Merge branches 'pm-cpuidle', 'pm-core' and 'pm-sleep'

Merge cpuidle updates, PM core updates and changes related to system
sleep handling for 6.3-rc1:

 - Make the TEO cpuidle governor check CPU utilization in order to refine
   idle state selection (Kajetan Puchalski).

 - Make Kconfig select the haltpoll cpuidle governor when the haltpoll
   cpuidle driver is selected and replace a default_idle() call in that
   driver with arch_cpu_idle() which allows MWAIT to be used (Li
   RongQing).

 - Add Emerald Rapids Xeon support to the intel_idle driver (Artem
   Bityutskiy).

 - Add ARCH_SUSPEND_POSSIBLE dependencies for ARMv4 cpuidle drivers to
   avoid randconfig build failures (Arnd Bergmann).

 - Make kobj_type structures used in the cpuidle sysfs interface
   constant (Thomas Weißschuh).

 - Make the cpuidle driver registration code update microsecond values
   of idle state parameters in accordance with their nanosecond values
   if they are provided (Rafael Wysocki).

 - Make the PSCI cpuidle driver prevent topology CPUs from being
   suspended on PREEMPT_RT (Krzysztof Kozlowski).

 - Document that pm_runtime_force_suspend() cannot be used with
   DPM_FLAG_SMART_SUSPEND (Richard Fitzgerald).

 - Add EXPORT macros for exporting PM functions from drivers (Richard
   Fitzgerald).

 - Drop "select SRCU" from system sleep Kconfig (Paul E. McKenney).

 - Remove /** from non-kernel-doc comments in hibernation code (Randy
   Dunlap).

* pm-cpuidle:
  cpuidle: psci: Do not suspend topology CPUs on PREEMPT_RT
  cpuidle: driver: Update microsecond values of state parameters as needed
  cpuidle: sysfs: make kobj_type structures constant
  cpuidle: add ARCH_SUSPEND_POSSIBLE dependencies
  intel_idle: add Emerald Rapids Xeon support
  cpuidle-haltpoll: Replace default_idle() with arch_cpu_idle()
  cpuidle-haltpoll: select haltpoll governor
  cpuidle: teo: Introduce util-awareness
  cpuidle: teo: Optionally skip polling states in teo_find_shallower_state()

* pm-core:
  PM: Add EXPORT macros for exporting PM functions
  PM: runtime: Document that force_suspend() is incompatible with SMART_SUSPEND

* pm-sleep:
  PM: sleep: Remove "select SRCU"
  PM: hibernate: swap: don't use /** for non-kernel-doc comments

Author: rafaeljw

arch/x86/kernel/process.c

@@ -721,6 +721,7 @@ void arch_cpu_idle(void)
 {
 	x86_idle();
 }
+EXPORT_SYMBOL_GPL(arch_cpu_idle);
 
 /*
  * We use this if we don't have any better idle routine..

drivers/base/power/runtime.c

@@ -1864,6 +1864,10 @@ static bool pm_runtime_need_not_resume(struct device *dev)
  * sure the device is put into low power state and it should only be used during
  * system-wide PM transitions to sleep states.  It assumes that the analogous
  * pm_runtime_force_resume() will be used to resume the device.
+ *
+ * Do not use with DPM_FLAG_SMART_SUSPEND as this can lead to an inconsistent
+ * state where this function has called the ->runtime_suspend callback but the
+ * PM core marks the driver as runtime active.
  */
 int pm_runtime_force_suspend(struct device *dev)
 {

drivers/cpuidle/Kconfig

@@ -74,6 +74,7 @@ endmenu
 config HALTPOLL_CPUIDLE
 	tristate "Halt poll cpuidle driver"
 	depends on X86 && KVM_GUEST
+	select CPU_IDLE_GOV_HALTPOLL
 	default y
 	help
 	 This option enables halt poll cpuidle driver, which allows to poll

drivers/cpuidle/Kconfig.arm

@@ -24,6 +24,14 @@ config ARM_PSCI_CPUIDLE
 	  It provides an idle driver that is capable of detecting and
 	  managing idle states through the PSCI firmware interface.
 
