Re: [PATCH v2 10/12] ARM: dts: microchip: sama7d65: add cells for temperature calibration

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] The ADC driver fails to propagate `-EPROBE_DEFER` when acquiring the NVMEM cell, leading to silent loss of the temperature channel and thermal protection.
--

commit ef1a2c61577cd00a6df4dd81d5825424af16746d
Author: Varshini Rajendran <varshini.rajendran@microchip.com>

ARM: dts: microchip: sama7d65: add cells for temperature calibration

This commit adds an NVMEM cell to the ADC node for temperature calibration
data.

> diff --git a/arch/arm/boot/dts/microchip/sama7d65.dtsi b/arch/arm/boot/dts/microchip/sama7d65.dtsi
> index 5867fda378b19..c336f863406de 100644
> --- a/arch/arm/boot/dts/microchip/sama7d65.dtsi
> +++ b/arch/arm/boot/dts/microchip/sama7d65.dtsi
> @@ -323,6 +323,8 @@ adc: adc@e1000000 {
>  			atmel,trigger-edge-type = <IRQ_TYPE_EDGE_RISING>;
>  			atmel,startup-time-ms = <4>;
>  			#io-channel-cells = <1>;
> +			nvmem-cells = <&temperature_calib>;
> +			nvmem-cell-names = "temperature_calib";

[Severity: High]
This is a pre-existing issue, but will adding these cells expose a probe
deferral issue in the ADC driver?

In drivers/iio/adc/at91-sama5d2_adc.c:at91_adc_temp_sensor_init(),
nvmem_cell_get() may return -EPROBE_DEFER:

	temp_calib = nvmem_cell_get(dev, "temperature_calib");
	if (IS_ERR(temp_calib)) {
		ret = PTR_ERR(temp_calib);
		if (ret != -ENOENT)
			dev_err(dev, "Failed to get temperature_calib cell!\n");
		return ret;
	}

However, in at91_adc_probe(), this returned error appears to be swallowed:

	ret = at91_adc_temp_sensor_init(st, &pdev->dev);
	/* Don't register temperature channel if initialization failed. */
	if (ret)
		num_channels = st->soc_info.platform->max_channels - 1;

If the NVMEM provider (OTPC) probes after the ADC driver, the ADC driver will
permanently skip registering the temperature channel instead of deferring
its probe.

Since the system's thermal zones might rely on this channel for CPU
temperature monitoring and emergency shutdown, could this lead to a silent
loss of thermal protection? 

Would it make sense to update the driver to use dev_err_probe() and properly
propagate -EPROBE_DEFER before these cells are added?

>  			status = "disabled";
>  		};

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260623105944.128840-1-varshini.rajendran@microchip.com?part=10