Re: [RFC 3/5] media: platform: rcar_drif: Add DRIF support

[Rob Herring <robh@kernel.org>]

On Wed, Oct 12, 2016 at 03:10:27PM +0100, Ramesh Shanmugasundaram wrote:
> This patch adds Digital Radio Interface (DRIF) support to R-Car Gen3 SoCs.
> The driver exposes each instance of DRIF as a V4L2 SDR device. A DRIF
> device represents a channel and each channel can have one or two
> sub-channels respectively depending on the target board.
> 
> DRIF supports only Rx functionality. It receives samples from a RF
> frontend tuner chip it is interfaced with. The combination of DRIF and the
> tuner device, which is registered as a sub-device, determines the receive
> sample rate and format.
> 
> In order to be compliant as a V4L2 SDR device, DRIF needs to bind with
> the tuner device, which can be provided by a third party vendor. DRIF acts
> as a slave device and the tuner device acts as a master transmitting the
> samples. The driver allows asynchronous binding of a tuner device that
> is registered as a v4l2 sub-device. The driver can learn about the tuner
> it is interfaced with based on port endpoint properties of the device in
> device tree. The V4L2 SDR device inherits the controls exposed by the
> tuner device.
> 
> The device can also be configured to use either one or both of the data
> pins at runtime based on the master (tuner) configuration.
> 
> Signed-off-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>
> ---
>  .../devicetree/bindings/media/renesas,drif.txt     |  109 ++
>  drivers/media/platform/Kconfig                     |   25 +
>  drivers/media/platform/Makefile                    |    1 +
>  drivers/media/platform/rcar_drif.c                 | 1534 ++++++++++++++++++++
>  4 files changed, 1669 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/media/renesas,drif.txt
>  create mode 100644 drivers/media/platform/rcar_drif.c
> 
> diff --git a/Documentation/devicetree/bindings/media/renesas,drif.txt b/Documentation/devicetree/bindings/media/renesas,drif.txt
> new file mode 100644
> index 0000000..24239d9
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/renesas,drif.txt
> @@ -0,0 +1,109 @@
> +Renesas R-Car Gen3 DRIF controller (DRIF)

Define what is DRIF here, not just in the commit text.

> +-----------------------------------------
> +
> +Required properties:
> +--------------------
> +- compatible: "renesas,drif-r8a7795" if DRIF controller is a part of R8A7795 SoC.

renesas,r8a7795-drif would be the normal ordering.

> +	      "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 each sub-channel.
> +- interrupts: associated with each sub-channel.
> +- clocks: phandles and clock specifiers for each sub-channel.
> +- clock-names: clock input name strings: "fck0", "fck1".
> +- pinctrl-0: pin control group to be used for this controller.
> +- pinctrl-names: must be "default".
> +- dmas: phandles to the DMA channels for each sub-channel.
> +- dma-names: names for the DMA channels: "rx0", "rx1".
> +
> +Required child nodes:
> +---------------------
> +- Each DRIF channel can have one or both of the sub-channels enabled in a
> +  setup. The sub-channels are represented as a child node. The name of the
> +  child nodes are "sub-channel0" and "sub-channel1" respectively. Each child
> +  node supports the "status" property only, which is used to enable/disable
> +  the respective sub-channel.
> +
> +Optional properties:
> +--------------------
> +- port: video interface child port node of a channel that defines the local

This is an audio device, why does it have a video port?

> +  and remote endpoints. The remote endpoint is assumed to a tuner subdevice
> +  endpoint.
> +- power-domains: phandle to respective power domain.
> +- 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-pol-high  : empty property indicates sync signal polarity.
> +			 When defined, active high or high->low sync signal.
> +			 When not defined, active low or low->high sync signal
> +			 (default)
> +- renesas,dtdl         : delay between sync signal and start of reception.
> +			 Must contain one of the following values:
> +			 0   (no bit delay)
> +			 50  (0.5-clock-cycle delay)
> +			 100 (1-clock-cycle delay) (default)
> +			 150 (1.5-clock-cycle delay)
> +			 200 (2-clock-cycle delay)
> +- renesas,syncdl       : delay between end of reception and sync signal edge.
> +			 Must contain one of the following values:
> +			 0   (no bit delay) (default)
> +			 50  (0.5-clock-cycle delay)
> +			 100 (1-clock-cycle delay)
> +			 150 (1.5-clock-cycle delay)
> +			 200 (2-clock-cycle delay)
> +			 300 (3-clock-cycle delay)
> +
> +Example
> +--------
> +
> +SoC common dtsi file
> +
> +drif0: rif@e6f40000 {
> +	compatible = "renesas,drif-r8a7795",
> +		   "renesas,rcar-gen3-drif";
> +	reg = <0 0xe6f40000 0 0x64>, <0 0xe6f50000 0 0x64>;
> +	interrupts = <GIC_SPI 12 IRQ_TYPE_LEVEL_HIGH>,
> +		   <GIC_SPI 13 IRQ_TYPE_LEVEL_HIGH>;
> +	clocks = <&cpg CPG_MOD 515>, <&cpg CPG_MOD 514>;
> +	clock-names = "fck0", "fck1";
> +	dmas = <&dmac1 0x20>, <&dmac1 0x22>;
> +	dma-names = "rx0", "rx1";
> +	power-domains = <&sysc R8A7795_PD_ALWAYS_ON>;
> +	status = "disabled";
> +
> +	sub-channel0 {
> +		status = "disabled";
> +	};
> +
> +	sub-channel1 {
> +		status = "disabled";
> +	};
> +
> +};
> +
> +Board specific dts file
> +
> +&drif0 {
> +	pinctrl-0 = <&drif0_pins>;
> +	pinctrl-names = "default";
> +	status = "okay";
> +
> +	sub-channel0 {
> +		status = "okay";
> +	};
> +
> +	sub-channel1 {
> +		status = "okay";
> +	};
> +
> +	port {
> +		drif0_ep: endpoint {
> +		     remote-endpoint = <&tuner_subdev_ep>;
> +		};
> +	};
> +};