Re: [PATCH v5 8/8] arm64: dts: renesas: r9a09g087: 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] Watchdog probe failure due to missing syscon compatible string in CPG/MSSR node and invalid physical memory bounds for the disjoint second register region.
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commit 026369134b14659a11e1791a537a1142aec5c877
Author: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>

arm64: dts: renesas: r9a09g087: Use CPG/MSSR syscon for WDTDCR access

This commit replaces the direct mapping of WDTDCR registers for watchdogs with
a renesas,sysc phandle to the CPG/MSSR node. It updates wdt0-wdt5 to remove
the second register region and use the syscon interface instead.

> diff --git a/arch/arm64/boot/dts/renesas/r9a09g087.dtsi b/arch/arm64/boot/dts/renesas/r9a09g087.dtsi
> index e8d4f76949ccb..40ffe56a40353 100644
> --- a/arch/arm64/boot/dts/renesas/r9a09g087.dtsi
> +++ b/arch/arm64/boot/dts/renesas/r9a09g087.dtsi
> @@ -327,61 +327,61 @@ channel1 {
>  
>  		wdt0: watchdog@80082000 {
>  			compatible = "renesas,r9a09g087-wdt", "renesas,r9a09g077-wdt";
> -			reg = <0 0x80082000 0 0x400>,
> -			      <0 0x81295100 0 0x04>;
> +			reg = <0 0x80082000 0 0x400>;

[Severity: High]
Does this change cause a silent mismatch with the actual hardware topology?

Generic syscons map only the first contiguous reg block. The driver computes
the WDTDCR offset as 0x15100. Since the first CPG block mapped is typically
0x80280000 with size 0x10000, accessing 0x15100 either fails the regmap bounds
check or mistakenly accesses 0x80295100 instead of the previously configured
0x81295100 located in the second CPG block.

>  			clocks = <&cpg CPG_CORE R9A09G087_CLK_PCLKL>;
>  			clock-names = "pclk";
>  			power-domains = <&cpg>;
> +			renesas,sysc = <&cpg 0>;

[Severity: High]
Will the watchdog driver probe fail indefinitely here?

When the rzv2h_wdt driver uses syscon_regmap_lookup_by_phandle_args() to parse
this renesas,sysc phandle, it evaluates syscon_node_to_regmap() on the cpg
node.

Because the cpg node in r9a09g087.dtsi lacks the syscon compatible string,
and the renesas-cpg-mssr driver doesn't register a custom regmap (e.g., via
of_syscon_register_regmap()), the lookup fails and returns
ERR_PTR(-EPROBE_DEFER). This prevents the watchdog hardware from functioning.

>  			status = "disabled";
>  		};

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260911111731.3404308-1-prabhakar.mahadev-lad.rj@bp.renesas.com?part=8