Re: [PATCH v2 10/15] arm64: dts: imx8mn-var-som-symphony: Add TPM2 support

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The device tree specifies `reset-gpios` for the TPM device, but the kernel lacks support to drive this GPIO, potentially leaving the TPM stuck in reset.
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commit 5bd051d2688db25353ab678262b0998bf9810906
Author: Stefano Radaelli <stefano.r@variscite.com>

arm64: dts: imx8mn-var-som-symphony: Add TPM2 support

This commit adds support for the ST33K TPM2 device on the VAR-SOM Symphony
carrier board over I2C. It also adds the PCA6408 GPIO expander node used to
control the TPM reset signal.

> diff --git a/arch/arm64/boot/dts/freescale/imx8mn-var-som-symphony.dts b/arch/arm64/boot/dts/freescale/imx8mn-var-som-symphony.dts
> index 53130b521b5b7..7d016ed5e911a 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mn-var-som-symphony.dts
> +++ b/arch/arm64/boot/dts/freescale/imx8mn-var-som-symphony.dts

[ ... ]

> @@ -160,6 +160,20 @@ typec1_dr_sw: endpoint {
>  };
>  
>  &i2c3 {
> +	pca6408: gpio@21 {
> +		compatible = "nxp,pcal6408";
> +		reg = <0x21>;
> +		gpio-controller;
> +		#gpio-cells = <2>;
> +	};
> +
> +	st33ktpm2xi2c: tpm@2e {
> +		compatible = "st,st33ktpm2xi2c", "tcg,tpm-tis-i2c";
> +		reg = <0x2e>;
> +		label = "tpm";
> +		reset-gpios = <&pca6408 4 GPIO_ACTIVE_LOW>;

[Severity: Medium]
Will the kernel actually use this reset-gpios property to release the TPM?

The commit message states the PCA6408 is used to control the reset signal
to release the TPM from reset. However, neither the tpm_tis_i2c driver nor
the TPM core appear to parse the reset-gpios property or request a reset GPIO.
There is also no gpio-hog configured in the pca6408 node to force the pin
state.

Does this setup rely entirely on the bootloader initializing the PCA6408
and leaving the GPIO driven to the correct state?

If the system goes through a suspend/resume sequence or if the PCA6408
defaults back to an input state, could the TPM become stuck in reset and
fail to probe?

> +	};

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1783330236.git.stefano.r@variscite.com?part=10