Re: [PATCH 3/3] arm64: dts: broadcom: bcm2712: Add the otp nodes to firmware

[Gregor Herburger <gregor.herburger@linutronix.de>]

On Thu, Apr 09, 2026 at 02:15:32PM +0200, Krzysztof Kozlowski wrote:
> On 09/04/2026 14:02, Gregor Herburger wrote:
> > Hi Krzysztof,
> > 
> > thanks for reviewing.
> > 
> > On Thu, Apr 09, 2026 at 10:15:12AM +0200, Krzysztof Kozlowski wrote:
> >> On Wed, Apr 08, 2026 at 10:00:17AM +0200, Gregor Herburger wrote:
> >>> The Raspberry Pi 5 has two OTP registers (private and customer), add these
> >>> to the devicetree.
> >>
> >> So this sentence confirms my question on bindings - your device
> >> raspberrypi,bcm2835-firmware has these, thus you do not need these child
> >> nodes at all. Neither compatibles.
> > 
> > I dont't think so. In my understanding the bcm2835-firmware does not
> > provide the otp registers but only provides the interface to the
> > registers. Though I don't know the details how this is done but [1] says
> > that only BCM2712 has 512bits and the others (like bcm2711) have
> 
> Still the same. s/otp/interface/ so your device provides interface.
> 
Ok understood.

> > 256bits. So both devicetrees have the raspberrypi,bcm2835-firmware node
> > but only the bcm2712 has the raspberrypi,firmware-otp-private node while the 
> 
> Why does bcm2712 use bcm2835 compatible?

I have no idea. But it is like this.
> 
> Nodes and properties are not a solution. See DTS101 question - "...
> because my new device, which is compatible with an older one, does not
> support ..." and answer: No.
> 
> 
> 
> > raspberrypi,firmware-otp-customer is available in all raspberrys.
> > 
> >> Drop entire DTS and binding patches.
> > 
> > If I drop the binding patch how to distinguish the variants? Should I
> > add a SoC specific compatible? e.g. `raspberrypi,bcm2712-firmware` and
> > use it in the firmware/raspberrypi driver to add the second otp region?
> 
> So you have different devices/variants? What is the "variant" here?

Seems so. I suppose there is at least a bcm2712 variant and a non-bcm2712
variant (which is currently confusingly named 'raspberrypi,bcm2835-firmware').
> 
> Writing-bindings asks you to have per device compatible. Why standard
> rules do not apply here? (see also DTS101)

I am not arguing that the rules do not apply here. I want to find out
what is the correct way to do it. 

Should there then be a 'raspberrypi,bcm2712-firmware' compatible with
'raspberrypi,bcm2835-firmware' fallback?

> 
> > 
> > Also what I don't understand why we have all the bindings for
> 
> Neither do I.
Ok good. That is what confused me.

Best regards,
Gregor