Re: [PATCH v11 1/2] clk: validate spread spectrum configuration

[sashiko-bot@kernel.org]

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

Pre-existing issues:
- [High] Integer division truncates valid spread spectrum configurations to zero, silently disabling the feature.
--

commit f9da34cc1be223c5bb63d6e1c7898cf344a88cfe
Author: Dario Binacchi <dario.binacchi@amarulasolutions.com>
clk: validate spread spectrum configuration

This commit adds validation to the clk_hw_set_spread_spectrum function to
ensure that the modulation frequency is non-zero and the spread ratio does
not exceed 10000 basis points (100%). This prevents invalid device tree
configurations from passing incorrect values to clock providers.

> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -2851,6 +2851,20 @@ int clk_hw_set_spread_spectrum(struct clk_hw *hw, const struct clk_spread_spectr
>  	if (!hw)
>  		return 0;
>  
> +	switch (ss_conf->method) {
> +	case CLK_SPREAD_NO:
> +		break;
> +	case CLK_SPREAD_CENTER:
> +	case CLK_SPREAD_UP:
> +	case CLK_SPREAD_DOWN:
> +		if (!ss_conf->modfreq_hz || !ss_conf->spread_bp ||
> +		    ss_conf->spread_bp > 10000)

[Severity: High]
This isn't a bug introduced by this patch, but looking at
scmi_clk_imx_set_spread_spectrum() in drivers/clk/clk-scmi-oem.c:

scmi_clk_imx_set_spread_spectrum() {
    ...
    val = FIELD_PREP(SCMI_CLOCK_IMX_SS_PERCENTAGE_MASK, ss_conf->spread_bp / 10000);
    ...
}

Does this integer division incorrectly assume spread_bp is a direct percentage
multiplier rather than basis points? For standard device tree configurations,
it seems this would truncate valid permyriad percentages (e.g., 100 for 1%)
to 0. Would this result in the hardware being programmed with a 0% spread
instead of the configured value, effectively disabling the feature silently?

> +			return -EINVAL;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
>  	core = hw->core;
>  
>  	clk_prepare_lock();

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260901090912.585681-1-dario.binacchi@amarulasolutions.com?part=1