27 Sep
2023
27 Sep
'23
6:07 a.m.
- fsl,lpa-widgets:
- $ref: /schemas/types.yaml#/definitions/non-unique-string-array
- description: |
A list of DAPM endpoints which mark paths between theseendpoints should
not be disabled when system enters in suspend state. LPA means low
power
audio case. On asymmetric multiprocessor, there are Cortex-A coreand
Cortex-M core, Linux is running on Cortex-A core, RTOS or other OS isrunning on Cortex-M core. The audio hardware devices can becontrolled by
Cortex-M. LPA can be explained as a mechanism that Cortex-Aallocates a
large buffer and fill audio data, then Cortex-A can enter into suspendfor the purpose of power saving. Cortex-M continues to play thesound
during suspend phase of Cortex-A. When the data in buffer isconsumed,
Cortex-M will trigger the Cortex-A to wakeup to fill data. LPArequires
some audio paths still enabled when Cortex-A enters into suspend.This is a fairly standard DSP playback case as far as I can see so it should work with DAPM without needing this obviously use case specific stuff peering into the Linux implementation. Generally this is done by tagging endpoint widgets and DAIs as ignore_suspend, DAPM will then figure out the rest of the widgets in the path.
Yes, indeed I meant to let driver get DAPM endpoints from the "fsl,lpa-widgets" property and then set these endpoints as ignore_suspend if the sound card is running in this use case. Do you think the description for the use case can be simplified since it's a common use case?
Regards, Chancel Liu