linux-kernel - RE: [PATCH v12 7/9] cpufreq: amd-pstate: fix the MSR highest perf will be reset issue while cpb boost off

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Date: Fri, 21 Jun 2024 05:56:36 +0000
From: "Yuan, Perry" <Perry.Yuan@....com>
To: "Shenoy, Gautham Ranjal" <gautham.shenoy@....com>,
	"rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>, "Limonciello,
 Mario" <Mario.Limonciello@....com>, "viresh.kumar@...aro.org"
	<viresh.kumar@...aro.org>
CC: "Huang, Shimmer" <Shimmer.Huang@....com>, "Du, Xiaojian"
	<Xiaojian.Du@....com>, "Meng, Li (Jassmine)" <Li.Meng@....com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v12 7/9] cpufreq: amd-pstate: fix the MSR highest perf
 will be reset issue while cpb boost off

[AMD Official Use Only - AMD Internal Distribution Only]

> -----Original Message-----
> From: Shenoy, Gautham Ranjal <gautham.shenoy@....com>
> Sent: Friday, June 21, 2024 1:46 PM
> To: Yuan, Perry <Perry.Yuan@....com>; rafael.j.wysocki@...el.com;
> Limonciello, Mario <Mario.Limonciello@....com>; viresh.kumar@...aro.org
> Cc: Huang, Shimmer <Shimmer.Huang@....com>; Du, Xiaojian
> <Xiaojian.Du@....com>; Meng, Li (Jassmine) <Li.Meng@....com>; linux-
> pm@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v12 7/9] cpufreq: amd-pstate: fix the MSR highest perf
> will be reset issue while cpb boost off
>
> Perry Yuan <perry.yuan@....com> writes:
>
> > From: Perry Yuan <Perry.Yuan@....com>
> >
> > Select the min perf to fix the highest perf value while update pstate
> > CPPC request MSR register, here it needs to limit the max perf value
> > when CPU boost is disabled in case of that highest perf value in the
> > MSR will be reset to original highest perf value which cause the BOOST
> > control failed.
>
> Perhaps we could rephrase this as
>
> "When Core Performance Boost is disabled by the user, the
> CPPC_REQ.max_perf should not exceed the nominal_perf since by definition
> the frequencies between nominal_perf and the highest_perf are in the boost
> range. Fix this in amd_pstate_update()"
>
> Also change the subject to
>
> "cpufreq:amd-pstate: Cap the CPPC.max_perf to nominal_perf if CPB is off"

Sure, will update the tile in v13,  will send out the V13 today to catch the merge window.
Thanks for the review.

Perry.

>
> ?
> >
> > Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> > Acked-by: Huang Rui <ray.huang@....com>
> > Reviewed-by: Mario Limonciello <mario.limonciello@....com>
>
> Other than that,
>
> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>
> > ---
> >  drivers/cpufreq/amd-pstate.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c
> > b/drivers/cpufreq/amd-pstate.c index 299e52d4b17e..f2ccef089acc 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -524,6 +524,7 @@ static void amd_pstate_update(struct amd_cpudata
> *cpudata, u32 min_perf,
> >                           u32 des_perf, u32 max_perf, bool fast_switch, int
> gov_flags)
> > {
> >     u64 prev = READ_ONCE(cpudata->cppc_req_cached);
> > +   u32 nominal_perf = READ_ONCE(cpudata->nominal_perf);
> >     u64 value = prev;
> >
> >     min_perf = clamp_t(unsigned long, min_perf, cpudata-
> >min_limit_perf,
> > @@ -543,6 +544,10 @@ static void amd_pstate_update(struct
> amd_cpudata *cpudata, u32 min_perf,
> >     value &= ~AMD_CPPC_DES_PERF(~0L);
> >     value |= AMD_CPPC_DES_PERF(des_perf);
> >
> > +   /* limit the max perf when core performance boost feature is
> disabled */
> > +   if (!amd_pstate_global_params.cpb_boost)
> > +           max_perf = min_t(unsigned long, nominal_perf, max_perf);
> > +
> >     value &= ~AMD_CPPC_MAX_PERF(~0L);
> >     value |= AMD_CPPC_MAX_PERF(max_perf);
> >
> > --
> > 2.34.1
>
> --
> Thanks and Regards
> gautham.