[PATCH v3 3/5] pwm-backlight: add support for PWM delays proprieties.

[Enric Balletbo i Serra]

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 at 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