Re: [PATCH v7 2/3] scmi-cpufreq: Get opp_shared_cpus from opp-v2 for EM

From: Nicola Mazzucato <nicola.mazzucato@arm.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org,
	sudeep.holla@arm.com, rjw@rjwysocki.net, vireshk@kernel.org,
	cristian.marussi@arm.com, morten.rasmussen@arm.com,
	chris.redpath@arm.com, ionela.voinescu@arm.com
Subject: Re: [PATCH v7 2/3] scmi-cpufreq: Get opp_shared_cpus from opp-v2 for EM
Date: Thu, 18 Feb 2021 13:02:11 +0000	[thread overview]
Message-ID: <8efd2c71-847d-398a-5605-1daf9c2a3e75@arm.com> (raw)
In-Reply-To: <20210218110013.2b4ow7fzldra2srj@vireshk-i7>

Hi Viresh,

On 2/18/21 11:00 AM, Viresh Kumar wrote:
> On 15-02-21, 07:51, Nicola Mazzucato wrote:
>> +	/*
>> +	 * Add OPPs only on those CPUs for which we haven't already done so.
>> +	 */
>>  	nr_opp = dev_pm_opp_get_opp_count(cpu_dev);
> 
> Please add a more detailed comment here explaining why you expect OPPs
> to be present here in advance. i.e. you _may_ have policy per CPU even
> though OPP core says OPPs are shared.. It is not straight forward to
> catch otherwise.

Sure, I'll put more details, thanks.

> 
>>  	if (nr_opp <= 0) {
>> -		dev_err(cpu_dev, "%s: No OPPs for this device: %d\n",
>> -			__func__, ret);
>> -
>> -		ret = -ENODEV;
>> -		goto out_free_priv;
>> +		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;
>> +		}
>> +
>> +		nr_opp = dev_pm_opp_get_opp_count(cpu_dev);
>> +		if (nr_opp <= 0) {
>> +			dev_err(cpu_dev, "%s: No OPPs for this device: %d\n",
>> +				__func__, ret);
>> +
>> +			ret = -ENODEV;
>> +			goto out_free_opp;
>> +		}
>> +
>> +		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_opp;
>> +		}
>> +
>> +		power_scale_mw = handle->perf_ops->power_scale_mw_get(handle);
>> +		em_dev_register_perf_domain(cpu_dev, nr_opp, &em_cb,
>> +					    opp_shared_cpus, power_scale_mw);
>>  	}
> 