Hi Ramesh,
Thank you for the patch.
On Wednesday 21 Dec 2016 08:10:37 Ramesh Shanmugasundaram wrote:
> Add binding documentation for Renesas R-Car Digital Radio Interface
> (DRIF) controller.
>
> Signed-off-by: Ramesh Shanmugasundaram
> <ramesh.shanmugasunda...@bp.renesas.com> ---
> .../devicetree/bindings/media/renesas,drif.txt | 202 ++++++++++++++++++
> 1 file changed, 202 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..1f3feaf
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/renesas,drif.txt
> @@ -0,0 +1,202 @@
> +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 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 properties of an internal channel when:
> + - It is the only enabled channel of the bond (or)
> + - If it acts as primary among enabled bonds
> +--------------------------------------------------------
> +- renesas,syncmd : sync mode
> + 0 (Frame start sync pulse mode. 1-bit width pulse
> + indicates start of a frame)
> + 1 (L/R sync or I2S mode) (default)
> +- renesas,lsb-first : empty property indicates lsb bit is received
> first.
> + When not defined msb bit is received first (default)
> +- renesas,syncac-active: Indicates sync signal polarity, 0/1 for low/high
> + respectively. The default is 1 (active high)
> +- renesas,dtdl : delay between sync signal and start of reception.
> + The possible values are represented in 0.5 clock
> + cycle units and the range is 0 to 4. The default
> + value is 2 (i.e.) 1 clock cycle delay.
> +- renesas,syncdl : delay between end of reception and sync signal
> edge.
> + The possible values are represented in 0.5 clock
> + cycle units and the range is 0 to 4 & 6. The default
> + value is 0 (i.e.) no delay.
Most of these properties are pretty similar to the video bus properties
defined at the endpoint level in
Documentation/devicetree/bindings/media/video-interfaces.txt. I believe it
would make sense to use OF graph and try to standardize these properties
similarly.
> +
> +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, primary-bond = 0
> +-----------------------------------------------------
> +
> +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,syncac-active = <1>;
> + 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";
> + renesas,syncac-active = <0>;
> + status = "okay";
> + port {
> + drif0_ep: endpoint {
> + remote-endpoint = <&tuner_ep>;
> + };
> + };
> +};
--
Regards,
Laurent Pinchart
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