On Mon, Mar 18, 2024 at 10:45:32AM +0100, Oleksij Rempel wrote:
> Add fallback support for currently not supported HW. Instead of
> completely fail, it is better to use some kind of basic devicetree with
> reduced functionality.
>
> Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> ---
> arch/arm/boards/skov-imx8mp/board.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/boards/skov-imx8mp/board.c b/arch/arm/boards/skov-imx8mp/board.c
> index 5424c3b9ab..a45fe8517f 100644
> --- a/arch/arm/boards/skov-imx8mp/board.c
> +++ b/arch/arm/boards/skov-imx8mp/board.c
> @@ -83,6 +83,12 @@ static const struct board_description imx8mp_variants[] = {
> .dts_compatible_hdmi = "skov,imx8mp-skov-revb-hdmi",
> .flags = SKOV_IMX8MP_HAS_HDMI,
> },
> + /* Keep this entry always on the last place. It will be used
> + * as fallback variant if not supported variant is detected.
> + */
> + {
> + .dts_compatible = "skov,imx8mp-skov-basic",
> + },
This increases ARRAY_SIZE(imx8mp_variants) to 3...
> };
>
> static int skov_imx8mp_fixup(struct device_node *root, void *data)
> @@ -168,13 +174,14 @@ static int skov_imx8mp_init_variant(struct skov_imx8mp_priv *priv)
> if (ret)
> return ret;
>
> - priv->variant_id = v;
>
> if (v >= ARRAY_SIZE(imx8mp_variants)) {
... so this doesn't trigger anymore for the still invalid variant 2.
Better make the basic variant a separate initializer outside of the
imx8mp_variants array. That also gets you rid of the "keep last" comment
above.
variant_id is written to the /chosen/skov,imx8mp-board-version property.
This looks wrong for the "basic" variant as this is not a fixed number
but instead depends on the highest number the bootloader knows (which
might be different from the last variant_id userspace knows).
> - dev_err(dev, "Invalid variant %u\n", v);
> - return -EINVAL;
> + dev_warn(dev, "Unsuported variant %u. Fall back to basic variant\n", v);
> + v = ARRAY_SIZE(imx8mp_variants) - 1;
> }
Sascha
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