[PATCH 0/3] PM / Domains: Add power on/off notifiers for genpd

[PATCH 0/3] PM / Domains: Add power on/off notifiers for genpd

[Ulf Hansson]

A device may have specific HW constraints that must be obeyed to, before its
corresponding PM domain (genpd) can be powered off - and vice verse at power
on. These constraints can't be managed through the regular runtime PM based
deployment for a device, because the access pattern for it, isn't always
request based. In other words, using the runtime PM callbacks to deal with the
constraints doesn't work for these cases.

For these reasons, this series introduces a power on/off notification mechanism
to genpd. To add/remove a notifier for a device, the device must already have
been attached to the genpd, which also means that it needs to be a part of the
PM domain topology.

The intent is to allow these genpd power on/off notifiers to replace the need
for the existing CPU_CLUSTER_PM_ENTER|EXIT notifiers. For example, those would
otherwise be needed in psci_pd_power_off() in cpuidle-psci-domain.c, when
powering off the CPU cluster.

Another series that enables drivers/soc/qcom/rpmh-rsc.c to make use of the new
genpd on/off notifiers, are soon to be posted. However, I would appreciate any
feedback on the approach taken, even before that series hits LKML.

Kind regards
Ulf Hansson


Ulf Hansson (3):
  PM / Domains: Rename power state enums for genpd
  PM / Domains: Allow to abort power off when no ->power_off() callback
  PM / Domains: Add support for PM domain on/off notifiers for genpd

 drivers/base/power/domain.c | 178 +++++++++++++++++++++++++++++-------
 include/linux/pm_domain.h   |  19 +++-
 2 files changed, 162 insertions(+), 35 deletions(-)

-- 
2.25.1

[PATCH 1/3] PM / Domains: Rename power state enums for genpd

[Ulf Hansson]

To clarify the code a bit, let's rename GPD_STATE_ACTIVE into
GENPD_STATE_ON and GPD_STATE_POWER_OFF to GENPD_STATE_OFF.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---
 drivers/base/power/domain.c | 32 ++++++++++++++++----------------
 include/linux/pm_domain.h   |  4 ++--
 2 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 2cb5e04cf86c..2ea99032b658 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -123,7 +123,7 @@ static const struct genpd_lock_ops genpd_spin_ops = {
 #define genpd_lock_interruptible(p)	p->lock_ops->lock_interruptible(p)
 #define genpd_unlock(p)			p->lock_ops->unlock(p)
 
-#define genpd_status_on(genpd)		(genpd->status == GPD_STATE_ACTIVE)
+#define genpd_status_on(genpd)		(genpd->status == GENPD_STATE_ON)
 #define genpd_is_irq_safe(genpd)	(genpd->flags & GENPD_FLAG_IRQ_SAFE)
 #define genpd_is_always_on(genpd)	(genpd->flags & GENPD_FLAG_ALWAYS_ON)
 #define genpd_is_active_wakeup(genpd)	(genpd->flags & GENPD_FLAG_ACTIVE_WAKEUP)
@@ -222,7 +222,7 @@ static void genpd_update_accounting(struct generic_pm_domain *genpd)
 	 * out of off and so update the idle time and vice
 	 * versa.
 	 */
-	if (genpd->status == GPD_STATE_ACTIVE) {
+	if (genpd->status == GENPD_STATE_ON) {
 		int state_idx = genpd->state_idx;
 
 		genpd->states[state_idx].idle_time =
@@ -563,7 +563,7 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
 			return ret;
 	}
 
-	genpd->status = GPD_STATE_POWER_OFF;
+	genpd->status = GENPD_STATE_OFF;
 	genpd_update_accounting(genpd);
 
 	list_for_each_entry(link, &genpd->child_links, child_node) {
@@ -616,7 +616,7 @@ static int genpd_power_on(struct generic_pm_domain *genpd, unsigned int depth)
 	if (ret)
 		goto err;
 
-	genpd->status = GPD_STATE_ACTIVE;
+	genpd->status = GENPD_STATE_ON;
 	genpd_update_accounting(genpd);
 
 	return 0;
@@ -961,7 +961,7 @@ static void genpd_sync_power_off(struct generic_pm_domain *genpd, bool use_lock,
 	if (_genpd_power_off(genpd, false))
 		return;
 
-	genpd->status = GPD_STATE_POWER_OFF;
+	genpd->status = GENPD_STATE_OFF;
 
 	list_for_each_entry(link, &genpd->child_links, child_node) {
 		genpd_sd_counter_dec(link->parent);
@@ -1008,7 +1008,7 @@ static void genpd_sync_power_on(struct generic_pm_domain *genpd, bool use_lock,
 
 	_genpd_power_on(genpd, false);
 
-	genpd->status = GPD_STATE_ACTIVE;
+	genpd->status = GENPD_STATE_ON;
 }
 
 /**
@@ -1287,7 +1287,7 @@ static int genpd_restore_noirq(struct device *dev)
 		 * so make it appear as powered off to genpd_sync_power_on(),
 		 * so that it tries to power it on in case it was really off.
 		 */
-		genpd->status = GPD_STATE_POWER_OFF;
+		genpd->status = GENPD_STATE_OFF;
 
 	genpd_sync_power_on(genpd, true, 0);
 	genpd_unlock(genpd);
@@ -1777,7 +1777,7 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
 	genpd->gov = gov;
 	INIT_WORK(&genpd->power_off_work, genpd_power_off_work_fn);
 	atomic_set(&genpd->sd_count, 0);
-	genpd->status = is_off ? GPD_STATE_POWER_OFF : GPD_STATE_ACTIVE;
+	genpd->status = is_off ? GENPD_STATE_OFF : GENPD_STATE_ON;
 	genpd->device_count = 0;
 	genpd->max_off_time_ns = -1;
 	genpd->max_off_time_changed = true;
@@ -2802,8 +2802,8 @@ static int genpd_summary_one(struct seq_file *s,
 			struct generic_pm_domain *genpd)
 {
 	static const char * const status_lookup[] = {
-		[GPD_STATE_ACTIVE] = "on",
-		[GPD_STATE_POWER_OFF] = "off"
+		[GENPD_STATE_ON] = "on",
+		[GENPD_STATE_OFF] = "off"
 	};
 	struct pm_domain_data *pm_data;
 	const char *kobj_path;
@@ -2881,8 +2881,8 @@ static int summary_show(struct seq_file *s, void *data)
 static int status_show(struct seq_file *s, void *data)
 {
 	static const char * const status_lookup[] = {
-		[GPD_STATE_ACTIVE] = "on",
-		[GPD_STATE_POWER_OFF] = "off"
+		[GENPD_STATE_ON] = "on",
+		[GENPD_STATE_OFF] = "off"
 	};
 
 	struct generic_pm_domain *genpd = s->private;
@@ -2895,7 +2895,7 @@ static int status_show(struct seq_file *s, void *data)
 	if (WARN_ON_ONCE(genpd->status >= ARRAY_SIZE(status_lookup)))
 		goto exit;
 
