[PATCH v5 1/5] pwm-backlight: enable/disable the PWM before/after LCD enable toggle.

Before this patch the enable signal was set before the PWM signal and
vice-versa on power off. This sequence is wrong, at least, it is on
the different panels datasheets that I checked, so I inverted the sequence
to follow the specs.

For reference the following panels have the mentioned sequence:
  - N133HSE-EA1 (Innolux)
  - N116BGE (Innolux)
  - N156BGE-L21 (Innolux)
  - B101EAN0 (Auo)
  - B101AW03 (Auo)
  - LTN101NT05 (Samsung)
  - CLAA101WA01A (Chunghwa)

Signed-off-by: Enric Balletbo i Serra <redacted>
Acked-by: Daniel Thompson <redacted>
Acked-by: Jingoo Han <jingoohan1@gmail.com>
---
Changes since v4:
 - Rebase on top of mainline.
 - Add the acks from Daniel Thompson and Jingoo Han.
Changes since v3:
 - List the part numbers for the panel checked (Daniel Thompson)
Changes since v2:
 - Add this as a separate patch (Thierry Reding)
Changes since v1:
 - None

 drivers/video/backlight/pwm_bl.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 1c2289d..698ec68 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c

@@ -54,10 +54,11 @@ 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->enable_gpio)
 		gpiod_set_value_cansleep(pb->enable_gpio, 1);
 
-	pwm_enable(pb->pwm);
 	pb->enabled = true;
 }
 

@@ -66,12 +67,12 @@ 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);
 
+	pwm_config(pb->pwm, 0, pb->period);
+	pwm_disable(pb->pwm);
+
 	regulator_disable(pb->power_supply);
 	pb->enabled = false;
 }

-- 
2.9.3

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 PMW delay proprieties accordingly.

Signed-off-by: Enric Balletbo i Serra <redacted>
---
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?

Changes since v4:
 - Rebase on top of mainline.
Changes since v3:
 - Use new -ms names for proprieties.
 - Fix the delay, should be 200ms instead of 20ms (Pavel)
Changes since v2:
 - Use new names for proprieties.
Changes since v1:
 - Add this new patch as minnie has differents timings

 arch/arm/boot/dts/rk3288-veyron-minnie.dts | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/boot/dts/rk3288-veyron-minnie.dts b/arch/arm/boot/dts/rk3288-veyron-minnie.dts
index 544de60..4c5307e6 100644
--- a/arch/arm/boot/dts/rk3288-veyron-minnie.dts
+++ b/arch/arm/boot/dts/rk3288-veyron-minnie.dts

@@ -123,6 +123,8 @@
 			240 241 242 243 244 245 246 247
 			248 249 250 251 252 253 254 255>;
 	power-supply = <&backlight_regulator>;
+	post-pwm-on-delay-ms = <200>;
+	pwm-off-delay-ms = <200>;
 };
 
 &emmc {

-- 
2.9.3

For veyron the binding should provide both PWM timings, the delay between
you enable the PWM and set the enable signal, and the delay between you
disable the PWM signal and clear the enable signal. Update the binding
accordingly, in this case the panels connected to the veyron boards have
a symmetric power sequence, hence the same value is used.

Signed-off-by: Enric Balletbo i Serra <redacted>
---
Changes since v4:
 - Rebased on top of mainline.
Changes since v3:
 - Use new -ms names for proprieties.
Changes since v2:
 - Use new names for proprieties.
Changes since v1:
 - Add this new patch to fix current binding on veyron.

 arch/arm/boot/dts/rk3288-veyron-chromebook.dtsi | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm/boot/dts/rk3288-veyron-chromebook.dtsi b/arch/arm/boot/dts/rk3288-veyron-chromebook.dtsi
index d752a31..5a8c7f3 100644
--- a/arch/arm/boot/dts/rk3288-veyron-chromebook.dtsi
+++ b/arch/arm/boot/dts/rk3288-veyron-chromebook.dtsi

@@ -96,7 +96,8 @@
 		pinctrl-names = "default";
 		pinctrl-0 = <&bl_en>;
 		pwms = <&pwm0 0 1000000 0>;
-		pwm-delay-us = <10000>;
+		post-pwm-on-delay-ms = <10>;
+		pwm-off-delay-ms = <10>;
 	};
 
 	gpio-charger {

-- 
2.9.3

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-ms and pwm-off-delay-ms proprieties to meet
the timings.

Signed-off-by: Enric Balletbo i Serra <redacted>
Acked-by: Pavel Machek <redacted>
Acked-by: Daniel Thompson <redacted>
Acked-by: Jingoo Han <jingoohan1@gmail.com>
---
Changes since v4:
 - Rebased on top of mainline.
 - Added the acks from Pavel Machek, Daniel thompson and Jingoo Han
Changes since v3:
 - Use two named members instead of pwm_delay[] (Daniel and Pavel)
 - Use msleep instead of usleep_range. (Pavel)
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 | 19 +++++++++++++++++++
 include/linux/pwm_backlight.h    |  2 ++
 2 files changed, 21 insertions(+)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 698ec68..8e3f124 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 +36,8 @@ struct pwm_bl_data {
 	struct gpio_desc	*enable_gpio;
 	unsigned int		scale;
 	bool			legacy;
+	unsigned int		post_pwm_on_delay;
+	unsigned int		pwm_off_delay;
 	int			(*notify)(struct device *,
 					  int brightness);
 	void			(*notify_after)(struct device *,

@@ -56,6 +59,9 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
 
 	pwm_enable(pb->pwm);
 
