Re: [RESEND PATCH V2 4/9] x86/msr: Add the MSR definition for AMD CPPC boost state

[Huang Rui <ray.huang@amd.com>]

+ Boris,

On Fri, Oct 21, 2022 at 12:05:21AM +0800, Limonciello, Mario wrote:
> [Public]
> 
> 
> 
> > -----Original Message-----
> > From: Yuan, Perry <Perry.Yuan@amd.com>
> > Sent: Thursday, October 20, 2022 11:01
> > To: Huang, Ray <Ray.Huang@amd.com>
> > Cc: rafael.j.wysocki@intel.com; viresh.kumar@linaro.org; Sharma, Deepak
> > <Deepak.Sharma@amd.com>; Limonciello, Mario
> > <Mario.Limonciello@amd.com>; Fontenot, Nathan
> > <Nathan.Fontenot@amd.com>; Deucher, Alexander
> > <Alexander.Deucher@amd.com>; Huang, Shimmer
> > <Shimmer.Huang@amd.com>; Du, Xiaojian <Xiaojian.Du@amd.com>; Meng,
> > Li (Jassmine) <Li.Meng@amd.com>; linux-pm@vger.kernel.org; linux-
> > kernel@vger.kernel.org
> > Subject: RE: [RESEND PATCH V2 4/9] x86/msr: Add the MSR definition for
> > AMD CPPC boost state
> > 
> > [AMD Official Use Only - General]
> > 
> > Hi Ray.
> > 
> > > -----Original Message-----
> > > From: Huang, Ray <Ray.Huang@amd.com>
> > > Sent: Monday, October 17, 2022 5:57 PM
> > > To: Yuan, Perry <Perry.Yuan@amd.com>
> > > Cc: rafael.j.wysocki@intel.com; viresh.kumar@linaro.org; Sharma, Deepak
> > > <Deepak.Sharma@amd.com>; Limonciello, Mario
> > > <Mario.Limonciello@amd.com>; Fontenot, Nathan
> > > <Nathan.Fontenot@amd.com>; Deucher, Alexander
> > > <Alexander.Deucher@amd.com>; Huang, Shimmer
> > > <Shimmer.Huang@amd.com>; Du, Xiaojian <Xiaojian.Du@amd.com>;
> > Meng,
> > > Li (Jassmine) <Li.Meng@amd.com>; linux-pm@vger.kernel.org; linux-
> > > kernel@vger.kernel.org
> > > Subject: Re: [RESEND PATCH V2 4/9] x86/msr: Add the MSR definition for
> > > AMD CPPC boost state
> > >
> > > On Tue, Oct 11, 2022 at 12:22:43AM +0800, Yuan, Perry wrote:
> > > > This MSR can be used to check whether the CPU frequency boost state is
> > > > enabled in the hardware control. User can change the boost state in
> > > > the BIOS setting,amd_pstate driver will update the boost state
> > > > according to this msr value.
> > > >
> > > > AMD Processor Programming Reference (PPR)
> > > > Link: https://www.amd.com/system/files/TechDocs/40332.pdf [p1095]
> > > > Link: https://www.amd.com/system/files/TechDocs/56569-A1-PUB.zip
> > > > [p162]
> > > >
> > > > Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
> > > > ---
> > > >  arch/x86/include/asm/msr-index.h | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/arch/x86/include/asm/msr-index.h
> > > > b/arch/x86/include/asm/msr-index.h
> > > > index 6674bdb096f3..e5ea1c9f747b 100644
> > > > --- a/arch/x86/include/asm/msr-index.h
> > > > +++ b/arch/x86/include/asm/msr-index.h
> > > > @@ -569,6 +569,7 @@
> > > >  #define MSR_AMD_CPPC_CAP2		0xc00102b2
> > > >  #define MSR_AMD_CPPC_REQ		0xc00102b3
> > > >  #define MSR_AMD_CPPC_STATUS		0xc00102b4
> > > > +#define MSR_AMD_CPPC_HW_CTL		0xc0010015
> > > >
> > > >  #define AMD_CPPC_LOWEST_PERF(x)		(((x) >> 0) & 0xff)
> > > >  #define AMD_CPPC_LOWNONLIN_PERF(x)	(((x) >> 8) & 0xff)
> > > > @@ -579,6 +580,8 @@
> > > >  #define AMD_CPPC_MIN_PERF(x)		(((x) & 0xff) << 8)
> > > >  #define AMD_CPPC_DES_PERF(x)		(((x) & 0xff) << 16)
> > > >  #define AMD_CPPC_ENERGY_PERF_PREF(x)	(((x) & 0xff) << 24)
> > > > +#define AMD_CPPC_PRECISION_BOOST_BIT   25
> > > > +#define AMD_CPPC_PRECISION_BOOST_ENABLED
> > > BIT_ULL(AMD_CPPC_PRECISION_BOOST_BIT)
> > >
> > > I had commented the MSR_AMD_CPPC_HW_CTL is duplicated with
> > > MSR_K7_HWCR
> > >
> > > https://lore.kernel.org/lkml/YtX+uF/nAIG0ykHN@amd.com/
> > > https://lore.kernel.org/lkml/YtX586RDd9Xw44IO@amd.com/
> > >
> > > Could you please make sure address the commments?
> > >
> > > Thanks,
> > > Ray
> > 
> > If I rename that the MSR definition string, that will cause lots of driver file
> > change.
> > So I suggest to add one new MSR macro for the CPPC, the MSR_K7_HWCR is
> > mismatching in the CPPC Pstate driver.
> > If you refuse to use this new one, I will reuse that old one.
> 
> To avoid changing too much stuff at once how about if you give an alias?
> IE something like:
> 
> #define MSR_AMD_CPPC_HW_CTL MSR_K7_HWCR
> 

The mainly concern is that HWCR is for legacy ACPI P-State control not for
CPPC. I talked with hardware guys before, it's not suggested to mix them up
together. This register has been defined for a long time even before Zen
processor.

Thanks,
Ray