Re: [PATCH v1 06/12] arm64: dts: imx8mp-var-som-symphony: enable PCIe

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Timeout and PCIe initialization failure during system resume due to I2C-based PCIe reset GPIO in NOIRQ phase.
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commit 1813e394a2d156f58d0fa0b95aed827b4d4e4bc4
Author: Stefano Radaelli <stefano.r@variscite.com>

arm64: dts: imx8mp-var-som-symphony: enable PCIe

Add the PCIe reference clock and enable the PCIe controller and PHY on
the Symphony carrier board.

> diff --git a/arch/arm64/boot/dts/freescale/imx8mp-var-som-symphony.dts b/arch/arm64/boot/dts/freescale/imx8mp-var-som-symphony.dts
> --- a/arch/arm64/boot/dts/freescale/imx8mp-var-som-symphony.dts
> +++ b/arch/arm64/boot/dts/freescale/imx8mp-var-som-symphony.dts
[ ... ]
> @@ -146,6 +152,18 @@ rtc@68 {
>  	};
>  };
>  
> +&pcie {
> +	reset-gpio = <&pcal6408 1 GPIO_ACTIVE_LOW>;

[Severity: High]
Does this configuration cause a timeout and PCIe initialization failure during
system resume?

The PCIe controller specifies an I2C-based GPIO expander (pcal6408) for its
reset-gpio. During system resume, the i.MX PCIe driver executes its hardware
initialization in the noirq phase (imx_pcie_resume_noirq() ->
dw_pcie_resume_noirq() -> imx_pcie_host_init()), which asserts and deasserts
the reset GPIO using gpiod_set_value_cansleep().

During the dpm_resume_noirq phase, local CPU interrupts are enabled but device
interrupts remain masked at the interrupt controller (because
resume_device_irqs() is called after noirq callbacks). As a result, the I2C
controller cannot receive device interrupts.

Furthermore, i2c_in_atomic_xfer_mode() evaluates to false because system_state
is SYSTEM_RUNNING and local IRQs are enabled, meaning the I2C core will not
fall back to atomic polling mode. The I2C transaction required to toggle the
GPIO will therefore wait for an interrupt that is masked, resulting in a
prolonged timeout and a failed transfer. This causes the PCIe resume to fail
and significantly delays the overall system resume process.

> +	status = "okay";
> +};

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Sashiko AI review · https://sashiko.dev/#/patchset/cover.1780487415.git.stefano.r@variscite.com?part=6