+	if (pb->post_pwm_on_delay)
+		msleep(pb->post_pwm_on_delay);
+
 	if (pb->enable_gpio)
 		gpiod_set_value_cansleep(pb->enable_gpio, 1);
 

@@ -70,6 +76,9 @@ 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_off_delay)
+		msleep(pb->pwm_off_delay);
+
 	pwm_config(pb->pwm, 0, pb->period);
 	pwm_disable(pb->pwm);
 

@@ -178,6 +187,14 @@ 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-ms",
+			     &data->post_pwm_on_delay);
+	of_property_read_u32(node, "pwm-off-delay-ms", &data->pwm_off_delay);
+
 	data->enable_gpio = -EINVAL;
 	return 0;
 }

@@ -276,6 +293,8 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 	pb->exit = data->exit;
 	pb->dev = &pdev->dev;
 	pb->enabled = false;
+	pb->post_pwm_on_delay = data->post_pwm_on_delay;
+	pb->pwm_off_delay = data->pwm_off_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 e8afbd7..8ea265a 100644
--- a/include/linux/pwm_backlight.h
+++ b/include/linux/pwm_backlight.h

@@ -14,6 +14,8 @@ struct platform_pwm_backlight_data {
 	unsigned int lth_brightness;
 	unsigned int pwm_period_ns;
 	unsigned int *levels;
+	unsigned int post_pwm_on_delay;
+	unsigned int pwm_off_delay;
 	/* TODO remove once all users are switched to gpiod_* API */
 	int enable_gpio;
 	int (*init)(struct device *dev);

-- 
2.9.3

Hardware needs a delay between setting an initial (non-zero) PWM and
enabling the backlight using GPIO. The post-pwm-on-delay-ms specifies
this delay in milli seconds. Hardware also needs a delay between disabing
the backlight using GPIO and setting PWM value to 0. The pwm-off-delay-ms
is this delay in milli seconds.

Signed-off-by: Enric Balletbo i Serra <redacted>
Acked-by: Pavel Machek <redacted>
---
Based on the original Huang Lin [off-list ref] work.

Changes since v4:
 - Rebase on top of mainline.
Changes since v3:
 - Replace us for ms.
 - Add Acked-by: Pavel Machek [off-list ref]
Changes since v2:
 - Use separate properties (Rob Herring)
Changes since v1:
 - As suggested by Daniel Thompson
   - Do not assume power-on delay and power-off delay will be the same

 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..3108109 100644
--- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
+++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt

@@ -17,6 +17,10 @@ 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])
+  - post-pwm-on-delay-ms: Delay in ms between setting an initial (non-zero) PWM
+                          and enabling the backlight using GPIO.
+  - pwm-off-delay-ms: Delay in ms between disabling the backlight using GPIO
+                      and setting PWM value to 0.
 
 [0]: Documentation/devicetree/bindings/pwm/pwm.txt
 [1]: Documentation/devicetree/bindings/gpio/gpio.txt

@@ -32,4 +36,6 @@ Example:
 
 		power-supply = <&vdd_bl_reg>;
 		enable-gpios = <&gpio 58 0>;
+		post-pwm-on-delay-ms = <10>;
+		pwm-off-delay-ms = <10>;
 	};

-- 
2.9.3

On Fri 2017-12-01 13:06:51, Enric Balletbo i Serra wrote:

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 PMW delay proprieties accordingly.

Signed-off-by: Enric Balletbo i Serra <redacted>

Patches 4,5:

Acked-by: Pavel Machek <redacted>

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

Hi,

2017-12-01 13:06 GMT+01:00 Enric Balletbo i Serra
[off-list ref]:

A gentle ping, It's been nearly two months since I sent this patchset,
there is anything else that prevents these patches to land or
incorporate in linux-next?

Thanks,
 Enric

On Tue, 30 Jan 2018, Enric Balletbo Serra wrote:

Hi,

2017-12-01 13:06 GMT+01:00 Enric Balletbo i Serra [off-list ref]:

quoted

Before this patch the enable signal was set before the PWM signal and
vice-versa on power off. This sequence is wrong, at least, it is on
the different panels datasheets that I checked, so I inverted the sequence
to follow the specs.

For reference the following panels have the mentioned sequence:
  - N133HSE-EA1 (Innolux)
  - N116BGE (Innolux)
  - N156BGE-L21 (Innolux)
  - B101EAN0 (Auo)
  - B101AW03 (Auo)
  - LTN101NT05 (Samsung)
  - CLAA101WA01A (Chunghwa)

Signed-off-by: Enric Balletbo i Serra <redacted>
Acked-by: Daniel Thompson <redacted>
Acked-by: Jingoo Han <jingoohan1@gmail.com>
---
Changes since v4:
 - Rebase on top of mainline.
 - Add the acks from Daniel Thompson and Jingoo Han.
Changes since v3:
 - List the part numbers for the panel checked (Daniel Thompson)
Changes since v2:
 - Add this as a separate patch (Thierry Reding)
Changes since v1:
 - None

 drivers/video/backlight/pwm_bl.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

A gentle ping, It's been nearly two months since I sent this patchset,
there is anything else that prevents these patches to land or
incorporate in linux-next?

Looks like Daniel should Ack 2/5 since he had comments on it before
and it still lacks a Backlight Ack.

With regards to -next, the merge-window is open (should close in a
little over a week), so the chances are, you'll get a long soak before
the next merge-window opens.

-- 
Lee Jones
Linaro Services Technical Lead
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