linux-kernel - Re: [PATCH 5/6] acpi/cppc: Add support for optional CPPC registers

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Date:   Sat, 30 Mar 2019 00:02:12 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     "Ghannam, Yazen" <Yazen.Ghannam@....com>
Cc:     "Pandruvada, Srinivas" <srinivas.pandruvada@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devel@...ica.org" <devel@...ica.org>,
        "Natarajan, Janakarajan" <Janakarajan.Natarajan@....com>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "lenb@...nel.org" <lenb@...nel.org>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
        "Moore, Robert" <robert.moore@...el.com>,
        "Schmauss, Erik" <erik.schmauss@...el.com>
Subject: Re: [PATCH 5/6] acpi/cppc: Add support for optional CPPC registers

On Friday, March 29, 2019 9:18:04 PM CET Ghannam, Yazen wrote:
> > -----Original Message-----
> > From: linux-acpi-owner@...r.kernel.org <linux-acpi-owner@...r.kernel.org> On Behalf Of Pandruvada, Srinivas
> > Sent: Wednesday, March 27, 2019 10:48 AM
> > To: linux-kernel@...r.kernel.org; devel@...ica.org; Natarajan, Janakarajan <Janakarajan.Natarajan@....com>; linux-
> > acpi@...r.kernel.org; linux-pm@...r.kernel.org
> > Cc: Ghannam, Yazen <Yazen.Ghannam@....com>; lenb@...nel.org; viresh.kumar@...aro.org; Moore, Robert
> > <robert.moore@...el.com>; Schmauss, Erik <erik.schmauss@...el.com>; rjw@...ysocki.net
> > Subject: Re: [PATCH 5/6] acpi/cppc: Add support for optional CPPC registers
> > 
> > On Fri, 2019-03-22 at 20:26 +0000, Natarajan, Janakarajan wrote:
> > > From: Yazen Ghannam <Yazen.Ghannam@....com>
> > >
> > > Newer AMD processors support a subset of the optional CPPC registers.
> > > Create show, store and helper routines for supported CPPC registers.
> > >
> > > Signed-off-by: Yazen Ghannam <Yazen.Ghannam@....com>
> > > [ carved out into a patch, cleaned up, productized ]
> > > Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@....com>
> > >
> > 
> > [..]
> > 
> > > +	/* desired_perf is the only mandatory value in perf_ctrls */
> > > +	if (cpc_read(cpu, desired_reg, &desired))
> > > +		ret = -EFAULT;
> > > +
> > > +	if (CPC_SUPPORTED(max_reg) && cpc_read(cpu, max_reg, &max))
> > > +		ret = -EFAULT;
> > > +
> > We should create and use different macro other than CPPC_SUPPORTED.
> > CPC_SUPPORTED doesn't validate the correctness of object type for a
> > field. For example "Maximum Performance Register" can only be buffer
> > not integer. In this way invalid field definitions can be ignored.
> > 
> 
> So create something like "CPPC_SUPPORTED_BUFFER" for buffer-only registers?
> 
> And then buffer/integer registers will continue to use "CPPC_SUPPORTED".
> 
> These seem to be the only two cases at this time. Is this okay?

Yes, something like that.

Thanks,
Rafael