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Subject[Resend][PATCH v4 3/5] PM / sleep: Make async suspend/resume of devices use device links
Date
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Make the device suspend/resume part of the core system
suspend/resume code use device links to ensure that supplier
and consumer devices will be suspended and resumed in the right
order in case of async suspend/resume.

The idea, roughly, is to use dpm_wait() to wait for all consumers
before a supplier device suspend and to wait for all suppliers
before a consumer device resume.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/base/base.h | 2 +
drivers/base/core.c | 4 +-
drivers/base/power/main.c | 85 ++++++++++++++++++++++++++++++++++++++++++----
3 files changed, 83 insertions(+), 8 deletions(-)

Index: linux-pm/drivers/base/base.h
===================================================================
--- linux-pm.orig/drivers/base/base.h
+++ linux-pm/drivers/base/base.h
@@ -163,3 +163,5 @@ extern void device_links_driver_cleanup(
extern void device_links_no_driver(struct device *dev);
extern bool device_links_busy(struct device *dev);
extern void device_links_unbind_consumers(struct device *dev);
+extern int device_links_read_lock(void);
+extern void device_links_read_unlock(int idx);
Index: linux-pm/drivers/base/core.c
===================================================================
--- linux-pm.orig/drivers/base/core.c
+++ linux-pm/drivers/base/core.c
@@ -227,12 +227,12 @@ void device_link_del(struct device_link
}
EXPORT_SYMBOL_GPL(device_link_del);

-static int device_links_read_lock(void)
+int device_links_read_lock(void)
{
return srcu_read_lock(&device_links_srcu);
}

-static void device_links_read_unlock(int idx)
+void device_links_read_unlock(int idx)
{
return srcu_read_unlock(&device_links_srcu, idx);
}
Index: linux-pm/drivers/base/power/main.c
===================================================================
--- linux-pm.orig/drivers/base/power/main.c
+++ linux-pm/drivers/base/power/main.c
@@ -246,6 +246,62 @@ static void dpm_wait_for_children(struct
device_for_each_child(dev, &async, dpm_wait_fn);
}

+static void dpm_wait_for_suppliers(struct device *dev, bool async)
+{
+ struct device_link *link;
+ int idx;
+
+ idx = device_links_read_lock();
+
+ /*
+ * If the supplier goes away right after we've checked the link to it,
+ * we'll wait for its completion to change the state, but that's fine,
+ * because the only things that will block as a result are the SRCU
+ * callbacks freeing the link objects for the links in the list we're
+ * walking.
+ */
+ list_for_each_entry_rcu(link, &dev->links_to_suppliers, c_node)
+ if (link->status != DEVICE_LINK_DORMANT)
+ dpm_wait(link->supplier, async);
+
+ device_links_read_unlock(idx);
+}
+
+static void dpm_wait_for_superior(struct device *dev, bool async)
+{
+ dpm_wait(dev->parent, async);
+ dpm_wait_for_suppliers(dev, async);
+}
+
+static void dpm_wait_for_consumers(struct device *dev, bool async)
+{
+ struct device_link *link;
+ int idx;
+
+ idx = device_links_read_lock();
+
+ /*
+ * The status of a device link can only be changed from "dormant" by a
+ * probe, but that cannot happen during system suspend/resume. In
+ * theory it can change to "dormant" at that time, but then it is
+ * reasonable to wait for the target device anyway (eg. if it goes
+ * away, it's better to wait for it to go away completely and then
+ * continue instead of trying to continue in parallel with its
+ * unregistration).
+ */
+ list_for_each_entry_rcu(link, &dev->links_to_consumers, s_node)
+ if (link->status != DEVICE_LINK_DORMANT)
+ dpm_wait(link->consumer, async);
+
+ device_links_read_unlock(idx);
+}
+
+static void dpm_wait_for_subordinate(struct device *dev, bool async)
+{
+ dpm_wait_for_children(dev, async);
+ dpm_wait_for_consumers(dev, async);
+}
+
/**
* pm_op - Return the PM operation appropriate for given PM event.
* @ops: PM operations to choose from.
@@ -490,7 +546,7 @@ static int device_resume_noirq(struct de
if (!dev->power.is_noirq_suspended)
goto Out;

- dpm_wait(dev->parent, async);
+ dpm_wait_for_superior(dev, async);

if (dev->pm_domain) {
info = "noirq power domain ";
@@ -620,7 +676,7 @@ static int device_resume_early(struct de
if (!dev->power.is_late_suspended)
goto Out;

- dpm_wait(dev->parent, async);
+ dpm_wait_for_superior(dev, async);

if (dev->pm_domain) {
info = "early power domain ";
@@ -752,7 +808,7 @@ static int device_resume(struct device *
goto Complete;
}

- dpm_wait(dev->parent, async);
+ dpm_wait_for_superior(dev, async);
dpm_watchdog_set(&wd, dev);
device_lock(dev);

@@ -1040,7 +1096,7 @@ static int __device_suspend_noirq(struct
if (dev->power.syscore || dev->power.direct_complete)
goto Complete;

- dpm_wait_for_children(dev, async);
+ dpm_wait_for_subordinate(dev, async);

if (dev->pm_domain) {
info = "noirq power domain ";
@@ -1187,7 +1243,7 @@ static int __device_suspend_late(struct
if (dev->power.syscore || dev->power.direct_complete)
goto Complete;

- dpm_wait_for_children(dev, async);
+ dpm_wait_for_subordinate(dev, async);

if (dev->pm_domain) {
info = "late power domain ";
@@ -1344,6 +1400,22 @@ static int legacy_suspend(struct device
return error;
}

+static void dpm_clear_suppliers_direct_complete(struct device *dev)
+{
+ struct device_link *link;
+ int idx;
+
+ idx = device_links_read_lock();
+
+ list_for_each_entry_rcu(link, &dev->links_to_suppliers, c_node) {
+ spin_lock_irq(&link->supplier->power.lock);
+ link->supplier->power.direct_complete = false;
+ spin_unlock_irq(&link->supplier->power.lock);
+ }
+
+ device_links_read_unlock(idx);
+}
+
/**
* device_suspend - Execute "suspend" callbacks for given device.
* @dev: Device to handle.
@@ -1360,7 +1432,7 @@ static int __device_suspend(struct devic
TRACE_DEVICE(dev);
TRACE_SUSPEND(0);

- dpm_wait_for_children(dev, async);
+ dpm_wait_for_subordinate(dev, async);

if (async_error)
goto Complete;
@@ -1456,6 +1528,7 @@ static int __device_suspend(struct devic

spin_unlock_irq(&parent->power.lock);
}
+ dpm_clear_suppliers_direct_complete(dev);
}

device_unlock(dev);
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