[PATCH v3 0/6] soundwire: Add multi link support

[PATCH v3 0/6] soundwire: Add multi link support

[Shreyas NC]

Currently, in the SoundWire subsystem, the concept of stream is
limited to a Master and one or more Slaves(Codecs). This series
aims to add support for multiple Master(s) sharing the same
reference clock and synchronized in the hardware.

This patch series adds:
 - Helpers to lock bus instances part of the stream
 - Boiler plate conversion of code to support a list of
   Master runtime
 - Support multi link bank switch to support synchronization
   between multiple masters
 - Add Intel platform ops for pre/post bank switch

changes in v3:
 - Added comments to explain the trigger for multi link
   bank switch
 - Added comments in the intel_post_bank_switch ops to explain
   how synchronous trigger of bank switch is handled.

Sanyog Kale (2):
  Documentation: soundwire: Add documentation for multi link
  soundwire: Add support to lock across bus instances

Shreyas NC (3):
  soundwire: Initialize completion for defer messages
  soundwire: Add support for multi link bank switch
  soundwire: intel: Add pre/post bank switch ops

Vinod Koul (1):
  soundwire: Handle multiple master instances in a stream

 Documentation/driver-api/soundwire/stream.rst |  29 +-
 drivers/soundwire/bus.c                       |   1 +
 drivers/soundwire/bus.h                       |   4 +
 drivers/soundwire/intel.c                     |  65 ++++
 drivers/soundwire/stream.c                    | 456 ++++++++++++++++++--------
 include/linux/soundwire/sdw.h                 |   8 +-
 6 files changed, 432 insertions(+), 131 deletions(-)

-- 
2.7.4

[PATCH v3 1/6] Documentation: soundwire: Add documentation for multi link

[Shreyas NC]

From: Sanyog Kale <sanyog.r.kale@intel.com>

Add example and documentation to describe multi link streams

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Sanyog Kale <sanyog.r.kale@intel.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Shreyas NC <shreyas.nc@intel.com>
---
 Documentation/driver-api/soundwire/stream.rst | 29 ++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/Documentation/driver-api/soundwire/stream.rst b/Documentation/driver-api/soundwire/stream.rst
index 29121aa..11623aab 100644
--- a/Documentation/driver-api/soundwire/stream.rst
+++ b/Documentation/driver-api/soundwire/stream.rst
@@ -75,7 +75,6 @@ Slaves are using single port. ::
 	                                                   |     (Data)    |
 	                                                   +---------------+
 
-
 Example 4: Stereo Stream with L and R channel is rendered by two different
 Ports of the Master and is received by only single Port of the Slave
 interface. ::
@@ -101,6 +100,34 @@ interface. ::
 	+--------------------+                             |                |
 							   +----------------+
 
+Example 5: Stereo Stream with L and R channel is rendered by 2 Masters, each
+rendering one channel, and is received by two different Slaves, each
+receiving one channel. Both Masters and both Slaves are using single port. ::
+
+	+---------------+                    Clock Signal  +---------------+
+	|    Master     +----------------------------------+     Slave     |
+	|   Interface   |                                  |   Interface   |
+	|       1       |                                  |       1       |
+	|               |                     Data Signal  |               |
+	|       L       +----------------------------------+       L       |
+	|     (Data)    |     Data Direction               |     (Data)    |
+	+---------------+  +----------------------->       +---------------+
+
+	+---------------+                    Clock Signal  +---------------+
+	|    Master     +----------------------------------+     Slave     |
+	|   Interface   |                                  |   Interface   |
+	|       2       |                                  |       2       |
+	|               |                     Data Signal  |               |
+	|       R       +----------------------------------+       R       |
+	|     (Data)    |     Data Direction               |     (Data)    |
+	+---------------+  +----------------------->       +---------------+
+
+Note: In multi-link cases like above, to lock, one would acquire a global
+lock and then go on locking bus instances. But, in this case the caller
+framework(ASoC DPCM) guarantees that stream operations on a card are
+always serialized. So, there is no race condition and hence no need for
+global lock.
+
 SoundWire Stream Management flow
 ================================
 
-- 
2.7.4

[PATCH v3 2/6] soundwire: Initialize completion for defer messages

[Shreyas NC]

Deferred messages are async messages used to synchronize
transitions mostly while doing a bank switch on multi links.
On successful transitions these messages are marked complete
and thereby confirming that all the buses performed bank switch
successfully.

So, initialize the completion structure for the same.

Signed-off-by: Sanyog Kale <sanyog.r.kale@intel.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Shreyas NC <shreyas.nc@intel.com>
---
 drivers/soundwire/bus.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index dcc0ff9..dbabd5e 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -175,6 +175,7 @@ static inline int do_transfer_defer(struct sdw_bus *bus,
 
 	defer->msg = msg;
 	defer->length = msg->len;
+	init_completion(&defer->complete);
 
 	for (i = 0; i <= retry; i++) {
 		resp = bus->ops->xfer_msg_defer(bus, msg, defer);
-- 
2.7.4

[PATCH v3 3/6] soundwire: Add support to lock across bus instances

[Shreyas NC]

From: Sanyog Kale <sanyog.r.kale@intel.com>

Currently, the stream concept is limited to a Master and one or
more Codecs.

This patch extends the concept to support multiple Master(s)
sharing the same reference clock and synchronized in the hardware.
Modify sdw_stream_runtime to support a list of sdw_master_runtime
for the same. The existing reference to a single m_rt is removed
in the next patch.

Typically to lock, one would acquire a global lock and then lock
bus instances. In this case, the caller framework(ASoC DPCM)
guarantees that stream operations on a card are always serialized.
So, there is no race condition and hence no need for global lock.

Bus lock(s) are acquired to reconfigure the bus while the stream
is set-up.
So, we add sdw_acquire_bus_lock()/sdw_release_bus_lock() APIs which
are used only to reconfigure the bus.

Signed-off-by: Sanyog Kale <sanyog.r.kale@intel.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Shreyas NC <shreyas.nc@intel.com>
---
 drivers/soundwire/bus.h       |  2 ++
 drivers/soundwire/stream.c    | 41 +++++++++++++++++++++++++++++++++++++++++
 include/linux/soundwire/sdw.h |  4 ++++
 3 files changed, 47 insertions(+)

diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h
index 3b15c4e..b6cfbdf 100644
--- a/drivers/soundwire/bus.h
+++ b/drivers/soundwire/bus.h
@@ -99,6 +99,7 @@ struct sdw_slave_runtime {
  * this stream, can be zero.
  * @slave_rt_list: Slave runtime list
  * @port_list: List of Master Ports configured for this stream, can be zero.
+ * @stream_node: sdw_stream_runtime master_list node
  * @bus_node: sdw_bus m_rt_list node
  */
 struct sdw_master_runtime {
@@ -108,6 +109,7 @@ struct sdw_master_runtime {
 	unsigned int ch_count;
 	struct list_head slave_rt_list;
 	struct list_head port_list;
+	struct list_head stream_node;
 	struct list_head bus_node;
 };
 
diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
index 8974a0f..eb942c6 100644
--- a/drivers/soundwire/stream.c
+++ b/drivers/soundwire/stream.c
@@ -747,6 +747,7 @@ struct sdw_stream_runtime *sdw_alloc_stream(char *stream_name)
 		return NULL;
 
 	stream->name = stream_name;
+	INIT_LIST_HEAD(&stream->master_list);
 	stream->state = SDW_STREAM_ALLOCATED;
 
 	return stream;
@@ -1234,6 +1235,46 @@ struct sdw_dpn_prop *sdw_get_slave_dpn_prop(struct sdw_slave *slave,
 	return NULL;
 }
 