-	if (genpd->status == GPD_STATE_POWER_OFF)
+	if (genpd->status == GENPD_STATE_OFF)
 		seq_printf(s, "%s-%u\n", status_lookup[genpd->status],
 			genpd->state_idx);
 	else
@@ -2938,7 +2938,7 @@ static int idle_states_show(struct seq_file *s, void *data)
 		ktime_t delta = 0;
 		s64 msecs;
 
-		if ((genpd->status == GPD_STATE_POWER_OFF) &&
+		if ((genpd->status == GENPD_STATE_OFF) &&
 				(genpd->state_idx == i))
 			delta = ktime_sub(ktime_get(), genpd->accounting_time);
 
@@ -2961,7 +2961,7 @@ static int active_time_show(struct seq_file *s, void *data)
 	if (ret)
 		return -ERESTARTSYS;
 
-	if (genpd->status == GPD_STATE_ACTIVE)
+	if (genpd->status == GENPD_STATE_ON)
 		delta = ktime_sub(ktime_get(), genpd->accounting_time);
 
 	seq_printf(s, "%lld ms\n", ktime_to_ms(
@@ -2984,7 +2984,7 @@ static int total_idle_time_show(struct seq_file *s, void *data)
 
 	for (i = 0; i < genpd->state_count; i++) {
 
-		if ((genpd->status == GPD_STATE_POWER_OFF) &&
+		if ((genpd->status == GENPD_STATE_OFF) &&
 				(genpd->state_idx == i))
 			delta = ktime_sub(ktime_get(), genpd->accounting_time);
 
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index ee11502a575b..66f3c5d64d81 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -64,8 +64,8 @@
 #define GENPD_FLAG_RPM_ALWAYS_ON (1U << 5)
 
 enum gpd_status {
-	GPD_STATE_ACTIVE = 0,	/* PM domain is active */
-	GPD_STATE_POWER_OFF,	/* PM domain is off */
+	GENPD_STATE_ON = 0,	/* PM domain is on */
+	GENPD_STATE_OFF,	/* PM domain is off */
 };
 
 struct dev_power_governor {
-- 
2.25.1

[PATCH 2/3] PM / Domains: Allow to abort power off when no ->power_off() callback

[Ulf Hansson]

In genpd_power_off() we may decide to abort the power off of the PM domain,
even beyond the point when the governor would accept it. The abort is done
if it turns out that a child domain has been requested to be powered on,
which means it's waiting for the lock of the parent to be released.

However, the abort is currently only considered if the genpd in question
has a ->power_off() callback assigned. This is unnecessary limiting,
especially if the genpd would have a parent of its own. Let's remove the
limitation and make the behaviour consistent.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---
 drivers/base/power/domain.c | 24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 2ea99032b658..4b787e1ff188 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -497,6 +497,7 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
 	struct pm_domain_data *pdd;
 	struct gpd_link *link;
 	unsigned int not_suspended = 0;
+	int ret;
 
 	/*
 	 * Do not try to power off the domain in the following situations:
@@ -544,24 +545,13 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
 	if (!genpd->gov)
 		genpd->state_idx = 0;
 
-	if (genpd->power_off) {
-		int ret;
-
-		if (atomic_read(&genpd->sd_count) > 0)
-			return -EBUSY;
+	/* Don't power off, if a child domain is waiting to power on. */
+	if (atomic_read(&genpd->sd_count) > 0)
+		return -EBUSY;
 
-		/*
-		 * If sd_count > 0 at this point, one of the subdomains hasn't
-		 * managed to call genpd_power_on() for the parent yet after
-		 * incrementing it.  In that case genpd_power_on() will wait
-		 * for us to drop the lock, so we can call .power_off() and let
-		 * the genpd_power_on() restore power for us (this shouldn't
-		 * happen very often).
-		 */
-		ret = _genpd_power_off(genpd, true);
-		if (ret)
-			return ret;
-	}
+	ret = _genpd_power_off(genpd, true);
+	if (ret)
+		return ret;
 
 	genpd->status = GENPD_STATE_OFF;
 	genpd_update_accounting(genpd);
-- 
2.25.1

[PATCH 3/3] PM / Domains: Add support for PM domain on/off notifiers for genpd

[Ulf Hansson]

A device may have specific HW constraints that must be obeyed to, before
its corresponding PM domain (genpd) can be powered off - and vice verse at
power on. These constraints can't be managed through the regular runtime PM
based deployment for a device, because the access pattern for it, isn't
always request based. In other words, using the runtime PM callbacks to
deal with the constraints doesn't work for these cases.

For these reasons, let's instead add a PM domain power on/off notification
mechanism to genpd. To add/remove a notifier for a device, the device must
already have been attached to the genpd, which also means that it needs to
be a part of the PM domain topology.

To add/remove a notifier, let's introduce two genpd specific functions:
 - dev_pm_genpd_add|remove_notifier()

Note that, to further clarify when genpd power on/off notifiers may be
used, one can compare with the existing CPU_CLUSTER_PM_ENTER|EXIT
notifiers. In the long run, the genpd power on/off notifiers should be able
to replace them, but that requires additional genpd based platform support
for the current users.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---
 drivers/base/power/domain.c | 130 ++++++++++++++++++++++++++++++++++--
 include/linux/pm_domain.h   |  15 +++++
 2 files changed, 141 insertions(+), 4 deletions(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 4b787e1ff188..9cb85a5e8342 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -545,13 +545,21 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
 	if (!genpd->gov)
 		genpd->state_idx = 0;
 
+	/* Notify consumers that we are about to power off. */
+	ret = raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_OFF,
+				      NULL);
+	if (ret)
+		return ret;
+
 	/* Don't power off, if a child domain is waiting to power on. */
-	if (atomic_read(&genpd->sd_count) > 0)
-		return -EBUSY;
+	if (atomic_read(&genpd->sd_count) > 0) {
+		ret = -EBUSY;
+		goto busy;
+	}
 
 	ret = _genpd_power_off(genpd, true);
 	if (ret)
-		return ret;
+		goto busy;
 
 	genpd->status = GENPD_STATE_OFF;
 	genpd_update_accounting(genpd);
@@ -564,6 +572,9 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
 	}
 
 	return 0;
+busy:
+	raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL);
+	return ret;
 }
 
