Documentation: soundwire: Add documentation for multi link

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: Shreyas NC <shreyas.nc@intel.com>
Acked-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/Documentation/driver-api/soundwire/stream.rst b/Documentation/driver-api/soundwire/stream.rst
index 29121aa55fb96a3e431859797ccc699eb8891f78..19482eedc3bf25ab667d5f86aeb2e7aed7208d2d 100644 (file)
--- a/Documentation/driver-api/soundwire/stream.rst
+++ b/Documentation/driver-api/soundwire/stream.rst
@@ -101,6 +101,34 @@ 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
 ================================