+/**
+ * sdw_acquire_bus_lock: Acquire bus lock for all Master runtime(s)
+ *
+ * @stream: SoundWire stream
+ *
+ * Acquire bus_lock for each of the master runtime(m_rt) part of this
+ * stream to reconfigure the bus.
+ */
+static void sdw_acquire_bus_lock(struct sdw_stream_runtime *stream)
+{
+	struct sdw_master_runtime *m_rt = NULL;
+	struct sdw_bus *bus = NULL;
+
+	/* Iterate for all Master(s) in Master list */
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		bus = m_rt->bus;
+
+		mutex_lock(&bus->bus_lock);
+	}
+}
+
+/**
+ * sdw_release_bus_lock: Release bus lock for all Master runtime(s)
+ *
+ * @stream: SoundWire stream
+ *
+ * Release the previously held bus_lock after reconfiguring the bus.
+ */
+static void sdw_release_bus_lock(struct sdw_stream_runtime *stream)
+{
+	struct sdw_master_runtime *m_rt = NULL;
+	struct sdw_bus *bus = NULL;
+
+	/* Iterate for all Master(s) in Master list */
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		bus = m_rt->bus;
+		mutex_unlock(&bus->bus_lock);
+	}
+}
+
 static int _sdw_prepare_stream(struct sdw_stream_runtime *stream)
 {
 	struct sdw_master_runtime *m_rt = stream->m_rt;
diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
index 962971e..ccd8dcdf 100644
--- a/include/linux/soundwire/sdw.h
+++ b/include/linux/soundwire/sdw.h
@@ -769,6 +769,9 @@ struct sdw_stream_params {
  * @state: Current state of the stream
  * @type: Stream type PCM or PDM
  * @m_rt: Master runtime
+ * @master_list: List of Master runtime(s) in this stream.
+ * master_list can contain only one m_rt per Master instance
+ * for a stream
  */
 struct sdw_stream_runtime {
 	char *name;
@@ -776,6 +779,7 @@ struct sdw_stream_runtime {
 	enum sdw_stream_state state;
 	enum sdw_stream_type type;
 	struct sdw_master_runtime *m_rt;
+	struct list_head master_list;
 };
 
 struct sdw_stream_runtime *sdw_alloc_stream(char *stream_name);
-- 
2.7.4

[PATCH v3 4/6] soundwire: Handle multiple master instances in a stream

[Shreyas NC]

From: Vinod Koul <vkoul@kernel.org>

For each SoundWire stream operation, we need to parse master
list and operate upon all master runtime.

This is a preparatory patch to do the boilerplate conversion
of stream handling from single master runtime to handle a
list of master runtime. The code to support bank switch for
multiple master instances is added in the next patch.

Signed-off-by: Sanyog Kale <sanyog.r.kale@intel.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Shreyas NC <shreyas.nc@intel.com>
---
 drivers/soundwire/stream.c    | 309 +++++++++++++++++++++++++-----------------
 include/linux/soundwire/sdw.h |   2 -
 2 files changed, 186 insertions(+), 125 deletions(-)

diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
index eb942c6..0e8a2eb5 100644
--- a/drivers/soundwire/stream.c
+++ b/drivers/soundwire/stream.c
@@ -681,35 +681,45 @@ static int sdw_bank_switch(struct sdw_bus *bus)
 
 static int do_bank_switch(struct sdw_stream_runtime *stream)
 {
-	struct sdw_master_runtime *m_rt = stream->m_rt;
+	struct sdw_master_runtime *m_rt = NULL;
 	const struct sdw_master_ops *ops;
-	struct sdw_bus *bus = m_rt->bus;
+	struct sdw_bus *bus = NULL;
 	int ret = 0;
 
-	ops = bus->ops;
 
-	/* Pre-bank switch */
-	if (ops->pre_bank_switch) {
-		ret = ops->pre_bank_switch(bus);
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		bus = m_rt->bus;
+		ops = bus->ops;
+
+		/* Pre-bank switch */
+		if (ops->pre_bank_switch) {
+			ret = ops->pre_bank_switch(bus);
+			if (ret < 0) {
+				dev_err(bus->dev,
+					"Pre bank switch op failed: %d", ret);
+				return ret;
+			}
+		}
+
+		/* Bank switch */
+		ret = sdw_bank_switch(bus);
 		if (ret < 0) {
-			dev_err(bus->dev, "Pre bank switch op failed: %d", ret);
+			dev_err(bus->dev, "Bank switch failed: %d", ret);
 			return ret;
 		}
 	}
 
-	/* Bank switch */
-	ret = sdw_bank_switch(bus);
-	if (ret < 0) {
-		dev_err(bus->dev, "Bank switch failed: %d", ret);
-		return ret;
-	}
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		bus = m_rt->bus;
+		ops = bus->ops;
 
-	/* Post-bank switch */
-	if (ops->post_bank_switch) {
-		ret = ops->post_bank_switch(bus);
-		if (ret < 0) {
-			dev_err(bus->dev,
+		/* Post-bank switch */
+		if (ops->post_bank_switch) {
+			ret = ops->post_bank_switch(bus);
+			if (ret < 0) {
+				dev_err(bus->dev,
 					"Post bank switch op failed: %d", ret);
+			}
 		}
 	}
 
@@ -754,6 +764,21 @@ struct sdw_stream_runtime *sdw_alloc_stream(char *stream_name)
 }
 EXPORT_SYMBOL(sdw_alloc_stream);
 
+static struct sdw_master_runtime
+*sdw_find_master_rt(struct sdw_bus *bus,
+			struct sdw_stream_runtime *stream)
+{
+	struct sdw_master_runtime *m_rt = NULL;
+
+	/* Retrieve Bus handle if already available */
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		if (m_rt->bus == bus)
+			return m_rt;
+	}
+
+	return NULL;
+}
+
 /**
  * sdw_alloc_master_rt() - Allocates and initialize Master runtime handle
  *
@@ -770,12 +795,11 @@ static struct sdw_master_runtime
 {
 	struct sdw_master_runtime *m_rt;
 
