Re: [PATCH 2/2] ARM: dts: imx6ull-dhcor: Add Marantec maveo box

Marek Vasut
2023-04-06T17:33:01Z

On 4/6/23 18:36, Krzysztof Kozlowski wrote:
> On 05/04/2023 20:24, Christoph Niedermaier wrote:
>> From: Marek Vasut [mailto:marex@denx.de]
>> Sent: Wednesday, April 5, 2023 6:25 PM
>>> On 4/5/23 18:02, Christoph Niedermaier wrote:
>>>
>>> [...]
>>>
>>>> +/ {
>>>> + model = "DH electronics i.MX6ULL DHCOR on maveo box";
>>>> + compatible = "dh,imx6ull-dhcor-maveo-box", "dh,imx6ull-dhcor-som",
>>>> + "fsl,imx6ull";
>>>> +
>>>> + aliases {
>>>> + /delete-property/ mmc0; /* Avoid double definitions */
>>>> + /delete-property/ mmc1;
>>>> + mmc2 = &usdhc2; /* eMMC should be mmc2 */
>>>
>>> Why not mmc0 ?
>>>
>>> Use root=PARTUUID= when booting to avoid any dependency on
>>> root=/dev/mmcblk2pN enumeration.
>>
>> This is due to software interchangeability with the DHCOM
>> i.MX6ULL, where the eMMC is always mmc2.
>
> That's not the reason to have aliases. The number should match numbering
> in your datasheet/schematics/user-guide, not what your software wants.
>
> Use PARTUUID for SW dependencies.

Regarding the PARTUUID, Christoph raised a valid concern I think. These
machines can come with A/B update scheme, where the PARTUUID could
become identical between two partitions. Or, you can write the same
image to both eMMC and SD card. I don't think PARTUUID is the silver
bullet solution, but I agree the enumeration is a great solution either.