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Date:   Thu, 17 Nov 2022 10:36:49 +0530
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Subject: Re: [PATCH 4/5] Documentation: amd-pstate: add driver working mode
 introduction
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To:     Perry Yuan <Perry.Yuan@amd.com>, rafael.j.wysocki@intel.com,
        ray.huang@amd.com, viresh.kumar@linaro.org,
        Mario.Limonciello@amd.com
Cc:     Nathan.Fontenot@amd.com, Alexander.Deucher@amd.com,
        Deepak.Sharma@amd.com, Shimmer.Huang@amd.com, Li.Meng@amd.com,
        Xiaojian.Du@amd.com, gautham.shenoy@amd.com,
        ananth.narayan@amd.com, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20221117024955.3319484-1-Perry.Yuan@amd.com>
 <20221117024955.3319484-5-Perry.Yuan@amd.com>
From:   Wyes Karny <wyes.karny@amd.com>
In-Reply-To: <20221117024955.3319484-5-Perry.Yuan@amd.com>
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On 11/17/2022 8:19 AM, Perry Yuan wrote:
> Introduce the `amd-pstate` driver new working mode with
> `amd-pstate=3Dpassive` added to kernel command line.
> If there is no passive mode enabled by user, amd-pstate driver will be
> disabled by default for now.
>=20
> Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>

Tested-by: Wyes Karny <wyes.karny@amd.com>

> ---
>  Documentation/admin-guide/pm/amd-pstate.rst | 30 +++++++++------------
>  1 file changed, 13 insertions(+), 17 deletions(-)
>=20
> 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 proce=
ssors.
>  Kernel Module Options for ``amd-pstate``
>  =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> =20
> -.. _shared_mem:
> -
> -``shared_mem``
> -Use a module param (shared_mem) to enable related processors manually wi=
th
> -**amd_pstate.shared_mem=3D1**.
> -Due to the performance issue on the processors with `Shared Memory Suppo=
rt
> -<perf_cap_>`_, we disable it presently and will re-enable this by defaul=
t
> -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 ap=
ic 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 cp=
uid 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 sv=
m extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wd=
t tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb cat_l3 c=
dp_l3 hw_pstate ssbd mba ibrs ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bm=
i2 erms invpcid cqm rdt_a rdseed adx smap clflushopt clwb sha_ni xsaveopt x=
savec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local clze=
ro irperf xsaveerptr rdpru wbnoinvd cppc arat npt lbrv svm_lock nrip_save t=
sc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic =
v_vmsave_vmload vgif v_spec_ctrl umip pku ospke vaes vpclmulqdq rdpid overf=
low_recov succor smca fsrm
> -
> -If the CPU flags have ``cppc``, then this processor supports `Full MSR S=
upport
> -<perf_cap_>`_. Otherwise, it supports `Shared Memory Support <perf_cap_>=
`_.
> +Passive Mode
> +------------
> +
> +``amd_pstate=3Dpassive``
> +
> +It will be enabled if the ``amd_pstate=3Dpassive`` is passed to the kern=
el in the command line.
> +In this mode, ``amd_pstate`` driver software specifies a desired QoS tar=
get in the CPPC
> +performance scale as a relative number. This can be expressed as percent=
age of nominal
> +performance (infrastructure max). Below the nominal sustained performanc=
e level,
> +desired performance expresses the average performance level of the proce=
ssor subject
> +to the Performance Reduction Tolerance register. Above the nominal perfo=
rmance level,
> +processor must provide at least nominal performance requested and go hig=
her if current
> +operating conditions allow.
> =20
> =20
>  ``cpupower`` tool support for ``amd-pstate``

--=20
Thanks & Regards,
Wyes