linux-kernel - Re: [PATCH V2 2/4] firmware: arm_scmi: Add perf_freq

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Date: Mon, 29 Jan 2024 15:53:43 +0000
From: Cristian Marussi <cristian.marussi@....com>
To: Sibi Sankar <quic_sibis@...cinc.com>
Cc: sudeep.holla@....com, rafael@...nel.org, viresh.kumar@...aro.org,
	morten.rasmussen@....com, dietmar.eggemann@....com,
	lukasz.luba@....com, linux-arm-kernel@...ts.infradead.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	quic_mdtipton@...cinc.com, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH V2 2/4] firmware: arm_scmi: Add perf_freq_xlate interface

On Wed, Jan 17, 2024 at 04:11:14PM +0530, Sibi Sankar wrote:
> Add a new perf_freq_xlate interface to the existing perf_ops to translate
> a given perf index to frequency.
> 
> This can be used by the cpufreq driver and framework to determine the
> throttled frequency from a given perf index and apply HW pressure
> accordingly.
> 
> Signed-off-by: Sibi Sankar <quic_sibis@...cinc.com>
> ---
> 
> v2:
> * Rename opp_xlate -> freq_xlate [Viresh]
> 
>  drivers/firmware/arm_scmi/perf.c | 21 +++++++++++++++++++++
>  include/linux/scmi_protocol.h    |  3 +++
>  2 files changed, 24 insertions(+)
> 
> diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
> index ae7681eda276..e286f04ee6e3 100644
> --- a/drivers/firmware/arm_scmi/perf.c
> +++ b/drivers/firmware/arm_scmi/perf.c
> @@ -977,6 +977,26 @@ static int scmi_notify_support(const struct scmi_protocol_handle *ph, u32 domain
>  	return 0;
>  }
>  
> +static int scmi_perf_freq_xlate(const struct scmi_protocol_handle *ph, u32 domain,
> +				int idx, unsigned long *freq)
> +{
> +	struct perf_dom_info *dom;
> +
> +	dom = scmi_perf_domain_lookup(ph, domain);
> +	if (IS_ERR(dom))
> +		return PTR_ERR(dom);
> +
> +	if (idx >= dom->opp_count)
> +		return -ERANGE;
> +
> +	if (!dom->level_indexing_mode)
> +		*freq = dom->opp[idx].perf * dom->mult_factor;
> +	else
> +		*freq = dom->opp[idx].indicative_freq * dom->mult_factor;
> +
> +	return 0;
> +}

Potentially, once the dom info are exposed you can also drop this
accessor and move all of these checks/calculations in the the SCMI cpufreq
driver...but maybe Sudeep/Viresh prefer to keep this accessor exposed
like others.

Thanks,
Cristian