-	m_rt = stream->m_rt;
-
 	/*
 	 * check if Master is already allocated (as a result of Slave adding
 	 * it first), if so skip allocation and go to configure
 	 */
+	m_rt = sdw_find_master_rt(bus, stream);
 	if (m_rt)
 		goto stream_config;
 
@@ -786,7 +810,7 @@ static struct sdw_master_runtime
 	/* Initialization of Master runtime handle */
 	INIT_LIST_HEAD(&m_rt->port_list);
 	INIT_LIST_HEAD(&m_rt->slave_rt_list);
-	stream->m_rt = m_rt;
+	list_add_tail(&m_rt->stream_node, &stream->master_list);
 
 	list_add_tail(&m_rt->bus_node, &bus->m_rt_list);
 
@@ -844,17 +868,21 @@ static void sdw_slave_port_release(struct sdw_bus *bus,
 			struct sdw_stream_runtime *stream)
 {
 	struct sdw_port_runtime *p_rt, *_p_rt;
-	struct sdw_master_runtime *m_rt = stream->m_rt;
+	struct sdw_master_runtime *m_rt;
 	struct sdw_slave_runtime *s_rt;
 
-	list_for_each_entry(s_rt, &m_rt->slave_rt_list, m_rt_node) {
-		if (s_rt->slave != slave)
-			continue;
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		list_for_each_entry(s_rt, &m_rt->slave_rt_list, m_rt_node) {
 
-		list_for_each_entry_safe(p_rt, _p_rt,
-				&s_rt->port_list, port_node) {
-			list_del(&p_rt->port_node);
-			kfree(p_rt);
+			if (s_rt->slave != slave)
+				continue;
+
+			list_for_each_entry_safe(p_rt, _p_rt,
+					&s_rt->port_list, port_node) {
+
+				list_del(&p_rt->port_node);
+				kfree(p_rt);
+			}
 		}
 	}
 }
@@ -871,16 +899,18 @@ static void sdw_release_slave_stream(struct sdw_slave *slave,
 			struct sdw_stream_runtime *stream)
 {
 	struct sdw_slave_runtime *s_rt, *_s_rt;
-	struct sdw_master_runtime *m_rt = stream->m_rt;
-
-	/* Retrieve Slave runtime handle */
-	list_for_each_entry_safe(s_rt, _s_rt,
-			&m_rt->slave_rt_list, m_rt_node) {
+	struct sdw_master_runtime *m_rt;
 
-		if (s_rt->slave == slave) {
-			list_del(&s_rt->m_rt_node);
-			kfree(s_rt);
-			return;
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		/* Retrieve Slave runtime handle */
+		list_for_each_entry_safe(s_rt, _s_rt,
+					&m_rt->slave_rt_list, m_rt_node) {
+
+			if (s_rt->slave == slave) {
+				list_del(&s_rt->m_rt_node);
+				kfree(s_rt);
+				return;
+			}
 		}
 	}
 }
@@ -888,6 +918,7 @@ static void sdw_release_slave_stream(struct sdw_slave *slave,
 /**
  * sdw_release_master_stream() - Free Master runtime handle
  *
+ * @m_rt: Master runtime node
  * @stream: Stream runtime handle.
  *
  * This function is to be called with bus_lock held
@@ -895,16 +926,18 @@ static void sdw_release_slave_stream(struct sdw_slave *slave,
  * handle. If this is called first then sdw_release_slave_stream() will have
  * no effect as Slave(s) runtime handle would already be freed up.
  */
-static void sdw_release_master_stream(struct sdw_stream_runtime *stream)
+static void sdw_release_master_stream(struct sdw_master_runtime *m_rt,
+			struct sdw_stream_runtime *stream)
 {
-	struct sdw_master_runtime *m_rt = stream->m_rt;
 	struct sdw_slave_runtime *s_rt, *_s_rt;
 
 	list_for_each_entry_safe(s_rt, _s_rt,
 			&m_rt->slave_rt_list, m_rt_node)
 		sdw_stream_remove_slave(s_rt->slave, stream);
 
+	list_del(&m_rt->stream_node);
 	list_del(&m_rt->bus_node);
+	kfree(m_rt);
 }
 
 /**
@@ -918,13 +951,22 @@ static void sdw_release_master_stream(struct sdw_stream_runtime *stream)
 int sdw_stream_remove_master(struct sdw_bus *bus,
 		struct sdw_stream_runtime *stream)
 {
+	struct sdw_master_runtime *m_rt, *_m_rt;
+
 	mutex_lock(&bus->bus_lock);
 
-	sdw_release_master_stream(stream);
-	sdw_master_port_release(bus, stream->m_rt);
-	stream->state = SDW_STREAM_RELEASED;
-	kfree(stream->m_rt);
-	stream->m_rt = NULL;
+	list_for_each_entry_safe(m_rt, _m_rt,
+			&stream->master_list, stream_node) {
+
+		if (m_rt->bus != bus)
+			continue;
+
+		sdw_master_port_release(bus, m_rt);
+		sdw_release_master_stream(m_rt, stream);
+	}
+
+	if (list_empty(&stream->master_list))
+		stream->state = SDW_STREAM_RELEASED;
 
 	mutex_unlock(&bus->bus_lock);
 
@@ -1127,7 +1169,7 @@ int sdw_stream_add_master(struct sdw_bus *bus,
 	stream->state = SDW_STREAM_CONFIGURED;
 
 stream_error:
-	sdw_release_master_stream(stream);
+	sdw_release_master_stream(m_rt, stream);
 error:
 	mutex_unlock(&bus->bus_lock);
 	return ret;
@@ -1195,7 +1237,7 @@ int sdw_stream_add_slave(struct sdw_slave *slave,
 	 * we hit error so cleanup the stream, release all Slave(s) and
 	 * Master runtime
 	 */
-	sdw_release_master_stream(stream);
+	sdw_release_master_stream(m_rt, stream);
 error:
 	mutex_unlock(&slave->bus->bus_lock);
 	return ret;
@@ -1277,31 +1319,36 @@ static void sdw_release_bus_lock(struct sdw_stream_runtime *stream)
 
 static int _sdw_prepare_stream(struct sdw_stream_runtime *stream)
 {
-	struct sdw_master_runtime *m_rt = stream->m_rt;
-	struct sdw_bus *bus = m_rt->bus;
+	struct sdw_master_runtime *m_rt = NULL;
+	struct sdw_bus *bus = NULL;
 	struct sdw_master_prop *prop = NULL;
 	struct sdw_bus_params params;
 	int ret;
 
-	prop = &bus->prop;
-	memcpy(&params, &bus->params, sizeof(params));
+	/* Prepare  Master(s) and Slave(s) port(s) associated with stream */
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		bus = m_rt->bus;
+		prop = &bus->prop;
+		memcpy(&params, &bus->params, sizeof(params));
 
-	/* TODO: Support Asynchronous mode */
-	if ((prop->max_freq % stream->params.rate) != 0) {
-		dev_err(bus->dev, "Async mode not supported");
-		return -EINVAL;
-	}
+		/* TODO: Support Asynchronous mode */
+		if ((prop->max_freq % stream->params.rate) != 0) {
+			dev_err(bus->dev, "Async mode not supported");
+			return -EINVAL;
+		}
 
