Merge branch 'rust/cpufreq-dt' into cpufreq/arm/linux-next

6 files changed, 408 insertions, 230 deletions

diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
index d64b07ec48e5..78702a08364f 100644
--- a/drivers/cpufreq/Kconfig
+++ b/drivers/cpufreq/Kconfig
@@ -217,6 +217,18 @@ config CPUFREQ_DT
 
 	  If in doubt, say N.
 
+config CPUFREQ_DT_RUST
+	tristate "Rust based Generic DT based cpufreq driver"
+	depends on HAVE_CLK && OF && RUST
+	select CPUFREQ_DT_PLATDEV
+	select PM_OPP
+	help
+	  This adds a Rust based generic DT based cpufreq driver for frequency
+	  management.  It supports both uniprocessor (UP) and symmetric
+	  multiprocessor (SMP) systems.
+
+	  If in doubt, say N.
+
 config CPUFREQ_VIRT
 	tristate "Virtual cpufreq driver"
 	depends on GENERIC_ARCH_TOPOLOGY
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 22ab45209f9b..d38526b8e063 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -15,6 +15,7 @@ obj-$(CONFIG_CPU_FREQ_GOV_COMMON)		+= cpufreq_governor.o
 obj-$(CONFIG_CPU_FREQ_GOV_ATTR_SET)	+= cpufreq_governor_attr_set.o
 
 obj-$(CONFIG_CPUFREQ_DT)		+= cpufreq-dt.o
+obj-$(CONFIG_CPUFREQ_DT_RUST)		+= rcpufreq_dt.o
 obj-$(CONFIG_CPUFREQ_DT_PLATDEV)	+= cpufreq-dt-platdev.o
 obj-$(CONFIG_CPUFREQ_VIRT)		+= virtual-cpufreq.o
 
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 6789eed1bb5b..b9d59c7425f5 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -821,19 +821,16 @@ static void amd_pstate_init_prefcore(struct amd_cpudata *cpudata)
 	schedule_work(&sched_prefcore_work);
 }
 
-static void amd_pstate_update_limits(unsigned int cpu)
+static void amd_pstate_update_limits(struct cpufreq_policy *policy)
 {
-	struct cpufreq_policy *policy __free(put_cpufreq_policy) = cpufreq_cpu_get(cpu);
 	struct amd_cpudata *cpudata;
 	u32 prev_high = 0, cur_high = 0;
 	bool highest_perf_changed = false;
+	unsigned int cpu = policy->cpu;
 
 	if (!amd_pstate_prefcore)
 		return;
 
-	if (!policy)
-		return;
-
 	if (amd_get_highest_perf(cpu, &cur_high))
 		return;
 
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 3841c9da6cac..2b91ba503b32 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -255,51 +255,6 @@ void cpufreq_cpu_put(struct cpufreq_policy *policy)
 }
 EXPORT_SYMBOL_GPL(cpufreq_cpu_put);
 
-/**
- * cpufreq_cpu_release - Unlock a policy and decrement its usage counter.
- * @policy: cpufreq policy returned by cpufreq_cpu_acquire().
- */
-void cpufreq_cpu_release(struct cpufreq_policy *policy)
-{
-	if (WARN_ON(!policy))
-		return;
-
-	lockdep_assert_held(&policy->rwsem);
-
-	up_write(&policy->rwsem);
-
-	cpufreq_cpu_put(policy);
-}
-
-/**
- * cpufreq_cpu_acquire - Find policy for a CPU, mark it as busy and lock it.
- * @cpu: CPU to find the policy for.
- *
- * Call cpufreq_cpu_get() to get a reference on the cpufreq policy for @cpu and
- * if the policy returned by it is not NULL, acquire its rwsem for writing.
- * Return the policy if it is active or release it and return NULL otherwise.
- *
- * The policy returned by this function has to be released with the help of
- * cpufreq_cpu_release() in order to release its rwsem and balance its usage
- * counter properly.
- */
-struct cpufreq_policy *cpufreq_cpu_acquire(unsigned int cpu)
-{
-	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
-
-	if (!policy)
-		return NULL;
-
-	down_write(&policy->rwsem);
-
-	if (policy_is_inactive(policy)) {
-		cpufreq_cpu_release(policy);
-		return NULL;
-	}
-
-	return policy;
-}
-
 /*********************************************************************
  *            EXTERNALLY AFFECTING FREQUENCY CHANGES                 *
  *********************************************************************/
@@ -1009,17 +964,16 @@ static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
 {
 	struct cpufreq_policy *policy = to_policy(kobj);
 	struct freq_attr *fattr = to_attr(attr);
-	ssize_t ret = -EBUSY;
 
 	if (!fattr->show)
 		return -EIO;
 
