PM / sleep: Make async suspend/resume of devices use device links

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>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 79 insertions, 6 deletions

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 420914061405..04bcb11ed8de 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -246,6 +246,62 @@ static void dpm_wait_for_children(struct device *dev, bool async)
        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.suppliers, c_node)
+                if (READ_ONCE(link->status) != DL_STATE_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.consumers, s_node)
+                if (READ_ONCE(link->status) != DL_STATE_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 device *dev, pm_message_t state, bool asyn
         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 device *dev, pm_message_t state, bool asyn
         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 *dev, pm_message_t state, bool async)
                 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 device *dev, pm_message_t state, bool a
         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 device *dev, pm_message_t state, bool as
         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 *dev, pm_message_t state,
         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.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 device *dev, pm_message_t state, bool async)
         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 device *dev, pm_message_t state, bool async)
 
                         spin_unlock_irq(&parent->power.lock);
                 }
+                dpm_clear_suppliers_direct_complete(dev);
         }
 
         device_unlock(dev);