-	/* Increment cumulative bus bandwidth */
-	/* TODO: Update this during Device-Device support */
-	bus->params.bandwidth += m_rt->stream->params.rate *
-		m_rt->ch_count * m_rt->stream->params.bps;
+		/* Increment cumulative bus bandwidth */
+		/* TODO: Update this during Device-Device support */
+		bus->params.bandwidth += m_rt->stream->params.rate *
+			m_rt->ch_count * m_rt->stream->params.bps;
+
+		/* Program params */
+		ret = sdw_program_params(bus);
+		if (ret < 0) {
+			dev_err(bus->dev, "Program params failed: %d", ret);
+			goto restore_params;
+		}
 
-	/* Program params */
-	ret = sdw_program_params(bus);
-	if (ret < 0) {
-		dev_err(bus->dev, "Program params failed: %d", ret);
-		goto restore_params;
 	}
 
 	ret = do_bank_switch(stream);
@@ -1310,12 +1357,16 @@ static int _sdw_prepare_stream(struct sdw_stream_runtime *stream)
 		goto restore_params;
 	}
 
-	/* Prepare port(s) on the new clock configuration */
-	ret = sdw_prep_deprep_ports(m_rt, true);
-	if (ret < 0) {
-		dev_err(bus->dev, "Prepare port(s) failed ret = %d",
-				ret);
-		return ret;
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		bus = m_rt->bus;
+
+		/* Prepare port(s) on the new clock configuration */
+		ret = sdw_prep_deprep_ports(m_rt, true);
+		if (ret < 0) {
+			dev_err(bus->dev, "Prepare port(s) failed ret = %d",
+					ret);
+			return ret;
+		}
 	}
 
 	stream->state = SDW_STREAM_PREPARED;
@@ -1343,35 +1394,40 @@ int sdw_prepare_stream(struct sdw_stream_runtime *stream)
 		return -EINVAL;
 	}
 
-	mutex_lock(&stream->m_rt->bus->bus_lock);
+	sdw_acquire_bus_lock(stream);
 
 	ret = _sdw_prepare_stream(stream);
 	if (ret < 0)
 		pr_err("Prepare for stream:%s failed: %d", stream->name, ret);
 
-	mutex_unlock(&stream->m_rt->bus->bus_lock);
+	sdw_release_bus_lock(stream);
 	return ret;
 }
 EXPORT_SYMBOL(sdw_prepare_stream);
 
 static int _sdw_enable_stream(struct sdw_stream_runtime *stream)
 {
-	struct sdw_master_runtime *m_rt = stream->m_rt;
-	struct sdw_bus *bus = m_rt->bus;
+	struct sdw_master_runtime *m_rt = NULL;
+	struct sdw_bus *bus = NULL;
 	int ret;
 
-	/* Program params */
-	ret = sdw_program_params(bus);
-	if (ret < 0) {
-		dev_err(bus->dev, "Program params failed: %d", ret);
-		return ret;
-	}
+	/* Enable Master(s) and Slave(s) port(s) associated with stream */
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		bus = m_rt->bus;
 
-	/* Enable port(s) */
-	ret = sdw_enable_disable_ports(m_rt, true);
-	if (ret < 0) {
-		dev_err(bus->dev, "Enable port(s) failed ret: %d", ret);
-		return ret;
+		/* Program params */
+		ret = sdw_program_params(bus);
+		if (ret < 0) {
+			dev_err(bus->dev, "Program params failed: %d", ret);
+			return ret;
+		}
+
+		/* Enable port(s) */
+		ret = sdw_enable_disable_ports(m_rt, true);
+		if (ret < 0) {
+			dev_err(bus->dev, "Enable port(s) failed ret: %d", ret);
+			return ret;
+		}
 	}
 
 	ret = do_bank_switch(stream);
@@ -1400,37 +1456,42 @@ int sdw_enable_stream(struct sdw_stream_runtime *stream)
 		return -EINVAL;
 	}
 
-	mutex_lock(&stream->m_rt->bus->bus_lock);
+	sdw_acquire_bus_lock(stream);
 
 	ret = _sdw_enable_stream(stream);
 	if (ret < 0)
 		pr_err("Enable for stream:%s failed: %d", stream->name, ret);
 
-	mutex_unlock(&stream->m_rt->bus->bus_lock);
+	sdw_release_bus_lock(stream);
 	return ret;
 }
 EXPORT_SYMBOL(sdw_enable_stream);
 
 static int _sdw_disable_stream(struct sdw_stream_runtime *stream)
 {
-	struct sdw_master_runtime *m_rt = stream->m_rt;
-	struct sdw_bus *bus = m_rt->bus;
+	struct sdw_master_runtime *m_rt = NULL;
+	struct sdw_bus *bus = NULL;
 	int ret;
 
-	/* Disable port(s) */
-	ret = sdw_enable_disable_ports(m_rt, false);
-	if (ret < 0) {
-		dev_err(bus->dev, "Disable port(s) failed: %d", ret);
-		return ret;
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		bus = m_rt->bus;
+		/* Disable port(s) */
+		ret = sdw_enable_disable_ports(m_rt, false);
+		if (ret < 0) {
+			dev_err(bus->dev, "Disable port(s) failed: %d", ret);
+			return ret;
+		}
 	}
-
 	stream->state = SDW_STREAM_DISABLED;
 
-	/* Program params */
-	ret = sdw_program_params(bus);
-	if (ret < 0) {
-		dev_err(bus->dev, "Program params failed: %d", ret);
-		return ret;
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		bus = m_rt->bus;
+		/* Program params */
+		ret = sdw_program_params(bus);
+		if (ret < 0) {
+			dev_err(bus->dev, "Program params failed: %d", ret);
+			return ret;
+		}
 	}
 
 	return do_bank_switch(stream);
@@ -1452,43 +1513,46 @@ int sdw_disable_stream(struct sdw_stream_runtime *stream)
 		return -EINVAL;
 	}
 
-	mutex_lock(&stream->m_rt->bus->bus_lock);
+	sdw_acquire_bus_lock(stream);
 
 	ret = _sdw_disable_stream(stream);
 	if (ret < 0)
 		pr_err("Disable for stream:%s failed: %d", stream->name, ret);
 
-	mutex_unlock(&stream->m_rt->bus->bus_lock);
+	sdw_release_bus_lock(stream);
 	return ret;
 }
 EXPORT_SYMBOL(sdw_disable_stream);
 
 static int _sdw_deprepare_stream(struct sdw_stream_runtime *stream)
 {
-	struct sdw_master_runtime *m_rt = stream->m_rt;
-	struct sdw_bus *bus = m_rt->bus;
+	struct sdw_master_runtime *m_rt = NULL;
+	struct sdw_bus *bus = NULL;
 	int ret = 0;
 
