ASoC: cs42l42: Add devicetree bindings for CS42L42

Add devicetree bindings documentation file for Cirrus
Logic CS42L42 codec.
Signed-off-by: James Schulman <james.schulman@cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/cs42l42.txt

+CS42L42 audio CODEC
+
+Required properties:
+
+  - compatible : "cirrus,cs42l42"
+
+  - reg : the I2C address of the device for I2C.
+
+  - VP-supply, VCP-supply, VD_FILT-supply, VL-supply, VA-supply :
+  power supplies for the device, as covered in
+  Documentation/devicetree/bindings/regulator/regulator.txt.
+
+Optional properties:
+
+  - reset-gpios : a GPIO spec for the reset pin. If specified, it will be
+  deasserted before communication to the codec starts.
+
+  - interrupt-parent : Specifies the phandle of the interrupt controller to
+  which the IRQs from CS42L42 are delivered to.
+
+  - interrupts : IRQ line info CS42L42.
+  (See Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
+  for further information relating to interrupt properties)
+
+  - cirrus,ts-inv : Boolean property. For jacks that invert the tip sense
+  polarity. Normal jacks will short tip sense pin to HS1 when headphones are
+  plugged in and leave tip sense floating when not plugged in. Inverting jacks
+  short tip sense when unplugged and float when plugged in.
+
+  0 = (Default) Non-inverted
+  1 = Inverted
+
+  - cirrus,ts-dbnc-rise : Debounce the rising edge of TIP_SENSE_PLUG. With no
+  debounce, the tip sense pin might be noisy on a plug event.
+
+  0 - 0ms,
+  1 - 125ms,
+  2 - 250ms,
+  3 - 500ms,
+  4 - 750ms,
+  5 - (Default) 1s,
+  6 - 1.25s,
+  7 - 1.5s,
+
+  - cirrus,ts-dbnc-fall : Debounce the falling edge of TIP_SENSE_UNPLUG.
+  With no debounce, the tip sense pin might be noisy on an unplug event.
+
+  0 - 0ms,
+  1 - 125ms,
+  2 - 250ms,
+  3 - 500ms,
+  4 - 750ms,
+  5 - (Default) 1s,
+  6 - 1.25s,
+  7 - 1.5s,
+
+  - cirrus,btn-det-init-dbnce : This sets how long the driver sleeps after
+  enabling button detection interrupts. After auto-detection and before
+  servicing button interrupts, the HS bias needs time to settle. If you
+  don't wait, there is possibility for erroneous button interrupt.
+
+  0ms - 200ms,
+  Default = 100ms
+
+  - cirrus,btn-det-event-dbnce : This sets how long the driver delays after
+  receiving a button press interrupt. With level detect interrupts, you want
+  to wait a small amount of time to make sure the button press is making a
+  clean connection with the bias resistors.
+
+  0ms - 20ms,
+  Default = 10ms
+
+  - cirrus,bias-lvls : For a level-detect headset button scheme, each button
+  will bias the mic pin to a certain voltage. To determine which button was
+  pressed, the driver will compare this biased voltage to sequential,
+  decreasing voltages and will stop when a comparator is tripped,
+  indicating a comparator voltage < bias voltage. This value represents a
+  percentage of the internally generated HS bias voltage. For different
+  hardware setups, a designer might want to tweak this. This is an array of
+  descending values for the comparator voltage.
+
+  Array of 4 values
+  Each 0-63
+  < x1 x2 x3 x4 >
+  Default = < 15 8 4 1>
+
+
+Example:
+
+cs42l42: cs42l42@48 {
+	compatible = "cirrus,cs42l42";
+	reg = <0x48>;
+	VA-supply = <&dummy_vreg>;
+	VP-supply = <&dummy_vreg>;
+	VCP-supply = <&dummy_vreg>;
+	VD_FILT-supply = <&dummy_vreg>;
+	VL-supply = <&dummy_vreg>;
+
+	reset-gpios = <&axi_gpio_0 1 0>;
+	interrupt-parent = <&gpio0>;
+	interrupts = <55 8>
+
+	cirrus,ts-inv = <0x00>;
+	cirrus,ts-dbnc-rise = <0x05>;
+	cirrus,ts-dbnc-fall = <0x00>;
+	cirrus,btn-det-init-dbnce = <100>;
+	cirrus,btn-det-event-dbnce = <10>;
+	cirrus,bias-lvls = <0x0F 0x08 0x04 0x01>;
+	cirrus,hs-bias-ramp-rate = <0x02>;
+};
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