linux-kernel - RE: [PATCH v2 04/21] ACPI: CPPC: add cppc enable register function

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Date:   Wed, 13 Oct 2021 12:28:40 +0000
From:   "Huang, Ray" <Ray.Huang@....com>
To:     "Fontenot, Nathan" <Nathan.Fontenot@....com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Borislav Petkov <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
CC:     "Sharma, Deepak" <Deepak.Sharma@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Limonciello, Mario" <Mario.Limonciello@....com>,
        "Su, Jinzhou (Joe)" <Jinzhou.Su@....com>,
        "Du, Xiaojian" <Xiaojian.Du@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>
Subject: RE: [PATCH v2 04/21] ACPI: CPPC: add cppc enable register function

[AMD Official Use Only]

Hi all,

Sorry to late response, I am just back from vacation.

> -----Original Message-----
> From: Fontenot, Nathan <Nathan.Fontenot@....com>
> Sent: Wednesday, September 29, 2021 1:06 AM
> To: Huang, Ray <Ray.Huang@....com>; Rafael J . Wysocki
> <rafael.j.wysocki@...el.com>; Viresh Kumar <viresh.kumar@...aro.org>;
> Shuah Khan <skhan@...uxfoundation.org>; Borislav Petkov <bp@...e.de>;
> Peter Zijlstra <peterz@...radead.org>; Ingo Molnar <mingo@...nel.org>;
> linux-pm@...r.kernel.org
> Cc: Sharma, Deepak <Deepak.Sharma@....com>; Deucher, Alexander
> <Alexander.Deucher@....com>; Limonciello, Mario
> <Mario.Limonciello@....com>; Su, Jinzhou (Joe) <Jinzhou.Su@....com>;
> Du, Xiaojian <Xiaojian.Du@....com>; linux-kernel@...r.kernel.org;
> x86@...nel.org
> Subject: Re: [PATCH v2 04/21] ACPI: CPPC: add cppc enable register function
> 
> On 9/26/2021 4:05 AM, Huang Rui wrote:
> > From: Jinzhou Su <Jinzhou.Su@....com>
> >
> > Add a new function to enable CPPC feature. This function
> > will write Continuous Performance Control package
> > EnableRegister field on the processor.
> >
> > Signed-off-by: Jinzhou Su <Jinzhou.Su@....com>
> > Signed-off-by: Huang Rui <ray.huang@....com>
> > ---
> >  drivers/acpi/cppc_acpi.c | 48
> ++++++++++++++++++++++++++++++++++++++++
> >  include/acpi/cppc_acpi.h |  5 +++++
> >  2 files changed, 53 insertions(+)
> >
> > diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> > index 2efe2ba97d96..b285960c35e7 100644
> > --- a/drivers/acpi/cppc_acpi.c
> > +++ b/drivers/acpi/cppc_acpi.c
> > @@ -1220,6 +1220,54 @@ int cppc_get_perf_ctrs(int cpunum, struct
> cppc_perf_fb_ctrs *perf_fb_ctrs)
> >  }
> >  EXPORT_SYMBOL_GPL(cppc_get_perf_ctrs);
> >
> > +/**
> > + * cppc_set_enable - Set to enable CPPC on the processor by writing the
> > + * Continuous Performance Control package EnableRegister feild.
> > + * @cpu: CPU for which to enable CPPC register.
> > + * @enable: 0 - disable, 1 - enable CPPC feature on the processor.
> > + *
> > + * Return: 0 for success, -ERRNO or -EIO otherwise.
> > + */
> > +int cppc_set_enable(int cpu, u32 enable)
> 
> This should take a bool instead of u32 for enable, you can only enable
> or diable cppc. The only caller I see is in patch 7/21 in which the
> enable arg is already a bool that's converted to a u32. This also allows
> for the removal of the enable value check.
> 

Yes, the bool type should be better than u32 here. Will update it in V3. 

> You should consider merging this patch with patch 7/21. This patch adds
> the cppc_set_enable() routine but has no users. The only caller I find is
> in patch 7/21.
> 

I am looking back again, this patch is to provide the new helper in cppc_acpi library under ACPI subsystem.
However, patch 7 is to enable the shared memory APIs in amd-pstate driver.
They are actually the different function implementations. I prefer using the separated patch here.   

Thanks,
Ray