linux-kernel - Re: [RFC PATCH 1/7] dt-bindings: rtc: sun6i: Add H616 and R329 compatibles

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Date:   Tue, 7 Sep 2021 09:44:43 -0500
From:   Rob Herring <robh@...nel.org>
To:     Samuel Holland <samuel@...lland.org>
Cc:     Maxime Ripard <mripard@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        linux-sunxi@...ts.linux.dev,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 1/7] dt-bindings: rtc: sun6i: Add H616 and R329 compatibles

On Fri, Sep 3, 2021 at 10:36 AM Samuel Holland <samuel@...lland.org> wrote:
>
> On 9/2/21 10:27 AM, Rob Herring wrote:
> > On Wed, Sep 01, 2021 at 12:39:45AM -0500, Samuel Holland wrote:
> >> For these new SoCs, start requiring a complete list of input clocks.
> >>
> >> For H616, this means bus, hosc, and pll-32k. For R329, this means ahb,
> >> bus, and hosc; and optionally ext-osc32k.
> >>
> >> I'm not sure how to best represent this in the binding...
> >>
> >> Signed-off-by: Samuel Holland <samuel@...lland.org>
> >> ---
> >>  .../bindings/rtc/allwinner,sun6i-a31-rtc.yaml | 55 +++++++++++++++++--
> >>  include/dt-bindings/clock/sun50i-rtc.h        | 12 ++++
> >>  2 files changed, 61 insertions(+), 6 deletions(-)
> >>  create mode 100644 include/dt-bindings/clock/sun50i-rtc.h
> >>
> >> diff --git a/Documentation/devicetree/bindings/rtc/allwinner,sun6i-a31-rtc.yaml b/Documentation/devicetree/bindings/rtc/allwinner,sun6i-a31-rtc.yaml
> >> index beeb90e55727..3e085db1294f 100644
> >> --- a/Documentation/devicetree/bindings/rtc/allwinner,sun6i-a31-rtc.yaml
> >> +++ b/Documentation/devicetree/bindings/rtc/allwinner,sun6i-a31-rtc.yaml
> >> @@ -26,6 +26,8 @@ properties:
> >>            - const: allwinner,sun50i-a64-rtc
> >>            - const: allwinner,sun8i-h3-rtc
> >>        - const: allwinner,sun50i-h6-rtc
> >> +      - const: allwinner,sun50i-h616-rtc
> >> +      - const: allwinner,sun50i-r329-rtc
> >
> > Can you please make all the single entry cases a single 'enum'.
> >
> >>
> >>    reg:
> >>      maxItems: 1
> >> @@ -37,7 +39,24 @@ properties:
> >>        - description: RTC Alarm 1
> >>
> >>    clocks:
> >> -    maxItems: 1
> >> +    minItems: 1
> >> +    maxItems: 4
> >> +
> >> +  clock-names:
> >> +    minItems: 1
> >> +    maxItems: 4
> >> +    items:
> >> +      - anyOf:
> >
> > This says the first entry is any of these. What about the rest of them?
>
> Oh, right. The list below is the list of all possible clocks.
>
> >> +          - const: ahb
> >> +            description: AHB parent for SPI bus clock
> >
> > The description should go in 'clocks'.
>
> Will do for v2.
>
> > The order should be defined as well with the first clock being the
> > one that existed previously.
>
> The only way I know how to further refine the list is with
> minItems/maxItems. My problem is that 1) some clocks are only valid for
> certain SoCs, and 2) some clocks are optional, depending on how the
> board is wired. So there is no single order where the "valid"
> combinations are prefixes of the "possible" combinations of clocks.
>
> Or in other words, how can I say "clocks #1 and #2 from this list are
> required, and #4 is optional, but #3 is not allowed"?

This says you have up to 4 clocks, but only defines the 1st 2:

maxItems: 4
items:
  - description: 1st clock
  - description: 2nd clock

But I think you will be better off with just defining the range
(minItems/maxItems) at the top level and then use if/then schemas.

>
> Some concrete examples, with the always-required clocks moved to the
> beginning:
>
> H6:
>  - bus: required
>  - hosc: required
>  - ahb: not allowed
>  - ext-osc32k: optional
>  - pll-32k: not allowed

Is this really 2 different 32k clock inputs to the h/w block? Doesn't
seem like it given both are never valid.

>
> H616:
>  - bus: required
>  - hosc: required
>  - ahb: not allowed
>  - ext-osc32k: not allowed
>  - pll-32k: required
>
> R329:
>  - bus: required
>  - hosc: required
>  - ahb: required
>  - ext-osc32k: optional
>  - pll-32k: not allowed
>
> Should I just move the entire clocks/clock-items properties to if/then
> blocks based on the compatible?

Probably so.

Rob