[PATCH 4/4] soundwire: intel_init: resume all devices on exit.

[Bard Liao <yung-chuan.liao@xxxxxxxxxxxxxxx>]

When the manager becomes pm_runtime active in the remove procedure,
peripherals will become attached, and do the initialization
process. We have to wait until all the devices are fully resumed
before the cleanup, otherwise there is a possible race condition where
asynchronous workqueues initiate transfers on the bus that cannot
complete. This will ensure there are no SoundWire registers accessed
after the bus is powered-down.

Signed-off-by: Bard Liao <yung-chuan.liao@xxxxxxxxxxxxxxx>
---
 drivers/soundwire/intel_init.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/soundwire/intel_init.c b/drivers/soundwire/intel_init.c
index 534c8795e7e8..a09134b97cd6 100644
--- a/drivers/soundwire/intel_init.c
+++ b/drivers/soundwire/intel_init.c
@@ -16,6 +16,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/soundwire/sdw_intel.h>
 #include "cadence_master.h"
+#include "bus.h"
 #include "intel.h"
 #include "intel_auxdevice.h"
 
@@ -356,6 +357,19 @@ EXPORT_SYMBOL_NS(sdw_intel_startup, SOUNDWIRE_INTEL_INIT);
  */
 void sdw_intel_exit(struct sdw_intel_ctx *ctx)
 {
+	struct sdw_intel_link_res *link;
+
+	/* we first resume links and devices and wait synchronously before the cleanup */
+	list_for_each_entry(link, &ctx->link_list, list) {
+		struct sdw_bus *bus = &link->cdns->bus;
+		int ret;
+
+		ret = device_for_each_child(bus->dev, NULL, intel_resume_child_device);
+		if (ret < 0)
+			dev_err(bus->dev, "%s: intel_resume_child_device failed: %d\n",
+				__func__, ret);
+	}
+
 	sdw_intel_cleanup(ctx);
 	kfree(ctx->ids);
 	kfree(ctx->ldev);
-- 
2.34.1