-	down_read(&policy->rwsem);
+	guard(cpufreq_policy_read)(policy);
+
 	if (likely(!policy_is_inactive(policy)))
-		ret = fattr->show(policy, buf);
-	up_read(&policy->rwsem);
+		return fattr->show(policy, buf);
 
-	return ret;
+	return -EBUSY;
 }
 
 static ssize_t store(struct kobject *kobj, struct attribute *attr,
@@ -1027,17 +981,16 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr,
 {
 	struct cpufreq_policy *policy = to_policy(kobj);
 	struct freq_attr *fattr = to_attr(attr);
-	ssize_t ret = -EBUSY;
 
 	if (!fattr->store)
 		return -EIO;
 
-	down_write(&policy->rwsem);
+	guard(cpufreq_policy_write)(policy);
+
 	if (likely(!policy_is_inactive(policy)))
-		ret = fattr->store(policy, buf, count);
-	up_write(&policy->rwsem);
+		return fattr->store(policy, buf, count);
 
-	return ret;
+	return -EBUSY;
 }
 
 static void cpufreq_sysfs_release(struct kobject *kobj)
@@ -1195,7 +1148,8 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy, unsigned int cp
 	if (cpumask_test_cpu(cpu, policy->cpus))
 		return 0;
 
-	down_write(&policy->rwsem);
+	guard(cpufreq_policy_write)(policy);
+
 	if (has_target())
 		cpufreq_stop_governor(policy);
 
@@ -1206,7 +1160,7 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy, unsigned int cp
 		if (ret)
 			pr_err("%s: Failed to start governor\n", __func__);
 	}
-	up_write(&policy->rwsem);
+
 	return ret;
 }
 
@@ -1226,9 +1180,10 @@ static void handle_update(struct work_struct *work)
 		container_of(work, struct cpufreq_policy, update);
 
 	pr_debug("handle_update for cpu %u called\n", policy->cpu);
-	down_write(&policy->rwsem);
+
+	guard(cpufreq_policy_write)(policy);
+
 	refresh_frequency_limits(policy);
-	up_write(&policy->rwsem);
 }
 
 static int cpufreq_notifier_min(struct notifier_block *nb, unsigned long freq,
@@ -1254,11 +1209,11 @@ static void cpufreq_policy_put_kobj(struct cpufreq_policy *policy)
 	struct kobject *kobj;
 	struct completion *cmp;
 
-	down_write(&policy->rwsem);
-	cpufreq_stats_free_table(policy);
-	kobj = &policy->kobj;
-	cmp = &policy->kobj_unregister;
-	up_write(&policy->rwsem);
+	scoped_guard(cpufreq_policy_write, policy) {
+		cpufreq_stats_free_table(policy);
+		kobj = &policy->kobj;
+		cmp = &policy->kobj_unregister;
+	}
 	kobject_put(kobj);
 
 	/*
@@ -1334,7 +1289,6 @@ static struct cpufreq_policy *cpufreq_policy_alloc(unsigned int cpu)
 	init_waitqueue_head(&policy->transition_wait);
 	INIT_WORK(&policy->update, handle_update);
 
-	policy->cpu = cpu;
 	return policy;
 
 err_min_qos_notifier:
@@ -1403,35 +1357,17 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
 	kfree(policy);
 }
 
-static int cpufreq_online(unsigned int cpu)
+static int cpufreq_policy_online(struct cpufreq_policy *policy,
+				 unsigned int cpu, bool new_policy)
 {
-	struct cpufreq_policy *policy;
-	bool new_policy;
 	unsigned long flags;
 	unsigned int j;
 	int ret;
 
