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Subject[PATCH v3 3/5] pwm-backlight: add support for PWM delays proprieties.
Date
Some panels (i.e. N116BGE-L41), in their power sequence specifications,
request a delay between set the PWM signal and enable the backlight and
between clear the PWM signal and disable the backlight. Add support for
the new post-pwm-on-delay-us and pwm-off-delay-us proprieties to meet
the timings.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
---
Changes since v2:
- Move the pwm/enable sequence to another patch (Thierry Reding)
Changes since v1:
- As suggested by Daniel Thompson
- Do not assume power-on delay and power-off delay will be the same
- Move the check of dt property to the parse dt function.

drivers/video/backlight/pwm_bl.c | 17 +++++++++++++++++
include/linux/pwm_backlight.h | 1 +
2 files changed, 18 insertions(+)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 909a686..528155d 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -10,6 +10,7 @@
* published by the Free Software Foundation.
*/

+#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/gpio.h>
#include <linux/module.h>
@@ -35,6 +36,7 @@ struct pwm_bl_data {
struct gpio_desc *enable_gpio;
unsigned int scale;
bool legacy;
+ unsigned int pwm_delay[2];
int (*notify)(struct device *,
int brightness);
void (*notify_after)(struct device *,
@@ -56,6 +58,9 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)

pwm_enable(pb->pwm);

+ if (pb->pwm_delay[0])
+ usleep_range(pb->pwm_delay[0], pb->pwm_delay[0] * 2);
+
if (pb->enable_gpio)
gpiod_set_value_cansleep(pb->enable_gpio, 1);

@@ -70,6 +75,9 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb)
if (pb->enable_gpio)
gpiod_set_value_cansleep(pb->enable_gpio, 0);

+ if (pb->pwm_delay[1])
+ usleep_range(pb->pwm_delay[1], pb->pwm_delay[1] * 2);
+
pwm_config(pb->pwm, 0, pb->period);
pwm_disable(pb->pwm);

@@ -175,6 +183,14 @@ static int pwm_backlight_parse_dt(struct device *dev,
data->max_brightness--;
}

+ /*
+ * These values are optional and set as 0 by default, the out values
+ * are modified only if a valid u32 value can be decoded.
+ */
+ of_property_read_u32(node, "post-pwm-on-delay-us",
+ &data->pwm_delay[0]);
+ of_property_read_u32(node, "pwm-off-delay-us", &data->pwm_delay[1]);
+
data->enable_gpio = -EINVAL;
return 0;
}
@@ -273,6 +289,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
pb->exit = data->exit;
pb->dev = &pdev->dev;
pb->enabled = false;
+ memcpy(pb->pwm_delay, data->pwm_delay, sizeof(pb->pwm_delay));

pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
GPIOD_ASIS);
diff --git a/include/linux/pwm_backlight.h b/include/linux/pwm_backlight.h
index efdd922..bf37131 100644
--- a/include/linux/pwm_backlight.h
+++ b/include/linux/pwm_backlight.h
@@ -13,6 +13,7 @@ struct platform_pwm_backlight_data {
unsigned int lth_brightness;
unsigned int pwm_period_ns;
unsigned int *levels;
+ unsigned int pwm_delay[2];
/* TODO remove once all users are switched to gpiod_* API */
int enable_gpio;
int (*init)(struct device *dev);
--
2.9.3
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