-	/* De-prepare port(s) */
-	ret = sdw_prep_deprep_ports(m_rt, false);
-	if (ret < 0) {
-		dev_err(bus->dev, "De-prepare port(s) failed: %d", ret);
-		return ret;
-	}
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+		bus = m_rt->bus;
+		/* De-prepare port(s) */
+		ret = sdw_prep_deprep_ports(m_rt, false);
+		if (ret < 0) {
+			dev_err(bus->dev, "De-prepare port(s) failed: %d", ret);
+			return ret;
+		}
 
-	stream->state = SDW_STREAM_DEPREPARED;
+		/* TODO: Update this during Device-Device support */
+		bus->params.bandwidth -= m_rt->stream->params.rate *
+			m_rt->ch_count * m_rt->stream->params.bps;
 
-	/* TODO: Update this during Device-Device support */
-	bus->params.bandwidth -= m_rt->stream->params.rate *
-		m_rt->ch_count * m_rt->stream->params.bps;
+		/* Program params */
+		ret = sdw_program_params(bus);
+		if (ret < 0) {
+			dev_err(bus->dev, "Program params failed: %d", ret);
+			return ret;
+		}
 
-	/* Program params */
-	ret = sdw_program_params(bus);
-	if (ret < 0) {
-		dev_err(bus->dev, "Program params failed: %d", ret);
-		return ret;
 	}
 
+	stream->state = SDW_STREAM_DEPREPARED;
 	return do_bank_switch(stream);
 }
 
@@ -1508,13 +1572,12 @@ int sdw_deprepare_stream(struct sdw_stream_runtime *stream)
 		return -EINVAL;
 	}
 
-	mutex_lock(&stream->m_rt->bus->bus_lock);
-
+	sdw_acquire_bus_lock(stream);
 	ret = _sdw_deprepare_stream(stream);
 	if (ret < 0)
 		pr_err("De-prepare for stream:%d failed: %d", ret, ret);
 
-	mutex_unlock(&stream->m_rt->bus->bus_lock);
+	sdw_release_bus_lock(stream);
 	return ret;
 }
 EXPORT_SYMBOL(sdw_deprepare_stream);
diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
index ccd8dcdf..03df709 100644
--- a/include/linux/soundwire/sdw.h
+++ b/include/linux/soundwire/sdw.h
@@ -768,7 +768,6 @@ struct sdw_stream_params {
  * @params: Stream parameters
  * @state: Current state of the stream
  * @type: Stream type PCM or PDM
- * @m_rt: Master runtime
  * @master_list: List of Master runtime(s) in this stream.
  * master_list can contain only one m_rt per Master instance
  * for a stream
@@ -778,7 +777,6 @@ struct sdw_stream_runtime {
 	struct sdw_stream_params params;
 	enum sdw_stream_state state;
 	enum sdw_stream_type type;
-	struct sdw_master_runtime *m_rt;
 	struct list_head master_list;
 };
 
-- 
2.7.4

[PATCH v3 5/6] soundwire: Add support for multi link bank switch

[Shreyas NC]

In cases of multiple Masters in a stream, synchronization
between multiple Master(s) is achieved by performing bank switch
together and using Master methods.

Add sdw_ml_bank_switch() to wait for completion of bank switch.

Signed-off-by: Sanyog Kale <sanyog.r.kale@intel.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Shreyas NC <shreyas.nc@intel.com>
---
 drivers/soundwire/bus.h       |   2 +
 drivers/soundwire/stream.c    | 116 ++++++++++++++++++++++++++++++++++++++----
 include/linux/soundwire/sdw.h |   2 +
 3 files changed, 110 insertions(+), 10 deletions(-)

diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h
index b6cfbdf..c77de05 100644
--- a/drivers/soundwire/bus.h
+++ b/drivers/soundwire/bus.h
@@ -4,6 +4,8 @@
 #ifndef __SDW_BUS_H
 #define __SDW_BUS_H
 
+#define DEFAULT_BANK_SWITCH_TIMEOUT 3000
+
 #if IS_ENABLED(CONFIG_ACPI)
 int sdw_acpi_find_slaves(struct sdw_bus *bus);
 #else
diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
index 0e8a2eb5..771c963 100644
--- a/drivers/soundwire/stream.c
+++ b/drivers/soundwire/stream.c
@@ -638,6 +638,8 @@ static int sdw_bank_switch(struct sdw_bus *bus)
 	if (!wr_msg)
 		return -ENOMEM;
 
+	bus->defer_msg.msg = wr_msg;
+
 	wbuf = kzalloc(sizeof(*wbuf), GFP_KERNEL);
 	if (!wbuf) {
 		ret = -ENOMEM;
@@ -658,17 +660,23 @@ static int sdw_bank_switch(struct sdw_bus *bus)
 					SDW_MSG_FLAG_WRITE, wbuf);
 	wr_msg->ssp_sync = true;
 
-	ret = sdw_transfer(bus, wr_msg);
+	if (bus->multi_link)
+		ret = sdw_transfer_defer(bus, wr_msg, &bus->defer_msg);
+	else
+		ret = sdw_transfer(bus, wr_msg);
+
 	if (ret < 0) {
 		dev_err(bus->dev, "Slave frame_ctrl reg write failed");
 		goto error;
 	}
 
-	kfree(wr_msg);
-	kfree(wbuf);
-	bus->defer_msg.msg = NULL;
-	bus->params.curr_bank = !bus->params.curr_bank;
-	bus->params.next_bank = !bus->params.next_bank;
+	if (!bus->multi_link) {
+		kfree(wr_msg);
+		kfree(wbuf);
+		bus->defer_msg.msg = NULL;
+		bus->params.curr_bank = !bus->params.curr_bank;
+		bus->params.next_bank = !bus->params.next_bank;
+	}
 
 	return 0;
 
@@ -679,36 +687,88 @@ static int sdw_bank_switch(struct sdw_bus *bus)
 	return ret;
 }
 
+/**
+ * sdw_ml_sync_bank_switch: Multilink register bank switch
+ *
+ * @bus: SDW bus instance
+ *
+ * Caller function should free the buffers on error
+ */
+static int sdw_ml_sync_bank_switch(struct sdw_bus *bus)
+{
+	unsigned long time_left;
+	int ret = 0;
+
+	if (!bus->multi_link)
+		return ret;
+
+	/* Wait for completion of transfer */
+	time_left = wait_for_completion_timeout(&bus->defer_msg.complete,
+						bus->bank_switch_timeout);
+
+	if (!time_left) {
+		dev_err(bus->dev, "Controller Timed out on bank switch");
+		return -ETIMEDOUT;
+	}
+
+	bus->params.curr_bank = !bus->params.curr_bank;
+	bus->params.next_bank = !bus->params.next_bank;
+
+	if (bus->defer_msg.msg) {
+		kfree(bus->defer_msg.msg->buf);
+		kfree(bus->defer_msg.msg);
+	}
+
+	return ret;
+}
+
 static int do_bank_switch(struct sdw_stream_runtime *stream)
 {
 	struct sdw_master_runtime *m_rt = NULL;
 	const struct sdw_master_ops *ops;
 	struct sdw_bus *bus = NULL;
+	bool multi_link = false;
 	int ret = 0;
 
