linux-kernel - Re: [PATCH] ARM: dts: exynos: Assign a fixed index to mmc devices on ODROID XU3/4 boards

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Message-ID: <4ac01b71-e806-18c8-13ce-6acdcc1a3b41@samsung.com>
Date:   Wed, 4 Nov 2020 13:24:02 +0100
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Markus Reichl <m.reichl@...etechno.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: dts: exynos: Assign a fixed index to mmc devices
 on ODROID XU3/4 boards

Hi Markus,

On 04.11.2020 11:08, Markus Reichl wrote:
> Recently introduced async probe on mmc devices can shuffle block IDs.
> Pin them to fixed values to ease booting in evironments where UUIDs
> are not practical. Use newly introduced aliases for mmcblk devices from [1].
>
> [1]
> https://patchwork.kernel.org/patch/11747669/

Wow, this is a long standing issue, called by others 'a feature'. Good 
that this has been finally solved.

> Signed-off-by: Markus Reichl <m.reichl@...etechno.de>
> ---
>   arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi b/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi
> index e35af40a55cb..91d2840ac8ca 100644
> --- a/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi
> +++ b/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi
> @@ -13,6 +13,11 @@
>   #include "exynos5422-odroid-core.dtsi"
>   
>   / {
> +	aliases {
> +		mmc0 = &mmc_2;
> +		mmc1 = &mmc_0;

Frankly, I would keep the MMC numbers the same as in u-boot and 
datasheets. 0 for the build-in eMMC and 2 for the SD-card. This would be 
much more natural. On the other hand, I would agree to do it differently 
only on Odroid HC1/HD2/MC1, which don't have build-in eMMC - just use 0 
there for the SD-card.

> +	};
> +
>   	gpio-keys {
>   		compatible = "gpio-keys";
>   		pinctrl-names = "default";

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland