Re: [PATCH 1/3] arm64: dts: ti: iot2050: Flip mmc device ordering on Advanced devices

Hi Nishanth,

On 07/09/21 10:23 pm, Nishanth Menon wrote:

On 22:17-20210907, Aswath Govindraju wrote:

quoted

Hi Nishanth,

On 07/09/21 9:05 pm, Nishanth Menon wrote:

quoted

On 17:30-20210907, Jan Kiszka wrote:

quoted

On 07.09.21 17:27, Nishanth Menon wrote:

quoted

On 17:20-20210907, Jan Kiszka wrote:

quoted

On 07.09.21 17:13, Nishanth Menon wrote:

quoted

On 16:22-20210907, Jan Kiszka wrote:

quoted

From: Jan Kiszka <jan.kiszka@siemens.com>

This ensures that the SD card will remain mmc0 across Basic and Advanced
devices, also avoiding surprises for users coming from the downstream
kernels.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 arch/arm64/boot/dts/ti/k3-am6548-iot2050-advanced.dts | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/boot/dts/ti/k3-am6548-iot2050-advanced.dts b/arch/arm64/boot/dts/ti/k3-am6548-iot2050-advanced.dts
index ec9617c13cdb..d1d5278e0b94 100644
--- a/arch/arm64/boot/dts/ti/k3-am6548-iot2050-advanced.dts
+++ b/arch/arm64/boot/dts/ti/k3-am6548-iot2050-advanced.dts

@@ -18,6 +18,11 @@ / {
 	compatible = "siemens,iot2050-advanced", "ti,am654";
 	model = "SIMATIC IOT2050 Advanced";
 
+	aliases {
+		mmc0 = &sdhci1;
+		mmc1 = &sdhci0;
+	};

Should we do this at SoC level?

Well, I wouldn't mind - but that would also impact your EVMs. For us,
this is fine as we are coming from that ordering above with our
downstream kernel/dts.

I think it'd probably be a welcome change. overall we've standardized on
partuuid.

Yeah, it's more about "dd if=emmc.img of=/dev/mmcblk1 - damn, the wrong
one again."

Let me know what you prefer, and I'll update my patch.

Lets do it at SoC level. I will follow it up with a patch for other K3
SoCs as well.


Unless someone has a strong opinion on this approach - if so, speak up
with reasons.

Making this change in SoC level for all K3 devices would force changes
to be made in U-Boot too, for consistency. In U-Boot, a major change
would be required in the environment variables to support this. As I
don't see any functional advantage by making this change, I feel that
this change would make things more confusing for users already using the
K3 devices. At present, the ordering is consistent across all the K3
devices, I feel that keeping it the same way would be better.

As for making changes only on IoT boards, if it is okay to have the
ordering changed between U-Boot and kernel, I don't see any problem
making this change in kernel alone.

arch/arm64/boot/dts/ti/k3-am65.dtsi has no ordering. u-boot is supposed
to copy from kernel the dtsi files as is. I think having mmc aliases in
kernel is a good thing as we do regard kernel as the canonical dts
source.

Yes, you are correct. Aliases are not added for mmc in U-Boot too, but
due to the ordering in the device tree, mmc0 is always sdhci0 and mmc1
is always sdhci1 in U-Boot. I agree that, in kernel as the probe order
is not guaranteed, fixing the order would be better by adding aliases
explicitly.

If you are suggesting we flip things so that mmc0 is sdhci0 and mmc1 is
sdhci1 -  that might be a valid suggestion - Jan, do you see a problem
in having consistency here (flip the aliases)?

Yes, I am suggesting a flip in the order and this order can be applied
across all the K3 SoC's

Thanks,
Aswath