[PATCH 04/13] soundwire: intel: fix race condition on system resume

[Bard Liao <yung-chuan.liao@linux.intel.com>]

From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>

Previous patches took care of the case where the master device is
pm_runtime 'suspended' when a system suspend occurs.

In the case where the master device was not suspended, e.g. if suspend
occurred while streaming audio, Intel validation noticed a race
condition: the pm_runtime suspend may conflict with the enumeration
started by the system resume.

This can be simply fixed by updating the status before exiting system
resume.

GitHub issue: https://github.com/thesofproject/linux/issues/1482
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
---
 drivers/soundwire/intel.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
index 284e5c9d240a..b7d8ea6b331e 100644
--- a/drivers/soundwire/intel.c
+++ b/drivers/soundwire/intel.c
@@ -1531,6 +1531,18 @@ static int intel_resume(struct device *dev)
 		return ret;
 	}
 
+	/*
+	 * after system resume, the pm_runtime suspend() may kick in
+	 * during the enumeration, before any children device force the
+	 * master device to remain active.  Using pm_runtime_get()
+	 * routines is not really possible, since it'd prevent the
+	 * master from suspending.
+	 * A reasonable compromise is to update the pm_runtime
+	 * counters and delay the pm_runtime suspend by several
+	 * seconds, by when all enumeration should be complete.
+	 */
+	pm_runtime_mark_last_busy(dev);
+
 	return ret;
 }
 
-- 
2.17.1