linux-kernel - [PATCH 0/6] cpufreq: Introduce boost frequency QoS

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Message-ID: <20260126101826.94030-1-pierre.gondois@arm.com>
Date: Mon, 26 Jan 2026 11:18:09 +0100
From: Pierre Gondois <pierre.gondois@....com>
To: linux-kernel@...r.kernel.org
Cc: Jie Zhan <zhanjie9@...ilicon.com>,
	zhenglifeng1@...wei.com,
	Ionela Voinescu <ionela.voinescu@....com>,
	Christian Loehle <christian.loehle@....com>,
	sumitg@...dia.com,
	Pierre Gondois <pierre.gondois@....com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Huang Rui <ray.huang@....com>,
	"Gautham R. Shenoy" <gautham.shenoy@....com>,
	Mario Limonciello <mario.limonciello@....com>,
	Perry Yuan <perry.yuan@....com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Len Brown <lenb@...nel.org>,
	Saravana Kannan <saravanak@...nel.org>,
	linux-pm@...r.kernel.org
Subject: [PATCH 0/6] cpufreq: Introduce boost frequency QoS

The Power Management Quality of Service (PM QoS) allows to
aggregate constraints from multiple entities. It is currently
used to manage the min/max frequency of a given policy.

Frequency constraints can come from:
- Thermal framework: acpi_thermal_cpufreq_init()
- Firmware: _PPC objects: acpi_processor_ppc_init()
- User: by setting policyX/scaling_[min|max]_freq
The minimum of the max frequency constraints is used to compute
the resulting maximum allowed frequency.

When enabling boost frequencies, the same frequency request object
(policy->max_freq_req) as to handle requests from users is used.
As a result, when setting:
- scaling_max_freq
- boost
The last sysfs file used overwrites the request from the other
sysfs file.

To avoid this:
1. Create a per-policy boost_freq_req to save the boost
constraints instead of overwriting the last scaling_max_freq
constraint.

2. policy_set_boost() calls the cpufreq set_boost callback.
Update the newly added boost_freq_req request from there:
- whenever boost is toggled
- to cover all possible paths

3. In the existing set_boost() callbacks:
- Don't update policy->max as this is done through the qos notifier
  cpufreq_notifier_max() which calls cpufreq_set_policy().
- Remove freq_qos_update_request() calls as the qos request is now
  done in policy_set_boost() and updates the new boost_freq_req

This patch-set additionally does:
- if a driver .init() callback sets policy->min and policy->max,
  these values are used are min/max_freq_req QoS constraints
- Remove policy->min and policy->max initialization in .init()
  callback if the value is identical to cpuinfo.min/max_freq
- RFC: allow decreasing cpuinfo.max_freq when using freq_table.

------------

E.g.:
On a Juno with available frequencies: 600.000, 1.000.000
Boost frequencies: 1.200.000
Using the cppc-cpufreq driver.

---
Without the patches:
# ## Init state
scaling_max_freq:1000000
cpuinfo_max_freq:1000000

# echo 700000 > scaling_max_freq
scaling_max_freq:700000
cpuinfo_max_freq:1000000

# echo 1 > ../boost
scaling_max_freq:1200000
cpuinfo_max_freq:1200000

# echo 800000 > scaling_max_freq
scaling_max_freq:800000
cpuinfo_max_freq:1200000

# echo 0 > ../boost
scaling_max_freq:1000000
cpuinfo_max_freq:1000000

---
With the patches:
# ## Init
scaling_max_freq:1000000
cpuinfo_max_freq:1000000

# echo 700000 > scaling_max_freq
scaling_max_freq:700000
cpuinfo_max_freq:1000000

# echo 1 > ../boost
scaling_max_freq:700000
cpuinfo_max_freq:1200000

# echo 800000 > scaling_max_freq
scaling_max_freq:800000
cpuinfo_max_freq:1200000

# echo 0 > ../boost
scaling_max_freq:800000
cpuinfo_max_freq:1000000

---

With the patches, the maximum scaling frequency requested is
conserved even though boosting is enabled/disabled.

---

v1: https://lore.kernel.org/all/20251204101344.192678-1-pierre.gondois@arm.com/#t
v2: https://lore.kernel.org/all/20251208105933.1369125-1-pierre.gondois@arm.com/#t
Changes:
- Fixed error path
- Integrated [PATCH 1/4] Revert "cpufreq: Fix re-boost issue after hotplugging a CPU"
  to another patch
v3:
Changes:
- Fixed error path
- Extracted the revert of:
  "cpufreq: Fix re-boost issue after hotplugging a CPU"
  for clarity purpose
- Set cpuinfo.max_freq as a max_freq_req QoS constraint by default
New patches:
- "cpufreq: Allow decreasing cpuinfo.max_freq"
- "cpufreq: Set policy->min and max as QoS constraints"

Pierre Gondois (6):
  cpufreq: Remove per-CPU QoS constraint
  cpufreq: Add boost_freq_req QoS request
  cpufreq: Centralize boost freq QoS requests
  cpufreq: Update .set_boost() callbacks to rely on boost_freq_req
  cpufreq: Set policy->min and max as real QoS constraints
  cpufreq/freq_table: Allow decreasing cpuinfo.max_freq

 drivers/cpufreq/acpi-cpufreq.c    |  1 +
 drivers/cpufreq/amd-pstate.c      | 26 +++++----
 drivers/cpufreq/cppc_cpufreq.c    | 10 +---
 drivers/cpufreq/cpufreq-nforce2.c |  4 +-
 drivers/cpufreq/cpufreq.c         | 87 +++++++++++++++++++++++--------
 drivers/cpufreq/freq_table.c      | 14 ++---
 drivers/cpufreq/gx-suspmod.c      |  9 ++--
 drivers/cpufreq/intel_pstate.c    |  3 --
 drivers/cpufreq/pcc-cpufreq.c     |  8 +--
 drivers/cpufreq/pxa3xx-cpufreq.c  |  4 +-
 drivers/cpufreq/virtual-cpufreq.c |  6 +--
 include/linux/cpufreq.h           |  1 +
 12 files changed, 101 insertions(+), 72 deletions(-)

--
2.43.0