Re: [PATCH v6 7/8] arm64: dts: renesas: r9a09g077: Use CPG/MSSR syscon for WDTDCR access

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] probe: watchdog driver perpetually fails to probe due to invalid syscon target
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commit 4e5d24eec602a0526d0eac3d1f59b54aa0dd4798
Author: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>

arm64: dts: renesas: r9a09g077: Use CPG/MSSR syscon for WDTDCR access

The WDTDCR registers for wdt0-wdt5 reside in the second register region of
the CPG/MSSR block. This multi-function block is now exposed via a unified
syscon regmap interface.

> diff --git a/arch/arm64/boot/dts/renesas/r9a09g077.dtsi b/arch/arm64/boot/dts/renesas/r9a09g077.dtsi
> index 40494159831d8..ad5189d55cef2 100644
> --- a/arch/arm64/boot/dts/renesas/r9a09g077.dtsi
> +++ b/arch/arm64/boot/dts/renesas/r9a09g077.dtsi
> @@ -327,61 +327,61 @@ channel1 {
>  
>  		wdt0: watchdog@80082000 {
>  			compatible = "renesas,r9a09g077-wdt";
> -			reg = <0 0x80082000 0 0x400>,
> -			      <0 0x81295100 0 0x04>;
> +			reg = <0 0x80082000 0 0x400>;
>  			clocks = <&cpg CPG_CORE R9A09G077_CLK_PCLKL>;
>  			clock-names = "pclk";
>  			power-domains = <&cpg>;
> +			renesas,sysc = <&cpg 0>;

[Severity: High]
Does the cpg node have the "syscon" compatible string?

Looking at the cpg node definition in arch/arm64/boot/dts/renesas/r9a09g077.dtsi:

		cpg: clock-controller@80280000 {
			compatible = "renesas,r9a09g077-cpg-mssr";
			reg = <0 0x80280000 0 0x10000>,
			      <0 0x81280000 0 0x10000>;

Because it lacks the "syscon" compatible string, and its driver does not
manually register a syscon regmap, won't syscon_regmap_lookup_by_phandle_args()
perpetually fail and return -EPROBE_DEFER during the watchdog driver probe?

Furthermore, if it were treated as a generic syscon, the generic driver only
maps the first memory region (size 0x10000), meaning max_register is 0xFFFC.
Since the WDTDCR offset is calculated as 0x15100 + n*4, won't all register
accesses be rejected by the regmap subsystem as out-of-bounds?

>  			status = "disabled";
>  		};

[ ... ]

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Sashiko AI review · https://sashiko.dev/#/patchset/20260923104054.3324830-1-prabhakar.mahadev-lad.rj@bp.renesas.com?part=7