-	pr_debug("%s: bringing CPU%u online\n", __func__, cpu);
-
-	/* Check if this CPU already has a policy to manage it */
-	policy = per_cpu(cpufreq_cpu_data, cpu);
-	if (policy) {
-		WARN_ON(!cpumask_test_cpu(cpu, policy->related_cpus));
-		if (!policy_is_inactive(policy))
-			return cpufreq_add_policy_cpu(policy, cpu);
+	guard(cpufreq_policy_write)(policy);
 
-		/* This is the only online CPU for the policy.  Start over. */
-		new_policy = false;
-		down_write(&policy->rwsem);
-		policy->cpu = cpu;
-		policy->governor = NULL;
-	} else {
-		new_policy = true;
-		policy = cpufreq_policy_alloc(cpu);
-		if (!policy)
-			return -ENOMEM;
-		down_write(&policy->rwsem);
-	}
+	policy->cpu = cpu;
+	policy->governor = NULL;
 
 	if (!new_policy && cpufreq_driver->online) {
 		/* Recover policy->cpus using related_cpus */
@@ -1454,7 +1390,7 @@ static int cpufreq_online(unsigned int cpu)
 		if (ret) {
 			pr_debug("%s: %d: initialization failed\n", __func__,
 				 __LINE__);
-			goto out_free_policy;
+			goto out_clear_policy;
 		}
 
 		/*
@@ -1605,7 +1541,55 @@ static int cpufreq_online(unsigned int cpu)
 		goto out_destroy_policy;
 	}
 
-	up_write(&policy->rwsem);
+	return 0;
+
+out_destroy_policy:
+	for_each_cpu(j, policy->real_cpus)
+		remove_cpu_dev_symlink(policy, j, get_cpu_device(j));
+
+out_offline_policy:
+	if (cpufreq_driver->offline)
+		cpufreq_driver->offline(policy);
+
+out_exit_policy:
+	if (cpufreq_driver->exit)
+		cpufreq_driver->exit(policy);
+
+out_clear_policy:
+	cpumask_clear(policy->cpus);
+
+	return ret;
+}
+
+static int cpufreq_online(unsigned int cpu)
+{
+	struct cpufreq_policy *policy;
+	bool new_policy;
+	int ret;
+
+	pr_debug("%s: bringing CPU%u online\n", __func__, cpu);
+
+	/* Check if this CPU already has a policy to manage it */
+	policy = per_cpu(cpufreq_cpu_data, cpu);
+	if (policy) {
+		WARN_ON(!cpumask_test_cpu(cpu, policy->related_cpus));
+		if (!policy_is_inactive(policy))
+			return cpufreq_add_policy_cpu(policy, cpu);
+
+		/* This is the only online CPU for the policy.  Start over. */
+		new_policy = false;
+	} else {
+		new_policy = true;
+		policy = cpufreq_policy_alloc(cpu);
+		if (!policy)
+			return -ENOMEM;
+	}
+
+	ret = cpufreq_policy_online(policy, cpu, new_policy);
+	if (ret) {
+		cpufreq_policy_free(policy);
+		return ret;
+	}
 
 	kobject_uevent(&policy->kobj, KOBJ_ADD);
 
@@ -1633,25 +1617,6 @@ static int cpufreq_online(unsigned int cpu)
 	pr_debug("initialization complete\n");
 
 	return 0;
-
-out_destroy_policy:
-	for_each_cpu(j, policy->real_cpus)
-		remove_cpu_dev_symlink(policy, j, get_cpu_device(j));
-
-out_offline_policy:
-	if (cpufreq_driver->offline)
-		cpufreq_driver->offline(policy);
-
-out_exit_policy:
-	if (cpufreq_driver->exit)
-		cpufreq_driver->exit(policy);
-
-out_free_policy:
-	cpumask_clear(policy->cpus);
-	up_write(&policy->rwsem);
-
-	cpufreq_policy_free(policy);
-	return ret;
 }
 
 /**
@@ -1741,11 +1706,10 @@ static int cpufreq_offline(unsigned int cpu)
 		return 0;
 	}
 
-	down_write(&policy->rwsem);
+	guard(cpufreq_policy_write)(policy);
 
 	__cpufreq_offline(cpu, policy);
 
-	up_write(&policy->rwsem);
 	return 0;
 }
 
@@ -1762,33 +1726,29 @@ static void cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif)
 	if (!policy)
 		return;
 
