On Mon, Jan 15, 2024 at 07:08:07PM +0200, Laurent Pinchart wrote:
> On Mon, Jan 15, 2024 at 05:48:18PM +0100, Geert Uytterhoeven wrote:
> > Hi Conor,
> >
> > On Mon, Jan 15, 2024 at 5:13 PM Conor Dooley <conor@xxxxxxxxxx> wrote:
> > > On Mon, Jan 15, 2024 at 02:45:39PM +0100, Geert Uytterhoeven wrote:
> > > > Some Timer Unit (TMU) instances with 3 channels support a fourth
> > > > interrupt: an input capture interrupt for the third channel.
> > > >
> > > > While at it, document the meaning of the four interrupts, and add
> > > > "interrupt-names" for clarity.
> > > >
> > > > Update the example to match reality.
> > > >
> > > > Inspired by a patch by Yoshinori Sato for SH.
> > > >
> > > > Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> >
> > > > --- a/Documentation/devicetree/bindings/timer/renesas,tmu.yaml
> > > > +++ b/Documentation/devicetree/bindings/timer/renesas,tmu.yaml
> > > > @@ -46,7 +46,19 @@ properties:
> > > >
> > > > interrupts:
> > > > minItems: 2
> > > > - maxItems: 3
> > > > + items:
> > > > + - description: Underflow interrupt 0
> > > > + - description: Underflow interrupt 1
> > > > + - description: Underflow interrupt 2
> > > > + - description: Input capture interrupt 2
> > >
> > > Seeing "input capture interrupt 2" makes me wonder, are there two (or
> > > more!) other input capture interrupts that are still out there,
> > > undocumented, and looking for a home?
>
> Maybe writing this as
>
> - description: Underflow interrupt, channel 0
> - description: Underflow interrupt, channel 1
> - description: Underflow interrupt, channel 2
> - description: Input capture interrupt, channel 2
I, for one, prefer this wording.
> would make it clearer ?
>
> I'm also wondering if we really need to add interrupt-names. Drivers
> can't depend on the names due to backward compatibility, what benefit
> does it bring to add them to the bindings ?
Adding a -names property and not making it required has always seemed
like a waste of time to me. Granted, making it required post-factum has
other problems, so I am inclined to agree that it adds nothing.
>
> > SoCs can have multiple TMU instances.
> > Each TMU instance has 2 or 3 timer channels.
> > Each timer channel has an underflow interrupt.
> > Only the third channel may have an optional input capture interrupt
> > (which is not supported yet by the Linux driver).
> > Hence each instance can have 2, 3, or 4 interrupts.
> >
> > See "RZ/G Series, 2nd Generation User's Manual: Hardware"[1],
> > Section 69 ("Timer Unit (TMU)":
> > - Figure 69.2: Block Diagram of TMU,
> > - Section 69: Interrupt
> >
> > Note that the documentation uses a monotonic increasing numbering
> > of the channels, across all instances.
> >
> > [1] https://www.renesas.com/us/en/products/microcontrollers-microprocessors/rz-mpus/rzg2h-ultra-high-performance-microprocessors-quad-core-arm-cortex-a57-and-quad-core-arm-cortex-a53-cpus-3d
>
> --
> Regards,
>
> Laurent Pinchart
>
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