kernel/linux.git/drivers/cpufreq/cppc_cpufreq.c, branch v5.15.209

cpufreq: CPPC: Avoid using CPUFREQ_ETERNAL as transition delay

2025-10-29T13:03:07+00:00

[ Upstream commit f965d111e68f4a993cc44d487d416e3d954eea11 ] If cppc_get_transition_latency() returns CPUFREQ_ETERNAL to indicate a failure to retrieve the transition latency value from the platform firmware, the CPPC cpufreq driver will use that value (converted to microseconds) as the policy transition delay, but it is way too large for any practical use. Address this by making the driver use the cpufreq's default transition latency value (in microseconds) as the transition delay if CPUFREQ_ETERNAL is returned by cppc_get_transition_latency(). Fixes: d4f3388afd48 ("cpufreq / CPPC: Set platform specific transition_delay_us") Cc: 5.19+ # 5.19 Signed-off-by: Rafael J. Wysocki Reviewed-by: Mario Limonciello (AMD) Reviewed-by: Jie Zhan Acked-by: Viresh Kumar Reviewed-by: Qais Yousef [ added CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS definition to include/linux/cpufreq.h ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

cpufreq: CPPC: Mark driver with NEED_UPDATE_LIMITS flag

2025-08-28T14:24:17+00:00

[ Upstream commit 0a1416a49e63c320f6e6c1c8d07e1b58c0d4a3f3 ] AMU counters on certain CPPC-based platforms tend to yield inaccurate delivered performance measurements on systems that are idle/mostly idle. This results in an inaccurate frequency being stored by cpufreq in its policy structure when the CPU is brought online. [1] Consequently, if the userspace governor tries to set the frequency to a new value, there is a possibility that it would be the erroneous value stored earlier. In such a scenario, cpufreq would assume that the requested frequency has already been set and return early, resulting in the correct/new frequency request never making it to the hardware. Since the operating frequency is liable to this sort of inconsistency, mark the CPPC driver with CPUFREQ_NEED_UPDATE_LIMITS so that it is always invoked when a target frequency update is requested. Link: https://lore.kernel.org/linux-pm/20250619000925.415528-3-pmalani@google.com/ [1] Suggested-by: Rafael J. Wysocki Signed-off-by: Prashant Malani Acked-by: Viresh Kumar Link: https://patch.msgid.link/20250722055611.130574-2-pmalani@google.com Signed-off-by: Rafael J. Wysocki Signed-off-by: Sasha Levin

cpufreq: cppc: Fix invalid return value in .get() callback

2025-05-02T05:44:29+00:00

[ Upstream commit 2b8e6b58889c672e1ae3601d9b2b070be4dc2fbc ] Returning a negative error code in a function with an unsigned return type is a pretty bad idea. It is probably worse when the justification for the change is "our static analisys tool found it". Fixes: cf7de25878a1 ("cppc_cpufreq: Fix possible null pointer dereference") Signed-off-by: Marc Zyngier Cc: "Rafael J. Wysocki" Cc: Viresh Kumar Reviewed-by: Lifeng Zheng Signed-off-by: Viresh Kumar Signed-off-by: Sasha Levin

cppc_cpufreq: Fix possible null pointer dereference

2024-06-16T11:39:21+00:00

[ Upstream commit cf7de25878a1f4508c69dc9f6819c21ba177dbfe ] cppc_cpufreq_get_rate() and hisi_cppc_cpufreq_get_rate() can be called from different places with various parameters. So cpufreq_cpu_get() can return null as 'policy' in some circumstances. Fix this bug by adding null return check. Found by Linux Verification Center (linuxtesting.org) with SVACE. Fixes: a28b2bfc099c ("cppc_cpufreq: replace per-cpu data array with a list") Signed-off-by: Aleksandr Mishin Signed-off-by: Viresh Kumar Signed-off-by: Sasha Levin

