[PATCH v3 6/7] dt-bindings: media: Add Renesas R-Car DRIF binding

[Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>]

Add binding documentation for Renesas R-Car Digital Radio Interface
(DRIF) controller.

Signed-off-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>
---
 .../devicetree/bindings/media/renesas,drif.txt     | 186 +++++++++++++++++++++
 1 file changed, 186 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/media/renesas,drif.txt

diff --git a/Documentation/devicetree/bindings/media/renesas,drif.txt b/Documentation/devicetree/bindings/media/renesas,drif.txt
new file mode 100644
index 0000000..6315609
--- /dev/null
+++ b/Documentation/devicetree/bindings/media/renesas,drif.txt
@@ -0,0 +1,186 @@
+Renesas R-Car Gen3 Digital Radio Interface controller (DRIF)
+------------------------------------------------------------
+
+R-Car Gen3 DRIF is a SPI like receive only slave device. A general
+representation of DRIF interfacing with a master device is shown below.
+
++---------------------+                +---------------------+
+|                     |-----SCK------->|CLK                  |
+|       Master        |-----SS-------->|SYNC  DRIFn (slave)  |
+|                     |-----SD0------->|D0                   |
+|                     |-----SD1------->|D1                   |
++---------------------+                +---------------------+
+
+As per the datasheet, each DRIF channel (drifn) is made up of two internal
+channels (drifn0 & drifn1). These two internal channels share the common
+CLK & SYNC. Each internal channel has its own dedicated resources like
+irq, dma channels, address space & clock. This internal split is not
+visible to the external master device.
+
+The device tree model represents each internal channel as a separate node.
+The internal channels sharing the CLK & SYNC are tied together by their
+phandles using a new property called "renesas,bonding". For the rest of
+the documentation, unless explicitly stated, the word channel implies an
+internal channel.
+
+When both internal channels are enabled they need to be managed together
+as one (i.e.) they cannot operate alone as independent devices. Out of the
+two, one of them needs to act as a primary device that accepts common
+properties of both the internal channels. This channel is identified by a
+new property called "renesas,primary-bond".
+
+To summarize,
+   - When both the internal channels that are bonded together are enabled,
+     the zeroth channel is selected as primary-bond. This channels accepts
+     properties common to all the members of the bond.
+   - When only one of the bonded channels need to be enabled, the property
+     "renesas,bonding" or "renesas,primary-bond" will have no effect. That
+     enabled channel can act alone as any other independent device.
+
+Required properties of an internal channel:
+-------------------------------------------
+- compatible: "renesas,r8a7795-drif" if DRIF controller is a part of R8A7795 SoC.
+	      "renesas,rcar-gen3-drif" for a generic R-Car Gen3 compatible device.
+	      When compatible with the generic version, nodes must list the
+	      SoC-specific version corresponding to the platform first
+	      followed by the generic version.
+- reg: offset and length of that channel.
+- interrupts: associated with that channel.
+- clocks: phandle and clock specifier of that channel.
+- clock-names: clock input name string: "fck".
+- dmas: phandles to the DMA channels.
+- dma-names: names of the DMA channel: "rx".
+- renesas,bonding: phandle to the other channel.
+
+Optional properties of an internal channel:
+-------------------------------------------
+- power-domains: phandle to the respective power domain.
+
+Required properties of an internal channel when:
+	- It is the only enabled channel of the bond (or)
+	- If it acts as primary among enabled bonds
+--------------------------------------------------------
+- pinctrl-0: pin control group to be used for this channel.
+- pinctrl-names: must be "default".
+- renesas,primary-bond: empty property indicating the channel acts as primary
+			among the bonded channels.
+- port: child port node of a channel that defines the local and remote
+	endpoints. The remote endpoint is assumed to be a third party tuner
+	device endpoint.
+
+Optional endpoint property:
+---------------------------
+- renesas,sync-active  : Indicates sync signal polarity, 0/1 for low/high
+			 respectively. This property maps to SYNCAC bit in the
+			 hardware manual. The default is 1 (active high)
+
+Example
+--------
+
+SoC common dtsi file
+
+		drif00: rif@e6f40000 {
+			compatible = "renesas,r8a7795-drif",
+				     "renesas,rcar-gen3-drif";
+			reg = <0 0xe6f40000 0 0x64>;
+			interrupts = <GIC_SPI 12 IRQ_TYPE_LEVEL_HIGH>;
+			clocks = <&cpg CPG_MOD 515>;
+			clock-names = "fck";
+			dmas = <&dmac1 0x20>, <&dmac2 0x20>;
+			dma-names = "rx", "rx";
+			power-domains = <&sysc R8A7795_PD_ALWAYS_ON>;
+			renesas,bonding = <&drif01>;
+			status = "disabled";
+		};
+
+		drif01: rif@e6f50000 {
+			compatible = "renesas,r8a7795-drif",
+				     "renesas,rcar-gen3-drif";
+			reg = <0 0xe6f50000 0 0x64>;
+			interrupts = <GIC_SPI 13 IRQ_TYPE_LEVEL_HIGH>;
+			clocks = <&cpg CPG_MOD 514>;
+			clock-names = "fck";
+			dmas = <&dmac1 0x22>, <&dmac2 0x22>;
+			dma-names = "rx", "rx";
+			power-domains = <&sysc R8A7795_PD_ALWAYS_ON>;
+			renesas,bonding = <&drif00>;
+			status = "disabled";
+		};
+
+
+Board specific dts file
+
+(1) Both internal channels enabled:
+-----------------------------------
+
+When interfacing with a third party tuner device with two data pins as shown
+below.
+
++---------------------+                +---------------------+
+|                     |-----SCK------->|CLK                  |
+|       Master        |-----SS-------->|SYNC  DRIFn (slave)  |
+|                     |-----SD0------->|D0                   |
+|                     |-----SD1------->|D1                   |
++---------------------+                +---------------------+
+
+pfc {
+	...
+
+	drif0_pins: drif0 {
+		groups = "drif0_ctrl_a", "drif0_data0_a",
+				 "drif0_data1_a";
+		function = "drif0";
+	};
+	...
+}
+
+&drif00 {
+	pinctrl-0 = <&drif0_pins>;
+	pinctrl-names = "default";
+	renesas,primary-bond;
+	status = "okay";
+	port {
+		drif0_ep: endpoint {
+		     remote-endpoint = <&tuner_ep>;
+		};
+	};
+};
+
+&drif01 {
+	status = "okay";
+};
+
+(2) Internal channel 1 alone is enabled:
+----------------------------------------
+
+When interfacing with a third party tuner device with one data pin as shown
+below.
+
++---------------------+                +---------------------+
+|                     |-----SCK------->|CLK                  |
+|       Master        |-----SS-------->|SYNC  DRIFn (slave)  |
+|                     |                |D0 (unused)          |
+|                     |-----SD-------->|D1                   |
++---------------------+                +---------------------+
+
+pfc {
+	...
+
+	drif0_pins: drif0 {
+		groups = "drif0_ctrl_a", "drif0_data1_a";
+		function = "drif0";
+	};
+	...
+}
+
+&drif01 {
+	pinctrl-0 = <&drif0_pins>;
+	pinctrl-names = "default";
+	status = "okay";
+	port {
+		drif0_ep: endpoint {
+		     remote-endpoint = <&tuner_ep>;
+		     renesas,syncac-active = <0>;
+		};
+	};
+};
-- 
1.9.1