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

[Huang Rui]

On Mon, Oct 24, 2022 at 10:56:50AM +0800, Yuan, Perry wrote:
> [AMD Official Use Only - General]
> 
> Hi Ray.
> 
> > -----Original Message-----
> > From: Huang, Ray <Ray.Huang@xxxxxxx>
> > Sent: Friday, October 21, 2022 1:22 PM
> > To: Limonciello, Mario <Mario.Limonciello@xxxxxxx>
> > Cc: Yuan, Perry <Perry.Yuan@xxxxxxx>; rafael.j.wysocki@xxxxxxxxx;
> > viresh.kumar@xxxxxxxxxx; Sharma, Deepak <Deepak.Sharma@xxxxxxx>;
> > Fontenot, Nathan <Nathan.Fontenot@xxxxxxx>; Deucher, Alexander
> > <Alexander.Deucher@xxxxxxx>; Huang, Shimmer
> > <Shimmer.Huang@xxxxxxx>; Du, Xiaojian <Xiaojian.Du@xxxxxxx>; Meng,
> > Li (Jassmine) <Li.Meng@xxxxxxx>; linux-pm@xxxxxxxxxxxxxxx; linux-
> > kernel@xxxxxxxxxxxxxxx; Borislav Petkov <bp@xxxxxxxxx>
> > Subject: Re: [RESEND PATCH V2 4/9] x86/msr: Add the MSR definition for
> > AMD CPPC boost state
> > 
> > + Boris,
> > 
> > On Fri, Oct 21, 2022 at 12:05:21AM +0800, Limonciello, Mario wrote:
> > > [Public]
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Yuan, Perry <Perry.Yuan@xxxxxxx>
> > > > Sent: Thursday, October 20, 2022 11:01
> > > > To: Huang, Ray <Ray.Huang@xxxxxxx>
> > > > Cc: rafael.j.wysocki@xxxxxxxxx; viresh.kumar@xxxxxxxxxx; Sharma,
> > > > Deepak <Deepak.Sharma@xxxxxxx>; Limonciello, Mario
> > > > <Mario.Limonciello@xxxxxxx>; Fontenot, Nathan
> > > > <Nathan.Fontenot@xxxxxxx>; Deucher, Alexander
> > > > <Alexander.Deucher@xxxxxxx>; Huang, Shimmer
> > <Shimmer.Huang@xxxxxxx>;
> > > > Du, Xiaojian <Xiaojian.Du@xxxxxxx>; Meng, Li (Jassmine)
> > > > <Li.Meng@xxxxxxx>; linux-pm@xxxxxxxxxxxxxxx; linux-
> > > > kernel@xxxxxxxxxxxxxxx
> > > > 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@xxxxxxx>
> > > > > Sent: Monday, October 17, 2022 5:57 PM
> > > > > To: Yuan, Perry <Perry.Yuan@xxxxxxx>
> > > > > Cc: rafael.j.wysocki@xxxxxxxxx; viresh.kumar@xxxxxxxxxx; Sharma,
> > > > > Deepak <Deepak.Sharma@xxxxxxx>; Limonciello, Mario
> > > > > <Mario.Limonciello@xxxxxxx>; Fontenot, Nathan
> > > > > <Nathan.Fontenot@xxxxxxx>; Deucher, Alexander
> > > > > <Alexander.Deucher@xxxxxxx>; Huang, Shimmer
> > > > > <Shimmer.Huang@xxxxxxx>; Du, Xiaojian <Xiaojian.Du@xxxxxxx>;
> > > > Meng,
> > > > > Li (Jassmine) <Li.Meng@xxxxxxx>; linux-pm@xxxxxxxxxxxxxxx; linux-
> > > > > kernel@xxxxxxxxxxxxxxx
> > > > > 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@xxxxxxx>
> > > > > > ---
> > > > > >  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@xxxxxxx/
> > > > > https://lore.kernel.org/lkml/YtX586RDd9Xw44IO@xxxxxxx/
> > > > >
> > > > > 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
> 
> I have removed the code not to write boost state to that MSR, just check the boost state from the MSR bit value.
> It will not cause any problems, I have tested and confirmed that the BIT value will be changed after BOOST ON/OFF switched in BIOS setting. 
> So we can just check the boost state here for pstate driver notification. 
> 

If we found MSR_K7_HWCR would impact the max frequency in CPPC, we should
report a defect or issue to firmware team. (Then we can add a quirk
function to workaround this in amd-pstate)

Thanks,
Ray