linux-kernel - Re: [PATCH v2 4/8] dt-bindings: timer: Add schema for realtek,otto-timer

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Message-ID: <8676afd3-8a95-4517-ae38-0f8539e81f19@kernel.org>
Date: Wed, 26 Jun 2024 09:13:50 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Chris Packham <Chris.Packham@...iedtelesis.co.nz>,
 "tglx@...utronix.de" <tglx@...utronix.de>, "robh@...nel.org"
 <robh@...nel.org>, "krzk+dt@...nel.org" <krzk+dt@...nel.org>,
 "conor+dt@...nel.org" <conor+dt@...nel.org>,
 "tsbogend@...ha.franken.de" <tsbogend@...ha.franken.de>,
 "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
 "paulburton@...nel.org" <paulburton@...nel.org>,
 "peterz@...radead.org" <peterz@...radead.org>,
 "mail@...ger-koblitz.de" <mail@...ger-koblitz.de>,
 "bert@...t.com" <bert@...t.com>, "john@...ozen.org" <john@...ozen.org>,
 "sander@...nheule.net" <sander@...nheule.net>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
 "kabel@...nel.org" <kabel@...nel.org>,
 "ericwouds@...il.com" <ericwouds@...il.com>
Subject: Re: [PATCH v2 4/8] dt-bindings: timer: Add schema for
 realtek,otto-timer

On 24/06/2024 07:21, Chris Packham wrote:
> 
> On 24/06/24 16:49, Krzysztof Kozlowski wrote:
>> On 24/06/2024 03:22, Chris Packham wrote:
>>> Add the devicetree schema for the realtek,otto-timer present on a number
>>> of Realtek SoCs.
>>>
>>> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>>> ---
>>>
>>> Notes:
>>>      Changes in v2:
>>>      - Use specific compatible
>> Where? I do not see changes.
> 
> In v1 it was rtl930x-timer, I've updated it to rtl9302-timer

Ah, I thought you wanted to switch from generic fallback to specific
compatible... fine.

> 
>>>      - Remove unnecessary label
>>>      - Remove unused irq flags (interrupt controller is one-cell)
>>>      - Set minItems for reg and interrupts based on compatible
>>>
>>>   .../bindings/timer/realtek,otto-timer.yaml    | 66 +++++++++++++++++++
>>>   1 file changed, 66 insertions(+)
>>>   create mode 100644 Documentation/devicetree/bindings/timer/realtek,otto-timer.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/timer/realtek,otto-timer.yaml b/Documentation/devicetree/bindings/timer/realtek,otto-timer.yaml
>>> new file mode 100644
>>> index 000000000000..13ea7aa946fe
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/timer/realtek,otto-timer.yaml
>>> @@ -0,0 +1,66 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/timer/realtek,otto-timer.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: Realtek Otto SoCs Timer/Counter
>>> +
>>> +description:
>>> +  Realtek SoCs support a number of timers/counters. These are used
>>> +  as a per CPU clock event generator and an overall CPU clocksource.
>>> +
>>> +maintainers:
>>> +  - Chris Packham <chris.packham@...iedtelesis.co.nz>
>>> +
>>> +properties:
>>> +  $nodename:
>>> +    pattern: "^timer@[0-9a-f]+$"
>>> +
>>> +  compatible:
>>> +    items:
>>> +      - enum:
>>> +          - realtek,rtl9302-timer
>>> +      - const: realtek,otto-timer
>>> +
>>> +  reg:
>>> +    maxItems: 5
>> Nothing improved.
>>
>>> +
>>> +  clocks:
>>> +    maxItems: 1
>>> +
>>> +  interrupts:
>>> +    maxItems: 5
>> Nothing improved.
>>
>>> +
>>> +allOf:
>>> +  - if:
>>> +      properties:
>>> +        compatible:
>>> +          contains:
>>> +            const: realtek,rtl9302-timer
>>> +    then:
>>> +      properties:
>>> +        reg:
>>> +          minItems: 2
>>> +        interrupts:
>>> +          minItems: 2
>> No, that's just incorrect. You do not have more than one variant, so it
>> is just 2 items. Or 5 items, not 2-5.
> 
> I've been told in the past that the device-tree should describe the 
> hardware. Which in this case has 5 timers. But I'm also told to give 
> them names which I struggle to do because some of them aren't used.

Used as in Linux driver? Does not matter.

> 
> So do you want something like this:
> 
> clocks:
>      items:
>          - description: CPU0 event clock
>          - description: system clock source
>          - description: unused
>          - description: unused
>          - description: unused

No, if your datasheet or any other source of information (e.g.
downstream sources) mention 5 items, then name properly 5 items.
Otherwise how do you know that there are 5, not 2, clocks/interrupts/reg?

Best regards,
Krzysztof