linux-kernel - Re: [PATCH v10 1/2] cpufreq: Add Kryo CPU scaling driver

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Date:   Wed, 23 May 2018 17:01:07 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ilia Lin <ilialin@...eaurora.org>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 1/2] cpufreq: Add Kryo CPU scaling driver

On 23 May 2018 at 16:36,  <ilialin@...eaurora.org> wrote:
>
>
>> -----Original Message-----
>> From: Sudeep Holla <sudeep.holla@....com>
>> Sent: Wednesday, May 23, 2018 13:40
>> To: Ilia Lin <ilialin@...eaurora.org>; vireshk@...nel.org; nm@...com;
>> sboyd@...nel.org; robh@...nel.org; mark.rutland@....com;
>> rjw@...ysocki.net; linux-pm@...r.kernel.org; devicetree@...r.kernel.org;
>> linux-kernel@...r.kernel.org
>> Cc: Sudeep Holla <sudeep.holla@....com>
>> Subject: Re: [PATCH v10 1/2] cpufreq: Add Kryo CPU scaling driver
>>
>>
>>
>> On 23/05/18 10:40, Ilia Lin wrote:
>> > In Certain QCOM SoCs like apq8096 and msm8996 that have KRYO
>> > processors, the CPU frequency subset and voltage value of each OPP
>> > varies based on the silicon variant in use. Qualcomm Process Voltage
>> > Scaling Tables defines the voltage and frequency value based on the
>> > msm-id in SMEM and speedbin blown in the efuse combination.
>> > The qcom-cpufreq-kryo driver reads the msm-id and efuse value from the
>> > SoC to provide the OPP framework with required information.
>> > This is used to determine the voltage and frequency value for each OPP
>> > of
>> > operating-points-v2 table when it is parsed by the OPP framework.
>> >
>> > Signed-off-by: Ilia Lin <ilialin@...eaurora.org>
>>
>> [...]
>>
>> > +   pdev = platform_device_register_simple("cpufreq-dt", -1, NULL, 0);
>> > +   if (!IS_ERR(pdev))
>> > +           return 0;
>> > +
>> > +   ret = PTR_ERR(pdev);
>> > +   dev_err(cpu_dev, "Failed to register platform device\n");
>> > +
>> > +free_opp:
>> > +   for_each_possible_cpu(cpu) {
>> > +           if (IS_ERR_OR_NULL(opp_tables[cpu]))
>> > +                   break;
>> > +           dev_pm_opp_put_supported_hw(opp_tables[cpu]);
>> > +   }
>> > +free_np:
>> > +   of_node_put(np);
>> > +
>> > +   return ret;
>> > +}
>> > +late_initcall(qcom_cpufreq_kryo_driver_init);
>>
>> Any particular reason why this *has* to be late initcall ?
>> Please change it to module_initcall otherwise.
>
> The purpose is to give the cpufreq-dt the time to register the driver and only then my driver will add the platform device.

That isn't required, the device and its driver can be registered in any order.