Re: [PATCH v2 6/6] drm/panel: Add Ilitek ILI9341 DBI panel driver

[Linus Walleij]

Hi Paul,

just a drive-by comment:

On Sat, Aug 22, 2020 at 6:33 PM Paul Cercueil <paul@xxxxxxxxxxxxxxx> wrote:

> +       gpiod_set_value_cansleep(priv->reset_gpiod, 0);
> +       usleep_range(20, 1000);
> +       gpiod_set_value_cansleep(priv->reset_gpiod, 1);

This implies that the reset line is active low.

I would specify in the DT GPIO handle that it is active low
and invert the above.

So:

reset-gpios = <&gpio 4 GPIO_ACTIVE_LOW>;

gpiod_set_value_cansleep(priv->reset_gpiod, 1);
usleep_range(20, 1000);
gpiod_set_value_cansleep(priv->reset_gpiod, 0);

> +       priv->reset_gpiod = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
> +       if (IS_ERR(priv->reset_gpiod)) {
> +               dev_err(dev, "Couldn't get our reset GPIO\n");
> +               return PTR_ERR(priv->reset_gpiod);
> +       }

This would then fetch the GPIO as asserted (device in reset)
unless changed, but that may be the right thing to do actually.

> +static const struct ili9341_pdata yx240qv29_pdata = {
> +       .mode = { DRM_SIMPLE_MODE(240, 320, 37, 49) },
> +       .width_mm = 0, // TODO
> +       .height_mm = 0, // TODO

When nothing else works and data sheets are incomplete I
just take out a ruler and measure on the actual device.

Yours,
Linus Walleij