[RFC PATCH 0/4] ACPI: processor: thermal: Recompute the frequency cap when boost changes

[Hugo Sales]

thermal_req is a fixed fraction of policy->cpuinfo.max_freq, computed
only when the cooling state is written, so it keeps the boost state of
that moment. The ACPI thermal zone writes step 0 on every resume, and
step 0 caps at cpuinfo.max_freq, so if boost was off at suspend, turning
it on after resume leaves the CPUs at their base clock. Steps 1 to 3 go
stale the same way

Ashton A. sent a one-line fix for the resume case, which stops step 0
from setting a cap. It fixes the resume case on my laptop, and my
Tested-by is in that thread:

  https://lore.kernel.org/all/20261028-acpi-thermal-stale-limit-v1-1-4b0ab3230f01@xxxxxxxxxxxxxxxx/

That patch is small, easy to backport and enough to fix the biggest
issue. This series applies on its own to bleeding-edge and fixes the
resume case and steps 1 to 3 by recomputing the cap when boost changes,
so please take one or the other, not both

Before d15ce412737a the CPUFREQ_ADJUST notifier recomputed the cap on
every policy update. This series brings that back without letting a
notifier touch the policy:

  1. cpufreq core: a CPUFREQ_UPDATE_CPUINFO policy notifier event, sent
     from policy_set_boost() after ->set_boost(). That covers
     amd-pstate, cppc_cpufreq and the cpufreq_boost_set_sw() drivers
  2. intel_pstate: send it from __intel_pstate_update_max_freq(), since
     no_turbo and HWP capability changes don't go through ->set_boost()
  3. processor_thermal: factor out the thermal_req update
  4. processor_thermal: recompute thermal_req on the new event, from the
     step each request was last set to, under a mutex shared with
     cpufreq_set_cur_state() and the request add and remove

Step 0 still sets a cap here, and patch 4 recomputes it with the other
steps, so the resume case needs no special case

The freq QoS notifiers can't do this. They fire only when the aggregate
limit changes, and while the thermal cap is below both maximums,
turning boost on moves boost_freq_req without moving the aggregate

I also looked at basing the steps on a fixed reference frequency, the
way cpufreq_cooling uses absolute table frequencies. There is no generic
way to read the boost maximum while boost is off (amd-pstate and cppc
keep it in driver data), and with boost off step 1 would often not
throttle at all

Rafael, Viresh, which do you prefer? This series adds a cpufreq event
with one user. If that isn't worth it, I'm happy to drop it and keep my
Tested-by on Ashton's patch

Tested on my laptop (Ryzen 9 5980HS, amd-pstate-epp) with the series
backported to 7.3. With boost off and cooling state 1, cpu0's
scaling_max_freq is 2640800, 80% of 3301000. Turning boost on raises it
to 3879405, 80% of 4849257, and turning boost off brings it back down.
Step 2 follows boost the same way, and at step 0 turning boost on gives
the full 4849257. Toggling boost while writing cooling states on all 16
CPUs left nothing in the kernel log, on a kernel without lockdep

Patch 1 changes Documentation/cpu-freq/core.rst only. Its zh_CN and
zh_TW translations need the same update from someone who can review
them

Hugo Sales (4):
  cpufreq: Add a CPUFREQ_UPDATE_CPUINFO policy notifier event
  cpufreq: intel_pstate: Send CPUFREQ_UPDATE_CPUINFO on max_freq changes
  ACPI: processor: thermal: Factor out the thermal_req update
  ACPI: processor: thermal: Recompute the frequency cap when boost
    changes

 Documentation/cpu-freq/core.rst  |  9 +++--
 drivers/acpi/processor_driver.c  |  2 ++
 drivers/acpi/processor_thermal.c | 58 ++++++++++++++++++++++++++------
 drivers/cpufreq/cpufreq.c        | 16 +++++++++
 drivers/cpufreq/intel_pstate.c   |  8 ++++-
 include/acpi/processor.h         |  4 +++
 include/linux/cpufreq.h          |  2 ++
 7 files changed, 85 insertions(+), 14 deletions(-)


base-commit: 5854d2ce4b0b9ccb37b154319d8283bad889a694
-- 
2.56.0