Message-Id: <20241206135600.4083965-1-beata.michalska@arm.com>
Date: Fri,  6 Dec 2024 13:55:56 +0000
From: Beata Michalska <beata.michalska@....com>
To: linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-pm@...r.kernel.org,
	ionela.voinescu@....com,
	sudeep.holla@....com,
	will@...nel.org,
	catalin.marinas@....com,
	rafael@...nel.org,
	viresh.kumar@...aro.org
Cc: sumitg@...dia.com,
	yang@...amperecomputing.com,
	vanshikonda@...amperecomputing.com,
	lihuisong@...wei.com,
	zhanjie9@...ilicon.com,
	Jonathan Corbet <corbet@....net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Phil Auld <pauld@...hat.com>,
	x86@...nel.org,
	linux-doc@...r.kernel.org
Subject: [PATCH v8 0/4] Add support for AArch64 AMUv1-based average freq

Hi All,

This series adds support for obtaining an average CPU frequency based on
a hardware provided feedback. The average frequency is being exposed via
dedicated yet optional cpufreq sysfs attribute - cpuinfo_avg_freq.
The architecture specific bits are being provided for AArch64, caching on
existing implementation for FIE and AMUv1 support: the frequency scale
factor, updated on each sched tick, serving as a base for retrieving
the frequency for a given CPU, representing an average frequency
reported between the ticks.

The changes have been rather lightly (due to some limitations) tested on
an FVP model.

Note that [PATCH 2/4] arm64: amu: Delay allocating cpumask for AMU FIE support
can be merged independently.
Additionally, this series depends on [6]

Relevant discussions:
[1] https://lore.kernel.org/all/20240229162520.970986-1-vanshikonda@os.amperecomputing.com/
[2] https://lore.kernel.org/all/7eozim2xnepacnnkzxlbx34hib4otycnbn4dqymfziqou5lw5u@5xzpv3t7sxo3/
[3] https://lore.kernel.org/all/20231212072617.14756-1-lihuisong@huawei.com/
[4] https://lore.kernel.org/lkml/ZIHpd6unkOtYVEqP@e120325.cambridge.arm.com/T/#m4e74cb5a0aaa353c60fedc6cfb95ab7a6e381e3c
[5] https://lore.kernel.org/all/20240603081331.3829278-1-beata.michalska@arm.com/
[6] https://lore.kernel.org/all/20240827154818.1195849-1-ionela.voinescu@arm.com/

v8:
- Drop introducing new function and reuse arch_freq_get_on_cpu, guarding its use
  in scaling_cur_freq sysfs handler with dedicated config for x86

v7:
- Dropping 'arch_topology: init capacity_freq_ref to 0' patch from the series
  as this one has been sent separately as an independent change
  [https://lore.kernel.org/all/20240827154818.1195849-1-ionela.voinescu@arm.com/]
- Including in the series change that introduces new sysfs entry [PATCH 1/4]
- Consequently modifying previously arch_freq_get_on_cpu to match reqs for new
  sysfs attribute
- Dropping an idea of considering a CPU that has been idle for a while as a
  valid source of information for obtaining an AMU-counter based frequency
- Some minor cosmetic changes

v6:
 - delay allocating cpumask for AMU FIE support instead of invalidating the mask
   upon failure to register cpufreq policy notifications
 - drop the change to cpufreq core (for cpuinfo_cur_freq) as this one will be
   sent as a separate change

v5:
 - Fix invalid access to cpumask
 - Reworked finding reference cpu when getting the freq

v4:
- dropping seqcount
- fixing identifying active cpu within given policy
- skipping full dynticks cpus when retrieving the freq
- bringing back plugging in arch_freq_get_on_cpu into cpuinfo_cur_freq

v3:
- dropping changes to cpufreq_verify_current_freq
- pulling in changes from Ionela initializing capacity_freq_ref to 0
  (thanks for that!)  and applying suggestions made by her during last review:
	- switching to arch_scale_freq_capacity and arch_scale_freq_ref when
	  reversing freq scale factor computation
	- swapping shift with multiplication
- adding time limit for considering last scale update as valid
- updating frequency scale factor upon entering idle

v2:
- Splitting the patches
- Adding comment for full dyntick mode
- Plugging arch_freq_get_on_cpu into cpufreq_verify_current_freq instead
  of in show_cpuinfo_cur_freq to allow the framework to stay more in sync
  with potential freq changes

CC: Jonathan Corbet <corbet@....net>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Ingo Molnar <mingo@...hat.com>
CC: Borislav Petkov <bp@...en8.de>
CC: Dave Hansen <dave.hansen@...ux.intel.com>
CC: H. Peter Anvin <hpa@...or.com>
CC: Phil Auld <pauld@...hat.com>
CC: x86@...nel.org
CC: linux-doc@...r.kernel.org

Beata Michalska (4):
  cpufreq: Introduce an optional cpuinfo_avg_freq sysfs entry
  arm64: amu: Delay allocating cpumask for AMU FIE support
  arm64: Provide an AMU-based version of arch_freq_get_on_cpu
  arm64: Update AMU-based freq scale factor on entering idle

 Documentation/admin-guide/pm/cpufreq.rst |  16 ++-
 arch/arm64/kernel/topology.c             | 144 +++++++++++++++++++----
 arch/x86/kernel/cpu/aperfmperf.c         |   2 +-
 arch/x86/kernel/cpu/proc.c               |   7 +-
 drivers/cpufreq/Kconfig.x86              |  12 ++
 drivers/cpufreq/cpufreq.c                |  36 +++++-
 include/linux/cpufreq.h                  |   2 +-
 7 files changed, 188 insertions(+), 31 deletions(-)

-- 
2.25.1

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