[PATCH v5 8/9] soundwire: Add support for multi link bank switch

[Shreyas NC <shreyas.nc@intel.com>]

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.c       |   5 ++
 drivers/soundwire/bus.h       |   2 +
 drivers/soundwire/stream.c    | 141 ++++++++++++++++++++++++++++++++++++++----
 include/linux/soundwire/sdw.h |   4 ++
 4 files changed, 140 insertions(+), 12 deletions(-)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index dbabd5e..1cbfedf 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -35,6 +35,11 @@ int sdw_add_bus_master(struct sdw_bus *bus)
 	INIT_LIST_HEAD(&bus->slaves);
 	INIT_LIST_HEAD(&bus->m_rt_list);
 
+	/*
+	 * Initialize multi_link flag
+	 * TODO: populate this flag by reading property from FW node
+	 */
+	bus->multi_link = false;
 	if (bus->ops->read_prop) {
 		ret = bus->ops->read_prop(bus);
 		if (ret < 0) {
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 71d7e0b..60b562a 100644
--- a/drivers/soundwire/stream.c
+++ b/drivers/soundwire/stream.c
@@ -626,9 +626,10 @@ static int sdw_program_params(struct sdw_bus *bus)
 	return ret;
 }
 
-static int sdw_bank_switch(struct sdw_bus *bus)
+static int sdw_bank_switch(struct sdw_bus *bus, int m_rt_count)
 {
 	int col_index, row_index;
+	bool multi_link;
 	struct sdw_msg *wr_msg;
 	u8 *wbuf = NULL;
 	int ret = 0;
@@ -638,6 +639,8 @@ 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 +661,29 @@ 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);
+	/*
+	 * Set the multi_link flag only when both the hardware supports
+	 * and there is a stream handled by multiple masters
+	 */
+	multi_link = bus->multi_link && (m_rt_count > 1);
+
+	if (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 +694,87 @@ 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;
+
+	if (!bus->multi_link)
+		return 0;
+
+	/* 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 0;
+}
+
 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 */
-		ret = sdw_bank_switch(bus);
+		/*
+		 * 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, stream->m_rt_count);
 		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;
@@ -719,7 +785,47 @@ 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;
 			}
+		} else if (bus->multi_link && stream->m_rt_count > 1) {
+			dev_err(bus->dev,
+				"Post bank switch ops not implemented");
+			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);
 		}
 	}
 
@@ -1170,6 +1276,17 @@ int sdw_stream_add_master(struct sdw_bus *bus,
 
 	stream->m_rt_count++;
 
+	/*
+	 * For multi link streams, add the second master only if
+	 * the bus supports it.
+	 * Check if bus->multi_link is set
+	 */
+	if (!bus->multi_link && stream->m_rt_count > 1) {
+		dev_err(bus->dev,
+			"Multilink not supported, link %d", bus->link_id);
+		goto stream_error;
+	}
+
 	goto unlock;
 
 stream_error:
diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
index 214e146..df31391 100644
--- a/include/linux/soundwire/sdw.h
+++ b/include/linux/soundwire/sdw.h
@@ -678,6 +678,9 @@ struct sdw_master_ops {
  * @defer_msg: Defer message
  * @clk_stop_timeout: Clock stop timeout computed
  * @bank_switch_timeout: Bank switch timeout computed
+ * @multi_link: Store bus property that indicates if multi links
+ * are supported. This flag is populated by drivers after reading
+ * appropriate firmware (ACPI/DT).
  */
 struct sdw_bus {
 	struct device *dev;
@@ -694,6 +697,7 @@ struct sdw_bus {
 	struct sdw_defer defer_msg;
 	unsigned int clk_stop_timeout;
 	u32 bank_switch_timeout;
+	bool multi_link;
 };
 
 int sdw_add_bus_master(struct sdw_bus *bus);
-- 
2.7.4