 /**
@@ -606,6 +617,9 @@ static int genpd_power_on(struct generic_pm_domain *genpd, unsigned int depth)
 	if (ret)
 		goto err;
 
+	/* Inform consumers that we have powered on. */
+	raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL);
+
 	genpd->status = GENPD_STATE_ON;
 	genpd_update_accounting(genpd);
 
@@ -948,9 +962,18 @@ static void genpd_sync_power_off(struct generic_pm_domain *genpd, bool use_lock,
 
 	/* Choose the deepest state when suspending */
 	genpd->state_idx = genpd->state_count - 1;
-	if (_genpd_power_off(genpd, false))
+
+	/* Notify consumers that we are about to power off. */
+	if (raw_notifier_call_chain(&genpd->power_notifiers,
+				    GENPD_STATE_OFF, NULL))
 		return;
 
+	if (_genpd_power_off(genpd, false)) {
+		raw_notifier_call_chain(&genpd->power_notifiers,
+					GENPD_STATE_ON, NULL);
+		return;
+	}
+
 	genpd->status = GENPD_STATE_OFF;
 
 	list_for_each_entry(link, &genpd->child_links, child_node) {
@@ -998,6 +1021,9 @@ static void genpd_sync_power_on(struct generic_pm_domain *genpd, bool use_lock,
 
 	_genpd_power_on(genpd, false);
 
+	/* Inform consumers that we have powered on. */
+	raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL);
+
 	genpd->status = GENPD_STATE_ON;
 }
 
@@ -1593,6 +1619,101 @@ int pm_genpd_remove_device(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(pm_genpd_remove_device);
 
+/**
+ * dev_pm_genpd_add_notifier - Add a genpd power on/off notifier for @dev
+ *
+ * @dev: Device that should be associated with the notifier
+ * @nb: The notifier block to register
+ *
+ * Users may call this function to add a genpd power on/off notifier for an
+ * attached @dev. Only one notifier per device is allowed. The notifier is
+ * sent when genpd is powering on/off the PM domain.
+ *
+ * It is assumed that the user guarantee that the genpd wouldn't be detached
+ * while this routine is getting called.
+ *
+ * Returns 0 on success and negative error values on failures.
+ */
+int dev_pm_genpd_add_notifier(struct device *dev, struct notifier_block *nb)
+{
+	struct generic_pm_domain *genpd;
+	struct generic_pm_domain_data *gpd_data;
+	int ret;
+
+	genpd = dev_to_genpd_safe(dev);
+	if (!genpd)
+		return -ENODEV;
+
+	if (WARN_ON(!dev->power.subsys_data ||
+		     !dev->power.subsys_data->domain_data))
+		return -EINVAL;
+
+	gpd_data = to_gpd_data(dev->power.subsys_data->domain_data);
+	if (gpd_data->power_nb)
+		return -EEXIST;
+
+	genpd_lock(genpd);
+	ret = raw_notifier_chain_register(&genpd->power_notifiers, nb);
+	genpd_unlock(genpd);
+
+	if (ret) {
+		dev_warn(dev, "failed to add notifier for PM domain %s\n",
+			 genpd->name);
+		return ret;
+	}
+
+	gpd_data->power_nb = nb;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dev_pm_genpd_add_notifier);
+
+/**
+ * dev_pm_genpd_remove_notifier - Remove a genpd power on/off notifier for @dev
+ *
+ * @dev: Device that is associated with the notifier
+ *
+ * Users may call this function to remove a genpd power on/off notifier for an
+ * attached @dev.
+ *
+ * It is assumed that the user guarantee that the genpd wouldn't be detached
+ * while this routine is getting called.
+ *
+ * Returns 0 on success and negative error values on failures.
+ */
+int dev_pm_genpd_remove_notifier(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+	struct generic_pm_domain_data *gpd_data;
+	int ret;
+
+	genpd = dev_to_genpd_safe(dev);
+	if (!genpd)
+		return -ENODEV;
+
+	if (WARN_ON(!dev->power.subsys_data ||
+		     !dev->power.subsys_data->domain_data))
+		return -EINVAL;
+
+	gpd_data = to_gpd_data(dev->power.subsys_data->domain_data);
+	if (!gpd_data->power_nb)
+		return -ENODEV;
+
+	genpd_lock(genpd);
+	ret = raw_notifier_chain_unregister(&genpd->power_notifiers,
+					    gpd_data->power_nb);
+	genpd_unlock(genpd);
+
+	if (ret) {
+		dev_warn(dev, "failed to remove notifier for PM domain %s\n",
+			 genpd->name);
+		return ret;
+	}
+
+	gpd_data->power_nb = NULL;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dev_pm_genpd_remove_notifier);
+
 static int genpd_add_subdomain(struct generic_pm_domain *genpd,
 			       struct generic_pm_domain *subdomain)
 {
@@ -1763,6 +1884,7 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
 	INIT_LIST_HEAD(&genpd->parent_links);
 	INIT_LIST_HEAD(&genpd->child_links);
 	INIT_LIST_HEAD(&genpd->dev_list);
+	RAW_INIT_NOTIFIER_HEAD(&genpd->power_notifiers);
 	genpd_lock_init(genpd);
 	genpd->gov = gov;
 	INIT_WORK(&genpd->power_off_work, genpd_power_off_work_fn);
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 66f3c5d64d81..3b2b561ce846 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -112,6 +112,7 @@ struct generic_pm_domain {
 	cpumask_var_t cpus;		/* A cpumask of the attached CPUs */
 	int (*power_off)(struct generic_pm_domain *domain);
 	int (*power_on)(struct generic_pm_domain *domain);
+	struct raw_notifier_head power_notifiers; /* Power on/off notifiers */
 	struct opp_table *opp_table;	/* OPP table of the genpd */
 	unsigned int (*opp_to_performance_state)(struct generic_pm_domain *genpd,
 						 struct dev_pm_opp *opp);
@@ -178,6 +179,7 @@ struct generic_pm_domain_data {
 	struct pm_domain_data base;
 	struct gpd_timing_data td;
 	struct notifier_block nb;
+	struct notifier_block *power_nb;
 	int cpu;
 	unsigned int performance_state;
 	void *data;
@@ -204,6 +206,8 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
 		  struct dev_power_governor *gov, bool is_off);
 int pm_genpd_remove(struct generic_pm_domain *genpd);
 int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state);
+int dev_pm_genpd_add_notifier(struct device *dev, struct notifier_block *nb);
+int dev_pm_genpd_remove_notifier(struct device *dev);
 
 extern struct dev_power_governor simple_qos_governor;
 extern struct dev_power_governor pm_domain_always_on_gov;
@@ -251,6 +255,17 @@ static inline int dev_pm_genpd_set_performance_state(struct device *dev,
 	return -ENOTSUPP;
 }
 
