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

[Marek Vasut]

On 4/6/23 18:36, Krzysztof Kozlowski wrote:
> On 05/04/2023 20:24, Christoph Niedermaier wrote:
> > From: Marek Vasut [mailto:marex@xxxxxxx]
> > 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.