^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) =================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2) SoundWire Locking
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) =================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) This document explains locking mechanism of the SoundWire Bus. Bus uses
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6) following locks in order to avoid race conditions in Bus operations on
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) shared resources.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) - Bus lock
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) - Message lock
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) Bus lock
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) ========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) SoundWire Bus lock is a mutex and is part of Bus data structure
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) (sdw_bus) which is used for every Bus instance. This lock is used to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) serialize each of the following operations(s) within SoundWire Bus instance.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) - Addition and removal of Slave(s), changing Slave status.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) - Prepare, Enable, Disable and De-prepare stream operations.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) - Access of Stream data structure.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) Message lock
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) SoundWire message transfer lock. This mutex is part of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) Bus data structure (sdw_bus). This lock is used to serialize the message
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) transfers (read/write) within a SoundWire Bus instance.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) Below examples show how locks are acquired.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) Example 1
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) ---------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) Message transfer.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) 1. For every message transfer
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) a. Acquire Message lock.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) b. Transfer message (Read/Write) to Slave1 or broadcast message on
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) Bus in case of bank switch.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) c. Release Message lock
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) ::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) +----------+ +---------+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) | | | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) | Bus | | Master |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) | | | Driver |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) | | | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) +----+-----+ +----+----+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) | bus->ops->xfer_msg() |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) <-------------------------------+ a. Acquire Message lock
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) | | b. Transfer message
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) +-------------------------------> c. Release Message lock
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) | return success/error | d. Return success/error
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) + +
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) Example 2
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) ---------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) Prepare operation.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) 1. Acquire lock for Bus instance associated with Master 1.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) 2. For every message transfer in Prepare operation
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76) a. Acquire Message lock.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) b. Transfer message (Read/Write) to Slave1 or broadcast message on
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) Bus in case of bank switch.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81) c. Release Message lock.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) 3. Release lock for Bus instance associated with Master 1 ::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) +----------+ +---------+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86) | | | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) | Bus | | Master |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) | | | Driver |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89) | | | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90) +----+-----+ +----+----+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91) | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92) | sdw_prepare_stream() |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) <-------------------------------+ 1. Acquire bus lock
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94) | | 2. Perform stream prepare
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96) | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) | bus->ops->xfer_msg() |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98) <-------------------------------+ a. Acquire Message lock
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99) | | b. Transfer message
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) +-------------------------------> c. Release Message lock
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) | return success/error | d. Return success/error
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) | return success/error | 3. Release bus lock
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) +-------------------------------> 4. Return success/error
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) + +
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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