+static inline int dev_pm_genpd_add_notifier(struct device *dev,
+					    struct notifier_block *nb)
+{
+	return -ENOTSUPP;
+}
+
+static inline int dev_pm_genpd_remove_notifier(struct device *dev)
+{
+	return -ENOTSUPP;
+}
+
 #define simple_qos_governor		(*(struct dev_power_governor *)(NULL))
 #define pm_domain_always_on_gov		(*(struct dev_power_governor *)(NULL))
 #endif
-- 
2.25.1

Re: [PATCH 3/3] PM / Domains: Add support for PM domain on/off notifiers for genpd

[Lina Iyer]

On Wed, Aug 19 2020 at 04:41 -0600, Ulf Hansson wrote:
>A device may have specific HW constraints that must be obeyed to, before
>its corresponding PM domain (genpd) can be powered off - and vice verse at
>power on. These constraints can't be managed through the regular runtime PM
>based deployment for a device, because the access pattern for it, isn't
>always request based. In other words, using the runtime PM callbacks to
>deal with the constraints doesn't work for these cases.
>
>For these reasons, let's instead add a PM domain power on/off notification
>mechanism to genpd. To add/remove a notifier for a device, the device must
>already have been attached to the genpd, which also means that it needs to
>be a part of the PM domain topology.
>
>To add/remove a notifier, let's introduce two genpd specific functions:
> - dev_pm_genpd_add|remove_notifier()
>
>Note that, to further clarify when genpd power on/off notifiers may be
>used, one can compare with the existing CPU_CLUSTER_PM_ENTER|EXIT
>notifiers. In the long run, the genpd power on/off notifiers should be able
>to replace them, but that requires additional genpd based platform support
>for the current users.
>
>Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
>---
> drivers/base/power/domain.c | 130 ++++++++++++++++++++++++++++++++++--
> include/linux/pm_domain.h   |  15 +++++
> 2 files changed, 141 insertions(+), 4 deletions(-)
>
>diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>index 4b787e1ff188..9cb85a5e8342 100644
>--- a/drivers/base/power/domain.c
>+++ b/drivers/base/power/domain.c
>@@ -545,13 +545,21 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
> 	if (!genpd->gov)
> 		genpd->state_idx = 0;
>
>+	/* Notify consumers that we are about to power off. */
>+	ret = raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_OFF,
>+				      NULL);
>+	if (ret)
>+		return ret;
>+
> 	/* Don't power off, if a child domain is waiting to power on. */
>-	if (atomic_read(&genpd->sd_count) > 0)
>-		return -EBUSY;
>+	if (atomic_read(&genpd->sd_count) > 0) {
>+		ret = -EBUSY;
>+		goto busy;
>+	}
>
> 	ret = _genpd_power_off(genpd, true);
> 	if (ret)
>-		return ret;
>+		goto busy;
>
> 	genpd->status = GENPD_STATE_OFF;
> 	genpd_update_accounting(genpd);
>@@ -564,6 +572,9 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
> 	}
>
> 	return 0;
>+busy:
>+	raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL);
It would be helpful to abstract these notification related calls into
functions of their own. So, for CPU PM domains, it would help to add
RCU_NONIDLE() around the notifiers, allowing the callbacks to add trace
functions.

