From 84e7de2b0b7f47eb416d6e39a61c89788d3fb339 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Lothar=20Wa=C3=9Fmann?= Date: Wed, 11 Oct 2017 12:15:43 +0200 Subject: [PATCH] backlight: pwm_bl: add configurable delay between re-enabling PWM and switching backlight power on When switching the backlight on, the LCD may need some time to adjust to the configured PWM duty cycle. Add a configurable delay between configuring the PWM and enabling the backlight regulator to account for this. --- .../bindings/leds/backlight/pwm-backlight.txt | 4 ++++ drivers/video/backlight/pwm_bl.c | 22 ++++++++++++++++--- 2 files changed, 23 insertions(+), 3 deletions(-) diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt index 764db86d441a..95594c341a57 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]) + - turn-on-delay-ms: delay in milliseconds between configuring the PWM + and switching PWM on. This may be required to eliminate + flicker when switching the PWM on after it has been + disabled. [0]: Documentation/devicetree/bindings/pwm/pwm.txt [1]: Documentation/devicetree/bindings/gpio/gpio.txt diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index 921f322dd287..9578f6516c65 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -23,6 +23,7 @@ #include #include #include +#include struct pwm_bl_data { struct pwm_device *pwm; @@ -35,6 +36,7 @@ struct pwm_bl_data { struct gpio_desc *enable_gpio; unsigned int scale; bool legacy; + int turn_on_delay_ms; int (*notify)(struct device *, int brightness); void (*notify_after)(struct device *, @@ -52,6 +54,17 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness) pwm_enable(pb->pwm); + if (pb->turn_on_delay_ms > 0) { + dev_dbg(pb->dev, "Sleeping %u..%uµs\n", + pb->turn_on_delay_ms * 1000, + pb->turn_on_delay_ms * 1100); + if (pb->turn_on_delay_ms > 20) + msleep(pb->turn_on_delay_ms); + else + usleep_range(pb->turn_on_delay_ms * 1000, + pb->turn_on_delay_ms * 1100); + } + err = regulator_enable(pb->power_supply); if (err < 0) dev_err(pb->dev, "failed to enable power supply\n"); @@ -108,8 +121,9 @@ static int pwm_backlight_update_status(struct backlight_device *bl) duty_cycle = compute_duty_cycle(pb, brightness); pwm_config(pb->pwm, duty_cycle, pb->period); pwm_backlight_power_on(pb, brightness); - } else + } else { pwm_backlight_power_off(pb); + } if (pb->notify_after) pb->notify_after(pb->dev, brightness); @@ -264,9 +278,9 @@ static int pwm_backlight_probe(struct platform_device *pdev) pb->scale = data->levels[i]; pb->levels = data->levels; - } else + } else { pb->scale = data->max_brightness; - + } pb->notify = data->notify; pb->notify_after = data->notify_after; pb->check_fb = data->check_fb; @@ -329,6 +343,8 @@ static int pwm_backlight_probe(struct platform_device *pdev) goto err_alloc; } + of_property_read_u32(node, "turn-on-delay-ms", &pb->turn_on_delay_ms); + dev_dbg(&pdev->dev, "got pwm for backlight\n"); /* -- 2.39.2