[PATCH 1/1] ARM: dts: orange-pi-zero-plus2: use fixed mmc indexes

[Chen-Yu Tsai]

On Wed, Feb 3, 2021 at 5:29 PM Maxime Ripard <maxime at cerno.tech> wrote:
>
> Hi,
>
> On Wed, Jan 27, 2021 at 08:46:20AM +0300, Sergey Matyukevich wrote:
> > Driver sunxi-mmc has recently been switched to asynchronous probe.
> > As a result, mmc indexes can be shuffled breaking existing setups
> > where UUIDs are not used for boot devices. Pin mmc indexes to keep
> > running the systems where fixed MMC or eMMC are specified,
> > e.g. root=/dev/mmcblk0p2.
> >
> > Signed-off-by: Sergey Matyukevich <geomatsi at gmail.com>
>
> I'm not sure, really.
>
> That would change the indices once again, and you shouldn't really rely
> on them anyway, there's never been any guarantee on the order of any
> device.

I assume one reason people want stable MMC indices is for setting the
root device. This could be done with UUID or PARTUUID. Another would
be setting the LED trigger to some MMC device, preferably in the DT
so it kicks in when the LED device is created. Though even that isn't
guaranteed since the MMC could probe after the LED. :(

Currently I'm using some shell script to parse the root device then
get the device name and program that as an LED trigger through sysfs.

> And whatever the outcome of that discussion, it definitely shouldn't be
> done for a single board.

I believe this should be done at the SoC level so we would have consistent
MMC indices across the board. However that seems to conflict with the order
swap we currently have in U-boot to support eMMCs seamlessly.

Regards
ChenYu