PM: runtime: Defer suspending suppliers

Because the PM-runtime status of the device is not updated in
__rpm_callback(), attempts to suspend the suppliers of the given
device triggered by the rpm_put_suppliers() call in there may
cause a supplier to be suspended completely before the status of
the consumer is updated to RPM_SUSPENDED, which is confusing.

To avoid that (1) modify __rpm_callback() to only decrease the
PM-runtime usage counter of each supplier and (2) make rpm_suspend()
try to suspend the suppliers after changing the consumer's status to
RPM_SUSPENDED, in analogy with the device's parent.

Link: https://lore.kernel.org/linux-pm/CAPDyKFqm06KDw_p8WXsM4dijDbho4bb6T4k50UqqvR1_COsp8g@mail.gmail.com/
Fixes: 21d5c57b3726 ("PM / runtime: Use device links")
Reported-by: elaine.zhang <zhangqing@rock-chips.com>
Diagnosed-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index a46a7e30881b19e00b1bda7b839ab263ec8be3ef..d54e540067bfa7f8a79cab5ee074be146301e5ab 100644 (file)
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -305,7 +305,7 @@ static int rpm_get_suppliers(struct device *dev)
        return 0;
 }
 
-static void rpm_put_suppliers(struct device *dev)
+static void __rpm_put_suppliers(struct device *dev, bool try_to_suspend)
 {
        struct device_link *link;
 
@@ -313,10 +313,30 @@ static void rpm_put_suppliers(struct device *dev)
                                device_links_read_lock_held()) {
 
                while (refcount_dec_not_one(&link->rpm_active))
-                       pm_runtime_put(link->supplier);
+                       pm_runtime_put_noidle(link->supplier);
+
+               if (try_to_suspend)
+                       pm_request_idle(link->supplier);
        }
 }
 
+static void rpm_put_suppliers(struct device *dev)
+{
+       __rpm_put_suppliers(dev, true);
+}
+
+static void rpm_suspend_suppliers(struct device *dev)
+{
+       struct device_link *link;
+       int idx = device_links_read_lock();
+
+       list_for_each_entry_rcu(link, &dev->links.suppliers, c_node,
+                               device_links_read_lock_held())
+               pm_request_idle(link->supplier);
+
+       device_links_read_unlock(idx);
+}
+
 /**
  * __rpm_callback - Run a given runtime PM callback for a given device.
  * @cb: Runtime PM callback to run.
@@ -344,8 +364,10 @@ static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
                        idx = device_links_read_lock();
 
                        retval = rpm_get_suppliers(dev);
-                       if (retval)
+                       if (retval) {
+                               rpm_put_suppliers(dev);
                                goto fail;
+                       }
 
                        device_links_read_unlock(idx);
                }
@@ -368,9 +390,9 @@ static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
                    || (dev->power.runtime_status == RPM_RESUMING && retval))) {
                        idx = device_links_read_lock();
 
- fail:
-                       rpm_put_suppliers(dev);
+                       __rpm_put_suppliers(dev, false);
 
+fail:
                        device_links_read_unlock(idx);
                }
 
@@ -642,8 +664,11 @@ static int rpm_suspend(struct device *dev, int rpmflags)
                goto out;
        }
 
+       if (dev->power.irq_safe)
+               goto out;
+
        /* Maybe the parent is now able to suspend. */
-       if (parent && !parent->power.ignore_children && !dev->power.irq_safe) {
+       if (parent && !parent->power.ignore_children) {
                spin_unlock(&dev->power.lock);
 
                spin_lock(&parent->power.lock);
@@ -652,6 +677,14 @@ static int rpm_suspend(struct device *dev, int rpmflags)
 
                spin_lock(&dev->power.lock);
        }
+       /* Maybe the suppliers are now able to suspend. */
+       if (dev->power.links_count > 0) {
+               spin_unlock_irq(&dev->power.lock);
+
+               rpm_suspend_suppliers(dev);
+
+               spin_lock_irq(&dev->power.lock);
+       }
 
  out:
        trace_rpm_return_int_rcuidle(dev, _THIS_IP_, retval);