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