linux-kernel - Re: [PATCH v1] arm64: dts: ti: k3-am62-verdin: Update tla2024 adc compatible

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Message-ID: <3d9de1b8-488b-4df5-b984-7581b1d02241@kernel.org>
Date: Tue, 1 Oct 2024 15:59:39 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Francesco Dolcini <francesco@...cini.it>, Nishanth Menon <nm@...com>
Cc: João Paulo Gonçalves
 <jpaulo.silvagoncalves@...il.com>, Vignesh Raghavendra <vigneshr@...com>,
 Tero Kristo <kristo@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, João Paulo Gonçalves
 <joao.goncalves@...adex.com>, linux-arm-kernel@...ts.infradead.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] arm64: dts: ti: k3-am62-verdin: Update tla2024 adc
 compatible

On 01/10/2024 15:01, Francesco Dolcini wrote:
> Hello Krzysztof,
> 
> On Tue, Oct 01, 2024 at 01:54:56PM +0200, Krzysztof Kozlowski wrote:
>> On 01/10/2024 13:14, João Paulo Gonçalves wrote:
>>> From: João Paulo Gonçalves <joao.goncalves@...adex.com>
>>>
>>> With commit f1c9ce0ced2d ("iio: adc: ti-ads1015: Add TLA2024 support") a
>>> new compatible was introduced for TLA2024 ADC. Update the device
>>> tree to use the correct compatible for the Verdin-AM62 hardware.
>>>
>>> Signed-off-by: João Paulo Gonçalves <joao.goncalves@...adex.com>
>>> ---
>>>  arch/arm64/boot/dts/ti/k3-am62-verdin.dtsi | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm64/boot/dts/ti/k3-am62-verdin.dtsi b/arch/arm64/boot/dts/ti/k3-am62-verdin.dtsi
>>> index 5bef31b8577b..f201722d81b3 100644
>>> --- a/arch/arm64/boot/dts/ti/k3-am62-verdin.dtsi
>>> +++ b/arch/arm64/boot/dts/ti/k3-am62-verdin.dtsi
>>> @@ -1220,7 +1220,7 @@ sensor@48 {
>>>  	};
>>>
>>>  	adc@49 {
>>> -		compatible = "ti,ads1015";
>>> +		compatible = "ti,tla2024";
>>
>> So it is not always TI, who breaks their users. :) (as pointed out in
>> LPC DT BoF).
> 
> So, let's adjust what I said at that time, I think is important, and I
> appreciate you giving me an excuse for doing that :-)
> 
> Lately as Toradex we are working a lot with TI, and one of the reasons is
> that they have a great software support, backed-up by a great strategy
> on the way they contribute to the various upstream projects they build
> their SDK on top (Linux, U-Boot, and more).
> 
> With that is normal that while working so closely with them we find
> issues, everybody have those, it's just that those are the one we
> care the most at the moment :-). Not to mention that we started working
> with TI a couple of years ago, so TI is still somehow "new" to us and we
> are still "learning".
> 
> On this regards I was recently working on updating our BSP to the
> latest SDK from TI, that is based on a v6.6 stable kernel and looking at
> the patches we had to apply on top, the total counts of the patches we
> do not have in mainline to support the board subject of this patch is
> just _zero_. This to me is a great achievement.
> 
> Nishant: this is also for you, and feel free to "market" this
> internally/externally :-)
> 
> 
>> If you want to break users, sure, but at least explain in commit msg why.
> 
> Now, on this specific topic, the actual device that is assembled on this
> board is a TI TLA2024, and it's like that since ever, the board never
> changed. The current compatible is not matching what is assembled on
> board. It works because the device is close enough to TI ADS1015.
> 
> With that said, I do not think this is breaking any actual compatibility
> issue.
> 
>  - The old DTB will keep working with old and new kernel.

New DTB stops working with old kernel and this is what we talked about
during LPC.

All out-of-tree users of this DTS, like other operating systems, will be
affected as well probably.

>  - The commit adding support for TI TLA2024 is in v5.19, and this board
>    is supported only from kernel v6.5, so you cannot run an older kernel
>    with this board. In addition to that I do not think that is
>    reasonable to have someone using a "new" dtb with an "old" kernel.
>  - The firmware, U-Boot, the only one that currently supports this board,
>    is not making any use of this compatible nor of this ADC.
Best regards,
Krzysztof