Hi John,
On Tue, 5 Aug 2025 at 11:22, John Madieu <john.madieu.xa@xxxxxxxxxxxxxx> wrote:
> > From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> > On Tue, 5 Aug 2025 at 10:27, John Madieu <john.madieu.xa@xxxxxxxxxxxxxx>
> > wrote:
> > > > From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> On Thu, 22 May 2025
> > > > at 20:23, John Madieu <john.madieu.xa@xxxxxxxxxxxxxx>
> > > > wrote:
> > > > > The RZ/G3E SoC integrates a Temperature Sensor Unit (TSU) block
> > > > > designed to monitor the chip's junction temperature. This sensor
> > > > > is connected to channel 1 of the APB port clock/reset and provides
> > > > temperature measurements.
> > > >
> > > > RZ/V2H and RZ/V2N have a second set of trim values for the second
> > > > TSU instance. So I guess you want to specify the offset in DT instead.
> > >
> > > What do you think of 'renesas,tsu-channel' property or alike Property
> > > to specify the channel being used ?
> >
> > While I agree instance IDs canbe useful (sometimes), the DT maintainers do
> > not like them very much, cfr. commit 6a57cf210711c068 ("docs: dt:
> > writing-bindings: Document discouraged instance IDs"), which prefers
> > cell/phandle arguments.
> >
> > For this particular case:
> > 1. The instance ID for the single TSU on RZ/G3E would be one, not zero
> > (oh, the SYS_LSI_OTPTSU1TRMVAL[01] register names do contain "TSU1"),
> > 2. It will break the moment a new SoC is released that stores trim
> > values at different offsets in the SYSC block.
> >
> > Hence a property containing a SYSC phandle and register offset sounds
> > better to me.
>
> This sounds good to me. I see something like:
>
> renesas,tsu-channel1 = <&sysc off1>;
> renesas,tsu-channel2 = <&sysc off2>; /* Optional, for V2H */
>
> /* or */
>
> renesas,tsu-channel-map = <&sysc off1 off2>;
>
> I would go for the first option to make it easier for V2H
> (while adding support for it later) so it can choose using
> either, or both, regardless of the index.
>
> What do you think ?
As the property would be part of the TSU node, it would always
refer to that specific channel/instance, so e.g.
renesas,tsu-trim = <&sysc 0x320>;
for the first TSU instance, and
renesas,tsu-trim = <&sysc 0x330>;
for the second instance.
P.S. Please don't write "V2H" on its own, as both R-Car V2H and RZ/V2H
exist in the Renesas SoC portfolio ;-)
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
