[PATCH 10/11] firmware: arm_scmi: Use bound iterators to minimize discovered rates

[Jonathan Cameron]

On Fri, 27 Feb 2026 15:32:24 +0000
Cristian Marussi <cristian.marussi at arm.com> wrote:

> Clock rates are guaranteed to be returned in ascending order for SCMI clock
> protocol versions greater than 1.0: in such a case, use bounded iterators
> to minimize the number of message exchanges needed to discover min and max
> rate.
> 
> Signed-off-by: Cristian Marussi <cristian.marussi at arm.com>

> +
> +static int
> +scmi_clock_describe_rates_get(const struct scmi_protocol_handle *ph,
> +			      u32 clk_id, struct clock_info *cinfo)
> +{
> +	struct scmi_clock_desc *clkd = &cinfo->clkds[clk_id];
> +	int ret;
> +
> +	/*
> +	 * Since only after SCMI Clock v1.0 the returned rates are guaranteed to
> +	 * be discovered in ascending order, lazy enumeration cannot be use for
> +	 * SCMI Clock v1.0 protocol.
> +	 */
> +	if (PROTOCOL_REV_MAJOR(ph->version) > 0x1)
> +		ret = scmi_clock_describe_rates_get_lazy(ph, clkd);
> +	else
> +		ret = scmi_clock_describe_rates_get_full(ph, clkd);
> +
> +	if (ret)
> +		return ret;
> +
> +	clkd->info.min_rate = clkd->rates[RATE_MIN];
>  	if (!clkd->rate_discrete) {
>  		clkd->info.max_rate = clkd->rates[RATE_MAX];
>  		dev_dbg(ph->dev, "Min %llu Max %llu Step %llu Hz\n",
>  			clkd->rates[RATE_MIN], clkd->rates[RATE_MAX],
>  			clkd->rates[RATE_STEP]);
>  	} else {
> -		sort(clkd->rates, clkd->num_rates,
> -		     sizeof(clkd->rates[0]), rate_cmp_func, NULL);
>  		clkd->info.max_rate = clkd->rates[clkd->num_rates - 1];
> +		dev_dbg(ph->dev, "Clock:%s DISCRETE:%d -> Min %llu Max %llu\n",
> +			clkd->info.name, clkd->rate_discrete,
> +			clkd->info.min_rate, clkd->info.max_rate);
>  	}
> -	clkd->info.min_rate = clkd->rates[RATE_MIN];
>  
> -	return 0;
> +	return ret;
Why?  Far as I can see it's still always zero if you get here.

>  }
>  
>  static int