+	  The driver has limitations when used with PREEMPT_RT:
+	  - If the idle states are described with the non-hierarchical layout,
+	    all idle states are still available.
+
+	  - If the idle states are described with the hierarchical layout,
+	    only the idle states defined per CPU are available, but not the ones
+	    being shared among a group of CPUs (aka cluster idle states).
+
 config ARM_PSCI_CPUIDLE_DOMAIN
 	bool "PSCI CPU idle Domain"
 	depends on ARM_PSCI_CPUIDLE
@@ -102,6 +110,7 @@ config ARM_MVEBU_V7_CPUIDLE
 config ARM_TEGRA_CPUIDLE
 	bool "CPU Idle Driver for NVIDIA Tegra SoCs"
 	depends on (ARCH_TEGRA || COMPILE_TEST) && !ARM64 && MMU
+	depends on ARCH_SUSPEND_POSSIBLE
 	select ARCH_NEEDS_CPU_IDLE_COUPLED if SMP
 	select ARM_CPU_SUSPEND
 	help
@@ -110,6 +119,7 @@ config ARM_TEGRA_CPUIDLE
 config ARM_QCOM_SPM_CPUIDLE
 	bool "CPU Idle Driver for Qualcomm Subsystem Power Manager (SPM)"
 	depends on (ARCH_QCOM || COMPILE_TEST) && !ARM64 && MMU
+	depends on ARCH_SUSPEND_POSSIBLE
 	select ARM_CPU_SUSPEND
 	select CPU_IDLE_MULTIPLE_DRIVERS
 	select DT_IDLE_STATES

drivers/cpuidle/cpuidle-haltpoll.c

@@ -32,7 +32,7 @@ static int default_enter_idle(struct cpuidle_device *dev,
 		local_irq_enable();
 		return index;
 	}
-	default_idle();
+	arch_cpu_idle();
 	return index;
 }
 

drivers/cpuidle/cpuidle-psci-domain.c

@@ -64,8 +64,11 @@ static int psci_pd_init(struct device_node *np, bool use_osi)
 
 	pd->flags |= GENPD_FLAG_IRQ_SAFE | GENPD_FLAG_CPU_DOMAIN;
 
-	/* Allow power off when OSI has been successfully enabled. */
-	if (use_osi)
+	/*
+	 * Allow power off when OSI has been successfully enabled.
+	 * PREEMPT_RT is not yet ready to enter domain idle states.
+	 */
+	if (use_osi && !IS_ENABLED(CONFIG_PREEMPT_RT))
 		pd->power_off = psci_pd_power_off;
 	else
 		pd->flags |= GENPD_FLAG_ALWAYS_ON;

drivers/cpuidle/cpuidle-psci.c

@@ -231,6 +231,9 @@ static int psci_dt_cpu_init_topology(struct cpuidle_driver *drv,
 	if (!psci_has_osi_support())
 		return 0;
 
+	if (IS_ENABLED(CONFIG_PREEMPT_RT))
+		return 0;
+
 	data->dev = psci_dt_attach_cpu(cpu);
 	if (IS_ERR_OR_NULL(data->dev))
 		return PTR_ERR_OR_ZERO(data->dev);

drivers/cpuidle/driver.c

@@ -183,11 +183,15 @@ static void __cpuidle_driver_init(struct cpuidle_driver *drv)
 			s->target_residency_ns = s->target_residency * NSEC_PER_USEC;
 		else if (s->target_residency_ns < 0)
 			s->target_residency_ns = 0;
+		else
+			s->target_residency = div_u64(s->target_residency_ns, NSEC_PER_USEC);
 
 		if (s->exit_latency > 0)
 			s->exit_latency_ns = s->exit_latency * NSEC_PER_USEC;
 		else if (s->exit_latency_ns < 0)
 			s->exit_latency_ns =  0;
+		else
+			s->exit_latency = div_u64(s->exit_latency_ns, NSEC_PER_USEC);
 	}
 }
 

drivers/cpuidle/governors/teo.c

@@ -2,8 +2,13 @@
 /*
  * Timer events oriented CPU idle governor
  *
+ * TEO governor:
  * Copyright (C) 2018 - 2021 Intel Corporation
  * Author: Rafael J. Wysocki <[email protected]>
+ *
+ * Util-awareness mechanism:
+ * Copyright (C) 2022 Arm Ltd.
+ * Author: Kajetan Puchalski <[email protected]>
  */
 
