RE: [PATCH 4/5] Documentation: amd-pstate: add driver working mode introduction

[Yuan, Perry]

[AMD Official Use Only - General]

Hi Gautham

> -----Original Message-----
> From: Shenoy, Gautham Ranjal <gautham.shenoy@xxxxxxx>
> Sent: Thursday, November 17, 2022 12:16 PM
> To: Yuan, Perry <Perry.Yuan@xxxxxxx>
> Cc: rafael.j.wysocki@xxxxxxxxx; Huang, Ray <Ray.Huang@xxxxxxx>;
> viresh.kumar@xxxxxxxxxx; Limonciello, Mario <Mario.Limonciello@xxxxxxx>;
> Fontenot, Nathan <Nathan.Fontenot@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>; Sharma, Deepak
> <Deepak.Sharma@xxxxxxx>; Huang, Shimmer
> <Shimmer.Huang@xxxxxxx>; Meng, Li (Jassmine) <Li.Meng@xxxxxxx>;
> Du, Xiaojian <Xiaojian.Du@xxxxxxx>; Karny, Wyes
> <Wyes.Karny@xxxxxxx>; Narayan, Ananth <Ananth.Narayan@xxxxxxx>;
> linux-pm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH 4/5] Documentation: amd-pstate: add driver working
> mode introduction
> 
> Hello Perry,
> 
> On Thu, Nov 17, 2022 at 10:49:54AM +0800, Perry Yuan wrote:
> > Introduce the `amd-pstate` driver new working mode with
> > `amd-pstate=passive` added to kernel command line.
> 
> It should be `amd_pstate=passive` here to be consistent with the early
> parameter and the rest of the documentation.

Thank you help to review,
Will fix  this with V2

Perry.

> 
> 
> > If there is no passive mode enabled by user, amd-pstate driver will be
> > disabled by default for now.
> >
> > Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
> > ---
> >  Documentation/admin-guide/pm/amd-pstate.rst | 30
> > +++++++++------------
> >  1 file changed, 13 insertions(+), 17 deletions(-)
> >
> > diff --git a/Documentation/admin-guide/pm/amd-pstate.rst
> > b/Documentation/admin-guide/pm/amd-pstate.rst
> > index 8f3d30c5a0d8..06e23538f79c 100644
> > --- a/Documentation/admin-guide/pm/amd-pstate.rst
> > +++ b/Documentation/admin-guide/pm/amd-pstate.rst
> > @@ -283,23 +283,19 @@ efficiency frequency management method on
> AMD processors.
> >  Kernel Module Options for ``amd-pstate``
> > =========================================
> >
> > -.. _shared_mem:
> > -
> > -``shared_mem``
> > -Use a module param (shared_mem) to enable related processors
> manually
> > with -**amd_pstate.shared_mem=1**.
> > -Due to the performance issue on the processors with `Shared Memory
> > Support -<perf_cap_>`_, we disable it presently and will re-enable
> > this by default -once we address performance issue with this solution.
> > -
> > -To check whether the current processor is using `Full MSR Support
> > <perf_cap_>`_ -or `Shared Memory Support <perf_cap_>`_ : ::
> > -
> > -  ray@hr-test1:~$ lscpu | grep cppc
> > -  Flags:                           fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
> mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt
> pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid
> extd_apicid aperfmperf rapl pni pclmulqdq monitor ssse3 fma cx16 sse4_1
> sse4_2 x2apic movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy
> svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit
> wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb cat_l3
> cdp_l3 hw_pstate ssbd mba ibrs ibpb stibp vmmcall fsgsbase bmi1 avx2 smep
> bmi2 erms invpcid cqm rdt_a rdseed adx smap clflushopt clwb sha_ni
> xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total
> cqm_mbm_local clzero irperf xsaveerptr rdpru wbnoinvd cppc arat npt lbrv
> svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists
> pausefilter pfthreshold avic v_vmsave_vmload vgif v_spec_ctrl umip pku
> ospke vaes vpclmulqdq rdpid overflow_recov succor smca fsrm
> > -
> > -If the CPU flags have ``cppc``, then this processor supports `Full
> > MSR Support -<perf_cap_>`_. Otherwise, it supports `Shared Memory
> Support <perf_cap_>`_.
> > +Passive Mode
> > +------------
> > +
> > +``amd_pstate=passive``
> > +
> > +It will be enabled if the ``amd_pstate=passive`` is passed to the kernel in
> the command line.
> > +In this mode, ``amd_pstate`` driver software specifies a desired QoS
> > +target in the CPPC performance scale as a relative number. This can
> > +be expressed as percentage of nominal performance (infrastructure
> > +max). Below the nominal sustained performance level, desired
> > +performance expresses the average performance level of the processor
> > +subject to the Performance Reduction Tolerance register. Above the
> > +nominal performance level, processor must provide at least nominal
> performance requested and go higher if current operating conditions allow.
> 
> Otherwise looks good to me.
> 
> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@xxxxxxx>
> 
> --
> Thanks and Regards
> gautham.