linux-kernel - Re: [PATCH] ARM: dts: exynos: Assign a fixed index to mmc devices on exynos4412 based ODROID boards

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Message-ID: <be911d41-c707-f482-4966-476b9330bde7@arm.com>
Date:   Thu, 5 Nov 2020 11:26:00 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Markus Reichl <m.reichl@...etechno.de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Rob Herring <robh+dt@...nel.org>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: dts: exynos: Assign a fixed index to mmc devices on
 exynos4412 based ODROID boards

On 2020-11-05 08:31, Markus Reichl wrote:
> Hi Marek,
> 
> on rk3399 the proposed ordering [1] is according to base address in DT.

FWIW, note that in RK3399's case the SoC itself provides no logical 
numbering to follow - the pin groups are named "EMMC", "SDIO0" and 
"SDMMC0" in the datasheet, while the TRM uses "emmc", "sdio" and "sdmmc" 
in signal and register names.

If the SoC *does* have an inherent notion of numbered interfaces, I 
would agree that following that numbering is the most logical thing to do.

Robin.

> 
> [1]
> https://patchwork.kernel.org/patch/11881427
> 
> Am 04.11.20 um 14:44 schrieb Marek Szyprowski:
>> On 04.11.2020 14:13, Marek Szyprowski wrote:
>>> On 04.11.2020 14:06, Markus Reichl wrote:
>>>> Am 04.11.20 um 13:25 schrieb Marek Szyprowski:
>>>>> On 04.11.2020 11:25, 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
>>>>>> ar not practical.
>>>>>> Use newly introduced aliases for mmcblk devices from [1].
>>>>>>
>>>>>> [1]
>>>>>> https://patchwork.kernel.org/patch/11747669/
>>>>>>
>>>>>> Signed-off-by: Markus Reichl <m.reichl@...etechno.de>
>>>>>> ---
>>>>>>    arch/arm/boot/dts/exynos4412-odroid-common.dtsi | 5 +++++
>>>>>>    1 file changed, 5 insertions(+)
>>>>>>
>>>>>> diff --git a/arch/arm/boot/dts/exynos4412-odroid-common.dtsi
>>>>>> b/arch/arm/boot/dts/exynos4412-odroid-common.dtsi
>>>>>> index a5c1ce1e396c..aa10d5bc7e1c 100644
>>>>>> --- a/arch/arm/boot/dts/exynos4412-odroid-common.dtsi
>>>>>> +++ b/arch/arm/boot/dts/exynos4412-odroid-common.dtsi
>>>>>> @@ -13,6 +13,11 @@
>>>>>>    #include "exynos-mfc-reserved-memory.dtsi"
>>>>>>      / {
>>>>>> +    aliases {
>>>>>> +        mmc0 = &sdhci_2;
>>>>>> +        mmc1 = &mshc_0;
>>>>> Like in the OdroidXU3-family patch, I would use 0 for the eMMC 
>>>>> (mshc_0)
>>>>> and 2 for the SD-card (sdhci_2).
>>>> How to deal then with sdhci_0 (from exynos4.dtsi) vc. mshc_0 (from
>>>> exynos4412.dts)?
>>> sdhci_0 and mshc_0 both operate on the same physical MMC0 bus, so this
>>> is not an issue. They cannot be used simultaneously. The latter is just
>>> faster, the first one has been left there mainly for the software
>>> compatibility.
>>
>> I've thought a bit more on this and I would simply prefer to add generic
>> MMC aliases to the top-level Exynos dtsi files (3250, 4210, 4412, 5250,
>> 5410, 5420) to keep Linux logical MMC bus numbers in sync with the HW
>> bus numbers on all boards.
>>
>> Best regards
>>
> 
> Gruß,
> 
> _______________________________________________
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> linux-arm-kernel@...ts.infradead.org
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> 

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