From 2f4647a149943b1f87e46858e9f13e02010347f7 Mon Sep 17 00:00:00 2001 From: Stefan Agner Date: Fri, 23 Oct 2015 16:44:43 -0700 Subject: [PATCH] backlight: gpio-backlight: Use default-on on GPIO request There are situations where the backlight should be on at boot time (e.g. if the boot loader already turned the display on). The DT bindings specify the "default-on" property for that purpose. Currently, the initial state of the GPIO at request time is always set to logical off (high or low depending on whether it is an active high or low GPIO). Since the GPIO is requested as an output, the GPIO will be driven low for a short period of time, which leads to a flickering display in the above use-case. Initialize the GPIO depending on the default-on property to be logical on or off. Signed-off-by: Stefan Agner Signed-off-by: Lee Jones --- drivers/video/backlight/gpio_backlight.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/video/backlight/gpio_backlight.c b/drivers/video/backlight/gpio_backlight.c index 5fbbc2ebdf93..18134416b154 100644 --- a/drivers/video/backlight/gpio_backlight.c +++ b/drivers/video/backlight/gpio_backlight.c @@ -89,6 +89,7 @@ static int gpio_backlight_probe(struct platform_device *pdev) struct backlight_device *bl; struct gpio_backlight *gbl; struct device_node *np = pdev->dev.of_node; + unsigned long flags = GPIOF_DIR_OUT; int ret; if (!pdata && !np) { @@ -114,9 +115,12 @@ static int gpio_backlight_probe(struct platform_device *pdev) gbl->def_value = pdata->def_value; } - ret = devm_gpio_request_one(gbl->dev, gbl->gpio, GPIOF_DIR_OUT | - (gbl->active ? GPIOF_INIT_LOW - : GPIOF_INIT_HIGH), + if (gbl->active) + flags |= gbl->def_value ? GPIOF_INIT_HIGH : GPIOF_INIT_LOW; + else + flags |= gbl->def_value ? GPIOF_INIT_LOW : GPIOF_INIT_HIGH; + + ret = devm_gpio_request_one(gbl->dev, gbl->gpio, flags, pdata ? pdata->name : "backlight"); if (ret < 0) { dev_err(&pdev->dev, "unable to request GPIO\n"); -- 2.20.1