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PM: EM: Add function for registering a PD without capacity update

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The intel_pstate driver manages CPU capacity changes itself and it does
not need an update of the capacity of all CPUs in the system to be
carried out after registering a PD.

Moreover, in some configurations (for instance, an SMT-capable
hybrid x86 system booted with nosmt in the kernel command line) the
em_check_capacity_update() call at the end of em_dev_register_perf_domain()
always fails and reschedules itself to run once again in 1 s, so
effectively it runs in vain every 1 s forever.

To address this, introduce a new variant of em_dev_register_perf_domain(),
called em_dev_register_pd_no_update(), that does not invoke
em_check_capacity_update(), and make intel_pstate use it instead of the
original.

Fixes: 7b010f9b9061 ("cpufreq: intel_pstate: EAS support for hybrid platforms")
Closes: https://lore.kernel.org/linux-pm/40212796-734c-4140-8a85-854f72b8144d@panix.com/
Reported-by: Kenneth R. Crudup <kenny@panix.com>
Tested-by: Kenneth R. Crudup <kenny@panix.com>
Cc: 6.16+ <stable@vger.kernel.org> # 6.16+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Rafael J. Wysocki 2025-09-05 15:44:45 +02:00
parent 76eeb9b8de
commit e042354147
3 changed files with 37 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/cpufreq/intel_pstate.c
View File

@ -1034,8 +1034,8 @@ static bool hybrid_register_perf_domain(unsigned int cpu)
if (!cpu_dev)
return false;
if (em_dev_register_perf_domain(cpu_dev, HYBRID_EM_STATE_COUNT, &cb,
cpumask_of(cpu), false))
if (em_dev_register_pd_no_update(cpu_dev, HYBRID_EM_STATE_COUNT, &cb,
cpumask_of(cpu), false))
return false;
cpudata->pd_registered = true;

10
include/linux/energy_model.h
View File

@ -171,6 +171,9 @@ int em_dev_update_perf_domain(struct device *dev,
int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
const struct em_data_callback *cb,
const cpumask_t *cpus, bool microwatts);
int em_dev_register_pd_no_update(struct device *dev, unsigned int nr_states,
const struct em_data_callback *cb,
const cpumask_t *cpus, bool microwatts);
void em_dev_unregister_perf_domain(struct device *dev);
struct em_perf_table *em_table_alloc(struct em_perf_domain *pd);
void em_table_free(struct em_perf_table *table);
@ -350,6 +353,13 @@ int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
{
return -EINVAL;
}
static inline
int em_dev_register_pd_no_update(struct device *dev, unsigned int nr_states,
const struct em_data_callback *cb,
const cpumask_t *cpus, bool microwatts)
{
return -EINVAL;
}
static inline void em_dev_unregister_perf_domain(struct device *dev)
{
}

29
kernel/power/energy_model.c
View File

@ -552,6 +552,30 @@ EXPORT_SYMBOL_GPL(em_cpu_get);
int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
const struct em_data_callback *cb,
const cpumask_t *cpus, bool microwatts)
{
int ret = em_dev_register_pd_no_update(dev, nr_states, cb, cpus, microwatts);
if (_is_cpu_device(dev))
em_check_capacity_update();
return ret;
}
EXPORT_SYMBOL_GPL(em_dev_register_perf_domain);
/**
* em_dev_register_pd_no_update() - Register a perf domain for a device
* @dev : Device to register the PD for
* @nr_states : Number of performance states in the new PD
* @cb : Callback functions for populating the energy model
* @cpus : CPUs to include in the new PD (mandatory if @dev is a CPU device)
* @microwatts : Whether or not the power values in the EM will be in uW
*
* Like em_dev_register_perf_domain(), but does not trigger a CPU capacity
* update after registering the PD, even if @dev is a CPU device.
*/
int em_dev_register_pd_no_update(struct device *dev, unsigned int nr_states,
const struct em_data_callback *cb,
const cpumask_t *cpus, bool microwatts)
{
struct em_perf_table *em_table;
unsigned long cap, prev_cap = 0;
@ -636,12 +660,9 @@ int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
unlock:
mutex_unlock(&em_pd_mutex);
if (_is_cpu_device(dev))
em_check_capacity_update();
return ret;
}
EXPORT_SYMBOL_GPL(em_dev_register_perf_domain);
EXPORT_SYMBOL_GPL(em_dev_register_pd_no_update);
/**
* em_dev_unregister_perf_domain() - Unregister Energy Model (EM) for a device