-
 	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
 		bus = m_rt->bus;
 		ops = bus->ops;
 
+		if (bus->multi_link) {
+			multi_link = true;
+			mutex_lock(&bus->msg_lock);
+		}
+
 		/* Pre-bank switch */
 		if (ops->pre_bank_switch) {
 			ret = ops->pre_bank_switch(bus);
 			if (ret < 0) {
 				dev_err(bus->dev,
 					"Pre bank switch op failed: %d", ret);
-				return ret;
+				goto msg_unlock;
 			}
 		}
 
-		/* Bank switch */
+		/*
+		 * Perform Bank switch operation.
+		 * For multi link cases, the actual bank switch is
+		 * synchronized across all Masters and happens later as a
+		 * part of post_bank_switch ops.
+		 */
 		ret = sdw_bank_switch(bus);
 		if (ret < 0) {
 			dev_err(bus->dev, "Bank switch failed: %d", ret);
-			return ret;
+			goto error;
+
 		}
 	}
 
+	/*
+	 * For multi link cases, it is expected that the bank switch is
+	 * triggered by the post_bank_switch for the first Master in the list
+	 * and for the other Masters the post_bank_switch() should return doing
+	 * nothing.
+	 */
 	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
 		bus = m_rt->bus;
 		ops = bus->ops;
@@ -719,8 +779,44 @@ static int do_bank_switch(struct sdw_stream_runtime *stream)
 			if (ret < 0) {
 				dev_err(bus->dev,
 					"Post bank switch op failed: %d", ret);
+				goto error;
 			}
 		}
+
+		/* Set the bank switch timeout to default, if not set */
+		if (!bus->bank_switch_timeout)
+			bus->bank_switch_timeout = DEFAULT_BANK_SWITCH_TIMEOUT;
+
+		/* Check if bank switch was successful */
+		ret = sdw_ml_sync_bank_switch(bus);
+		if (ret < 0) {
+			dev_err(bus->dev,
+				"multi link bank switch failed: %d", ret);
+			goto error;
+		}
+
+		mutex_unlock(&bus->msg_lock);
+	}
+
+	return ret;
+
+error:
+	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+
+		bus = m_rt->bus;
+
+		kfree(bus->defer_msg.msg->buf);
+		kfree(bus->defer_msg.msg);
+	}
+
+msg_unlock:
+
+	if (multi_link) {
+		list_for_each_entry(m_rt, &stream->master_list, stream_node) {
+			bus = m_rt->bus;
+			if (mutex_is_locked(&bus->msg_lock))
+				mutex_unlock(&bus->msg_lock);
+		}
 	}
 
 	return ret;
diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
index 03df709..f006029 100644
--- a/include/linux/soundwire/sdw.h
+++ b/include/linux/soundwire/sdw.h
@@ -673,6 +673,7 @@ struct sdw_master_ops {
  * @params: Current bus parameters
  * @prop: Master properties
  * @m_rt_list: List of Master instance of all stream(s) running on Bus. This
+ * @multi_link: if multi links are supported
  * is used to compute and program bus bandwidth, clock, frame shape,
  * transport and port parameters
  * @defer_msg: Defer message
@@ -691,6 +692,7 @@ struct sdw_bus {
 	struct sdw_bus_params params;
 	struct sdw_master_prop prop;
 	struct list_head m_rt_list;
+	bool multi_link;
 	struct sdw_defer defer_msg;
 	unsigned int clk_stop_timeout;
 	u32 bank_switch_timeout;
-- 
2.7.4

[PATCH v3 6/6] soundwire: intel: Add pre/post bank switch ops

[Shreyas NC]

To support multi link on Intel platforms, we need to update
SDW SHIM registers.

So, add pre/post bank switch ops for the same in Intel driver.

Signed-off-by: Sanyog Kale <sanyog.r.kale@intel.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Shreyas NC <shreyas.nc@intel.com>
---
 drivers/soundwire/intel.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
index 0a8990e..da7f91f 100644
--- a/drivers/soundwire/intel.c
+++ b/drivers/soundwire/intel.c
@@ -398,6 +398,69 @@ static int intel_config_stream(struct sdw_intel *sdw,
 }
 
 /*
+ * bank switch routines
+ */
+
+static int intel_pre_bank_switch(struct sdw_bus *bus)
+{
+	struct sdw_cdns *cdns = bus_to_cdns(bus);
+	struct sdw_intel *sdw = cdns_to_intel(cdns);
+	void __iomem *shim = sdw->res->shim;
+	int sync_reg;
+
+	/* Write to register only for multi-link */
+	if (!bus->multi_link)
+		return 0;
+
+	/* Read SYNC register */
+	sync_reg = intel_readl(shim, SDW_SHIM_SYNC);
+	sync_reg |= SDW_SHIM_SYNC_CMDSYNC << sdw->instance;
+	intel_writel(shim, SDW_SHIM_SYNC, sync_reg);
+
+	return 0;
+}
+
+static int intel_post_bank_switch(struct sdw_bus *bus)
+{
+	struct sdw_cdns *cdns = bus_to_cdns(bus);
+	struct sdw_intel *sdw = cdns_to_intel(cdns);
+	void __iomem *shim = sdw->res->shim;
+	int sync_reg, ret;
+
+	/* Write to register only for multi-link */
+	if (!bus->multi_link)
+		return 0;
+
+	/* Read SYNC register */
+	sync_reg = intel_readl(shim, SDW_SHIM_SYNC);
+
+	/*
+	 * post_bank_switch() ops is called from the bus in loop for
+	 * all the Masters in the steam with the expectation that
+	 * we trigger the bankswitch for the only first Master in the list
+	 * and do nothing for the other Masters
+	 *
+	 * So, set the SYNCGO bit only if CMDSYNC bit is set for any Master.
+	 */
+	if (!(sync_reg & SDW_SHIM_SYNC_CMDSYNC_MASK))
+		return 0;
+
+	/*
+	 * Set SyncGO bit to synchronously trigger a bank switch for
+	 * all the masters. A write to SYNCGO bit clears CMDSYNC bit for all
+	 * the Masters.
+	 */
+	sync_reg |= SDW_SHIM_SYNC_SYNCGO;
+
+	ret = intel_clear_bit(shim, SDW_SHIM_SYNC, sync_reg,
+					SDW_SHIM_SYNC_SYNCGO);
+	if (ret < 0)
+		dev_err(sdw->cdns.dev, "Post bank switch failed: %d", ret);
+
+	return ret;
+}
+
+/*
  * DAI routines
  */
 
