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

From: Aswath Govindraju <a-govindraju@ti.com>
To: Nishanth Menon <nm@ti.com>, Jan Kiszka <jan.kiszka@siemens.com>
Cc: Tero Kristo <kristo@kernel.org>, Rob Herring <robh+dt@kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>, <devicetree@vger.kernel.org>,
	Bao Cheng Su <baocheng.su@siemens.com>,
	Chao Zeng <chao.zeng@siemens.com>
Subject: Re: [PATCH 1/3] arm64: dts: ti: iot2050: Flip mmc device ordering on Advanced devices
Date: Tue, 7 Sep 2021 22:17:25 +0530	[thread overview]
Message-ID: <482dddc1-b1f8-15db-a0c5-0d6def5d859f@ti.com> (raw)
In-Reply-To: <20210907153547.53cc2zx23rx72kqf@thyself>

Hi Nishanth,

On 07/09/21 9:05 pm, Nishanth Menon wrote:
> On 17:30-20210907, Jan Kiszka wrote:
>> On 07.09.21 17:27, Nishanth Menon wrote:
>>> On 17:20-20210907, Jan Kiszka wrote:
>>>> On 07.09.21 17:13, Nishanth Menon wrote:
>>>>> On 16:22-20210907, Jan Kiszka wrote:
>>>>>> 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.

Thanks,
Aswath