Re: [PATCH v4 3/4] scmi-cpufreq: get opp_shared_cpus from opp-v2 for EM

From: Viresh Kumar <viresh.kumar@linaro.org>
To: Nicola Mazzucato <nicola.mazzucato@arm.com>
Cc: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org,
	devicetree@vger.kernel.org, sudeep.holla@arm.com,
	rjw@rjwysocki.net, vireshk@kernel.org, robh+dt@kernel.org,
	sboyd@kernel.org, nm@ti.com, daniel.lezcano@linaro.org,
	morten.rasmussen@arm.com, chris.redpath@arm.com
Subject: Re: [PATCH v4 3/4] scmi-cpufreq: get opp_shared_cpus from opp-v2 for EM
Date: Tue, 8 Dec 2020 16:31:48 +0530	[thread overview]
Message-ID: <20201208110148.7scxsjlkbzmxr43f@vireshk-i7> (raw)
In-Reply-To: <83b8400f-8dc4-000e-d790-0bf584a75f48@arm.com>

On 08-12-20, 10:58, Nicola Mazzucato wrote:
> 
> 
> On 12/8/20 7:26 AM, Viresh Kumar wrote:
> > On 08-12-20, 07:22, Nicola Mazzucato wrote:
> >> On 12/8/20 5:50 AM, Viresh Kumar wrote:
> >>> On 02-12-20, 17:23, Nicola Mazzucato wrote:
> >>>>  	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() ?
> >>
> >> Sorry, I am not sure to understand your question here. If there are no opps for
> >> a device we want to add them to it
> > 
> > Earlier we used to call handle->perf_ops->device_opps_add() and
> > dev_pm_opp_set_sharing_cpus() before calling dev_pm_opp_get_opp_count(), why is
> > the order changed now ?
> 
> True. The order has changed to take into account the fact that when we have
> per-cpu + opp-shared, we don't need to add opps for devices which already have them.

The opp-shared thing is mostly a dummy thing to get you some information here.
What else has changed here ? I still don't understand why the OPPs would get
added and so the duplicate OPPs messages. Does this already happen ?

-- 
viresh