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Message-Id: <20240117095714.1524808-12-lukasz.luba@arm.com>
Date: Wed, 17 Jan 2024 09:57:02 +0000
From: Lukasz Luba <lukasz.luba@....com>
To: linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org,
rafael@...nel.org
Cc: lukasz.luba@....com,
dietmar.eggemann@....com,
rui.zhang@...el.com,
amit.kucheria@...durent.com,
amit.kachhap@...il.com,
daniel.lezcano@...aro.org,
viresh.kumar@...aro.org,
len.brown@...el.com,
pavel@....cz,
mhiramat@...nel.org,
qyousef@...alina.io,
wvw@...gle.com,
xuewen.yan94@...il.com
Subject: [PATCH v7 11/23] PM: EM: Introduce em_dev_update_perf_domain() for EM updates
Add API function em_dev_update_perf_domain() which allows the EM to be
changed safely.
Concurrent updaters are serialized with a mutex and the removal of memory
that will not be used any more is carried out with the help of RCU.
Signed-off-by: Lukasz Luba <lukasz.luba@....com>
---
include/linux/energy_model.h | 8 +++++++
kernel/power/energy_model.c | 44 ++++++++++++++++++++++++++++++++++++
2 files changed, 52 insertions(+)
diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
index e44c5080407f..494df6942cf7 100644
--- a/include/linux/energy_model.h
+++ b/include/linux/energy_model.h
@@ -183,6 +183,8 @@ struct em_data_callback {
struct em_perf_domain *em_cpu_get(int cpu);
struct em_perf_domain *em_pd_get(struct device *dev);
+int em_dev_update_perf_domain(struct device *dev,
+ struct em_perf_table __rcu *new_table);
int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
struct em_data_callback *cb, cpumask_t *span,
bool microwatts);
@@ -377,6 +379,12 @@ struct em_perf_table __rcu *em_table_alloc(struct em_perf_domain *pd)
return NULL;
}
static inline void em_table_free(struct em_perf_table __rcu *table) {}
+static inline
+int em_dev_update_perf_domain(struct device *dev,
+ struct em_perf_table __rcu *new_table)
+{
+ return -EINVAL;
+}
#endif
#endif
diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
index ffe94614f004..190042640935 100644
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -209,6 +209,50 @@ static int em_allocate_perf_table(struct em_perf_domain *pd,
return 0;
}
+/**
+ * em_dev_update_perf_domain() - Update runtime EM table for a device
+ * @dev : Device for which the EM is to be updated
+ * @new_table : The new EM table that is going to be used from now
+ *
+ * Update EM runtime modifiable table for the @dev using the provided @table.
+ *
+ * This function uses a mutex to serialize writers, so it must not be called
+ * from a non-sleeping context.
+ *
+ * Return 0 on success or an error code on failure.
+ */
+int em_dev_update_perf_domain(struct device *dev,
+ struct em_perf_table __rcu *new_table)
+{
+ struct em_perf_table __rcu *old_table;
+ struct em_perf_domain *pd;
+
+ if (!dev)
+ return -EINVAL;
+
+ /* Serialize update/unregister or concurrent updates */
+ mutex_lock(&em_pd_mutex);
+
+ if (!dev->em_pd) {
+ mutex_unlock(&em_pd_mutex);
+ return -EINVAL;
+ }
+ pd = dev->em_pd;
+
+ kref_get(&new_table->kref);
+
+ old_table = pd->em_table;
+ rcu_assign_pointer(pd->em_table, new_table);
+
+ em_cpufreq_update_efficiencies(dev, new_table->state);
+
+ em_table_free(old_table);
+
+ mutex_unlock(&em_pd_mutex);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(em_dev_update_perf_domain);
+
static int em_create_runtime_table(struct em_perf_domain *pd)
{
struct em_perf_table __rcu *table;
--
2.25.1
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