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[PATCH v2 1/4] dt-bindings: pwm-backlight: add pwm-delay-us property

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  [PATCH v2 1/4] dt-bindings: pwm-backlight: add pwm-delay-us property Enric Balletbo i Serra <enric.balletbo@collabora.com> - 2017-06-30 13:30 +0200
    Re: [PATCH v2 1/4] dt-bindings: pwm-backlight: add pwm-delay-us  property Pavel Machek <pavel@ucw.cz> - 2017-06-30 13:30 +0200
    [PATCH v2 2/4] pwm-backlight: add support for pwm-delay-us property Enric Balletbo i Serra <enric.balletbo@collabora.com> - 2017-06-30 13:30 +0200
    [PATCH v2 4/4] ARM: dts: rockchip: add pwm-delay-us backlight setting. Enric Balletbo i Serra <enric.balletbo@collabora.com> - 2017-06-30 13:30 +0200

#1678706 — [PATCH v2 1/4] dt-bindings: pwm-backlight: add pwm-delay-us property

From: huang lin <hl@rock-chips.com>

Add a pwm-delay-us property to specify the delay between setting an
initial (non-zero) PWM value and enabling the backlight, and also the
delay between disabling the backlight and setting PWM value to 0.

Signed-off-by: huang lin <hl@rock-chips.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
---
Changes since v1:
 - As suggested by Daniel Thompson
   - Do not assume power-on delay and power-off delay will be the same

v1: https://lkml.org/lkml/2017/6/28/219

 Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
index 764db86..49b037e 100644
--- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
+++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
@@ -17,6 +17,11 @@ Optional properties:
                "pwms" property (see PWM binding[0])
   - enable-gpios: contains a single GPIO specifier for the GPIO which enables
                   and disables the backlight (see GPIO binding[1])
+  - pwm-delay-us: delay between setting an initial (non-zero) PWM value and
+                  enabling the backlight, and also the delay between disabling
+                  the backlight and setting PWM value to 0.
+                  The 1st cell is the pre-delay in micro seconds.
+                  The 2nd cell is the post-delay in micro seconds.
 
 [0]: Documentation/devicetree/bindings/pwm/pwm.txt
 [1]: Documentation/devicetree/bindings/gpio/gpio.txt
@@ -32,4 +37,5 @@ Example:
 
 		power-supply = <&vdd_bl_reg>;
 		enable-gpios = <&gpio 58 0>;
+		pwm-delay-us = <10000 10000>;
 	};
-- 
2.9.3

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#1678709 — Re: [PATCH v2 1/4] dt-bindings: pwm-backlight: add pwm-delay-us property

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On Fri 2017-06-30 13:21:06, Enric Balletbo i Serra wrote:
> From: huang lin <hl@rock-chips.com>
> 
> Add a pwm-delay-us property to specify the delay between setting an
> initial (non-zero) PWM value and enabling the backlight, and also the
> delay between disabling the backlight and setting PWM value to 0.
> 
> Signed-off-by: huang lin <hl@rock-chips.com>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> ---
> Changes since v1:
>  - As suggested by Daniel Thompson
>    - Do not assume power-on delay and power-off delay will be the same
> 
> v1: https://lkml.org/lkml/2017/6/28/219
> 
>  Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> index 764db86..49b037e 100644
> --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> @@ -17,6 +17,11 @@ Optional properties:
>                 "pwms" property (see PWM binding[0])
>    - enable-gpios: contains a single GPIO specifier for the GPIO which enables
>                    and disables the backlight (see GPIO binding[1])
> +  - pwm-delay-us: delay between setting an initial (non-zero) PWM value and
> +                  enabling the backlight, and also the delay between disabling
> +                  the backlight and setting PWM value to 0.

"Hardware needs a delay between setting an initial (non-zero) PWM and
enabling the backlight using GPIO. The 1st cell specifies this delay
in micro seconds. Hardware also needs a delay between disabing the
backlight using GPIO and setting PWM value to 0. The 2nd cell is this
delay in micro seconds."

Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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#1678711 — [PATCH v2 2/4] pwm-backlight: add support for pwm-delay-us property

From: huang lin <hl@rock-chips.com>

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 pwm-delay-us property to meet the timing.

Note that this patch inverts current sequence. Before this patch the
enable signal was set before the PWM signal and vice-versa on power off.

I assumed that this sequence was wrong, at least it is on different panel
datasheets that I checked, so I inverted the sequence to follow:

  On power on, set the PWM signal, wait, and set the LED_EN signal.
  On power off, clear the LED_EN signal, wait, and stop the PWM signal.

Signed-off-by: huang lin <hl@rock-chips.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
---
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.

v1: https://lkml.org/lkml/2017/6/28/219

 drivers/video/backlight/pwm_bl.c | 24 ++++++++++++++++++++----
 include/linux/pwm_backlight.h    |  1 +
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 002f1ce..0f5470e 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 *,
@@ -54,10 +56,14 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
 	if (err < 0)
 		dev_err(pb->dev, "failed to enable power supply\n");
 
+	pwm_enable(pb->pwm);
+
+	if (pb->pwm_delay[0])
+		usleep_range(pb->pwm_delay[0], pb->pwm_delay[0] + 2000);
+
 	if (pb->enable_gpio)
 		gpiod_set_value_cansleep(pb->enable_gpio, 1);
 
-	pwm_enable(pb->pwm);
 	pb->enabled = true;
 }
 
@@ -66,12 +72,15 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb)
 	if (!pb->enabled)
 		return;
 
-	pwm_config(pb->pwm, 0, pb->period);
-	pwm_disable(pb->pwm);
-
 	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] + 2000);
+
+	pwm_config(pb->pwm, 0, pb->period);
+	pwm_disable(pb->pwm);
+
 	regulator_disable(pb->power_supply);
 	pb->enabled = false;
 }
@@ -174,6 +183,12 @@ static int pwm_backlight_parse_dt(struct device *dev,
 		data->max_brightness--;
 	}
 
+	/* read pwm to enable pre/post delays from DT property */
+	ret = of_property_read_u32_array(node, "pwm-delay-us", data->pwm_delay,
+					 ARRAY_SIZE(data->pwm_delay));
+	if (ret < 0)
+		return ret;
+
 	data->enable_gpio = -EINVAL;
 	return 0;
 }
@@ -272,6 +287,7 @@ 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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#1678712 — [PATCH v2 4/4] ARM: dts: rockchip: add pwm-delay-us backlight setting.

The minnie devices comes with an AUO B101EAN01 panel which is different
from default veyron devices, thus the power on/off timing sequence is
slightly different. The datasheet specifies a pwm delay of 200 ms, so
update the pwm-delay-us accordingly.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
---
Heiko,
 I'm not able to test this patch in a minnie device because I don't have
one, so could you do a quick try, please?

Thanks,
 Enric

Changes since v1:
 - Add this new patch as minnie has differents timings.

 arch/arm/boot/dts/rk3288-veyron-minnie.dts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/boot/dts/rk3288-veyron-minnie.dts b/arch/arm/boot/dts/rk3288-veyron-minnie.dts
index 544de60..8680a83 100644
--- a/arch/arm/boot/dts/rk3288-veyron-minnie.dts
+++ b/arch/arm/boot/dts/rk3288-veyron-minnie.dts
@@ -123,6 +123,7 @@
 			240 241 242 243 244 245 246 247
 			248 249 250 251 252 253 254 255>;
 	power-supply = <&backlight_regulator>;
+	pwm-delay-us = <200000 200000>;
 };
 
 &emmc {
-- 
2.9.3

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