[PATCH v2] firmware: arm_scmi: Warn if domain frequency multiplier is 0 or rounded off

[Cristian Marussi]

On Fri, Jan 19, 2024 at 03:23:37PM +0000, Sudeep Holla wrote:
> When (sustained_freq_khz * 1000) is less than sustained_perf_level, the
> multiplier will be less than 1 and hence rounded down as 0. Similarly if
> it is not multiple of sustained_perf_level the dom_info->mult_factor will
> contain rounded down value and will end up impacting all the frequency
> calculations done using it.
> 
> Add warning if and when the domain frequency multiplier is 0 or rounded
> down so that it gives a clue to get the firmware tables fixed.
> 
> Suggested-by: Pierre Gondois <Pierre.Gondois at arm.com>
> Reviewed-by: Pierre Gondois <pierre.gondois at arm.com>
> Reviewed-by: Cristian Marussi <cristian.marussi at arm.com>
> Signed-off-by: Sudeep Holla <sudeep.holla at arm.com>
> ---

LGTM.

Thanks,
Cristian

>  drivers/firmware/arm_scmi/perf.c | 19 +++++++++++++++++--
>  1 file changed, 17 insertions(+), 2 deletions(-)
> 
> v1->v2:
> 	- Added comment regarding the requirements on sustained_freq_khz
> 	  and sustained_perf_level obtained from the SCMI firmware
> 	- Changed pr_warn to dev_warn
> 
> diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
> index 8ea2a7b3d35d..9fe123e1f3c7 100644
> --- a/drivers/firmware/arm_scmi/perf.c
> +++ b/drivers/firmware/arm_scmi/perf.c
> @@ -270,15 +270,30 @@ scmi_perf_domain_attributes_get(const struct scmi_protocol_handle *ph,
>  					le32_to_cpu(attr->sustained_freq_khz);
>  		dom_info->sustained_perf_level =
>  					le32_to_cpu(attr->sustained_perf_level);
> +		/*
> +		 * sustained_freq_khz = mult_factor * sustained_perf_level
> +		 * mult_factor must be non zero positive integer(not fraction)
> +		 */
>  		if (!dom_info->sustained_freq_khz ||
>  		    !dom_info->sustained_perf_level ||
> -		    dom_info->level_indexing_mode)
> +		    dom_info->level_indexing_mode) {
>  			/* CPUFreq converts to kHz, hence default 1000 */
>  			dom_info->mult_factor =	1000;
> -		else
> +		} else {
>  			dom_info->mult_factor =
>  					(dom_info->sustained_freq_khz * 1000UL)
>  					/ dom_info->sustained_perf_level;
> +			if ((dom_info->sustained_freq_khz * 1000UL) %
> +			    dom_info->sustained_perf_level)
> +				dev_warn(ph->dev,
> +					 "multiplier for domain %d rounded\n",
> +					 dom_info->id);
> +		}
> +		if (!dom_info->mult_factor)
> +			dev_warn(ph->dev,
> +			         "Wrong sustained perf/frequency(domain %d)\n",
> +				 dom_info->id);
> +
>  		strscpy(dom_info->info.name, attr->name,
>  			SCMI_SHORT_NAME_MAX_SIZE);
>  	}
> -- 
> 2.43.0
>