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Date: Mon, 11 Jan 2016 06:40:05 +0000 From: Lee Jones <lee.jones@...aro.org> To: Stefan Agner <stefan@...er.ch> Cc: jingoohan1@...il.com, linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] backlight: gpio-backlight: use default-on on GPIO request On Fri, 23 Oct 2015, Stefan Agner wrote: > 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 <stefan@...er.ch> > --- > drivers/video/backlight/gpio_backlight.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) Applied, thanks. > diff --git a/drivers/video/backlight/gpio_backlight.c b/drivers/video/backlight/gpio_backlight.c > index 5fbbc2e..1813441 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"); -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog
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