--Lina

>+	return ret;
> }
>
> /**
>@@ -606,6 +617,9 @@ static int genpd_power_on(struct generic_pm_domain *genpd, unsigned int depth)
> 	if (ret)
> 		goto err;
>
>+	/* Inform consumers that we have powered on. */
>+	raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL);
>+
> 	genpd->status = GENPD_STATE_ON;
> 	genpd_update_accounting(genpd);
>
>@@ -948,9 +962,18 @@ static void genpd_sync_power_off(struct generic_pm_domain *genpd, bool use_lock,
>
> 	/* Choose the deepest state when suspending */
> 	genpd->state_idx = genpd->state_count - 1;
>-	if (_genpd_power_off(genpd, false))
>+
>+	/* Notify consumers that we are about to power off. */
>+	if (raw_notifier_call_chain(&genpd->power_notifiers,
>+				    GENPD_STATE_OFF, NULL))
> 		return;
>
>+	if (_genpd_power_off(genpd, false)) {
>+		raw_notifier_call_chain(&genpd->power_notifiers,
>+					GENPD_STATE_ON, NULL);
>+		return;
>+	}
>+
> 	genpd->status = GENPD_STATE_OFF;
>
> 	list_for_each_entry(link, &genpd->child_links, child_node) {
>@@ -998,6 +1021,9 @@ static void genpd_sync_power_on(struct generic_pm_domain *genpd, bool use_lock,
>
> 	_genpd_power_on(genpd, false);
>
>+	/* Inform consumers that we have powered on. */
>+	raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL);
>+
> 	genpd->status = GENPD_STATE_ON;
> }
>
>@@ -1593,6 +1619,101 @@ int pm_genpd_remove_device(struct device *dev)
> }
> EXPORT_SYMBOL_GPL(pm_genpd_remove_device);
>
>+/**
>+ * dev_pm_genpd_add_notifier - Add a genpd power on/off notifier for @dev
>+ *
>+ * @dev: Device that should be associated with the notifier
>+ * @nb: The notifier block to register
>+ *
>+ * Users may call this function to add a genpd power on/off notifier for an
>+ * attached @dev. Only one notifier per device is allowed. The notifier is
>+ * sent when genpd is powering on/off the PM domain.
>+ *
>+ * It is assumed that the user guarantee that the genpd wouldn't be detached
>+ * while this routine is getting called.
>+ *
>+ * Returns 0 on success and negative error values on failures.
>+ */
>+int dev_pm_genpd_add_notifier(struct device *dev, struct notifier_block *nb)
>+{
>+	struct generic_pm_domain *genpd;
>+	struct generic_pm_domain_data *gpd_data;
>+	int ret;
>+
>+	genpd = dev_to_genpd_safe(dev);
>+	if (!genpd)
>+		return -ENODEV;
>+
>+	if (WARN_ON(!dev->power.subsys_data ||
>+		     !dev->power.subsys_data->domain_data))
>+		return -EINVAL;
>+
>+	gpd_data = to_gpd_data(dev->power.subsys_data->domain_data);
>+	if (gpd_data->power_nb)
>+		return -EEXIST;
>+
>+	genpd_lock(genpd);
>+	ret = raw_notifier_chain_register(&genpd->power_notifiers, nb);
>+	genpd_unlock(genpd);
>+
>+	if (ret) {
>+		dev_warn(dev, "failed to add notifier for PM domain %s\n",
>+			 genpd->name);
>+		return ret;
>+	}
>+
>+	gpd_data->power_nb = nb;
>+	return 0;
>+}
>+EXPORT_SYMBOL_GPL(dev_pm_genpd_add_notifier);
>+
>+/**
>+ * dev_pm_genpd_remove_notifier - Remove a genpd power on/off notifier for @dev
>+ *
>+ * @dev: Device that is associated with the notifier
>+ *
>+ * Users may call this function to remove a genpd power on/off notifier for an
>+ * attached @dev.
>+ *
>+ * It is assumed that the user guarantee that the genpd wouldn't be detached
>+ * while this routine is getting called.
>+ *
>+ * Returns 0 on success and negative error values on failures.
>+ */
>+int dev_pm_genpd_remove_notifier(struct device *dev)
>+{
>+	struct generic_pm_domain *genpd;
>+	struct generic_pm_domain_data *gpd_data;
>+	int ret;
>+
>+	genpd = dev_to_genpd_safe(dev);
>+	if (!genpd)
>+		return -ENODEV;
>+
>+	if (WARN_ON(!dev->power.subsys_data ||
>+		     !dev->power.subsys_data->domain_data))
>+		return -EINVAL;
>+
>+	gpd_data = to_gpd_data(dev->power.subsys_data->domain_data);
>+	if (!gpd_data->power_nb)
>+		return -ENODEV;
>+
>+	genpd_lock(genpd);
>+	ret = raw_notifier_chain_unregister(&genpd->power_notifiers,
>+					    gpd_data->power_nb);
>+	genpd_unlock(genpd);
>+
>+	if (ret) {
>+		dev_warn(dev, "failed to remove notifier for PM domain %s\n",
>+			 genpd->name);
>+		return ret;
>+	}
>+
>+	gpd_data->power_nb = NULL;
>+	return 0;
>+}
>+EXPORT_SYMBOL_GPL(dev_pm_genpd_remove_notifier);
>+
> static int genpd_add_subdomain(struct generic_pm_domain *genpd,
> 			       struct generic_pm_domain *subdomain)
> {
>@@ -1763,6 +1884,7 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
> 	INIT_LIST_HEAD(&genpd->parent_links);
> 	INIT_LIST_HEAD(&genpd->child_links);
> 	INIT_LIST_HEAD(&genpd->dev_list);
>+	RAW_INIT_NOTIFIER_HEAD(&genpd->power_notifiers);
> 	genpd_lock_init(genpd);
> 	genpd->gov = gov;
> 	INIT_WORK(&genpd->power_off_work, genpd_power_off_work_fn);
>diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
>index 66f3c5d64d81..3b2b561ce846 100644
>--- a/include/linux/pm_domain.h
>+++ b/include/linux/pm_domain.h
>@@ -112,6 +112,7 @@ struct generic_pm_domain {
> 	cpumask_var_t cpus;		/* A cpumask of the attached CPUs */
> 	int (*power_off)(struct generic_pm_domain *domain);
> 	int (*power_on)(struct generic_pm_domain *domain);
>+	struct raw_notifier_head power_notifiers; /* Power on/off notifiers */
> 	struct opp_table *opp_table;	/* OPP table of the genpd */
> 	unsigned int (*opp_to_performance_state)(struct generic_pm_domain *genpd,
> 						 struct dev_pm_opp *opp);
>@@ -178,6 +179,7 @@ struct generic_pm_domain_data {
> 	struct pm_domain_data base;
> 	struct gpd_timing_data td;
> 	struct notifier_block nb;
>+	struct notifier_block *power_nb;
> 	int cpu;
> 	unsigned int performance_state;
> 	void *data;
>@@ -204,6 +206,8 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
> 		  struct dev_power_governor *gov, bool is_off);
> int pm_genpd_remove(struct generic_pm_domain *genpd);
> int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state);
>+int dev_pm_genpd_add_notifier(struct device *dev, struct notifier_block *nb);
>+int dev_pm_genpd_remove_notifier(struct device *dev);
>
> extern struct dev_power_governor simple_qos_governor;
> extern struct dev_power_governor pm_domain_always_on_gov;
>@@ -251,6 +255,17 @@ static inline int dev_pm_genpd_set_performance_state(struct device *dev,
> 	return -ENOTSUPP;
> }
>
>+static inline int dev_pm_genpd_add_notifier(struct device *dev,
>+					    struct notifier_block *nb)
>+{
>+	return -ENOTSUPP;
>+}
>+
>+static inline int dev_pm_genpd_remove_notifier(struct device *dev)
>+{
>+	return -ENOTSUPP;
>+}
>+
> #define simple_qos_governor		(*(struct dev_power_governor *)(NULL))
> #define pm_domain_always_on_gov		(*(struct dev_power_governor *)(NULL))
> #endif
>-- 
>2.25.1
>

Re: [PATCH 3/3] PM / Domains: Add support for PM domain on/off notifiers for genpd

[Ulf Hansson]

