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Documentation: SoundWire: clarify TDM mode support

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The current description of stream topologies does not explicitly
mention 'mirror' topologies used for audio amplifiers, where all
amplifiers see the same data and generate a different output based on
configuration or dynamic information. Add examples and notes to
explain how channels can be transmitted and mapped.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20200419185117.4233-1-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This commit is contained in:
Pierre-Louis Bossart 2020-04-20 02:51:14 +08:00 committed by Vinod Koul
parent 91b5cfc020
commit 01de995075
1 changed files with 86 additions and 3 deletions
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89
Documentation/driver-api/soundwire/stream.rst
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@ -75,8 +75,33 @@ Slaves are using single port. ::
| (Data) |
+---------------+
Example 4: Stereo Stream with L and R channels is rendered by
Master. Both of the L and R channels are received by two different
Slaves. Master and both Slaves are using single port handling
L+R. Each Slave device processes the L + R data locally, typically
based on static configuration or dynamic orientation, and may drive
one or more speakers. ::
Example 4: Stereo Stream with L and R channel is rendered by two different
+---------------+ Clock Signal +---------------+
| Master +---------+------------------------+ Slave |
| Interface | | | Interface |
| | | | 1 |
| | | Data Signal | |
| L + R +---+------------------------------+ L + R |
| (Data) | | | Data Direction | (Data) |
+---------------+ | | +-------------> +---------------+
| |
| |
| | +---------------+
| +----------------------> | Slave |
| | Interface |
| | 2 |
| | |
+----------------------------> | L + R |
| (Data) |
+---------------+
Example 5: 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. ::
@ -101,7 +126,7 @@ interface. ::
+--------------------+ | |
+----------------+
Example 5: Stereo Stream with L and R channel is rendered by 2 Masters, each
Example 6: 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. ::
@ -123,12 +148,70 @@ receiving one channel. Both Masters and both Slaves are using single port. ::
| (Data) | Data Direction | (Data) |
+---------------+ +-----------------------> +---------------+
Note: In multi-link cases like above, to lock, one would acquire a global
Example 7: Stereo Stream with L and R channel is rendered by 2
Masters, each rendering both channels. Each Slave receives L + R. This
is the same application as Example 4 but with Slaves placed on
separate links. ::
+---------------+ Clock Signal +---------------+
| Master +----------------------------------+ Slave |
| Interface | | Interface |
| 1 | | 1 |
| | Data Signal | |
| L + R +----------------------------------+ L + R |
| (Data) | Data Direction | (Data) |
+---------------+ +-----------------------> +---------------+
+---------------+ Clock Signal +---------------+
| Master +----------------------------------+ Slave |
| Interface | | Interface |
| 2 | | 2 |
| | Data Signal | |
| L + R +----------------------------------+ L + R |
| (Data) | Data Direction | (Data) |
+---------------+ +-----------------------> +---------------+
Example 8: 4-channel Stream is rendered by 2 Masters, each rendering a
2 channels. Each Slave receives 2 channels. ::
+---------------+ Clock Signal +---------------+
| Master +----------------------------------+ Slave |
| Interface | | Interface |
| 1 | | 1 |
| | Data Signal | |
| L1 + R1 +----------------------------------+ L1 + R1 |
| (Data) | Data Direction | (Data) |
+---------------+ +-----------------------> +---------------+
+---------------+ Clock Signal +---------------+
| Master +----------------------------------+ Slave |
| Interface | | Interface |
| 2 | | 2 |
| | Data Signal | |
| L2 + R2 +----------------------------------+ L2 + R2 |
| (Data) | Data Direction | (Data) |
+---------------+ +-----------------------> +---------------+
Note1: 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.
Note2: A Slave device may be configured to receive all channels
transmitted on a link for a given Stream (Example 4) or just a subset
of the data (Example 3). The configuration of the Slave device is not
handled by a SoundWire subsystem API, but instead by the
snd_soc_dai_set_tdm_slot() API. The platform or machine driver will
typically configure which of the slots are used. For Example 4, the
same slots would be used by all Devices, while for Example 3 the Slave
Device1 would use e.g. Slot 0 and Slave device2 slot 1.
Note3: Multiple Sink ports can extract the same information for the
same bitSlots in the SoundWire frame, however multiple Source ports
shall be configured with different bitSlot configurations. This is the
same limitation as with I2S/PCM TDM usages.
SoundWire Stream Management flow
================================