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Subject[PATCH 02/10] soundwire: bus: fix race condition with enumeration_complete signaling
Date
This patch adds the signaling needed for Slave drivers to wait until
the enumeration completes so that race conditions when issuing
read/write commands are avoided. The calls for wait_for_completion()
will be added in codec drivers in follow-up patches.

The order between init_completion() and complete() is deterministic,
the Slave is marked as UNATTACHED either during a Master-initiated
HardReset, or when the hardware detects the Slave no longer reports as
ATTACHED.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
---
drivers/soundwire/bus.c | 20 ++++++++++++++++++++
drivers/soundwire/slave.c | 1 +
2 files changed, 21 insertions(+)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index 4980dfd6f3a3..a2267c3a1d2d 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -610,6 +610,26 @@ static void sdw_modify_slave_status(struct sdw_slave *slave,
enum sdw_slave_status status)
{
mutex_lock(&slave->bus->bus_lock);
+
+ dev_vdbg(&slave->dev,
+ "%s: changing status slave %d status %d new status %d\n",
+ __func__, slave->dev_num, slave->status, status);
+
+ if (status == SDW_SLAVE_UNATTACHED) {
+ dev_dbg(&slave->dev,
+ "%s: initializing completion for Slave %d\n",
+ __func__, slave->dev_num);
+
+ init_completion(&slave->enumeration_complete);
+
+ } else if ((status == SDW_SLAVE_ATTACHED) &&
+ (slave->status == SDW_SLAVE_UNATTACHED)) {
+ dev_dbg(&slave->dev,
+ "%s: signaling completion for Slave %d\n",
+ __func__, slave->dev_num);
+
+ complete(&slave->enumeration_complete);
+ }
slave->status = status;
mutex_unlock(&slave->bus->bus_lock);
}
diff --git a/drivers/soundwire/slave.c b/drivers/soundwire/slave.c
index 08db0488e02d..e767a78066ee 100644
--- a/drivers/soundwire/slave.c
+++ b/drivers/soundwire/slave.c
@@ -46,6 +46,7 @@ static int sdw_slave_add(struct sdw_bus *bus,
slave->dev.of_node = of_node_get(to_of_node(fwnode));
slave->bus = bus;
slave->status = SDW_SLAVE_UNATTACHED;
+ init_completion(&slave->enumeration_complete);
slave->dev_num = 0;
init_completion(&slave->probe_complete);
slave->probed = false;
--
2.20.1
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