-	down_write(&policy->rwsem);
+	scoped_guard(cpufreq_policy_write, policy) {
+		if (cpu_online(cpu))
+			__cpufreq_offline(cpu, policy);
 
-	if (cpu_online(cpu))
-		__cpufreq_offline(cpu, policy);
+		remove_cpu_dev_symlink(policy, cpu, dev);
 
-	remove_cpu_dev_symlink(policy, cpu, dev);
+		if (!cpumask_empty(policy->real_cpus))
+			return;
 
-	if (!cpumask_empty(policy->real_cpus)) {
-		up_write(&policy->rwsem);
-		return;
-	}
+		/*
+		 * Unregister cpufreq cooling once all the CPUs of the policy
+		 * are removed.
+		 */
+		if (cpufreq_thermal_control_enabled(cpufreq_driver)) {
+			cpufreq_cooling_unregister(policy->cdev);
+			policy->cdev = NULL;
+		}
 
-	/*
-	 * Unregister cpufreq cooling once all the CPUs of the policy are
-	 * removed.
-	 */
-	if (cpufreq_thermal_control_enabled(cpufreq_driver)) {
-		cpufreq_cooling_unregister(policy->cdev);
-		policy->cdev = NULL;
+		/* We did light-weight exit earlier, do full tear down now */
+		if (cpufreq_driver->offline && cpufreq_driver->exit)
+			cpufreq_driver->exit(policy);
 	}
 
-	/* We did light-weight exit earlier, do full tear down now */
-	if (cpufreq_driver->offline && cpufreq_driver->exit)
-		cpufreq_driver->exit(policy);
-
-	up_write(&policy->rwsem);
-
 	cpufreq_policy_free(policy);
 }
 
@@ -1858,27 +1818,26 @@ static unsigned int cpufreq_verify_current_freq(struct cpufreq_policy *policy, b
  */
 unsigned int cpufreq_quick_get(unsigned int cpu)
 {
-	struct cpufreq_policy *policy;
-	unsigned int ret_freq = 0;
+	struct cpufreq_policy *policy __free(put_cpufreq_policy) = NULL;
 	unsigned long flags;
 
 	read_lock_irqsave(&cpufreq_driver_lock, flags);
 
 	if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get) {
-		ret_freq = cpufreq_driver->get(cpu);
+		unsigned int ret_freq = cpufreq_driver->get(cpu);
+
 		read_unlock_irqrestore(&cpufreq_driver_lock, flags);
+
 		return ret_freq;
 	}
 
 	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
 	policy = cpufreq_cpu_get(cpu);
-	if (policy) {
-		ret_freq = policy->cur;
-		cpufreq_cpu_put(policy);
-	}
+	if (policy)
+		return policy->cur;
 
-	return ret_freq;
+	return 0;
 }
 EXPORT_SYMBOL(cpufreq_quick_get);
 
@@ -1890,15 +1849,13 @@ EXPORT_SYMBOL(cpufreq_quick_get);
  */
 unsigned int cpufreq_quick_get_max(unsigned int cpu)
 {
-	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
-	unsigned int ret_freq = 0;
+	struct cpufreq_policy *policy __free(put_cpufreq_policy);
 
-	if (policy) {
-		ret_freq = policy->max;
-		cpufreq_cpu_put(policy);
-	}
+	policy = cpufreq_cpu_get(cpu);
+	if (policy)
+		return policy->max;
 
-	return ret_freq;
+	return 0;
 }
 EXPORT_SYMBOL(cpufreq_quick_get_max);
 
@@ -1910,15 +1867,13 @@ EXPORT_SYMBOL(cpufreq_quick_get_max);
  */
 __weak unsigned int cpufreq_get_hw_max_freq(unsigned int cpu)
 {
-	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
-	unsigned int ret_freq = 0;
+	struct cpufreq_policy *policy __free(put_cpufreq_policy);
 
-	if (policy) {
-		ret_freq = policy->cpuinfo.max_freq;
-		cpufreq_cpu_put(policy);
-	}
+	policy = cpufreq_cpu_get(cpu);
+	if (policy)
+		return policy->cpuinfo.max_freq;
 
-	return ret_freq;
+	return 0;
 }
 EXPORT_SYMBOL(cpufreq_get_hw_max_freq);
 
