Re: [PATCH 1/1] arm64: dts: meson: g12b: odroid-n2: Assign a fixed index to mmc devices

Alexander Stein [off-list ref] writes:

Hi,

Am Freitag, 29. Januar 2021, 09:07:45 CET schrieb Neil Armstrong:

quoted

On 28/01/2021 00:08, Alexander Stein wrote:

quoted

Recently introduced async probe on mmc devices can shuffle block IDs.
Pin them to fixed values to ease booting in environments where UUIDs
are not practical. Use newly introduced aliases for mmcblk devices from 

[1].

quoted

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[1]
https://patchwork.kernel.org/patch/11747669/

I understand the goal, and this should be done for _all_ boards, not only 

the Odroid-N2.

I see. So there are 2 options:
1.
Set the mapping for all 3 sd_emmc_* in the top-most .dtsi
Upside: very easy patch
Downside: When sd_emmc_a is not enabled "mmc0" will never be available.
Might be confusing.

sd_emmc_a is (almost?) always the iface used for SDIO devices, which are
not always present.

I would recommend we go with a single mapping in the top-level .dtsi

  SD card -> mmc0  (sd_emmc_b)
  eMMC    -> mmc1  (sd_emmc_c)
  SDIO    -> mmc2  (sd_emmc_a)

it's not exactly obvious why we don't go 0,1,2 == A,B,C but just
document it in the top-level .dtsi.

This approach also has the benefit of having the devices show up how
many/most boards showed up before the async probe changes.

Kevin