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

[Francesco Dolcini <francesco@dolcini.it>]

On Tue, Oct 01, 2024 at 03:59:39PM +0200, Krzysztof Kozlowski wrote:
> On 01/10/2024 15:01, Francesco Dolcini wrote:
> > 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@toradex.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@toradex.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.

My mind at that time was really on using old DTB with a new kernel, not that
other way around.

In any case, I do not think that this comment applies on this specific case,
as I wrote you cannot really run this board on a kernel that does not support
the ti,tla2024 compatible.

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

Well, yes. From what I know those user do not exist and this is just
theoretical, but, I might be as well wrong and I see your point.

So, let me try to sum it up, I see 2 options:

 1 - we drop this change. this is fine for me.
 2 - we add a comment in the commit message that this is a breaking change, and
     while I am not aware of any impact with real software that is available today,
     I might have incomplete information.

Francesco