Re: [PATCH v1 4/8] dt-bindings: timer: Add EcoNet HPT CPU Timer

[Caleb James DeLisle]

On 24/03/2025 08:13, Krzysztof Kozlowski wrote:
> On 24/03/2025 00:53, Caleb James DeLisle wrote:
> > > > > > +  compatible:
> > > > > > +    const: econet,timer-hpt
> > > > > Soc components must have soc-based compatible and then filename matching
> > > > > whatever you use as fallback.
> > > > I have so far been unable to find good documentation on writing DT bindings
> > > > specifically for SoC devices. If you have anything to point me to, I will read it.
> > > > If not, even a good example of someone else doing it right is helpful.
> > > >
> > > > Currently, I see qcom,pdc.yaml appears to do what you say, so I in absence
> > > > of any other advice, I can try to do what they do.
> > > Just don't use generic fallback.
> >
> > Ok I watched your "Accepted in Less Than 10 Iterations" lecture (I'm doing my
> > homework). If I understand this correctly, you prefer that I use something specific
> > like econet,en751221-timer as the fallback case, so for example on EN751627,
> > it would be:
> >
> > compatible = "econet,en751627-timer", "econet,en751221-timer";
> Yes
>
> > The reason why I didn't do this is because this timer seems to show up in a lot of
> > places. Vendor code says that it's older than EN751221, and (if my reading is
> Just like every other SoC component for every other SoC.
>
> > correct) it has found it's way into chips branded TrendChip, MediaTek and Ralink
> > as well as EcoNet.
> >
> > Now that I'll be adding strict checks on the number of register blocks, this way
> > also has the advantage of allowing a case for users of the timer in SoCs we don't
> > know about:
> >
> > // Only valid with 2 register blocks
> > compatible = "econet,en751627-timer", "econet,timer-hpt";
> >
> > // Only valid with 1 register block
> > compatible = "econet,en751612-timer", "econet,timer-hpt";
> Above do not differ...
>
> > // No restriction because we don't know how many timers the SoC has
> > compatible = "econet,timer-hpt";
> How can you not know? This is strictly defined on given hardware.
I mean I don't know, the person writing the DTS for that SoC needs to know.


Per your preference, I'll do the following:


// 2 blocks accepted

compatible = "econet,en751627-timer", "econet,en751221-timer";

// 1 block accepted

compatible = "econet,en751221-timer";


If someone has an SoC with more than 2 timers, it is not supported so they
should update the binding, or (in downstream) they might write an invalid
DTS. FWIW I have no evidence of any >2 core processor which uses this, so
2 timers is probably the maximum.


Lastly I'll change the driver name to timer-econet-en751221.c to avoid the
proliferation of different names.


Thanks,

Caleb