[PATCH V2 0/3] cpufreq: cppc: Add support for frequency invariance

[Viresh Kumar]

Hello,

Changes since V1:

- Few of the patches migrating users to ->exit() callback are posted separately.

- The CPPC patch was completely reverted and so the support for FIE is again
  added here from scratch.

- The start_cpu() and stop_cpu() interface is reworked a little so stop_cpu() is
  only ever called for a CPU if start_cpu() was called for it earlier.

- A new patch to implement RCU locking in arch_topology core to avoid some
  races.

- Some cleanup and very clear/separate paths for FIE in cppc driver now.


-------------------------8<-------------------------

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 was reverted earlier for the 5.13 kernel after Qian Cai reported kernel
oops during suspend/resume.

This is based of pm/linux-next + a cleanup patchset:

https://lore.kernel.org/linux-pm/cover.1623825358.git.viresh.kumar@xxxxxxxxxx/

All the patches are pushed here together for people to run.

https://git.kernel.org/pub/scm/linux/kernel/git/vireshk/pm.git/log/?h=cpufreq/cppc

This is tested on my Hikey platform (without the actual read/write to
performance counters), with this script for over an hour:

while true; do
    for i in `seq 1 7`;
    do
        echo 0 > /sys/devices/system/cpu/cpu$i/online;
    done;

    for i in `seq 1 7`;
    do
        echo 1 > /sys/devices/system/cpu/cpu$i/online;
    done;
done


Vincent will be giving this patchset a try on ThunderX2.

Meanwhile it is up for review. Ideally I would like to get this merged for 5.14,
but lets see how it goes.

Thanks.

--
Viresh

Viresh Kumar (3):
  cpufreq: Add start_cpu() and stop_cpu() callbacks
  arch_topology: Avoid use-after-free for scale_freq_data
  cpufreq: CPPC: Add support for frequency invariance

 Documentation/cpu-freq/cpu-drivers.rst |   7 +-
 drivers/base/arch_topology.c           |  27 ++-
 drivers/cpufreq/Kconfig.arm            |  10 ++
 drivers/cpufreq/cppc_cpufreq.c         | 232 +++++++++++++++++++++++--
 drivers/cpufreq/cpufreq.c              |  19 +-
 include/linux/arch_topology.h          |   1 +
 include/linux/cpufreq.h                |   5 +-
 kernel/sched/core.c                    |   1 +
 8 files changed, 272 insertions(+), 30 deletions(-)

-- 
2.31.1.272.g89b43f80a514