On Tue, 25 Aug 2020 at 18:16, Lina Iyer <ilina@codeaurora.org> wrote:
>
> On Wed, Aug 19 2020 at 04:41 -0600, Ulf Hansson wrote:
> >A device may have specific HW constraints that must be obeyed to, before
> >its corresponding PM domain (genpd) can be powered off - and vice verse at
> >power on. These constraints can't be managed through the regular runtime PM
> >based deployment for a device, because the access pattern for it, isn't
> >always request based. In other words, using the runtime PM callbacks to
> >deal with the constraints doesn't work for these cases.
> >
> >For these reasons, let's instead add a PM domain power on/off notification
> >mechanism to genpd. To add/remove a notifier for a device, the device must
> >already have been attached to the genpd, which also means that it needs to
> >be a part of the PM domain topology.
> >
> >To add/remove a notifier, let's introduce two genpd specific functions:
> > - dev_pm_genpd_add|remove_notifier()
> >
> >Note that, to further clarify when genpd power on/off notifiers may be
> >used, one can compare with the existing CPU_CLUSTER_PM_ENTER|EXIT
> >notifiers. In the long run, the genpd power on/off notifiers should be able
> >to replace them, but that requires additional genpd based platform support
> >for the current users.
> >
> >Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> >---
> > drivers/base/power/domain.c | 130 ++++++++++++++++++++++++++++++++++--
> > include/linux/pm_domain.h   |  15 +++++
> > 2 files changed, 141 insertions(+), 4 deletions(-)
> >
> >diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> >index 4b787e1ff188..9cb85a5e8342 100644
> >--- a/drivers/base/power/domain.c
> >+++ b/drivers/base/power/domain.c
> >@@ -545,13 +545,21 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
> >       if (!genpd->gov)
> >               genpd->state_idx = 0;
> >
> >+      /* Notify consumers that we are about to power off. */
> >+      ret = raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_OFF,
> >+                                    NULL);
> >+      if (ret)
> >+              return ret;
> >+
> >       /* Don't power off, if a child domain is waiting to power on. */
> >-      if (atomic_read(&genpd->sd_count) > 0)
> >-              return -EBUSY;
> >+      if (atomic_read(&genpd->sd_count) > 0) {
> >+              ret = -EBUSY;
> >+              goto busy;
> >+      }
> >
> >       ret = _genpd_power_off(genpd, true);
> >       if (ret)
> >-              return ret;
> >+              goto busy;
> >
> >       genpd->status = GENPD_STATE_OFF;
> >       genpd_update_accounting(genpd);
> >@@ -564,6 +572,9 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
> >       }
> >
> >       return 0;
> >+busy:
> >+      raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL);
> It would be helpful to abstract these notification related calls into
> functions of their own. So, for CPU PM domains, it would help to add
> RCU_NONIDLE() around the notifiers, allowing the callbacks to add trace
> functions.

Thanks for the suggestion! It makes perfect sense to me - and would
also be consistent with how CPU PM notifiers are managed,

[,,,]

Kind regards
Uffe

Re: [PATCH 3/3] PM / Domains: Add support for PM domain on/off notifiers for genpd

[Lina Iyer]

-----Original Message-----
Date: Wed, 19 Aug 2020 12:40:57 +0200
From: Ulf Hansson <ulf.hansson@linaro.org>
To: "Rafael J . Wysocki" <rjw@rjwysocki.net>, Kevin Hilman
 <khilman@kernel.org>, linux-pm@vger.kernel.org
Cc: Sudeep Holla <sudeep.holla@arm.com>, Lorenzo Pieralisi
 <Lorenzo.Pieralisi@arm.com>, Daniel Lezcano <daniel.lezcano@linaro.org>,
 Lina Iyer <ilina@codeaurora.org>, Lukasz Luba <lukasz.luba@arm.com>, Vincent
 Guittot <vincent.guittot@linaro.org>, Stephen Boyd <sboyd@kernel.org>, Bjorn
 Andersson <bjorn.andersson@linaro.org>, Benjamin Gaignard
 <benjamin.gaignard@st.com>, Ulf Hansson <ulf.hansson@linaro.org>,
 linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH 3/3] PM / Domains: Add support for PM domain on/off notifiers
 for genpd

A device may have specific HW constraints that must be obeyed to, before
its corresponding PM domain (genpd) can be powered off - and vice verse at
power on. These constraints can't be managed through the regular runtime PM
based deployment for a device, because the access pattern for it, isn't
always request based. In other words, using the runtime PM callbacks to
deal with the constraints doesn't work for these cases.

For these reasons, let's instead add a PM domain power on/off notification
mechanism to genpd. To add/remove a notifier for a device, the device must
already have been attached to the genpd, which also means that it needs to
be a part of the PM domain topology.

To add/remove a notifier, let's introduce two genpd specific functions:
 - dev_pm_genpd_add|remove_notifier()

Note that, to further clarify when genpd power on/off notifiers may be
used, one can compare with the existing CPU_CLUSTER_PM_ENTER|EXIT
notifiers. In the long run, the genpd power on/off notifiers should be able
to replace them, but that requires additional genpd based platform support
for the current users.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---
 drivers/base/power/domain.c | 130 ++++++++++++++++++++++++++++++++++--
 include/linux/pm_domain.h   |  15 +++++
 2 files changed, 141 insertions(+), 4 deletions(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 4b787e1ff188..9cb85a5e8342 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -545,13 +545,21 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
 	if (!genpd->gov)
 		genpd->state_idx = 0;
 
+	/* Notify consumers that we are about to power off. */
+	ret = raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_OFF,
+				      NULL);
+	if (ret)
+		return ret;
+
 	/* Don't power off, if a child domain is waiting to power on. */
-	if (atomic_read(&genpd->sd_count) > 0)
-		return -EBUSY;
+	if (atomic_read(&genpd->sd_count) > 0) {
+		ret = -EBUSY;
+		goto busy;
+	}
 
 	ret = _genpd_power_off(genpd, true);
 	if (ret)
-		return ret;
+		goto busy;
 
 	genpd->status = GENPD_STATE_OFF;
 	genpd_update_accounting(genpd);
@@ -564,6 +572,9 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
 	}
 
 	return 0;
+busy:
+	raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL);
+	return ret;
 }
 
 /**
@@ -606,6 +617,9 @@ static int genpd_power_on(struct generic_pm_domain *genpd, unsigned int depth)
 	if (ret)
 		goto err;
 
+	/* Inform consumers that we have powered on. */
+	raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL);
+
 	genpd->status = GENPD_STATE_ON;
 	genpd_update_accounting(genpd);
 
@@ -948,9 +962,18 @@ static void genpd_sync_power_off(struct generic_pm_domain *genpd, bool use_lock,
 
 	/* Choose the deepest state when suspending */
 	genpd->state_idx = genpd->state_count - 1;
-	if (_genpd_power_off(genpd, false))
+
+	/* Notify consumers that we are about to power off. */
+	if (raw_notifier_call_chain(&genpd->power_notifiers,
+				    GENPD_STATE_OFF, NULL))
 		return;
If any of the notified returns an error, we probably should inform that
the genpd failed as well. 

