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

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Message-ID: <wouo4k7rd7y57jzez3qdrz27fscozofuksgs4ivft75y6cwvqa@zfq3wgerwaza>
Date: Thu, 19 Dec 2024 10:02:10 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Prabhakar <prabhakar.csengg@...il.com>
Cc: Geert Uytterhoeven <geert+renesas@...der.be>, 
	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>, Wolfram Sang <wsa+renesas@...g-engineering.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 Wed, Dec 18, 2024 at 12:34:12AM +0000, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> 
> The RZ/V2H(P) CPG block includes Error Reset Registers (CPG_ERROR_RSTm).
> A system reset is triggered in response to error interrupt factors, and
> the corresponding bit is set in the CPG_ERROR_RSTm register. These
> registers can be utilized by various IP blocks as needed.
> 
> In the event of a watchdog overflow or underflow, a system reset is issued,
> and the CPG_ERROR_RST2[0/1/2/3] bits are set depending on the watchdog in
> use: CM33 = 0, CA55 = 1, CR8_0 = 2, CR8_1 = 3. For the watchdog driver to
> determine and report the current boot status, it needs to read the
> CPG_ERROR_RST2[0/1/2/3]bits and provide this information to the user upon
> request.
> 
> 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.

>     };
> 
> 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.

> 
> 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.

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").

> +    $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.

Best regards,
Krzysztof