Add binding documentation for Renesas R-Car Digital Radio Interface
(DRIF) controller.
Signed-off-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@xxxxxxxxxxxxxx>
---
.../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
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