-- Lina

+	if (_genpd_power_off(genpd, false)) {
+		raw_notifier_call_chain(&genpd->power_notifiers,
+					GENPD_STATE_ON, NULL);
+		return;
+	}
+
 	genpd->status = GENPD_STATE_OFF;
 
 	list_for_each_entry(link, &genpd->child_links, child_node) {
@@ -998,6 +1021,9 @@ static void genpd_sync_power_on(struct generic_pm_domain *genpd, bool use_lock,
 
 	_genpd_power_on(genpd, false);
 
+	/* Inform consumers that we have powered on. */
+	raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL);
+
 	genpd->status = GENPD_STATE_ON;
 }
 
@@ -1593,6 +1619,101 @@ int pm_genpd_remove_device(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(pm_genpd_remove_device);
 
+/**
+ * dev_pm_genpd_add_notifier - Add a genpd power on/off notifier for @dev
+ *
+ * @dev: Device that should be associated with the notifier
+ * @nb: The notifier block to register
+ *
+ * Users may call this function to add a genpd power on/off notifier for an
+ * attached @dev. Only one notifier per device is allowed. The notifier is
+ * sent when genpd is powering on/off the PM domain.
+ *
+ * It is assumed that the user guarantee that the genpd wouldn't be detached
+ * while this routine is getting called.
+ *
+ * Returns 0 on success and negative error values on failures.
+ */
+int dev_pm_genpd_add_notifier(struct device *dev, struct notifier_block *nb)
+{
+	struct generic_pm_domain *genpd;
+	struct generic_pm_domain_data *gpd_data;
+	int ret;
+
+	genpd = dev_to_genpd_safe(dev);
+	if (!genpd)
+		return -ENODEV;
+
+	if (WARN_ON(!dev->power.subsys_data ||
+		     !dev->power.subsys_data->domain_data))
+		return -EINVAL;
+
+	gpd_data = to_gpd_data(dev->power.subsys_data->domain_data);
+	if (gpd_data->power_nb)
+		return -EEXIST;
+
+	genpd_lock(genpd);
+	ret = raw_notifier_chain_register(&genpd->power_notifiers, nb);
+	genpd_unlock(genpd);
+
+	if (ret) {
+		dev_warn(dev, "failed to add notifier for PM domain %s\n",
+			 genpd->name);
+		return ret;
+	}
+
+	gpd_data->power_nb = nb;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dev_pm_genpd_add_notifier);
+
+/**
+ * dev_pm_genpd_remove_notifier - Remove a genpd power on/off notifier for @dev
+ *
+ * @dev: Device that is associated with the notifier
+ *
+ * Users may call this function to remove a genpd power on/off notifier for an
+ * attached @dev.
+ *
+ * It is assumed that the user guarantee that the genpd wouldn't be detached
+ * while this routine is getting called.
+ *
+ * Returns 0 on success and negative error values on failures.
+ */
+int dev_pm_genpd_remove_notifier(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+	struct generic_pm_domain_data *gpd_data;
+	int ret;
+
+	genpd = dev_to_genpd_safe(dev);
+	if (!genpd)
+		return -ENODEV;
+
+	if (WARN_ON(!dev->power.subsys_data ||
+		     !dev->power.subsys_data->domain_data))
+		return -EINVAL;
+
+	gpd_data = to_gpd_data(dev->power.subsys_data->domain_data);
+	if (!gpd_data->power_nb)
+		return -ENODEV;
+
+	genpd_lock(genpd);
+	ret = raw_notifier_chain_unregister(&genpd->power_notifiers,
+					    gpd_data->power_nb);
+	genpd_unlock(genpd);
+
+	if (ret) {
+		dev_warn(dev, "failed to remove notifier for PM domain %s\n",
+			 genpd->name);
+		return ret;
+	}
+
+	gpd_data->power_nb = NULL;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dev_pm_genpd_remove_notifier);
+
 static int genpd_add_subdomain(struct generic_pm_domain *genpd,
 			       struct generic_pm_domain *subdomain)
 {
@@ -1763,6 +1884,7 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
 	INIT_LIST_HEAD(&genpd->parent_links);
 	INIT_LIST_HEAD(&genpd->child_links);
 	INIT_LIST_HEAD(&genpd->dev_list);
+	RAW_INIT_NOTIFIER_HEAD(&genpd->power_notifiers);
 	genpd_lock_init(genpd);
 	genpd->gov = gov;
 	INIT_WORK(&genpd->power_off_work, genpd_power_off_work_fn);
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 66f3c5d64d81..3b2b561ce846 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -112,6 +112,7 @@ struct generic_pm_domain {
 	cpumask_var_t cpus;		/* A cpumask of the attached CPUs */
 	int (*power_off)(struct generic_pm_domain *domain);
 	int (*power_on)(struct generic_pm_domain *domain);
+	struct raw_notifier_head power_notifiers; /* Power on/off notifiers */
 	struct opp_table *opp_table;	/* OPP table of the genpd */
 	unsigned int (*opp_to_performance_state)(struct generic_pm_domain *genpd,
 						 struct dev_pm_opp *opp);
@@ -178,6 +179,7 @@ struct generic_pm_domain_data {
 	struct pm_domain_data base;
 	struct gpd_timing_data td;
 	struct notifier_block nb;
+	struct notifier_block *power_nb;
 	int cpu;
 	unsigned int performance_state;
 	void *data;
@@ -204,6 +206,8 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
 		  struct dev_power_governor *gov, bool is_off);
 int pm_genpd_remove(struct generic_pm_domain *genpd);
 int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state);
+int dev_pm_genpd_add_notifier(struct device *dev, struct notifier_block *nb);
+int dev_pm_genpd_remove_notifier(struct device *dev);
 
 extern struct dev_power_governor simple_qos_governor;
 extern struct dev_power_governor pm_domain_always_on_gov;
@@ -251,6 +255,17 @@ static inline int dev_pm_genpd_set_performance_state(struct device *dev,
 	return -ENOTSUPP;
 }
 
+static inline int dev_pm_genpd_add_notifier(struct device *dev,
+					    struct notifier_block *nb)
+{
+	return -ENOTSUPP;
+}
+
+static inline int dev_pm_genpd_remove_notifier(struct device *dev)
+{
+	return -ENOTSUPP;
+}
+
 #define simple_qos_governor		(*(struct dev_power_governor *)(NULL))
 #define pm_domain_always_on_gov		(*(struct dev_power_governor *)(NULL))
 #endif
-- 
2.25.1

Re: [PATCH 3/3] PM / Domains: Add support for PM domain on/off notifiers for genpd

[Rafael J. Wysocki]

