ASoC: dmic: introduce mode switch delay

On startup, applications such as PulseAudio or CRAS enable playback or
capture on all PCM devices to verify that configurations are correct,
and close them immediately. For DMICs, this can result in the clock
being turned off very quickly, which may not compatible with internal
state machine transition requirements.

This patch add a mode-switch delay which will prevent the clock from
being turned off without complying with manufacturer timing
specifications. While the DMIC clock may be controlled at a lower level,
be it with hardware or firmware, applying the delay during the
STOP_TRIGGER phase ensures that there is no race condition, e.g. with
the hardware/firmware turning off the clock earlier

Signed-off-by: Sathyanarayana Nujella <sathyanarayana.nujella@intel.com>
Signed-off-by: Jairaj Arava <jairaj.arava@intel.com>
Signed-off-by: Harsha Priya <harshapriya.n@intel.com>
Signed-off-by: Jenny TC <jenny.tc@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/sound/dmic.txt b/Documentation/devicetree/bindings/sound/dmic.txt
index e957b4136716..32e871037269 100644
--- a/Documentation/devicetree/bindings/sound/dmic.txt
+++ b/Documentation/devicetree/bindings/sound/dmic.txt
@@ -9,6 +9,7 @@ Optional properties:
 	- dmicen-gpios: GPIO specifier for dmic to control start and stop
 	- num-channels: Number of microphones on this DAI
 	- wakeup-delay-ms: Delay (in ms) after enabling the DMIC
+	- modeswitch-delay-ms: Delay (in ms) to complete DMIC mode switch
 
 Example node:
 
@@ -17,4 +18,5 @@ Example node:
 		dmicen-gpios = <&gpio4 3 GPIO_ACTIVE_HIGH>;
 		num-channels = <1>;
 		wakeup-delay-ms <50>;
+		modeswitch-delay-ms <35>;
 	};