linux-kernel - Re: [PATCH] drm: panel: simple-panel: get the enable gpio as-is

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Message-ID: <CAGb2v65RiMyiW4RSv3PE2_Doru1KMohEkHCc+v2-WH-MgiKxAA@mail.gmail.com>
Date:   Mon, 7 Nov 2016 18:12:43 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Icenowy Zheng <icenowy@...c.xyz>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>, Chen-Yu Tsai <wens@...e.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm: panel: simple-panel: get the enable gpio as-is

On Sun, Nov 6, 2016 at 7:09 PM, Icenowy Zheng <icenowy@...c.xyz> wrote:
> The enable gpio of simple-panel may be used by a simplefb or other
> driver on the panel's display before the KMS driver get load.
>
> Get the GPIO as-is, so the panel won't be disabled, and the simplefb
> can work.
>
> Signed-off-by: Icenowy Zheng <icenowy@...c.xyz>
> ---
>  drivers/gpu/drm/panel/panel-simple.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
> index 113db3c..ccee4c1 100644
> --- a/drivers/gpu/drm/panel/panel-simple.c
> +++ b/drivers/gpu/drm/panel/panel-simple.c
> @@ -312,7 +312,7 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
>                 return PTR_ERR(panel->supply);
>
>         panel->enable_gpio = devm_gpiod_get_optional(dev, "enable",
> -                                                    GPIOD_OUT_LOW);
> +                                                    GPIOD_ASIS);

The GPIO requested as-is might be in input mode. You should change the
gpiod_set_value calls to gpiod_direction_output calls. The later also
allows you to give an initial value. Not sure if it checks for cansleep
like the set_value calls though.

Regards
ChenYu

>         if (IS_ERR(panel->enable_gpio)) {
>                 err = PTR_ERR(panel->enable_gpio);
>                 dev_err(dev, "failed to request GPIO: %d\n", err);
> --
> 2.10.1
>