gpio_flags;
+ unsigned int scale;
int (*notify)(struct device *,
int brightness);
void (*notify_after)(struct device *,
@@ -42,23 +43,20 @@
void (*exit)(struct device *);
};
-static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness,
- int max)
+static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
{
+ unsigned int lth = pb->lth_brightness;
int duty_cycle, err;
if (pb->enabled)
return;
- if (pb->levels) {
+ if (pb->levels)
duty_cycle = pb->levels[brightness];
- max = pb->levels[max];
- } else {
+ else
duty_cycle = brightness;
- }
- duty_cycle = (duty_cycle * (pb->period - pb->lth_brightness) / max) +
- pb->lth_brightness;
+ duty_cycle = (duty_cycle * (pb->period - lth) / pb->scale) + lth;
pwm_config(pb->pwm, duty_cycle, pb->period);
@@ -100,7 +98,6 @@
{
struct pwm_bl_data *pb = bl_get_data(bl);
int brightness = bl->props.brightness;
- int max = bl->props.max_brightness;
if (bl->props.power != FB_BLANK_UNBLANK ||
bl->props.fb_blank != FB_BLANK_UNBLANK ||
@@ -111,7 +108,7 @@
brightness = pb->notify(pb->dev, brightness);
if (brightness > 0)
- pwm_backlight_power_on(pb, brightness, max);
+ pwm_backlight_power_on(pb, brightness);
else
pwm_backlight_power_off(pb);
@@ -218,7 +215,6 @@
struct backlight_properties props;
struct backlight_device *bl;
struct pwm_bl_data *pb;
- unsigned int max;
int ret;
if (!data) {
@@ -245,10 +241,15 @@
}
if (data->levels) {
- max = data->levels[data->max_brightness];
+ unsigned int i;
+
+ for (i = 0; i <= data->max_brightness; i++)
+ if (data->levels[i] > pb->scale)
+ pb->scale = data->levels[i];
+
pb->levels = data->levels;
} else
- max = data->max_brightness;
+ pb->scale = data->max_brightness;
pb->enable_gpio = data->enable_gpio;
pb->enable_gpio_flags = data->enable_gpio_flags;
@@ -304,7 +305,7 @@
pwm_set_period(pb->pwm, data->pwm_period_ns);
pb->period = pwm_get_period(pb->pwm);
- pb->lth_brightness = data->lth_brightness * (pb->period / max);
+ pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
memset(&props, 0, sizeof(struct backlight_properties));
props.type = BACKLIGHT_RAW;
