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

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>

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index f366d35c58404ffbde88c312e29e4f93c545ea1a..0d5d283a5429b3a90cef36dd369cbb7a6b29e807 100644 (file)
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -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;

diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
index 7fa1eb3cc8239998c04988ff3cee33781c40f967..61d50571ad88ac235d4cc7b237c728182bb5c8db 100644 (file)
--- a/include/linux/energy_model.h
+++ b/include/linux/energy_model.h
@@ -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)
 {
 }

diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
index ea7995a25780f3106b9a87ae7e425746af7da2a5..8df55397414a12c0a69baa6ae3f98580124ebe08 100644 (file)
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -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