Re: [PATCH] ARM: dts: sunxi: Add MMC alias for consistent enumeration

[Andre Przywara <andre.przywara@arm.com>]

On Wed, 1 Jan 2025 16:58:28 +0800
Chen-Yu Tsai <wens@csie.org> wrote:

Hi,

> On Thu, Dec 19, 2024 at 6:58 PM Stefan Gloor <code@stefan-gloor.ch> wrote:
> >
> > Add explicit alias for MMC devices, so that (e)MMC and micro SD cards
> > are enumerated consistently. This should fix spurious boot failures when
> > specifying a hard-coded root partition, e.g., mmcblk0p2.  
> 
> IIRC we have chosen against adding explicit MMC aliases for the sunxi
> platforms. Please try using UUID= or PARTUUID= for root partition
> references.

Yes, and LABEL= would be another way.

Alternatively you could use U-Boot's DT when booting the board. U-Boot
will add those aliases during build time (because it needs them for its
own purposes), and by using $fdtcontroladdr (instead of $fdt_addr_r,
on the bootz command line) you get this for free, and even save yourself
from loading some DT.
We sync the DTs regularly from the kernel to U-Boot now, and at the
moment they are identical between the kernel and U-Boot, so you don't
lose anything.

Cheers,
Andre

> > Link: https://github.com/linux-sunxi/meta-sunxi/pull/431
> > Signed-off-by: Stefan Gloor <code@stefan-gloor.ch>
> > ---
> >  arch/arm/boot/dts/allwinner/sun7i-a20-olinuxino-micro.dts | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/arch/arm/boot/dts/allwinner/sun7i-a20-olinuxino-micro.dts b/arch/arm/boot/dts/allwinner/sun7i-a20-olinuxino-micro.dts
> > index a1b89b2a2999..9cd1eb690134 100644
> > --- a/arch/arm/boot/dts/allwinner/sun7i-a20-olinuxino-micro.dts
> > +++ b/arch/arm/boot/dts/allwinner/sun7i-a20-olinuxino-micro.dts
> > @@ -60,6 +60,8 @@ aliases {
> >                 serial2 = &uart7;
> >                 spi0 = &spi1;
> >                 spi1 = &spi2;
> > +               mmc0 = &mmc0;
> > +               mmc1 = &mmc3;
> >         };
> >
> >         chosen {
> > --
> > 2.45.2
> >
> >  
>