sound/soc/clocking.rst

2 Audio Clocking
5 This text describes the audio clocking terms in ASoC and digital audio in
6 general. Note: Audio clocking can be complex!
10 ------------
12 Every audio subsystem is driven by a master clock (sometimes referred to as MCLK
13 or SYSCLK). This audio master clock can be derived from a number of sources
14 (e.g. crystal, PLL, CPU clock) and is responsible for producing the correct
15 audio playback and capture sample rates.
17 Some master clocks (e.g. PLLs and CPU based clocks) are configurable in that
23 ----------
24 The Digital Audio Interface is usually driven by a Bit Clock (often referred to
25 as BCLK). This clock is used to drive the digital audio data across the link
26 between the codec and CPU.
28 The DAI also has a frame clock to signal the start of each audio frame. This
32 Bit Clock can be generated as follows:-
34 - BCLK = MCLK / x, or
35 - BCLK = LRC * x, or
36 - BCLK = LRC * Channels * Word Size
38 This relationship depends on the codec or SoC CPU in particular. In general
43 audio clocks as it usually gives more accurate sample rates than the CPU.