On Wed, Aug 26, 2020 at 8:38 AM Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
> On Tue, 25 Aug 2020 at 18:16, Lina Iyer <ilina@codeaurora.org> wrote:
> >
> > On Wed, Aug 19 2020 at 04:41 -0600, Ulf Hansson wrote:
> > >A device may have specific HW constraints that must be obeyed to, before
> > >its corresponding PM domain (genpd) can be powered off - and vice verse at
> > >power on. These constraints can't be managed through the regular runtime PM
> > >based deployment for a device, because the access pattern for it, isn't
> > >always request based. In other words, using the runtime PM callbacks to
> > >deal with the constraints doesn't work for these cases.
> > >
> > >For these reasons, let's instead add a PM domain power on/off notification
> > >mechanism to genpd. To add/remove a notifier for a device, the device must
> > >already have been attached to the genpd, which also means that it needs to
> > >be a part of the PM domain topology.
> > >
> > >To add/remove a notifier, let's introduce two genpd specific functions:
> > > - dev_pm_genpd_add|remove_notifier()
> > >
> > >Note that, to further clarify when genpd power on/off notifiers may be
> > >used, one can compare with the existing CPU_CLUSTER_PM_ENTER|EXIT
> > >notifiers. In the long run, the genpd power on/off notifiers should be able
> > >to replace them, but that requires additional genpd based platform support
> > >for the current users.
> > >
> > >Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> > >---
> > > drivers/base/power/domain.c | 130 ++++++++++++++++++++++++++++++++++--
> > > include/linux/pm_domain.h   |  15 +++++
> > > 2 files changed, 141 insertions(+), 4 deletions(-)
> > >
> > >diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > >index 4b787e1ff188..9cb85a5e8342 100644
> > >--- a/drivers/base/power/domain.c
> > >+++ b/drivers/base/power/domain.c
> > >@@ -545,13 +545,21 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
> > >       if (!genpd->gov)
> > >               genpd->state_idx = 0;
> > >
> > >+      /* Notify consumers that we are about to power off. */
> > >+      ret = raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_OFF,
> > >+                                    NULL);
> > >+      if (ret)
> > >+              return ret;
> > >+
> > >       /* Don't power off, if a child domain is waiting to power on. */
> > >-      if (atomic_read(&genpd->sd_count) > 0)
> > >-              return -EBUSY;
> > >+      if (atomic_read(&genpd->sd_count) > 0) {
> > >+              ret = -EBUSY;
> > >+              goto busy;
> > >+      }
> > >
> > >       ret = _genpd_power_off(genpd, true);
> > >       if (ret)
> > >-              return ret;
> > >+              goto busy;
> > >
> > >       genpd->status = GENPD_STATE_OFF;
> > >       genpd_update_accounting(genpd);
> > >@@ -564,6 +572,9 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
> > >       }
> > >
> > >       return 0;
> > >+busy:
> > >+      raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL);
> > It would be helpful to abstract these notification related calls into
> > functions of their own. So, for CPU PM domains, it would help to add
> > RCU_NONIDLE() around the notifiers, allowing the callbacks to add trace
> > functions.
>
> Thanks for the suggestion! It makes perfect sense to me - and would
> also be consistent with how CPU PM notifiers are managed,

So I thought that you wanted to send a v2, but I cannot find it.

Cheers!

Re: [PATCH 3/3] PM / Domains: Add support for PM domain on/off notifiers for genpd

[Ulf Hansson]

On Mon, 21 Sep 2020 at 18:11, Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> On Wed, Aug 26, 2020 at 8:38 AM Ulf Hansson <ulf.hansson@linaro.org> wrote:
> >
> > On Tue, 25 Aug 2020 at 18:16, Lina Iyer <ilina@codeaurora.org> wrote:
> > >
> > > On Wed, Aug 19 2020 at 04:41 -0600, Ulf Hansson wrote:
> > > >A device may have specific HW constraints that must be obeyed to, before
> > > >its corresponding PM domain (genpd) can be powered off - and vice verse at
> > > >power on. These constraints can't be managed through the regular runtime PM
> > > >based deployment for a device, because the access pattern for it, isn't
> > > >always request based. In other words, using the runtime PM callbacks to
> > > >deal with the constraints doesn't work for these cases.
> > > >
> > > >For these reasons, let's instead add a PM domain power on/off notification
> > > >mechanism to genpd. To add/remove a notifier for a device, the device must
> > > >already have been attached to the genpd, which also means that it needs to
> > > >be a part of the PM domain topology.
> > > >
> > > >To add/remove a notifier, let's introduce two genpd specific functions:
> > > > - dev_pm_genpd_add|remove_notifier()
> > > >
> > > >Note that, to further clarify when genpd power on/off notifiers may be
> > > >used, one can compare with the existing CPU_CLUSTER_PM_ENTER|EXIT
> > > >notifiers. In the long run, the genpd power on/off notifiers should be able
> > > >to replace them, but that requires additional genpd based platform support
> > > >for the current users.
> > > >
> > > >Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> > > >---
> > > > drivers/base/power/domain.c | 130 ++++++++++++++++++++++++++++++++++--
> > > > include/linux/pm_domain.h   |  15 +++++
> > > > 2 files changed, 141 insertions(+), 4 deletions(-)
> > > >
> > > >diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > > >index 4b787e1ff188..9cb85a5e8342 100644
> > > >--- a/drivers/base/power/domain.c
> > > >+++ b/drivers/base/power/domain.c
> > > >@@ -545,13 +545,21 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
> > > >       if (!genpd->gov)
> > > >               genpd->state_idx = 0;
> > > >
> > > >+      /* Notify consumers that we are about to power off. */
> > > >+      ret = raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_OFF,
> > > >+                                    NULL);
> > > >+      if (ret)
> > > >+              return ret;
> > > >+
> > > >       /* Don't power off, if a child domain is waiting to power on. */
> > > >-      if (atomic_read(&genpd->sd_count) > 0)
> > > >-              return -EBUSY;
> > > >+      if (atomic_read(&genpd->sd_count) > 0) {
> > > >+              ret = -EBUSY;
> > > >+              goto busy;
> > > >+      }
> > > >
> > > >       ret = _genpd_power_off(genpd, true);
> > > >       if (ret)
> > > >-              return ret;
> > > >+              goto busy;
> > > >
> > > >       genpd->status = GENPD_STATE_OFF;
> > > >       genpd_update_accounting(genpd);
> > > >@@ -564,6 +572,9 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
> > > >       }
> > > >
> > > >       return 0;
> > > >+busy:
> > > >+      raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL);
> > > It would be helpful to abstract these notification related calls into
> > > functions of their own. So, for CPU PM domains, it would help to add
> > > RCU_NONIDLE() around the notifiers, allowing the callbacks to add trace
> > > functions.
> >
> > Thanks for the suggestion! It makes perfect sense to me - and would
> > also be consistent with how CPU PM notifiers are managed,
>
> So I thought that you wanted to send a v2, but I cannot find it.

Yes, I am about to post it. I just wanted to give people more time to comment.

Kind regards
Uffe