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Message-ID: <5a2d2365-effb-2663-1ace-fddb59ee61b7@collabora.com>
Date:   Wed, 29 Jun 2022 15:44:26 -0300
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Subject: Re: [PATCH] ARM: dts: bcm2711-rpi: Use aliases to set custom MMC
 device index
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To:     Stefan Wahren <stefan.wahren@i2se.com>,
        krzysztof.kozlowski+dt@linaro.org, nsaenz@kernel.org,
        robh+dt@kernel.org
Cc:     bcm-kernel-feedback-list@broadcom.com, devicetree@vger.kernel.org,
        linux-rpi-kernel@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        pbrobinson@gmail.com, f.fainelli@gmail.com
References: <20220614141208.15614-1-ariel.dalessandro@collabora.com>
 <c3c62929-77ba-6bae-1e0c-4d4ece9c9b32@i2se.com>
From:   Ariel D'Alessandro <ariel.dalessandro@collabora.com>
In-Reply-To: <c3c62929-77ba-6bae-1e0c-4d4ece9c9b32@i2se.com>
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Hi Stefan,

Sorry for the delay.

On 6/14/22 17:47, Stefan Wahren wrote:
> Hi Ariel,
> 
> Am 14.06.22 um 16:12 schrieb Ariel D'Alessandro:
>> Add MMC aliases to ensure that the /dev/mmcblk ID for the first
>> eMMC/SD card won't change depending on the probe order of the MMC
>> drivers.
> 
> this changes the emmc2 from mmc1 to mmc0 in my case (RPi 4,
> multi_v7_defconfig), which i consider as a regression / unexpected
> change in userspace.
> 
> Could you please explain your actual motivation of your patch?

That's a good point. The original reason comes from u-boot in fact, I
just sent the patch here as u-boot is syncing the dts files from the kernel.

U-boot uses the same defconfig `configs/rpi_arm64_defconfig` for
different RPi versions, which have different mmcblk ids numbering.

In order to use bootcount support in u-boot, the config option
CONFIG_SYS_BOOTCOUNT_EXT_DEVPART needs to be filled with the fixed
dev/part ids. In general I'd expect mmcblk0 to be eMMC/SD, which is not
in this case, at least for RPi4.

Anyway, this is probably something to be discussed on the u-boot mailing
list, not here.

Thanks,
Ariel

> 
>>
>> Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>
>> ---
>>
>> Changes in v2:
>> * Moved alias from bcm2711-rpi-4-b.dts to bcm2711-rpi.dtsi
>>
>>   arch/arm/boot/dts/bcm2711-rpi.dtsi | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm/boot/dts/bcm2711-rpi.dtsi
>> b/arch/arm/boot/dts/bcm2711-rpi.dtsi
>> index ca266c5d9f9b..a39b2f68e4cc 100644
>> --- a/arch/arm/boot/dts/bcm2711-rpi.dtsi
>> +++ b/arch/arm/boot/dts/bcm2711-rpi.dtsi
>> @@ -13,6 +13,7 @@ memory@0 {
>>       aliases {
>>           emmc2bus = &emmc2bus;
>>           ethernet0 = &genet;
>> +        mmc0 = &emmc2;    /* mmcblk0 for eMMC/SD */
>>           pcie0 = &pcie0;
>>           blconfig = &blconfig;
>>       };