Re: [PATCH 2/3] iio: adc: sun20i-gpadc: add A523 gpadc support

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Missing validation for 0 clocks returned by devm_clk_bulk_get_all_enabled() leading to a kernel panic on register access.
--

commit daf3632321b60ce8511b98ae1ad1e4b009e48e3c
Author: Michal Piekos <michal.piekos@mmpsystems.pl>

iio: adc: sun20i-gpadc: add A523 gpadc support

This commit adds support for the A523 gpadc by switching from a single
clock initialization to using devm_clk_bulk_get_all_enabled() to handle
both the bus and module clocks.

> diff --git a/drivers/iio/adc/sun20i-gpadc-iio.c b/drivers/iio/adc/sun20i-gpadc-iio.c
> index 861c14da75add..dd4c7e6e3d76e 100644
> --- a/drivers/iio/adc/sun20i-gpadc-iio.c
> +++ b/drivers/iio/adc/sun20i-gpadc-iio.c
[ ... ]
> @@ -205,9 +205,9 @@ static int sun20i_gpadc_probe(struct platform_device *pdev)
>  	if (IS_ERR(info->regs))
>  		return PTR_ERR(info->regs);
>  
> -	clk = devm_clk_get_enabled(dev, NULL);
> -	if (IS_ERR(clk))
> -		return dev_err_probe(dev, PTR_ERR(clk), "failed to enable bus clock\n");
> +	ret = devm_clk_bulk_get_all_enabled(dev, &clks);
> +	if (ret < 0)
> +		return dev_err_probe(dev, ret, "failed to enable clocks\n");

If the device tree node lacks clock definitions,
devm_clk_bulk_get_all_enabled() will return 0. Because this error handling
only checks for negative return values, could this allow the driver probe
to proceed with zero clocks enabled?

On Allwinner hardware, accessing the registers of an unclocked IP block
typically triggers a synchronous external abort or bus fault. If ret is 0,
the probe later performs a register write:

sun20i_gpadc_probe() {
    ...
	writel(FIELD_PREP(SUN20I_GPADC_CTRL_ADC_AUTOCALI_EN_MASK, 1) |
	       FIELD_PREP(SUN20I_GPADC_CTRL_WORK_MODE_MASK, SUN20I_GPADC_WORK_MODE_SINGLE),
	       info->regs + SUN20I_GPADC_CTRL);
    ...
}

Should we also verify that the number of clocks returned is greater than
zero to prevent a potential panic during the register configuration?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260510-sunxi-a523-gpadc-v1-0-4f6b0f4000fb@mmpsystems.pl?part=2