Add properties to describe TDM slot idle behaviour. These properties can
be used to describe how a DAI is supposed to behave when not active.

For example, Apple Silicon laptops split a single I2S bus between two
physical lines which are combined at an OR gate in front of the
receiving port. One codec on each line is expected to transmit zeroes
during the active TDM slots of the opposite line, or we will have corrupted
data at the receiver.

Signed-off-by: James Calligeros <jcalligeros99@gmail.com>
---
 .../bindings/sound/tdm-slot.yaml         | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/Documentation/devicetree/bindings/sound/tdm-slot.yaml b/Documentation/devicetree/bindings/sound/tdm-slot.yaml
index ca71e3660f62..457a899e8872 100644
--- a/Documentation/devicetree/bindings/sound/tdm-slot.yaml
+++ b/Documentation/devicetree/bindings/sound/tdm-slot.yaml
@@ -20,6 +20,20 @@ properties:
     $ref: /schemas/types.yaml#/definitions/uint32
     description: Width, in bits, of each slot
 
+  dai-tdm-idle-mode:
+    $ref: /schemas/types.yaml#/definitions/string
+    enum:
+      - none
+      - off
+      - zero
+      - pulldown
+      - hiz
+      - pullup
+      - drivehigh
+    description: Drive mode for inactive/idle TDM slots. For hardware that
+      implements .set_tdm_idle(). Optional. "None" represents undefined
+      behaviour and is the same as not setting this property.
+
 patternProperties:
   '^dai-tdm-slot-[rt]x-mask$':
     $ref: /schemas/types.yaml#/definitions/uint32-array
@@ -30,4 +44,9 @@ patternProperties:
       a mask. The first element of the array is slot 0 (LSB). Any nonzero
       value will be treated as 1.
 
+  '^dai-tdm-slot-[rt]x-idle-mask$':
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: Idle slot mask. Optional. A bit being set to 1 indicates
+      that the corresponding TDM slot is inactive/idle.
+
 additionalProperties: true

-- 
2.53.0

On Sun, 01 Mar 2026 18:05:22 +1000, James Calligeros wrote:
> Add properties to describe TDM slot idle behaviour. These properties can
> be used to describe how a DAI is supposed to behave when not active.
> 
> For example, Apple Silicon laptops split a single I2S bus between two
> physical lines which are combined at an OR gate in front of the
> receiving port. One codec on each line is expected to transmit zeroes
> during the active TDM slots of the opposite line, or we will have corrupted
> data at the receiver.
> 
> Signed-off-by: James Calligeros <jcalligeros99@gmail.com>
> ---
>  .../bindings/sound/tdm-slot.yaml         | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>