Add DMIC slew rate controls

Merge series from Seven Lee <wtli@nuvoton.com>:

Determine DMIC slew rate via property setup.

Change:
V3 -> V4:
 - add "maximum: 7" description.

V2 -> V3:
 - Update description of DMIC slew rate and remove
   "selection" key words from property name
 - Corrected variable name of DMIC slew rate from c file

V1 -> V2:
 - Corrected description of DMIC slew rate.

Seven Lee (2):
  ASoC: dt-bindings: nau8821: Add DMIC slew rate.
  ASoC: nau8821: Add slew rate controls.

 .../devicetree/bindings/sound/nuvoton,nau8821.yaml       | 9 +++++++++
 sound/soc/codecs/nau8821.c                               | 7 +++++++
 sound/soc/codecs/nau8821.h                               | 3 +++
 3 files changed, 19 insertions(+)

--
2.25.1

1 files changed, 9 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/sound/nuvoton,nau8821.yaml b/Documentation/devicetree/bindings/sound/nuvoton,nau8821.yaml
index 3e54abd4ca74..3380b6aa9542 100644
--- a/Documentation/devicetree/bindings/sound/nuvoton,nau8821.yaml
+++ b/Documentation/devicetree/bindings/sound/nuvoton,nau8821.yaml
@@ -89,6 +89,14 @@ properties:
     $ref: /schemas/types.yaml#/definitions/uint32
     default: 3072000
 
+  nuvoton,dmic-slew-rate:
+    description: The range 0 to 7 represents the speed of DMIC slew rate.
+        The lowest value 0 means the slowest rate and the highest value
+        7 means the fastest rate.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    maximum: 7
+    default: 0
+
   nuvoton,left-input-single-end:
     description: Enable left input with single-ended settings if set.
         For the headset mic application, the single-ended control is
@@ -127,6 +135,7 @@ examples:
             nuvoton,jack-insert-debounce = <7>;
             nuvoton,jack-eject-debounce = <0>;
             nuvoton,dmic-clk-threshold = <3072000>;
+            nuvoton,dmic-slew-rate= <0>;
             #sound-dai-cells = <0>;
         };
     };