@@ -1938,19 +1893,18 @@ static unsigned int __cpufreq_get(struct cpufreq_policy *policy)
  */
 unsigned int cpufreq_get(unsigned int cpu)
 {
-	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
-	unsigned int ret_freq = 0;
+	struct cpufreq_policy *policy __free(put_cpufreq_policy);
 
-	if (policy) {
-		down_read(&policy->rwsem);
-		if (cpufreq_driver->get)
-			ret_freq = __cpufreq_get(policy);
-		up_read(&policy->rwsem);
+	policy = cpufreq_cpu_get(cpu);
+	if (!policy)
+		return 0;
 
-		cpufreq_cpu_put(policy);
-	}
+	guard(cpufreq_policy_read)(policy);
 
-	return ret_freq;
+	if (cpufreq_driver->get)
+		return __cpufreq_get(policy);
+
+	return 0;
 }
 EXPORT_SYMBOL(cpufreq_get);
 
@@ -2009,9 +1963,9 @@ void cpufreq_suspend(void)
 
 	for_each_active_policy(policy) {
 		if (has_target()) {
-			down_write(&policy->rwsem);
-			cpufreq_stop_governor(policy);
-			up_write(&policy->rwsem);
+			scoped_guard(cpufreq_policy_write, policy) {
+				cpufreq_stop_governor(policy);
+			}
 		}
 
 		if (cpufreq_driver->suspend && cpufreq_driver->suspend(policy))
@@ -2052,9 +2006,9 @@ void cpufreq_resume(void)
 			pr_err("%s: Failed to resume driver: %s\n", __func__,
 				cpufreq_driver->name);
 		} else if (has_target()) {
-			down_write(&policy->rwsem);
-			ret = cpufreq_start_governor(policy);
-			up_write(&policy->rwsem);
+			scoped_guard(cpufreq_policy_write, policy) {
+				ret = cpufreq_start_governor(policy);
+			}
 
 			if (ret)
 				pr_err("%s: Failed to start governor for CPU%u's policy\n",
@@ -2421,15 +2375,9 @@ int cpufreq_driver_target(struct cpufreq_policy *policy,
 			  unsigned int target_freq,
 			  unsigned int relation)
 {
-	int ret;
-
-	down_write(&policy->rwsem);
+	guard(cpufreq_policy_write)(policy);
 
-	ret = __cpufreq_driver_target(policy, target_freq, relation);
-
-	up_write(&policy->rwsem);
-
-	return ret;
+	return __cpufreq_driver_target(policy, target_freq, relation);
 }
 EXPORT_SYMBOL_GPL(cpufreq_driver_target);
 
@@ -2611,7 +2559,8 @@ EXPORT_SYMBOL_GPL(cpufreq_unregister_governor);
  */
 int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu)
 {
-	struct cpufreq_policy *cpu_policy;
+	struct cpufreq_policy *cpu_policy __free(put_cpufreq_policy);
+
 	if (!policy)
 		return -EINVAL;
 
@@ -2621,7 +2570,6 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu)
 
 	memcpy(policy, cpu_policy, sizeof(*policy));
 
-	cpufreq_cpu_put(cpu_policy);
 	return 0;
 }
 EXPORT_SYMBOL(cpufreq_get_policy);
@@ -2769,6 +2717,21 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
 	return ret;
 }
 
+static void cpufreq_policy_refresh(struct cpufreq_policy *policy)
+{
+	guard(cpufreq_policy_write)(policy);
+
+	/*
+	 * BIOS might change freq behind our back
+	 * -> ask driver for current freq and notify governors about a change
+	 */
+	if (cpufreq_driver->get && has_target() &&
+	    (cpufreq_suspended || WARN_ON(!cpufreq_verify_current_freq(policy, false))))
+		return;
+
+	refresh_frequency_limits(policy);
+}
+
 /**
  * cpufreq_update_policy - Re-evaluate an existing cpufreq policy.
  * @cpu: CPU to re-evaluate the policy for.
@@ -2780,23 +2743,13 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
  */
 void cpufreq_update_policy(unsigned int cpu)
 {
-	struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpu);
+	struct cpufreq_policy *policy __free(put_cpufreq_policy);
 
+	policy = cpufreq_cpu_get(cpu);
 	if (!policy)
 		return;
 
