diff mbox series

[3/3] soundwire: bus: pm_runtime_request_resume on peripheral attachment

Message ID 20220420023241.14335-4-yung-chuan.liao@linux.intel.com
State New
Headers show
Series soundwire: pm runtime improvements | expand

Commit Message

Liao, Bard April 20, 2022, 2:32 a.m. UTC 
From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>

In typical use cases, the peripheral becomes pm_runtime active as a
result of the ALSA/ASoC framework starting up a DAI. The parent/child
hierarchy guarantees that the manager device will be fully resumed
beforehand.

There is however a corner case where the manager device may become
pm_runtime active, but without ALSA/ASoC requesting any functionality
from the peripherals. In this case, the hardware peripheral device
will report as ATTACHED and its initialization routine will be
executed. If this initialization routine initiates any sort of
deferred processing, there is a possibility that the manager could
suspend without the peripheral suspend sequence being invoked: from
the pm_runtime framework perspective, the peripheral is *already*
suspended.

To avoid such disconnects between hardware state and pm_runtime state,
this patch adds an asynchronous pm_request_resume() upon successful
attach/initialization which will result in the proper resume/suspend
sequence to be followed on the peripheral side.

BugLink: https://github.com/thesofproject/linux/issues/3459
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
---
 drivers/soundwire/bus.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)
diff mbox series

Patch

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index 354d3f89366f..8b7a680f388e 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -1838,6 +1838,18 @@  int sdw_handle_slave_status(struct sdw_bus *bus,
 				__func__, slave->dev_num);
 
 			complete(&slave->initialization_complete);
+
+			/*
+			 * If the manager became pm_runtime active, the peripherals will be
+			 * restarted and attach, but their pm_runtime status may remain
+			 * suspended. If the 'update_slave_status' callback initiates
+			 * any sort of deferred processing, this processing would not be
+			 * cancelled on pm_runtime suspend.
+			 * To avoid such zombie states, we queue a request to resume.
+			 * This would be a no-op in case the peripheral was being resumed
+			 * by e.g. the ALSA/ASoC framework.
+			 */
+			pm_request_resume(&slave->dev);
 		}
 	}