[PATCH V6 0/4] cpufreq: cppc: Add support for frequency invariance

[Viresh Kumar <viresh.kumar@linaro.org>]

Hello,

CPPC cpufreq driver is used for ARM servers and this patch series tries
to provide counter-based frequency invariance support for them in the
absence for architecture specific counters (like AMUs).

This is tested by:
- Vincent Guittot on ThunderX2.
- Ionela Voinescu on Juno R2.
- /me with hacks on Hikey, as I don't have access to the right hardware.

This is based of 5.12-rc2. I will merge these via the arm-cpufreq tree
directly.

Changes since V5:
- New patch to rename freq_scale to arch_freq_scale (Will Deacon).
- Separate patch to export arch_freq_scale and helpers (Will Deacon).
- Some improvements in the last patch like commit log, moving more stuff
  to policy init, new fie_disabled flag, etc. (Ionela Voinescu).
- Added Reviewed/Acked/Tested-by tags.

Changes since V4:
- Move some code to policy specific initialization for cppc driver.
- Initialize kthread specific stuff only once in cppc driver.
- Added a kerneldoc comment in cppc driver and improved changelog as
  well.

Changes since V3:
- rebuild_sched_domains_energy() stuff moved from arm64 to drivers/base.
- Added Reviewed/Tested-by Ionela for the first patch.
- Remove unused max_freq field from structure in cppc driver.
- s/cppc_f_i/cppc_freq_inv.
- Fix an per-cpu access, there was a bug in earlier version.
- Create a single kthread which can run on any CPU and takes care of
  work from all the CPUs.
- Do the whole FIE thing under a new CONFIG option for cppc driver.
- Few minor improvements.

Changes since V2:
- Not sending as an RFC anymore.
- Several renames, reordering of code in 1/2 based on Ionela's comments.
- Several rebase changes for 2/2.
- The freq_scale calculations are optimized a bit.
- Better overall commenting and commit logs.

Changes since V1:
- The interface for setting the callbacks is improved, so different
  parts looking to provide their callbacks don't need to think about
  each other.

- Moved to per-cpu storage for storing the callback related data, AMU
  counters have higher priority with this.

--
Viresh

Viresh Kumar (4):
  arch_topology: Rename freq_scale as arch_freq_scale
  arch_topology: Allow multiple entities to provide sched_freq_tick()
    callback
  arch_topology: Export arch_freq_scale and helpers
  cpufreq: CPPC: Add support for frequency invariance

 arch/arm64/include/asm/topology.h |  10 +-
 arch/arm64/kernel/topology.c      | 109 +++++--------
 drivers/base/arch_topology.c      |  89 ++++++++++-
 drivers/cpufreq/Kconfig.arm       |  10 ++
 drivers/cpufreq/cppc_cpufreq.c    | 245 ++++++++++++++++++++++++++++--
 include/linux/arch_topology.h     |  19 ++-
 kernel/sched/core.c               |   1 +
 7 files changed, 385 insertions(+), 98 deletions(-)


base-commit: a38fd8748464831584a19438cbb3082b5a2dab15
-- 
2.25.0.rc1.19.g042ed3e048af