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

Kevin Hilman khilman at baylibre.com
Mon Feb 1 19:50:35 EST 2021

Alexander Stein <alexander.stein at mailbox.org> writes:

> Hi,
> Am Freitag, 29. Januar 2021, 09:07:45 CET schrieb Neil Armstrong:
>> On 28/01/2021 00:08, Alexander Stein wrote:
>> > 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].
>> > [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.


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