cpufreq: CPPC: Fix performance/frequency conversion

2022-04-13T18:59:11+00:00

[ Upstream commit ec1c7ad47664f964c1101fe555b6fde0cb124b38 ] CPUfreq governors request CPU frequencies using information on current CPU usage. The CPPC driver converts them to performance requests. Frequency targets are computed as: target_freq = (util / cpu_capacity) * max_freq target_freq is then clamped between [policy->min, policy->max]. The CPPC driver converts performance values to frequencies (and vice-versa) using cppc_cpufreq_perf_to_khz() and cppc_cpufreq_khz_to_perf(). These functions both use two different factors depending on the range of the input value. For cppc_cpufreq_khz_to_perf(): - (NOMINAL_PERF / NOMINAL_FREQ) or - (LOWEST_PERF / LOWEST_FREQ) and for cppc_cpufreq_perf_to_khz(): - (NOMINAL_FREQ / NOMINAL_PERF) or - ((NOMINAL_PERF - LOWEST_FREQ) / (NOMINAL_PERF - LOWEST_PERF)) This means: 1- the functions are not inverse for some values: (perf_to_khz(khz_to_perf(x)) != x) 2- cppc_cpufreq_perf_to_khz(LOWEST_PERF) can sometimes give a different value from LOWEST_FREQ due to integer approximation 3- it is implied that performance and frequency are proportional (NOMINAL_FREQ / NOMINAL_PERF) == (LOWEST_PERF / LOWEST_FREQ) This patch changes the conversion functions to an affine function. This fixes the 3 points above. Suggested-by: Lukasz Luba Suggested-by: Morten Rasmussen Signed-off-by: Pierre Gondois Signed-off-by: Viresh Kumar Signed-off-by: Sasha Levin

cpufreq: CPPC: Add support for frequency invariance

2021-07-01T02:02:14+00:00

The Frequency Invariance Engine (FIE) is providing a frequency scaling correction factor that helps achieve more accurate load-tracking. Normally, this scaling factor can be obtained directly with the help of the cpufreq drivers as they know the exact frequency the hardware is running at. But that isn't the case for CPPC cpufreq driver. Another way of obtaining that is using the arch specific counter support, which is already present in kernel, but that hardware is optional for platforms. This patch updates the CPPC driver to register itself with the topology core to provide its own implementation (cppc_scale_freq_tick()) of topology_scale_freq_tick() which gets called by the scheduler on every tick. Note that the arch specific counters have higher priority than CPPC counters, if available, though the CPPC driver doesn't need to have any special handling for that. On an invocation of cppc_scale_freq_tick(), we schedule an irq work (since we reach here from hard-irq context), which then schedules a normal work item and cppc_scale_freq_workfn() updates the per_cpu arch_freq_scale variable based on the counter updates since the last tick. To allow platforms to disable this CPPC counter-based frequency invariance support, this is all done under CONFIG_ACPI_CPPC_CPUFREQ_FIE, which is enabled by default. This also exports sched_setattr_nocheck() as the CPPC driver can be built as a module. Cc: linux-acpi@vger.kernel.org Tested-by: Vincent Guittot Reviewed-by: Ionela Voinescu Tested-by: Qian Cai Signed-off-by: Viresh Kumar

cpufreq: CPPC: Pass structure instance by reference

2021-07-01T02:02:09+00:00

Don't pass structure instance by value, pass it by reference instead. Tested-by: Vincent Guittot Reviewed-by: Ionela Voinescu Tested-by: Qian Cai Signed-off-by: Viresh Kumar

cpufreq: CPPC: Fix potential memleak in cppc_cpufreq_cpu_init

2021-07-01T02:02:01+00:00

It's a classic example of memleak, we allocate something, we fail and never free the resources. Make sure we free all resources on policy ->init() failures. Fixes: a28b2bfc099c ("cppc_cpufreq: replace per-cpu data array with a list") Tested-by: Vincent Guittot Reviewed-by: Ionela Voinescu Tested-by: Qian Cai Signed-off-by: Viresh Kumar

cpufreq: CPPC: Migrate to ->exit() callback instead of ->stop_cpu()

2021-06-30T16:49:29+00:00

Commit 367dc4aa932b ("cpufreq: Add stop CPU callback to cpufreq_driver interface") added the ->stop_cpu() callback to allow the drivers to do clean up before the CPU is completely down and its state can't be modified. At that time the CPU hotplug framework used to call the cpufreq core's registered notifier for different events like CPU_DOWN_PREPARE and CPU_POST_DEAD. The ->stop_cpu() callback was called during the CPU_DOWN_PREPARE event. This is no longer the case, cpuhp_cpufreq_offline() is called only once by the CPU hotplug core now and we don't really need two separate callbacks for cpufreq drivers, i.e. ->stop_cpu() and -exit() callback itself. Migrate to using the ->exit() callback instead of ->stop_cpu(). Signed-off-by: Viresh Kumar [ rjw: Minor edits in the changelog and subject ] Signed-off-by: Rafael J. Wysocki

Revert "cpufreq: CPPC: Add support for frequency invariance"

2021-06-14T13:55:02+00:00

This reverts commit 4c38f2df71c8e33c0b64865992d693f5022eeaad. There are few races in the frequency invariance support for CPPC driver, namely the driver doesn't stop the kthread_work and irq_work on policy exit during suspend/resume or CPU hotplug. A proper fix won't be possible for the 5.13-rc, as it requires a lot of changes. Lets revert the patch instead for now. Fixes: 4c38f2df71c8 ("cpufreq: CPPC: Add support for frequency invariance") Reported-by: Qian Cai Signed-off-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki