[PATCH 1/2] arm64: dts: imx8mm-kontron-n801x-som: Fix the SPI chipselect polarity

[Frieder Schrempf]

On 16.07.21 15:28, Fabio Estevam wrote:
> The conversion of the spi-imx driver to use GPIO descriptors
> in commit 8cdcd8aeee28 ("spi: imx/fsl-lpspi: Convert to GPIO descriptors")
> helped to detect the following SPI chipselect polarity mismatch on an
> imx6q-sabresd for example:
>     
> [    4.854337] m25p80 at 0 enforce active low on chipselect handle
>    
> Prior to the above commit, the chipselect polarity passed via cs-gpios
> property was ignored and considered active-low.
>     
> The reason for such mismatch is clearly explained in the comments inside
> drivers/gpio/gpiolib-of.c:
>     
> * SPI children have active low chip selects
> * by default. This can be specified negatively
> * by just omitting "spi-cs-high" in the
> * device node, or actively by tagging on
> * GPIO_ACTIVE_LOW as flag in the device
> * tree. If the line is simultaneously
> * tagged as active low in the device tree
> * and has the "spi-cs-high" set, we get a
> * conflict and the "spi-cs-high" flag will
> * take precedence.
>     
> To properly represent the SPI chipselect polarity, change it to active-low
> when the "spi-cs-high" property is absent.
> 
> Signed-off-by: Fabio Estevam <festevam at gmail.com>

Thanks for the fix!

Reviewed-by: Frieder Schrempf <frieder.schrempf at kontron.de>

Shouldn't we consider to add the following tag, as this is clearly a bug in the original implementation of the DTS and the commit that uncovers this is already in multiple stable releases?

Fixes: 8668d8b2e67f ("arm64: dts: Add the Kontron i.MX8M Mini SoMs and baseboards")

> ---
>  arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi b/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi
> index d0456daefda8..5a2805c51361 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi
> @@ -63,7 +63,7 @@ opp-750M {
>  &ecspi1 {
>  	pinctrl-names = "default";
>  	pinctrl-0 = <&pinctrl_ecspi1>;
> -	cs-gpios = <&gpio5 9 GPIO_ACTIVE_HIGH>;
> +	cs-gpios = <&gpio5 9 GPIO_ACTIVE_LOW>;
>  	status = "okay";
>  
>  	spi-flash at 0 {
>