Re: [PATCH v7 9/9] arm64: dts: Add support for LX2160 Twins board in single configuration

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The `gpio-mux` node for the fan tachometer multiplexer lacks an in-kernel consumer, which permanently locks the GPIOs and prevents the mux from being switched.
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commit 3c28f80d13a11b4ba012fa933362f3d2ffeec63c
Author: Josua Mayer <josua@solid-run.com>

arm64: dts: Add support for LX2160 Twins board in single configuration

This commit adds device tree support for the SolidRun LX2160A Twins board
in a single CPU configuration. It adds hardware support for various
interfaces including SFP ports, OCP, USB, microSD, and power supplies.

> diff --git a/arch/arm64/boot/dts/freescale/fsl-lx2160a-half-twins.dts b/arch/arm64/boot/dts/freescale/fsl-lx2160a-half-twins.dts
> new file mode 100644
> index 0000000000000..d16e273072754
> --- /dev/null
> +++ b/arch/arm64/boot/dts/freescale/fsl-lx2160a-half-twins.dts

[ ... ]

> +	mux-controller {
> +		compatible = "gpio-mux";
> +		#mux-control-cells = <0>;
> +		/*
> +		 * This gpio controlled mux can route the tacho signals of 6 PWM FAN connectors
> +		 * to the tacho inputs of both CEX-7 modules (twins).
> +		 *
> +		 * The first twin controls this mux and monitors four fan connectors, two intended
> +		 * for itself, and two for the OCP card.
> +		 *
> +		 * The second twin monitors only two fan connectors intended for itself.
> +		 *
> +		 * The table below maps selector GPIO states to monitored fan connector per twin:
> +		 *
> +		 * | SEL1 | SEL0 | Twin 1 | Twin 2 |
> +		 * | ---: | ---: | :------| ------ |
> +		 * |    0 |    0 | J10    |  J5024 |
> +		 * |    0 |    1 | J5016  |  J5024 |
> +		 * |    1 |    0 | J5026  |  J5025 |
> +		 * |    1 |    1 | J5013  |  J5025 |
> +		 */
> +		mux-gpios = <&expander0 8 GPIO_ACTIVE_HIGH>, /* SEL0 */
> +			    <&expander0 15 GPIO_ACTIVE_HIGH>; /* SEL1 */
> +	};

[Severity: Medium]
Does this mux-controller lack an in-kernel consumer?

When the gpio-mux driver probes, it exclusively requests and locks these GPIOs.
However, there appears to be no consumer node in the device tree referencing
this multiplexer to actually switch it.

Since the Linux mux subsystem doesn't provide a userspace interface for
switching, and the GPIO subsystem denies userspace access to locked pins, does
this completely prevent both the kernel and userspace from switching the fan
tachometer multiplexer?

If so, doesn't this permanently lock the fan monitoring functionality in its
default state?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260524-lx2160-pci-v7-0-09370c23b952@solid-run.com?part=9