[PATCH] sunxi: Bring back SD card as MMC device 0

[Jagan Teki]

On Mon, Apr 26, 2021 at 4:57 PM Andre Przywara <andre.przywara at arm.com> wrote:
>
> On Sun, 25 Apr 2021 18:03:05 +0530
> Jagan Teki <jagan at amarulasolutions.com> wrote:
>
> Hi Jagan,
>
> thanks for your input!
>
> > On Sun, Apr 25, 2021 at 3:30 PM Andre Przywara <andre.przywara at arm.com> wrote:
> > >
> > > On Fri, 16 Apr 2021 12:08:09 +0100
> > > Andre Przywara <andre.przywara at arm.com> wrote:
> > >
> > > Hi,
> > >
> > > > Commit 2243d19e5618 ("mmc: mmc-uclass: Use dev_seq() to read aliases
> > > > node's index") now actually enforces U-Boot's device enumeration policy,
> > > > where explicitly named devices come first, then any other non-named
> > > > devices follow, without filling gaps.
> > > >
> > > > For quite a while we have had an "mmc1 = &mmc2;" alias in our
> > > > sunxi-u-boot.dtsi, which now leads to the problem that the SD card
> > > > (which was always mmc device 0) now gets to be number 2.
> > > > I guess this breaks quite some boot scripts, and is confusing at least.
> > > >
> > > > Just add an explicit mmc0 alias in the very same file to fix this and
> > > > restore the old behaviour.
> > >
> > > Can someone please say if this is the right solution?
> > > I think the SD card has always been mmc device 0 in U-Boot, so I think
> > > it's worth keeping that. Just not sure if this is the right way of
> > > fixing that?
> >
> > Playing with aliases always gets confused and might get a different
> > behavior, IMHO.
>
> I am not so sure about that, since aliases force a fixed numbering, so
> it should be less confusing. We have the same problem in the kernel
> now, and Samuel sent some patches to have aliases in the mainline DTs
> as well [1].

Okay.

>
> > Detect the dev number by U-Boot itself and look at
> > traverse bootenv by all possible dev numbers in sunxi-common.h, but
>
> OK, I will have a look at how the automatic distro boot behaves with
> this change. My concern was more the interactive user, who is used to
> have the SD card at device 0 (I certainly am).
>
> > this has one slide effect that we mark mmc2 as devnum 1 for the sake
> > of fastboot so if we mark fastboot number for specific board properly
> > (by static or runtime) then explicit aliases wouldn't required.
>
> Ah, good point, thanks for the heads up. I guess this is the actual
> reason for the alias in our -u-boot.dtsi? Maybe we find a different way
> to let fastboot find the eMMC? Then we can drop the extra mmc1 alias,
> get our numbering back, and can cope with the incoming aliases from the
> mainline DTs as well?

Agreed.