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

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Message-ID: <80fb6869-4955-25a1-ed1c-118dbf61b206@sholland.org>
Date:   Tue, 7 Sep 2021 21:26:14 -0500
From:   Samuel Holland <samuel@...lland.org>
To:     Rob Herring <robh@...nel.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 9/7/21 9:44 AM, Rob Herring wrote:
> 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.

Ah, thanks for the suggestions.

>>
>> 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.

Yes, there are two separate 32k inputs. Both are valid at the same time
on some SoCs like T5 (patch 7), but not on any of those I listed here.

Regards,
Samuel

>>
>> 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
>