linux-kernel - Re: [PATCH 4/6] dt-bindings: watchdog: renesas: Document `renesas,r9a09g057-syscon-wdt-errorrst` property

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Message-ID: <53c2fc82-2b09-4f7e-a89f-c7c16c38cb8e@kernel.org>
Date: Thu, 19 Dec 2024 17:01:25 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: "Lad, Prabhakar" <prabhakar.csengg@...il.com>,
 Geert Uytterhoeven <geert+renesas@...der.be>,
 Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc: Michael Turquette <mturquette@...libre.com>,
 Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Wim Van Sebroeck <wim@...ux-watchdog.org>,
 Guenter Roeck <linux@...ck-us.net>, Magnus Damm <magnus.damm@...il.com>,
 linux-renesas-soc@...r.kernel.org, linux-clk@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-watchdog@...r.kernel.org, Biju Das <biju.das.jz@...renesas.com>,
 Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
 Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH 4/6] dt-bindings: watchdog: renesas: Document
 `renesas,r9a09g057-syscon-wdt-errorrst` property

On 19/12/2024 11:06, Lad, Prabhakar wrote:
>>> To facilitate this operation, add `renesas,r9a09g057-syscon-wdt-errorrst`
>>> property to the WDT node, which maps to the `syscon` CPG node, enabling
>>> retrieval of the necessary information. For example:
>>>
>>>     wdt1: watchdog@...00000 {
>>>         compatible = "renesas,r9a09g057-wdt";
>>>         renesas,r9a09g057-syscon-wdt-errorrst = <&cpg 0xb40 1>;
>>>         ...
>>
>> Drop, obvious.
>>
> Ok.
> 
>>>     };
>>>
>>> The `renesas,r9a09g057-syscon-wdt-errorrst` property consists of three
>>> cells:
>>> 1. The first cell is a phandle to the CPG node.
>>> 2. The second cell specifies the offset of the CPG_ERROR_RSTm register
>>>    within the SYSCON.
>>> 3. The third cell indicates the specific bit within the CPG_ERROR_RSTm
>>>    register.
>>
>> Don't describe the contents of patch.  Drop paragraph. There is no need
>> to make commit msg unnecessary long. Focus on explaining unknown parts
>> of commit: why? or who is affected by ABI break? why breaking ABI?
>> instead of repeating diff.
>>
> Ok, I'll drop the para. There isnt any ABI breakage as the driver
> patch [0] will skip supporting watchdog bootstatus if this property is
> not present.
> 
> [0] https://lore.kernel.org/all/20241218003414.490498-6-prabhakar.mahadev-lad.rj@bp.renesas.com/

Really? I see in rzv2h_wdt_probe():

+		if (ret)
+			return ret;

so to me you are failing the probe, not skipping anything.

> 
>>>
>>> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
>>> ---
>>>  .../bindings/watchdog/renesas,wdt.yaml          | 17 +++++++++++++++++
>>>  1 file changed, 17 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/watchdog/renesas,wdt.yaml b/Documentation/devicetree/bindings/watchdog/renesas,wdt.yaml
>>> index 29ada89fdcdc..8d29f5f1be7e 100644
>>> --- a/Documentation/devicetree/bindings/watchdog/renesas,wdt.yaml
>>> +++ b/Documentation/devicetree/bindings/watchdog/renesas,wdt.yaml
>>> @@ -112,6 +112,19 @@ properties:
>>>
>>>    timeout-sec: true
>>>
>>> +  renesas,r9a09g057-syscon-wdt-errorrst:
>>
>> There are never, *never* SoC names in property names, because we want
>> properties to be re-usable.
>>
> I should have mentioned this in my commit message (my bad). The
> renesas,wdt.yaml binding file is being used for all the SoCs
> currently. To avoid any conflicts by just having vendor specific
> property I added SoC name to the preoperty.

I know what you did and I replied: that's a no go for reasons I stated.

> 
> @Geert/Wolfram - Maybe we need to split the binding on per SoC bases?

You can but I don't understand why exactly.

> 
>> Make the property generic for all your devices and be sure to disallow
>> it everywhere the CPG_ERROR_RSTm *does not* exist (which is different
>> from "where CPG_ERROR_RSTm is not used by watchdog driver").
>>
> This patch already disallows `renesas,r9a09g057-syscon-wdt-errorrst`
> for the rest of the SoCs and only allows for RZ/V2H(P) SoC or am I
> missing something?

No, that's fine, but to avoid disallowing it for others you named it per
SoC.

> 
>>> +    $ref: /schemas/types.yaml#/definitions/phandle-array
>>> +    description:
>>> +      The first cell is a phandle to the SYSCON entry required to obtain
>>> +      the current boot status. The second cell specifies the CPG_ERROR_RSTm
>>> +      register offset within the SYSCON, and the third cell indicates the
>>> +      bit within the CPG_ERROR_RSTm register.
>>> +    items:
>>> +      - items:
>>> +          - description: Phandle to the CPG node
>>> +          - description: The CPG_ERROR_RSTm register offset
>>> +          - description: The bit within CPG_ERROR_RSTm register of interest
>>> +
>>>  required:
>>>    - compatible
>>>    - reg
>>> @@ -182,7 +195,11 @@ allOf:
>>>        properties:
>>>          interrupts: false
>>>          interrupt-names: false
>>> +      required:
>>> +        - renesas,r9a09g057-syscon-wdt-errorrst
>>
>> No, ABI break.
>>
> As mentioned above we won't break ABI, this required flag is for future changes.

Then why is this required? Or at least explain this in the commit msg.

Best regards,
Krzysztof