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d33bd88ac0
If the BIOS sets a _PPC frequency limit upfront, it will fail to take
effect due to a call ordering issue. Namely, freq_qos_update_request()
is called before freq_qos_add_request() for the given request causing
the constraint update to be ignored. The call sequence in question is
as follows:
cpufreq_policy_online()
acpi_cpufreq_cpu_init()
acpi_processor_register_performance()
acpi_processor_get_performance_info()
acpi_processor_get_platform_limit()
freq_qos_update_request(&perflib_req) <- inactive QoS request
blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
CPUFREQ_CREATE_POLICY)
acpi_processor_notifier()
acpi_processor_ppc_init()
freq_qos_add_request(&perflib_req) <- QoS request activation
Address this by adding an acpi_processor_get_platform_limit() call
to acpi_processor_ppc_init(), after the perflib_req activation via
freq_qos_add_request(), which causes the initial _PPC limit to be
picked up as appropriate. However, also ensure that the _PPC limit
will not be picked up in the cases when the cpufreq driver does not
call acpi_processor_register_performance() by adding a pr->performance
check to the related_cpus loop in acpi_processor_ppc_init().
Fixes: d15ce41273 ("ACPI: cpufreq: Switch to QoS requests instead of cpufreq notifier")
Signed-off-by: Jiayi Li <lijiayi@kylinos.cn>
Link: https://patch.msgid.link/20250721032606.3459369-1-lijiayi@kylinos.cn
[ rjw: Consolidate pr-related checks in acpi_processor_ppc_init() ]
[ rjw: Subject and changelog adjustments ]
Cc: 5.4+ <stable@vger.kernel.org> # 5.4+: 2d8b39a62a ACPI: processor: Avoid NULL pointer dereferences at init time
Cc: 5.4+ <stable@vger.kernel.org> # 5.4+: 3000ce3c52 cpufreq: Use per-policy frequency QoS
Cc: 5.4+ <stable@vger.kernel.org> # 5.4+: a1bb46c36c ACPI: processor: Add QoS requests for all CPUs
Cc: 5.4+ <stable@vger.kernel.org> # 5.4+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.