@@ -750,6 +813,8 @@ static struct sdw_master_ops sdw_intel_ops = {
 	.xfer_msg_defer = cdns_xfer_msg_defer,
 	.reset_page_addr = cdns_reset_page_addr,
 	.set_bus_conf = cdns_bus_conf,
+	.pre_bank_switch = intel_pre_bank_switch,
+	.post_bank_switch = intel_post_bank_switch,
 };
 
 /*
-- 
2.7.4

Re: [PATCH v3 5/6] soundwire: Add support for multi link bank switch

[Pierre-Louis Bossart]

> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> index 0e8a2eb5..771c963 100644
> --- a/drivers/soundwire/stream.c
> +++ b/drivers/soundwire/stream.c
> @@ -638,6 +638,8 @@ static int sdw_bank_switch(struct sdw_bus *bus)
>   	if (!wr_msg)
>   		return -ENOMEM;
>   
> +	bus->defer_msg.msg = wr_msg;
> +
>   	wbuf = kzalloc(sizeof(*wbuf), GFP_KERNEL);
>   	if (!wbuf) {
>   		ret = -ENOMEM;
> @@ -658,17 +660,23 @@ static int sdw_bank_switch(struct sdw_bus *bus)
>   					SDW_MSG_FLAG_WRITE, wbuf);
>   	wr_msg->ssp_sync = true;
>   
> -	ret = sdw_transfer(bus, wr_msg);
> +	if (bus->multi_link)
> +		ret = sdw_transfer_defer(bus, wr_msg, &bus->defer_msg);
> +	else
> +		ret = sdw_transfer(bus, wr_msg);
> +

Re-reading this v3, I wonder if there is a small logic flaw here or an 
intended behavior.

the bus->multi_link field is a hardware capability, it provides 
information on whether the hardware can support synchronized bank 
switches across multiple Master interfaces. This is independent of the 
streams being handled, it's a bus property - not a stream one.

However the default/typical case is a stream handled by a single master, 
so when the hardware is capable of handling multiple masters this does 
not mean you should use the deferred transfer, the regular case would 
work just fine for a regular stream. If your SSP rate is faster than the 
common sync signal it might even be beneficial not to use the deferred 
transfer.

in other words, should the code be written with something like
if (bus->multi_link && master_rt_count > 1)
with master_rt_count being determined based on the stream properties.

Or was the intent that you always rely on the deferred mechanism, even 
if the stream is not handled by multiple masters? In that case, do we 
even need the regular bank switch?

>   	if (ret < 0) {
>   		dev_err(bus->dev, "Slave frame_ctrl reg write failed");
>   		goto error;
>   	}
>   
> -	kfree(wr_msg);
> -	kfree(wbuf);
> -	bus->defer_msg.msg = NULL;
> -	bus->params.curr_bank = !bus->params.curr_bank;
> -	bus->params.next_bank = !bus->params.next_bank;
> +	if (!bus->multi_link) {
> +		kfree(wr_msg);
> +		kfree(wbuf);
> +		bus->defer_msg.msg = NULL;
> +		bus->params.curr_bank = !bus->params.curr_bank;
> +		bus->params.next_bank = !bus->params.next_bank;
> +	}
>   
>   	return 0;
>   
> @@ -679,36 +687,88 @@ static int sdw_bank_switch(struct sdw_bus *bus)
>   	return ret;
>   }
>   
> +/**
> + * sdw_ml_sync_bank_switch: Multilink register bank switch
> + *
> + * @bus: SDW bus instance
> + *
> + * Caller function should free the buffers on error
> + */
> +static int sdw_ml_sync_bank_switch(struct sdw_bus *bus)
> +{
> +	unsigned long time_left;
> +	int ret = 0;
> +
> +	if (!bus->multi_link)
> +		return ret;
> +
> +	/* Wait for completion of transfer */
> +	time_left = wait_for_completion_timeout(&bus->defer_msg.complete,
> +						bus->bank_switch_timeout);
> +
> +	if (!time_left) {
> +		dev_err(bus->dev, "Controller Timed out on bank switch");
> +		return -ETIMEDOUT;
> +	}
> +
> +	bus->params.curr_bank = !bus->params.curr_bank;
> +	bus->params.next_bank = !bus->params.next_bank;
> +
> +	if (bus->defer_msg.msg) {
> +		kfree(bus->defer_msg.msg->buf);
> +		kfree(bus->defer_msg.msg);
> +	}
> +
> +	return ret;
> +}
> +
>   static int do_bank_switch(struct sdw_stream_runtime *stream)
>   {
>   	struct sdw_master_runtime *m_rt = NULL;
>   	const struct sdw_master_ops *ops;
>   	struct sdw_bus *bus = NULL;
> +	bool multi_link = false;
>   	int ret = 0;
>   
> -
>   	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
>   		bus = m_rt->bus;
>   		ops = bus->ops;
>   
> +		if (bus->multi_link) {
> +			multi_link = true;
> +			mutex_lock(&bus->msg_lock);
> +		}
> +
>   		/* Pre-bank switch */
>   		if (ops->pre_bank_switch) {
>   			ret = ops->pre_bank_switch(bus);
>   			if (ret < 0) {
>   				dev_err(bus->dev,
>   					"Pre bank switch op failed: %d", ret);
> -				return ret;
> +				goto msg_unlock;
>   			}
>   		}
>   
> -		/* Bank switch */
> +		/*
> +		 * Perform Bank switch operation.
> +		 * For multi link cases, the actual bank switch is
> +		 * synchronized across all Masters and happens later as a
> +		 * part of post_bank_switch ops.
> +		 */
>   		ret = sdw_bank_switch(bus);
>   		if (ret < 0) {
>   			dev_err(bus->dev, "Bank switch failed: %d", ret);
> -			return ret;
> +			goto error;
> +
>   		}
>   	}
>   
> +	/*
> +	 * For multi link cases, it is expected that the bank switch is
> +	 * triggered by the post_bank_switch for the first Master in the list
> +	 * and for the other Masters the post_bank_switch() should return doing
> +	 * nothing.
> +	 */
>   	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
>   		bus = m_rt->bus;
>   		ops = bus->ops;
> @@ -719,8 +779,44 @@ static int do_bank_switch(struct sdw_stream_runtime *stream)
>   			if (ret < 0) {
>   				dev_err(bus->dev,
>   					"Post bank switch op failed: %d", ret);
> +				goto error;
>   			}
>   		}
> +
> +		/* Set the bank switch timeout to default, if not set */
> +		if (!bus->bank_switch_timeout)
> +			bus->bank_switch_timeout = DEFAULT_BANK_SWITCH_TIMEOUT;
> +
> +		/* Check if bank switch was successful */
> +		ret = sdw_ml_sync_bank_switch(bus);
> +		if (ret < 0) {
> +			dev_err(bus->dev,
> +				"multi link bank switch failed: %d", ret);
> +			goto error;
> +		}
> +
> +		mutex_unlock(&bus->msg_lock);
> +	}
> +
> +	return ret;
> +
> +error:
> +	list_for_each_entry(m_rt, &stream->master_list, stream_node) {
> +
> +		bus = m_rt->bus;
> +
> +		kfree(bus->defer_msg.msg->buf);
> +		kfree(bus->defer_msg.msg);
> +	}
> +
> +msg_unlock:
> +
> +	if (multi_link) {
> +		list_for_each_entry(m_rt, &stream->master_list, stream_node) {
> +			bus = m_rt->bus;
> +			if (mutex_is_locked(&bus->msg_lock))
> +				mutex_unlock(&bus->msg_lock);
> +		}
>   	}
>   
>   	return ret;
> diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
> index 03df709..f006029 100644
> --- a/include/linux/soundwire/sdw.h
> +++ b/include/linux/soundwire/sdw.h
> @@ -673,6 +673,7 @@ struct sdw_master_ops {
>    * @params: Current bus parameters
>    * @prop: Master properties
>    * @m_rt_list: List of Master instance of all stream(s) running on Bus. This
> + * @multi_link: if multi links are supported
>    * is used to compute and program bus bandwidth, clock, frame shape,
>    * transport and port parameters
>    * @defer_msg: Defer message
> @@ -691,6 +692,7 @@ struct sdw_bus {
>   	struct sdw_bus_params params;
>   	struct sdw_master_prop prop;
>   	struct list_head m_rt_list;
> +	bool multi_link;
>   	struct sdw_defer defer_msg;
>   	unsigned int clk_stop_timeout;
>   	u32 bank_switch_timeout;
> 

