Re: [PATCH v2 28/29] serial: sh-sci: Add device tree bindings documentation

Laurent Pinchart
2013-11-11T13:26:11Z

Hi Mark,

Thank you for the quick and detailed review.

On Monday 11 November 2013 09:40:39 Mark Rutland wrote:
> Hi Laurent,
>
> I have a few comments.
>
> On Sun, Nov 10, 2013 at 03:33:40AM +0000, Laurent Pinchart wrote:
> > Document the device tree bindings for the sci serial port devices.
> >
> > Cc: devicetree@vger.kernel.org
> > Signed-off-by: Laurent Pinchart
> > <laurent.pinchart+renesas@ideasonboard.com>
> > Acked-by: Simon Horman <horms+renesas@verge.net.au>
> > ---
> >
> > .../bindings/serial/renesas,sci-serial.txt | 42 +++++++++++++++++
> > 1 file changed, 42 insertions(+)
> > create mode 100644
> > Documentation/devicetree/bindings/serial/renesas,sci-serial.txt>
> > diff --git
> > a/Documentation/devicetree/bindings/serial/renesas,sci-serial.txt
> > b/Documentation/devicetree/bindings/serial/renesas,sci-serial.txt new
> > file mode 100644
> > index 0000000..66d3bca
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/serial/renesas,sci-serial.txt
> > @@ -0,0 +1,42 @@
> > +* Renesas SH-Mobile Serial Communication Interface
> > +
> > +Required properties:
> > +
> > + - compatible: one of the following types (scif, scifa, scifb, hscif).
>
> Minor nit, but would be nice to have "Should contain one of the
> following:". We might have future variants whereby the compatible string
> will actually be a string list.

Sure, I can do that.

> > +
> > + - "renesas,scif-r8a7790" for R8A7790 (R-Car H2) SCIF compatible UART.
> > + - "renesas,scifa-r8a7790" for R8A7790 (R-Car H2) SCIFA compatible
> > UART. + - "renesas,scifb-r8a7790" for R8A7790 (R-Car H2) SCIFB
> > compatible UART. + - "renesas,hscif-r8a7790" for R8A7790 (R-Car H2)
> > HSCIF compatible UART. + - "renesas,scif-generic" for generic SCIF
> > compatible UART.
> > + - "renesas,scifa-generic" for generic SCIFA compatible UART.
> > + - "renesas,scifb-generic" for generic SCIFB compatible UART.
> > + - "renesas,hscif-generic" for generic HSCIF compatible UART.
>
> Is the "-generic" suffix necessary? Why not just "renesas,scif" etc?

You're right, I'll remove the suffix.

> > +
> > + When compatible with the generic version, nodes must also list the
> > + SoC-specific version corresponding to the platform.
>
> Presumably the SoC-specific version should come first; it would be nice
> to note that.

Indeed, I'll do so.

> > +
> > + - reg: Base address and length of the memory resource used by the UART.
>
> I assume by memory resource you mean the memory-mapped registers?
> Resource sounds like Linux-internal nomenclature leaking.

I'll fix it as well, although we could decide on a definition of "resource"
that isn't Linux-specific :-)

> > +
> > + - interrupt-parent: Reference to the parent interrupt controller.
>
> I don't think this is strictly necessary. It's implicit by default and
> can be added optionally when a system is wired in a complex way. As it's
> a completely standard optional property I'm not even sure it needs to be
> documented.
>
> > + - interrupts: Interrupt number.
>
> Minor nit: "Should contain an interrupt-specifier for ..."
>
> I saw the cover mentioned multiple interrupts. Which logical interrupt
> output of the device are you expecting here?

SCI devices come in several flavours, with individual interrupt sources wired
up to different interrupt lines, or multiplexed all together. As the DT
bindings support the later only at the moment, there's only a single interrupt
to handle.

Should we come up with a standard way of saying in the bindings that a device
uses the interrupt bindings defined in interrupt-controller/interrupts.txt ?
This will become even more important with the interrupts-extended property, we
don't want every DT bindings document to detail all possible way to specify
interrupts.

> > +
> > + - clocks: Reference to the SCIx UART interface clock.
>
> Minor nit: s/Reference to/A phandle + clock-specifier pair for/
>
> > + - clock-names: Should be "sci_ick".
>
> As we're using clock-names, it would be nicer still to define clocks in
> terms of clock-names so as to make it easier to update the document in
> future and make the expected use of clock-names clearer:
>
> - clocks: Should

"Should", or "must" ?

> contain a phandle + clock-specifier pair for each entry
> in clock-names.
>
> - clock-names: Should contain "sci_ick".

Shouldn't that be

"Should contain "sci_ick" for the SCIx UART interface clock."

? Otherwise the bindings wouldn't tell which clock the clocks property should
reference.

> > +
> > +Note: Each enabled SCIx UART should have an alias correctly numbered in
> > the +"aliases" node.
> > +
> > +Example:
> > + aliases {
> > + serial0 = &scifa0;
> > + };
> > +
> > + scifa0: serial@e6c40000 {
> > + compatible = "renesas,scifa-r8a7790", "renesas,scifa-generic";
> > + reg = <0 0xe6c40000 0 64>;
> > + interrupt-parent = <&gic>;
> > + interrupts = <0 144 4>;
> > + clocks = <&mstp2_clks 4>;
> > + clock-names = "sci_ick";
> > + };
>
> Otherwise this looks good to me.

--
Regards,

Laurent Pinchart