linux-kernel - Re: [PATCH] arm64: dts: mediatek: Add fallback compatible for mt8192's flash

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Message-ID: <20220502161203.pfmjyep4escqwjix@notapiano>
Date:   Mon, 2 May 2022 12:12:03 -0400
From:   Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
To:     Matthias Brugger <matthias.bgg@...il.com>
Cc:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>, kernel@...labora.com,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] arm64: dts: mediatek: Add fallback compatible for
 mt8192's flash

On Fri, Apr 29, 2022 at 03:57:45PM -0400, Nícolas F. R. A. Prado wrote:
> The dt-binding for Mediatek's SPI NOR flash controller expects a mt8173
> fallback compatible for mt8192, so add it in mt8192.dtsi.
> 
> The driver already sets custom data based on the mt8192 compatible, so
> this fallback compatible won't be used and is added purely to suppress
> the dt-binding warning.
> 
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>

By the way, I wonder if this patch should be accompanied by a patch adding the 
mediatek,mt8192-nor standalone compatible as deprecated in the dt-binding. I
feel like the answer is in theory yes, but in practice no.

The fact that the mediatek,mt8192-nor standalone compatible was accepted in the
devicetree means that it should show in the dt-binding, since it's an acceptable
binding. But since the binding already shows up there with a fallback binding,
then this standalone binding should be considered deprecated.

But in practice, the mediatek,mt8192-nor is the more specific binding so
documenting its standalone use as deprecated wouldn't accomplish much.

What do you think?

Thanks,
Nícolas

> 
> ---
> 
>  arch/arm64/boot/dts/mediatek/mt8192.dtsi | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/mediatek/mt8192.dtsi b/arch/arm64/boot/dts/mediatek/mt8192.dtsi
> index 26dbe9ecc528..32a836105ea7 100644
> --- a/arch/arm64/boot/dts/mediatek/mt8192.dtsi
> +++ b/arch/arm64/boot/dts/mediatek/mt8192.dtsi
> @@ -896,7 +896,7 @@ pcie_intc0: interrupt-controller {
>  		};
>  
>  		nor_flash: spi@...34000 {
> -			compatible = "mediatek,mt8192-nor";
> +			compatible = "mediatek,mt8192-nor", "mediatek,mt8173-nor";
>  			reg = <0 0x11234000 0 0xe0>;
>  			interrupts = <GIC_SPI 431 IRQ_TYPE_LEVEL_HIGH 0>;
>  			clocks = <&topckgen CLK_TOP_SFLASH_SEL>,
> -- 
> 2.36.0
>