Re: [PATCH v2,2/2] arm64: dts: mediatek: mt8183: set bus rx width to disable quad mode

[Doug Anderson]

Hi,

On Wed, Aug 16, 2023 at 3:43 AM Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> wrote:
>
> Some of the SKUs are using gigadevice gd25lq64c flash chip. The chip
> default enables quad mode, which results in the write protect pin set to
> IO pin. In mt8183 kukui, we won't use quad enable for all SKUs, so apply
> the property to disable spi nor's quad mode.
>
> Signed-off-by: Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx>
> ---
>  arch/arm64/boot/dts/mediatek/mt8183-kukui.dtsi | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm64/boot/dts/mediatek/mt8183-kukui.dtsi b/arch/arm64/boot/dts/mediatek/mt8183-kukui.dtsi
> index 6ce16a265e053..ef472b522f2e7 100644
> --- a/arch/arm64/boot/dts/mediatek/mt8183-kukui.dtsi
> +++ b/arch/arm64/boot/dts/mediatek/mt8183-kukui.dtsi
> @@ -877,6 +877,7 @@ w25q64dw: flash@0 {
>                 compatible = "winbond,w25q64dw", "jedec,spi-nor";
>                 reg = <0>;
>                 spi-max-frequency = <25000000>;
> +               spi-rx-bus-width = <2>;

This feels wrong to me. Is your controller actually capable of "dual
SPI"? If so, why wasn't the rx-bus-width specified before? ...and if
you're truly capable of "dual SPI" then why aren't you also setting
the tx-bus-width?

My best guess (I can look up the schematic if needed) is that you're
actually _single_ lane, not dual lane SPI. Thus, a more accurate
description would probably be:

spi-rx-bus-width = <1>;
spi-tx-bus-width = <1>;

...but... I think that the default of rx/tx bus width isn't specified
is "1". Thus I think you should drop this patch.

-Doug