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[PATCH v2] pwm-backlight: fix the panel power sequence

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  [PATCH v2] pwm-backlight: fix the panel power sequence YH Huang <yh.huang@mediatek.com> - 2015-10-16 11:20 +0200
    Re: [PATCH v2] pwm-backlight: fix the panel power sequence Philipp Zabel <p.zabel@pengutronix.de> - 2015-10-16 11:40 +0200

#1248508 — [PATCH v2] pwm-backlight: fix the panel power sequence

In order to match the panel power sequence, disable the enable_gpio
in the probe function. Also, reorder the code in the power_on and
power_off function to match the timing.

Signed-off-by: YH Huang <yh.huang@mediatek.com>
---
Change in v2:
Fix the build error.
---
 drivers/video/backlight/pwm_bl.c |   14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index eff379b..d8c9c62 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(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(pb->enable_gpio, 0);
 
+	pwm_config(pb->pwm, 0, pb->period);
+	pwm_disable(pb->pwm);
+
 	regulator_disable(pb->power_supply);
 	pb->enabled = false;
 }
@@ -242,7 +243,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 	pb->enabled = false;
 
 	pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
-						  GPIOD_OUT_HIGH);
+						  GPIOD_ASIS);
 	if (IS_ERR(pb->enable_gpio)) {
 		ret = PTR_ERR(pb->enable_gpio);
 		goto err_alloc;
@@ -264,6 +265,9 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 		pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 	}
 
+	if (pb->enable_gpio)
+		gpiod_direction_output(pb->enable_gpio, 0);
+
 	pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 	if (IS_ERR(pb->power_supply)) {
 		ret = PTR_ERR(pb->power_supply);
-- 
1.7.9.5

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#1248521

Am Freitag, den 16.10.2015, 17:17 +0800 schrieb YH Huang:
> In order to match the panel power sequence, disable the enable_gpio
> in the probe function. Also, reorder the code in the power_on and
> power_off function to match the timing.

Could you also have a look at the "pwm-backlight: Avoid backlight
flicker when probed from DT" patch?
I think in case of a panel left enabled by the bootloader, your patch
will disable the backlight for a short time.

best regards
Philipp

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