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SubjectRe: [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@agner.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
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