 /**
@@ -99,14 +104,55 @@
  *      select the given idle state instead of the candidate one.
  *
  * 3. By default, select the candidate state.
+ *
+ * Util-awareness mechanism:
+ *
+ * The idea behind the util-awareness extension is that there are two distinct
+ * scenarios for the CPU which should result in two different approaches to idle
+ * state selection - utilized and not utilized.
+ *
+ * In this case, 'utilized' means that the average runqueue util of the CPU is
+ * above a certain threshold.
+ *
+ * When the CPU is utilized while going into idle, more likely than not it will
+ * be woken up to do more work soon and so a shallower idle state should be
+ * selected to minimise latency and maximise performance. When the CPU is not
+ * being utilized, the usual metrics-based approach to selecting the deepest
+ * available idle state should be preferred to take advantage of the power
+ * saving.
+ *
+ * In order to achieve this, the governor uses a utilization threshold.
+ * The threshold is computed per-CPU as a percentage of the CPU's capacity
+ * by bit shifting the capacity value. Based on testing, the shift of 6 (~1.56%)
+ * seems to be getting the best results.
+ *
+ * Before selecting the next idle state, the governor compares the current CPU
+ * util to the precomputed util threshold. If it's below, it defaults to the
+ * TEO metrics mechanism. If it's above, the closest shallower idle state will
+ * be selected instead, as long as is not a polling state.
  */
 
 #include <linux/cpuidle.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
+#include <linux/sched.h>
 #include <linux/sched/clock.h>
+#include <linux/sched/topology.h>
 #include <linux/tick.h>
 
+/*
+ * The number of bits to shift the CPU's capacity by in order to determine
+ * the utilized threshold.
+ *
+ * 6 was chosen based on testing as the number that achieved the best balance
+ * of power and performance on average.
+ *
+ * The resulting threshold is high enough to not be triggered by background
+ * noise and low enough to react quickly when activity starts to ramp up.
+ */
+#define UTIL_THRESHOLD_SHIFT 6
+
+
 /*
  * The PULSE value is added to metrics when they grow and the DECAY_SHIFT value
  * is used for decreasing metrics on a regular basis.
@@ -137,9 +183,11 @@ struct teo_bin {
  * @time_span_ns: Time between idle state selection and post-wakeup update.
  * @sleep_length_ns: Time till the closest timer event (at the selection time).
  * @state_bins: Idle state data bins for this CPU.
- * @total: Grand total of the "intercepts" and "hits" mertics for all bins.
+ * @total: Grand total of the "intercepts" and "hits" metrics for all bins.
  * @next_recent_idx: Index of the next @recent_idx entry to update.
  * @recent_idx: Indices of bins corresponding to recent "intercepts".
+ * @util_threshold: Threshold above which the CPU is considered utilized
+ * @utilized: Whether the last sleep on the CPU happened while utilized
  */
 struct teo_cpu {
 	s64 time_span_ns;
@@ -148,10 +196,29 @@ struct teo_cpu {
 	unsigned int total;
 	int next_recent_idx;
 	int recent_idx[NR_RECENT];
+	unsigned long util_threshold;
+	bool utilized;
 };
 
 static DEFINE_PER_CPU(struct teo_cpu, teo_cpus);
 
+/**
+ * teo_cpu_is_utilized - Check if the CPU's util is above the threshold
+ * @cpu: Target CPU
+ * @cpu_data: Governor CPU data for the target CPU
+ */
+#ifdef CONFIG_SMP
+static bool teo_cpu_is_utilized(int cpu, struct teo_cpu *cpu_data)
+{
+	return sched_cpu_util(cpu) > cpu_data->util_threshold;
+}
+#else
+static bool teo_cpu_is_utilized(int cpu, struct teo_cpu *cpu_data)
+{
+	return false;
+}
+#endif
+
 /**
  * teo_update - Update CPU metrics after wakeup.
  * @drv: cpuidle driver containing state data.
@@ -258,15 +325,17 @@ static s64 teo_middle_of_bin(int idx, struct cpuidle_driver *drv)
  * @dev: Target CPU.
  * @state_idx: Index of the capping idle state.
  * @duration_ns: Idle duration value to match.
+ * @no_poll: Don't consider polling states.
  */
 static int teo_find_shallower_state(struct cpuidle_driver *drv,
 				    struct cpuidle_device *dev, int state_idx,
-				    s64 duration_ns)
+				    s64 duration_ns, bool no_poll)
 {
 	int i;
 
 	for (i = state_idx - 1; i >= 0; i--) {
-		if (dev->states_usage[i].disable)
+		if (dev->states_usage[i].disable ||
+				(no_poll && drv->states[i].flags & CPUIDLE_FLAG_POLLING))
 			continue;
 
 		state_idx = i;
@@ -321,6 +390,22 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 			goto end;
 	}
 