Re: [PATCH v3 5/6] soundwire: Add support for multi link bank switch

[Shreyas NC]

On Thu, Jun 14, 2018 at 01:34:13PM -0500, Pierre-Louis Bossart wrote:
> 
> >diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> >index 0e8a2eb5..771c963 100644
> >--- a/drivers/soundwire/stream.c
> >+++ b/drivers/soundwire/stream.c
> >@@ -638,6 +638,8 @@ static int sdw_bank_switch(struct sdw_bus *bus)
> >  	if (!wr_msg)
> >  		return -ENOMEM;
> >+	bus->defer_msg.msg = wr_msg;
> >+
> >  	wbuf = kzalloc(sizeof(*wbuf), GFP_KERNEL);
> >  	if (!wbuf) {
> >  		ret = -ENOMEM;
> >@@ -658,17 +660,23 @@ static int sdw_bank_switch(struct sdw_bus *bus)
> >  					SDW_MSG_FLAG_WRITE, wbuf);
> >  	wr_msg->ssp_sync = true;
> >-	ret = sdw_transfer(bus, wr_msg);
> >+	if (bus->multi_link)
> >+		ret = sdw_transfer_defer(bus, wr_msg, &bus->defer_msg);
> >+	else
> >+		ret = sdw_transfer(bus, wr_msg);
> >+
> 
> Re-reading this v3, I wonder if there is a small logic flaw here or an
> intended behavior.
> 
> the bus->multi_link field is a hardware capability, it provides information
> on whether the hardware can support synchronized bank switches across
> multiple Master interfaces. This is independent of the streams being
> handled, it's a bus property - not a stream one.
> 
> However the default/typical case is a stream handled by a single master, so
> when the hardware is capable of handling multiple masters this does not mean
> you should use the deferred transfer, the regular case would work just fine
> for a regular stream. If your SSP rate is faster than the common sync signal
> it might even be beneficial not to use the deferred transfer.
> 
> in other words, should the code be written with something like
> if (bus->multi_link && master_rt_count > 1)
> with master_rt_count being determined based on the stream properties.
> 
> Or was the intent that you always rely on the deferred mechanism, even if
> the stream is not handled by multiple masters? In that case, do we even need
> the regular bank switch?

After discussing with folks here, I understand that intent was to have an
unified flow for both Multi and Single instance cases. Yes, we can always
use the sdw_transfer_defer() and remove the references to bus->multi_link
possibly. So, I will fix this up and post v4.

Thanks for the catch :)


--Shreyas

-- 

Re: [PATCH v3 5/6] soundwire: Add support for multi link bank switch

[Vinod]

On 18-06-18, 15:20, Shreyas NC wrote:
> On Thu, Jun 14, 2018 at 01:34:13PM -0500, Pierre-Louis Bossart wrote:
> > 
> > >diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> > >index 0e8a2eb5..771c963 100644
> > >--- a/drivers/soundwire/stream.c
> > >+++ b/drivers/soundwire/stream.c
> > >@@ -638,6 +638,8 @@ static int sdw_bank_switch(struct sdw_bus *bus)
> > >  	if (!wr_msg)
> > >  		return -ENOMEM;
> > >+	bus->defer_msg.msg = wr_msg;
> > >+
> > >  	wbuf = kzalloc(sizeof(*wbuf), GFP_KERNEL);
> > >  	if (!wbuf) {
> > >  		ret = -ENOMEM;
> > >@@ -658,17 +660,23 @@ static int sdw_bank_switch(struct sdw_bus *bus)
> > >  					SDW_MSG_FLAG_WRITE, wbuf);
> > >  	wr_msg->ssp_sync = true;
> > >-	ret = sdw_transfer(bus, wr_msg);
> > >+	if (bus->multi_link)
> > >+		ret = sdw_transfer_defer(bus, wr_msg, &bus->defer_msg);
> > >+	else
> > >+		ret = sdw_transfer(bus, wr_msg);
> > >+
> > 
> > Re-reading this v3, I wonder if there is a small logic flaw here or an
> > intended behavior.
> > 
> > the bus->multi_link field is a hardware capability, it provides information
> > on whether the hardware can support synchronized bank switches across
> > multiple Master interfaces. This is independent of the streams being
> > handled, it's a bus property - not a stream one.

Pierre,

You are right that multi-link is a hw capability BUT it is also a 
property of a stream. I can envision machines where bus may have the
capability but the system configuration may have links being not clubbed
in one board and made a multi-link stream in another board :)

> > However the default/typical case is a stream handled by a single master, so
> > when the hardware is capable of handling multiple masters this does not mean
> > you should use the deferred transfer, the regular case would work just fine
> > for a regular stream. If your SSP rate is faster than the common sync signal
> > it might even be beneficial not to use the deferred transfer.
> > 
> > in other words, should the code be written with something like
> > if (bus->multi_link && master_rt_count > 1)
> > with master_rt_count being determined based on the stream properties.

Yes that makes sense to me

> > Or was the intent that you always rely on the deferred mechanism, even if
> > the stream is not handled by multiple masters? In that case, do we even need
> > the regular bank switch?
> 
> After discussing with folks here, I understand that intent was to have an
> unified flow for both Multi and Single instance cases. Yes, we can always
> use the sdw_transfer_defer() and remove the references to bus->multi_link
> possibly. So, I will fix this up and post v4.

Shreyas,

That sounds like a good plan to me

-- 
~Vinod