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Subject[PATCH 03/10] soundwire: bus: fix race condition with initialization_complete signaling
Date
Waiting for the enumeration to be complete may not be enough for a
Slave driver, there is a possible race condition between resume
operations and initializations handled in an interrupt thread, which
can results in settings not being fully restored after system or
pm_runtime resume.

This patch builds on the changes added for enumeration_complete,
init_completion() is called when the Slave device becomes UNATTACHED,
as done with enumeration_complete.

The difference with the enumeration_complete case is that complete()
is signaled after the Slave device is fully initialized after the
.update_status() callback is called.

A Slave device driver can decide to wait on either of the two
complete() cases, depending on its initialization code and
requirements.

Signed-off-by: Rander Wang <rander.wang@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
---
drivers/soundwire/bus.c | 8 ++++++++
drivers/soundwire/slave.c | 1 +
2 files changed, 9 insertions(+)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index a2267c3a1d2d..ea04cf5f5bdc 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -621,6 +621,7 @@ static void sdw_modify_slave_status(struct sdw_slave *slave,
__func__, slave->dev_num);

init_completion(&slave->enumeration_complete);
+ init_completion(&slave->initialization_complete);

} else if ((status == SDW_SLAVE_ATTACHED) &&
(slave->status == SDW_SLAVE_UNATTACHED)) {
@@ -1025,6 +1026,7 @@ int sdw_handle_slave_status(struct sdw_bus *bus,
{
enum sdw_slave_status prev_status;
struct sdw_slave *slave;
+ bool attached_initializing;
int i, ret = 0;

/* first check if any Slaves fell off the bus */
@@ -1070,6 +1072,8 @@ int sdw_handle_slave_status(struct sdw_bus *bus,
if (!slave)
continue;

+ attached_initializing = false;
+
switch (status[i]) {
case SDW_SLAVE_UNATTACHED:
if (slave->status == SDW_SLAVE_UNATTACHED)
@@ -1096,6 +1100,8 @@ int sdw_handle_slave_status(struct sdw_bus *bus,
if (prev_status == SDW_SLAVE_ALERT)
break;

+ attached_initializing = true;
+
ret = sdw_initialize_slave(slave);
if (ret)
dev_err(bus->dev,
@@ -1114,6 +1120,8 @@ int sdw_handle_slave_status(struct sdw_bus *bus,
if (ret)
dev_err(slave->bus->dev,
"Update Slave status failed:%d\n", ret);
+ if (attached_initializing)
+ complete(&slave->initialization_complete);
}

return ret;
diff --git a/drivers/soundwire/slave.c b/drivers/soundwire/slave.c
index e767a78066ee..aace57fae7f8 100644
--- a/drivers/soundwire/slave.c
+++ b/drivers/soundwire/slave.c
@@ -47,6 +47,7 @@ static int sdw_slave_add(struct sdw_bus *bus,
slave->bus = bus;
slave->status = SDW_SLAVE_UNATTACHED;
init_completion(&slave->enumeration_complete);
+ init_completion(&slave->initialization_complete);
slave->dev_num = 0;
init_completion(&slave->probe_complete);
slave->probed = false;
--
2.20.1
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