+	cpu_data->utilized = teo_cpu_is_utilized(dev->cpu, cpu_data);
+	/*
+	 * If the CPU is being utilized over the threshold and there are only 2
+	 * states to choose from, the metrics need not be considered, so choose
+	 * the shallowest non-polling state and exit.
+	 */
+	if (drv->state_count < 3 && cpu_data->utilized) {
+		for (i = 0; i < drv->state_count; ++i) {
+			if (!dev->states_usage[i].disable &&
+			    !(drv->states[i].flags & CPUIDLE_FLAG_POLLING)) {
+				idx = i;
+				goto end;
+			}
+		}
+	}
+
 	/*
 	 * Find the deepest idle state whose target residency does not exceed
 	 * the current sleep length and the deepest idle state not deeper than
@@ -452,6 +537,13 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 	if (idx > constraint_idx)
 		idx = constraint_idx;
 
+	/*
+	 * If the CPU is being utilized over the threshold, choose a shallower
+	 * non-polling state to improve latency
+	 */
+	if (cpu_data->utilized)
+		idx = teo_find_shallower_state(drv, dev, idx, duration_ns, true);
+
 end:
 	/*
 	 * Don't stop the tick if the selected state is a polling one or if the
@@ -469,7 +561,7 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 		 */
 		if (idx > idx0 &&
 		    drv->states[idx].target_residency_ns > delta_tick)
-			idx = teo_find_shallower_state(drv, dev, idx, delta_tick);
+			idx = teo_find_shallower_state(drv, dev, idx, delta_tick, false);
 	}
 
 	return idx;
@@ -508,9 +600,11 @@ static int teo_enable_device(struct cpuidle_driver *drv,
 			     struct cpuidle_device *dev)
 {
 	struct teo_cpu *cpu_data = per_cpu_ptr(&teo_cpus, dev->cpu);
+	unsigned long max_capacity = arch_scale_cpu_capacity(dev->cpu);
 	int i;
 
 	memset(cpu_data, 0, sizeof(*cpu_data));
+	cpu_data->util_threshold = max_capacity >> UTIL_THRESHOLD_SHIFT;
 
 	for (i = 0; i < NR_RECENT; i++)
 		cpu_data->recent_idx[i] = -1;

drivers/cpuidle/sysfs.c

@@ -200,7 +200,7 @@ static void cpuidle_sysfs_release(struct kobject *kobj)
 	complete(&kdev->kobj_unregister);
 }
 
-static struct kobj_type ktype_cpuidle = {
+static const struct kobj_type ktype_cpuidle = {
 	.sysfs_ops = &cpuidle_sysfs_ops,
 	.release = cpuidle_sysfs_release,
 };
@@ -447,7 +447,7 @@ static void cpuidle_state_sysfs_release(struct kobject *kobj)
 	complete(&state_obj->kobj_unregister);
 }
 
-static struct kobj_type ktype_state_cpuidle = {
+static const struct kobj_type ktype_state_cpuidle = {
 	.sysfs_ops = &cpuidle_state_sysfs_ops,
 	.default_groups = cpuidle_state_default_groups,
 	.release = cpuidle_state_sysfs_release,
@@ -594,7 +594,7 @@ static struct attribute *cpuidle_driver_default_attrs[] = {
 };
 ATTRIBUTE_GROUPS(cpuidle_driver_default);
 
-static struct kobj_type ktype_driver_cpuidle = {
+static const struct kobj_type ktype_driver_cpuidle = {
 	.sysfs_ops = &cpuidle_driver_sysfs_ops,
 	.default_groups = cpuidle_driver_default_groups,
 	.release = cpuidle_driver_sysfs_release,