-	/*
-	 * BIOS might change freq behind our back
-	 * -> ask driver for current freq and notify governors about a change
-	 */
-	if (cpufreq_driver->get && has_target() &&
-	    (cpufreq_suspended || WARN_ON(!cpufreq_verify_current_freq(policy, false))))
-		goto unlock;
-
-	refresh_frequency_limits(policy);
-
-unlock:
-	cpufreq_cpu_release(policy);
+	cpufreq_policy_refresh(policy);
 }
 EXPORT_SYMBOL(cpufreq_update_policy);
 
@@ -2805,7 +2758,7 @@ EXPORT_SYMBOL(cpufreq_update_policy);
  * @cpu: CPU to update the policy limits for.
  *
  * Invoke the driver's ->update_limits callback if present or call
- * cpufreq_update_policy() for @cpu.
+ * cpufreq_policy_refresh() for @cpu.
  */
 void cpufreq_update_limits(unsigned int cpu)
 {
@@ -2816,9 +2769,9 @@ void cpufreq_update_limits(unsigned int cpu)
 		return;
 
 	if (cpufreq_driver->update_limits)
-		cpufreq_driver->update_limits(cpu);
+		cpufreq_driver->update_limits(policy);
 	else
-		cpufreq_update_policy(cpu);
+		cpufreq_policy_refresh(policy);
 }
 EXPORT_SYMBOL_GPL(cpufreq_update_limits);
 
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 4aad79d26c64..f5ca04b98b92 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1353,9 +1353,11 @@ static void intel_pstate_update_policies(void)
 		cpufreq_update_policy(cpu);
 }
 
-static void __intel_pstate_update_max_freq(struct cpudata *cpudata,
-					   struct cpufreq_policy *policy)
+static void __intel_pstate_update_max_freq(struct cpufreq_policy *policy,
+					   struct cpudata *cpudata)
 {
+	guard(cpufreq_policy_write)(policy);
+
 	if (hwp_active)
 		intel_pstate_get_hwp_cap(cpudata);
 
@@ -1365,42 +1367,34 @@ static void __intel_pstate_update_max_freq(struct cpudata *cpudata,
 	refresh_frequency_limits(policy);
 }
 
-static void intel_pstate_update_limits(unsigned int cpu)
+static bool intel_pstate_update_max_freq(struct cpudata *cpudata)
 {
-	struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpu);
-	struct cpudata *cpudata;
+	struct cpufreq_policy *policy __free(put_cpufreq_policy);
 
+	policy = cpufreq_cpu_get(cpudata->cpu);
 	if (!policy)
-		return;
+		return false;
 
-	cpudata = all_cpu_data[cpu];
+	__intel_pstate_update_max_freq(policy, cpudata);
 
-	__intel_pstate_update_max_freq(cpudata, policy);
+	return true;
+}
 
-	/* Prevent the driver from being unregistered now. */
-	mutex_lock(&intel_pstate_driver_lock);
+static void intel_pstate_update_limits(struct cpufreq_policy *policy)
+{
+	struct cpudata *cpudata = all_cpu_data[policy->cpu];
 
-	cpufreq_cpu_release(policy);
+	__intel_pstate_update_max_freq(policy, cpudata);
 
 	hybrid_update_capacity(cpudata);
-
-	mutex_unlock(&intel_pstate_driver_lock);
 }
 
 static void intel_pstate_update_limits_for_all(void)
 {
 	int cpu;
 
-	for_each_possible_cpu(cpu) {
-		struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpu);
-
-		if (!policy)
-			continue;
-
-		__intel_pstate_update_max_freq(all_cpu_data[cpu], policy);
-
-		cpufreq_cpu_release(policy);
-	}
+	for_each_possible_cpu(cpu)
+		intel_pstate_update_max_freq(all_cpu_data[cpu]);
 
 	mutex_lock(&hybrid_capacity_lock);
 
@@ -1840,13 +1834,8 @@ static void intel_pstate_notify_work(struct work_struct *work)
 {
 	struct cpudata *cpudata =
 		container_of(to_delayed_work(work), struct cpudata, hwp_notify_work);
-	struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpudata->cpu);
-
-	if (policy) {
-		__intel_pstate_update_max_freq(cpudata, policy);
-
-		cpufreq_cpu_release(policy);
 
