linux-kernel - Re: [PATCH v4 3/4] scmi-cpufreq: get opp_shared

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Message-ID: <20201208055053.kggxw26kxtnpneua@vireshk-i7>
Date:   Tue, 8 Dec 2020 11:20:53 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Nicola Mazzucato <nicola.mazzucato@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        sudeep.holla@....com, rjw@...ysocki.net, vireshk@...nel.org,
        robh+dt@...nel.org, sboyd@...nel.org, nm@...com,
        daniel.lezcano@...aro.org, morten.rasmussen@....com,
        chris.redpath@....com
Subject: Re: [PATCH v4 3/4] scmi-cpufreq: get opp_shared_cpus from opp-v2 for
 EM

On 02-12-20, 17:23, Nicola Mazzucato wrote:
> By design, SCMI performance domains define the granularity of
> performance controls, they do not describe any underlying hardware
> dependencies (although they may match in many cases).
> 
> It is therefore possible to have some platforms where hardware may have
> the ability to control CPU performance at different granularity and choose
> to describe fine-grained performance control through SCMI.
> 
> In such situations, the energy model would be provided with inaccurate
> information based on controls, while it still needs to know the
> performance boundaries.
> 
> To restore correct functionality, retrieve information of CPUs under the
> same v/f domain from operating-points-v2 in DT, and pass it on to EM.
> 
> Signed-off-by: Nicola Mazzucato <nicola.mazzucato@....com>
> ---
>  drivers/cpufreq/scmi-cpufreq.c | 51 +++++++++++++++++++++++-----------
>  1 file changed, 35 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
> index 491a0a24fb1e..f505efcc62b1 100644
> --- a/drivers/cpufreq/scmi-cpufreq.c
> +++ b/drivers/cpufreq/scmi-cpufreq.c
> @@ -127,6 +127,7 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>  	struct cpufreq_frequency_table *freq_table;
>  	struct em_data_callback em_cb = EM_DATA_CB(scmi_get_cpu_power);
>  	bool power_scale_mw;
> +	cpumask_var_t opp_shared_cpus;
>  
>  	cpu_dev = get_cpu_device(policy->cpu);
>  	if (!cpu_dev) {
> @@ -134,30 +135,45 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>  		return -ENODEV;
>  	}
>  
> -	ret = handle->perf_ops->device_opps_add(handle, cpu_dev);
> -	if (ret) {
> -		dev_warn(cpu_dev, "failed to add opps to the device\n");
> -		return ret;
> -	}
> +	if (!zalloc_cpumask_var(&opp_shared_cpus, GFP_KERNEL))
> +		return -ENOMEM;
>  
>  	ret = scmi_get_sharing_cpus(cpu_dev, policy->cpus);
>  	if (ret) {
>  		dev_warn(cpu_dev, "failed to get sharing cpumask\n");
> -		return ret;
> +		goto out_free_cpumask;
>  	}
>  
> -	ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
> -	if (ret) {
> -		dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
> -			__func__, ret);
> -		return ret;
> +	/*
> +	 * The OPP 'sharing cpus' info may come from dt through an empty opp
> +	 * table and opp-shared. If found, it takes precedence over the SCMI
> +	 * domain IDs info.
> +	 */
> +	ret = dev_pm_opp_of_get_sharing_cpus(cpu_dev, opp_shared_cpus);
> +	if (ret || !cpumask_weight(opp_shared_cpus)) {
> +		/*
> +		 * Either opp-table is not set or no opp-shared was found,
> +		 * use the information from SCMI domain IDs.
> +		 */
> +		cpumask_copy(opp_shared_cpus, policy->cpus);
>  	}
>  
>  	nr_opp = dev_pm_opp_get_opp_count(cpu_dev);
>  	if (nr_opp <= 0) {
> -		dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n");
> -		ret = -EPROBE_DEFER;
> -		goto out_free_opp;
> +		ret = handle->perf_ops->device_opps_add(handle, cpu_dev);
> +		if (ret) {
> +			dev_warn(cpu_dev, "failed to add opps to the device\n");
> +			goto out_free_cpumask;
> +		}
> +
> +		ret = dev_pm_opp_set_sharing_cpus(cpu_dev, opp_shared_cpus);
> +		if (ret) {
> +			dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
> +				__func__, ret);
> +			goto out_free_cpumask;
> +		}
> +

Why do we need to call above two after calling
dev_pm_opp_get_opp_count() ? And we don't check the return value of
the below call anymore, moreover we have to call it twice now.

> +		nr_opp = dev_pm_opp_get_opp_count(cpu_dev);
>  	}
>  
>  	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> @@ -191,15 +207,18 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>  		handle->perf_ops->fast_switch_possible(handle, cpu_dev);
>  
>  	power_scale_mw = handle->perf_ops->power_scale_mw_get(handle);
> -	em_dev_register_perf_domain(cpu_dev, nr_opp, &em_cb, policy->cpus,
> +	em_dev_register_perf_domain(cpu_dev, nr_opp, &em_cb, opp_shared_cpus,
>  				    power_scale_mw);
>  
> -	return 0;
> +	ret = 0;

ret is already 0 here.

> +	goto out_free_cpumask;
>  
>  out_free_priv:
>  	kfree(priv);
>  out_free_opp:
>  	dev_pm_opp_remove_all_dynamic(cpu_dev);
> +out_free_cpumask:
> +	free_cpumask_var(opp_shared_cpus);
>  
>  	return ret;
>  }
> -- 
> 2.27.0

-- 
viresh