[alsa-devel] [PATCH v2 18/19] soundwire: stream: do not update parameters during DISABLED-PREPARED transition

[Pierre-Louis Bossart]

After a system suspend, the ALSA/ASoC core will invoke the .prepare()
callback and a TRIGGER_START when INFO_RESUME is not supported.

Likewise, when an underflow occurs, the .prepare callback will be invoked.

In both cases, the stream can be in DISABLED mode, and will transition
into the PREPARED mode. We however don't want the bus bandwidth to be
recomputed.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
---
 drivers/soundwire/stream.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
index 38375c9124e4..3447ef7d55e3 100644
--- a/drivers/soundwire/stream.c
+++ b/drivers/soundwire/stream.c
@@ -1460,7 +1460,8 @@ static void sdw_release_bus_lock(struct sdw_stream_runtime *stream)
 	}
 }
 
-static int _sdw_prepare_stream(struct sdw_stream_runtime *stream)
+static int _sdw_prepare_stream(struct sdw_stream_runtime *stream,
+			       bool update_params)
 {
 	struct sdw_master_runtime *m_rt;
 	struct sdw_bus *bus = NULL;
@@ -1480,6 +1481,9 @@ static int _sdw_prepare_stream(struct sdw_stream_runtime *stream)
 			return -EINVAL;
 		}
 
+		if (!update_params)
+			goto program_params;
+
 		/* Increment cumulative bus bandwidth */
 		/* TODO: Update this during Device-Device support */
 		bus->params.bandwidth += m_rt->stream->params.rate *
@@ -1495,6 +1499,7 @@ static int _sdw_prepare_stream(struct sdw_stream_runtime *stream)
 			}
 		}
 
+program_params:
 		/* Program params */
 		ret = sdw_program_params(bus);
 		if (ret < 0) {
@@ -1544,6 +1549,7 @@ static int _sdw_prepare_stream(struct sdw_stream_runtime *stream)
  */
 int sdw_prepare_stream(struct sdw_stream_runtime *stream)
 {
+	bool update_params = true;
 	int ret;
 
 	if (!stream) {
@@ -1567,7 +1573,16 @@ int sdw_prepare_stream(struct sdw_stream_runtime *stream)
 		goto state_err;
 	}
 
-	ret = _sdw_prepare_stream(stream);
+	/*
+	 * when the stream is DISABLED, this means sdw_prepare_stream()
+	 * is called as a result of an underflow or a resume operation.
+	 * In this case, the bus parameters shall not be recomputed, but
+	 * still need to be re-applied
+	 */
+	if (stream->state == SDW_STREAM_DISABLED)
+		update_params = false;
+
+	ret = _sdw_prepare_stream(stream, update_params);
 
 	if (ret < 0)
 		pr_err("Prepare for stream:%s failed: %d\n", stream->name, ret);
-- 
2.20.1