+	if (intel_pstate_update_max_freq(cpudata)) {
 		/*
 		 * The driver will not be unregistered while this function is
 		 * running, so update the capacity without acquiring the driver
diff --git a/drivers/cpufreq/rcpufreq_dt.rs b/drivers/cpufreq/rcpufreq_dt.rs
new file mode 100644
index 000000000000..94ed81644fe1
--- /dev/null
+++ b/drivers/cpufreq/rcpufreq_dt.rs
@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust based implementation of the cpufreq-dt driver.
+
+use kernel::{
+    c_str,
+    clk::Clk,
+    cpu, cpufreq,
+    cpumask::CpumaskVar,
+    device::{Core, Device},
+    error::code::*,
+    fmt,
+    macros::vtable,
+    module_platform_driver, of, opp, platform,
+    prelude::*,
+    str::CString,
+    sync::Arc,
+};
+
+/// Finds exact supply name from the OF node.
+fn find_supply_name_exact(dev: &Device, name: &str) -> Option<CString> {
+    let prop_name = CString::try_from_fmt(fmt!("{}-supply", name)).ok()?;
+    dev.property_present(&prop_name)
+        .then(|| CString::try_from_fmt(fmt!("{name}")).ok())
+        .flatten()
+}
+
+/// Finds supply name for the CPU from DT.
+fn find_supply_names(dev: &Device, cpu: u32) -> Option<KVec<CString>> {
+    // Try "cpu0" for older DTs, fallback to "cpu".
+    let name = (cpu == 0)
+        .then(|| find_supply_name_exact(dev, "cpu0"))
+        .flatten()
+        .or_else(|| find_supply_name_exact(dev, "cpu"))?;
+
+    let mut list = KVec::with_capacity(1, GFP_KERNEL).ok()?;
+    list.push(name, GFP_KERNEL).ok()?;
+
+    Some(list)
+}
+
+/// Represents the cpufreq dt device.
+struct CPUFreqDTDevice {
+    opp_table: opp::Table,
+    freq_table: opp::FreqTable,
+    _mask: CpumaskVar,
+    _token: Option<opp::ConfigToken>,
+    _clk: Clk,
+}
+
+#[derive(Default)]
+struct CPUFreqDTDriver;
+
+#[vtable]
+impl opp::ConfigOps for CPUFreqDTDriver {}
+
+#[vtable]
+impl cpufreq::Driver for CPUFreqDTDriver {
+    const NAME: &'static CStr = c_str!("cpufreq-dt");
+    const FLAGS: u16 = cpufreq::flags::NEED_INITIAL_FREQ_CHECK | cpufreq::flags::IS_COOLING_DEV;
+    const BOOST_ENABLED: bool = true;
+
+    type PData = Arc<CPUFreqDTDevice>;
+
+    fn init(policy: &mut cpufreq::Policy) -> Result<Self::PData> {
+        let cpu = policy.cpu();
+        // SAFETY: The CPU device is only used during init; it won't get hot-unplugged. The cpufreq
+        // core  registers with CPU notifiers and the cpufreq core/driver won't use the CPU device,
+        // once the CPU is hot-unplugged.
+        let dev = unsafe { cpu::from_cpu(cpu)? };
+        let mut mask = CpumaskVar::new_zero(GFP_KERNEL)?;
+
+        mask.set(cpu);
+
+        let token = find_supply_names(dev, cpu)
+            .map(|names| {
+                opp::Config::<Self>::new()
+                    .set_regulator_names(names)?
+                    .set(dev)
+            })
+            .transpose()?;
+
+        // Get OPP-sharing information from "operating-points-v2" bindings.
+        let fallback = match opp::Table::of_sharing_cpus(dev, &mut mask) {
+            Ok(()) => false,
+            Err(e) if e == ENOENT => {
+                // "operating-points-v2" not supported. If the platform hasn't
+                // set sharing CPUs, fallback to all CPUs share the `Policy`
+                // for backward compatibility.
+                opp::Table::sharing_cpus(dev, &mut mask).is_err()
+            }
+            Err(e) => return Err(e),
+        };
+
+        // Initialize OPP tables for all policy cpus.
+        //
+        // For platforms not using "operating-points-v2" bindings, we do this
+        // before updating policy cpus. Otherwise, we will end up creating
+        // duplicate OPPs for the CPUs.
+        //
+        // OPPs might be populated at runtime, don't fail for error here unless
