archive mirror
 help / color / mirror / Atom feed
From: "Rafael J. Wysocki" <>
To: Linux PM <>
Cc: LKML <>,
	Len Brown <>,
	Srinivas Pandruvada <>,
	Linux ACPI <>
Subject: [PATCH 0/2] cpufreq: intel_pstate: Make HWP calibration work on all hybrid platforms
Date: Mon, 24 Oct 2022 21:18:19 +0200	[thread overview]
Message-ID: <2258064.ElGaqSPkdT@kreacher> (raw)

Hi All,

The HWP calibration in intel_pstate is needed to map HWP performance levels to
frequencies, which are used in the cpufreq sysfs interface, in a reliable way.
On all non-hybrid "core" platforms it is sufficient to multiply the HWP
performance levels by 100000 to obtain the corresponding frequencies, but on
hybrid ones there is a difference between P-cores and E-cores.

Previous attempts to make this work were based on using CPPC (and in particular
the nominal performance values provided by _CPC), but it turns out that the
CPPC information is not sufficiently reliable for this purpose and the only
way to do it is to use a hard-coded scaling factors for P-cores and for E-cores
(which fortunately is the same as in the non-hybrid case).  Fortunately, the
same scaling factor for P-cores works on all of the hybrid platforms to date.

The first patch in the series ensures that all of the CPUs will use correct
information from MSRs by avoiding the situations in which an MSR values read
on one CPU will be used for performance scaling of another CPU.

The second one implements the approach outlined above.

Please see the changelogs for details.


             reply	other threads:[~2022-10-24 22:50 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-24 19:18 Rafael J. Wysocki [this message]
2022-10-24 19:21 ` [PATCH v1 1/2] cpufreq: intel_pstate: Read all MSRs on the target CPU Rafael J. Wysocki
2022-10-24 19:22 ` [PATCH v1 2/2] cpufreq: intel_pstate: hybrid: Use known scaling factor for P-cores Rafael J. Wysocki
2022-10-24 22:14 ` [PATCH 0/2] cpufreq: intel_pstate: Make HWP calibration work on all hybrid platforms srinivas pandruvada
2022-10-25 13:03   ` Rafael J. Wysocki

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=2258064.ElGaqSPkdT@kreacher \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).