Re: [PATCH net-next v7 1/3] dt-bindings: ptp: renesas,rcar-gen4-gptp: Add R-Car Gen4

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] ptp: devm_ioremap_resource() conflict with rtsn Ethernet driver
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commit 2999d29f8c3c04d8ff6cdf49a3fa0d43c2a42ee4
Author: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>

dt-bindings: ptp: renesas,rcar-gen4-gptp: Add R-Car Gen4

This commit adds device tree bindings for the R-Car Gen4 gPTP timer. The
timer provides clock synchronization and is shared among different Ethernet
devices across Gen4 platforms.

> diff --git a/Documentation/devicetree/bindings/ptp/renesas,rcar-gen4-gptp.yaml b/Documentation/devicetree/bindings/ptp/renesas,rcar-gen4-gptp.yaml
> new file mode 100644
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/ptp/renesas,rcar-gen4-gptp.yaml

[ ... ]

> +examples:
> +  - |
> +    #include <dt-bindings/clock/r8a779g0-cpg-mssr.h>
> +    #include <dt-bindings/power/r8a779g0-sysc.h>
> +
> +    ptp@e6449000 {
> +            compatible = "renesas,r8a779g0-gptp", "renesas,rcar-gen4-gptp";
> +            reg = <0xe6449000 0x500>;

[Severity: High]
Does this new node's memory region conflict with the existing Ethernet TSN
driver?

The existing renesas,ethertsn binding also claims this exact same memory
region for the generalized Precision Time Protocol target.

During probe in drivers/net/ethernet/renesas/rtsn.c:rtsn_probe(), the
existing Ethernet driver requests this region:

        res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "gptp");
        ...
        priv->gptp = devm_ioremap_resource(&pdev->dev, res);

Because both drivers use devm_ioremap_resource(), which attempts to acquire
exclusive access to the underlying physical memory via
devm_request_mem_region(), whichever driver probes second will fail with
-EBUSY. This will cause a driver probe failure and make the device unusable.

How should this shared memory resource be managed so both drivers can probe
successfully?

> +            clocks = <&cpg CPG_MOD 2723>;
> +            power-domains = <&sysc R8A779G0_PD_ALWAYS_ON>;
> +            resets = <&cpg 2723>;
> +    };

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Sashiko AI review · https://sashiko.dev/#/patchset/20261007185920.4042783-1-niklas.soderlund+renesas@ragnatech.se?part=1