soundwire: bus: add stream refcount

The notion of stream is by construction based on a multi-bus
capability, to allow for aggregation of Peripheral devices or
functions located on different segments. We currently count how many
master_rt contexts are used by a stream, but we don't have the dual
refcount of how many streams are allocated on a given bus. This
refcount will be useful to check if BTP/BRA streams can be allocated.

Note that the stream_refcount is modified in sdw_master_rt_alloc() and
sdw_master_rt_free() which are both called with the bus_lock mutex
held, so there's no need for refcount_ primitives for additional
protection.

Signed-off-by: Pierre-Louis Bossart <[email protected]>
Reviewed-by: Rander Wang <[email protected]>
Signed-off-by: Bard Liao <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Vinod Koul <[email protected]>

Author: plbossart

drivers/soundwire/stream.c

@@ -1181,6 +1181,8 @@ static struct sdw_master_runtime
 	m_rt->bus = bus;
 	m_rt->stream = stream;
 
+	bus->stream_refcount++;
+
 	return m_rt;
 }
 
@@ -1217,6 +1219,7 @@ static void sdw_master_rt_free(struct sdw_master_runtime *m_rt,
 			       struct sdw_stream_runtime *stream)
 {
 	struct sdw_slave_runtime *s_rt, *_s_rt;
+	struct sdw_bus *bus = m_rt->bus;
 
 	list_for_each_entry_safe(s_rt, _s_rt, &m_rt->slave_rt_list, m_rt_node) {
 		sdw_slave_port_free(s_rt->slave, stream);
@@ -1226,6 +1229,8 @@ static void sdw_master_rt_free(struct sdw_master_runtime *m_rt,
 	list_del(&m_rt->stream_node);
 	list_del(&m_rt->bus_node);
 	kfree(m_rt);
+
+	bus->stream_refcount--;
 }
 
 /**

include/linux/soundwire/sdw.h

@@ -903,6 +903,7 @@ struct sdw_master_ops {
  * meaningful if multi_link is set. If set to 1, hardware-based
  * synchronization will be used even if a stream only uses a single
  * SoundWire segment.
+ * @stream_refcount: number of streams currently using this bus
  */
 struct sdw_bus {
 	struct device *dev;
@@ -933,6 +934,7 @@ struct sdw_bus {
 	u32 bank_switch_timeout;
 	bool multi_link;
 	int hw_sync_min_links;
+	int stream_refcount;
 };
 
 int sdw_bus_master_add(struct sdw_bus *bus, struct device *parent,