+        // it is -EPROBE_DEFER.
+        let mut opp_table = match opp::Table::from_of_cpumask(dev, &mut mask) {
+            Ok(table) => table,
+            Err(e) => {
+                if e == EPROBE_DEFER {
+                    return Err(e);
+                }
+
+                // The table is added dynamically ?
+                opp::Table::from_dev(dev)?
+            }
+        };
+
+        // The OPP table must be initialized, statically or dynamically, by this point.
+        opp_table.opp_count()?;
+
+        // Set sharing cpus for fallback scenario.
+        if fallback {
+            mask.setall();
+            opp_table.set_sharing_cpus(&mut mask)?;
+        }
+
+        let mut transition_latency = opp_table.max_transition_latency_ns() as u32;
+        if transition_latency == 0 {
+            transition_latency = cpufreq::ETERNAL_LATENCY_NS;
+        }
+
+        policy
+            .set_dvfs_possible_from_any_cpu(true)
+            .set_suspend_freq(opp_table.suspend_freq())
+            .set_transition_latency_ns(transition_latency);
+
+        let freq_table = opp_table.cpufreq_table()?;
+        // SAFETY: The `freq_table` is not dropped while it is getting used by the C code.
+        unsafe { policy.set_freq_table(&freq_table) };
+
+        // SAFETY: The returned `clk` is not dropped while it is getting used by the C code.
+        let clk = unsafe { policy.set_clk(dev, None)? };
+
+        mask.copy(policy.cpus());
+
+        Ok(Arc::new(
+            CPUFreqDTDevice {
+                opp_table,
+                freq_table,
+                _mask: mask,
+                _token: token,
+                _clk: clk,
+            },
+            GFP_KERNEL,
+        )?)
+    }
+
+    fn exit(_policy: &mut cpufreq::Policy, _data: Option<Self::PData>) -> Result {
+        Ok(())
+    }
+
+    fn online(_policy: &mut cpufreq::Policy) -> Result {
+        // We did light-weight tear down earlier, nothing to do here.
+        Ok(())
+    }
+
+    fn offline(_policy: &mut cpufreq::Policy) -> Result {
+        // Preserve policy->data and don't free resources on light-weight
+        // tear down.
+        Ok(())
+    }
+
+    fn suspend(policy: &mut cpufreq::Policy) -> Result {
+        policy.generic_suspend()
+    }
+
+    fn verify(data: &mut cpufreq::PolicyData) -> Result {
+        data.generic_verify()
+    }
+
+    fn target_index(policy: &mut cpufreq::Policy, index: cpufreq::TableIndex) -> Result {
+        let Some(data) = policy.data::<Self::PData>() else {
+            return Err(ENOENT);
+        };
+
+        let freq = data.freq_table.freq(index)?;
+        data.opp_table.set_rate(freq)
+    }
+
+    fn get(policy: &mut cpufreq::Policy) -> Result<u32> {
+        policy.generic_get()
+    }
+
+    fn set_boost(_policy: &mut cpufreq::Policy, _state: i32) -> Result {
+        Ok(())
+    }
+
+    fn register_em(policy: &mut cpufreq::Policy) {
+        policy.register_em_opp()
+    }
+}
+
+kernel::of_device_table!(
+    OF_TABLE,
+    MODULE_OF_TABLE,
+    <CPUFreqDTDriver as platform::Driver>::IdInfo,
+    [(of::DeviceId::new(c_str!("operating-points-v2")), ())]
+);
+
+impl platform::Driver for CPUFreqDTDriver {
+    type IdInfo = ();
+    const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
+
+    fn probe(
+        pdev: &platform::Device<Core>,
+        _id_info: Option<&Self::IdInfo>,
+    ) -> Result<Pin<KBox<Self>>> {
+        cpufreq::Registration::<CPUFreqDTDriver>::new_foreign_owned(pdev.as_ref())?;
+        Ok(KBox::new(Self {}, GFP_KERNEL)?.into())
+    }
+}
+
+module_platform_driver! {
+    type: CPUFreqDTDriver,
+    name: "cpufreq-dt",
+    author: "Viresh Kumar <viresh.kumar@linaro.org>",
+    description: "Generic CPUFreq DT driver",
+    license: "GPL v2",
+}