linux-kernel - Re: [PATCH v11 1/2] dt-bindings: media: Add Allwinner V3s Camera Sensor Interface (CSI)

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Message-ID: <20180928093833.gwmskm2jvby6x4s6@paasikivi.fi.intel.com>
Date:   Fri, 28 Sep 2018 12:38:33 +0300
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Yong Deng <yong.deng@...ewell.com>
Cc:     Maxime Ripard <maxime.ripard@...tlin.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Chen-Yu Tsai <wens@...e.org>,
        "\"David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Jacob Chen <jacob-chen@...wrt.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Thierry Reding <treding@...dia.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Todor Tomov <todor.tomov@...aro.org>,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH v11 1/2] dt-bindings: media: Add Allwinner V3s Camera
 Sensor Interface (CSI)

Hi Yong,

On Wed, Sep 26, 2018 at 04:40:04PM +0800, Yong Deng wrote:
> Add binding documentation for Allwinner V3s CSI.
> 
> Acked-by: Maxime Ripard <maxime.ripard@...tlin.com>
> Acked-by: Sakari Ailus <sakari.ailus@...ux.intel.com>

I know... but I have a few more comments.

> Reviewed-by: Rob Herring <robh@...nel.org>
> Signed-off-by: Yong Deng <yong.deng@...ewell.com>
> ---
>  .../devicetree/bindings/media/sun6i-csi.txt        | 59 ++++++++++++++++++++++
>  1 file changed, 59 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/media/sun6i-csi.txt
> 
> diff --git a/Documentation/devicetree/bindings/media/sun6i-csi.txt b/Documentation/devicetree/bindings/media/sun6i-csi.txt
> new file mode 100644
> index 000000000000..2ff47a9507a6
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/sun6i-csi.txt
> @@ -0,0 +1,59 @@
> +Allwinner V3s Camera Sensor Interface
> +-------------------------------------
> +
> +Allwinner V3s SoC features two CSI module. CSI0 is used for MIPI CSI-2
> +interface and CSI1 is used for parallel interface.
> +
> +Required properties:
> +  - compatible: value must be "allwinner,sun8i-v3s-csi"
> +  - reg: base address and size of the memory-mapped region.
> +  - interrupts: interrupt associated to this IP
> +  - clocks: phandles to the clocks feeding the CSI
> +    * bus: the CSI interface clock
> +    * mod: the CSI module clock
> +    * ram: the CSI DRAM clock
> +  - clock-names: the clock names mentioned above
> +  - resets: phandles to the reset line driving the CSI
> +
> +Each CSI node should contain one 'port' child node with one child 'endpoint'
> +node, according to the bindings defined in
> +Documentation/devicetree/bindings/media/video-interfaces.txt. As mentioned
> +above, the endpoint's bus type should be MIPI CSI-2 for CSI0 and parallel or
> +Bt656 for CSI1.

Which port represents CSI0 and which one is CSI1? That needs to be
documented.

> +
> +Endpoint node properties for CSI1

How about CSI0? I'd expect at least data-lanes, and clock-lanes as well if
the hardware supports lane mapping.

> +---------------------------------
> +
> +- remote-endpoint	: (required) a phandle to the bus receiver's endpoint
> +			   node
> +- bus-width:		: (required) must be 8, 10, 12 or 16
> +- pclk-sample		: (optional) (default: sample on falling edge)

Could you add that video-interfaces.txt contains documentation of these
properties as well? There's a reference above but only discusses port and
endpoint nodes.

> +- hsync-active		: (only required for parallel)
> +- vsync-active		: (only required for parallel)

As you support both Bt656 and parallel (with sync signals), you can detect
the interface type from the presence of these properties. I think you
should also say that these properties are not allowed on Bt656. So I'd
change this to e.g.

	(required; parallel-only)

> +
> +Example:
> +
> +csi1: csi@...4000 {
> +	compatible = "allwinner,sun8i-v3s-csi";
> +	reg = <0x01cb4000 0x1000>;
> +	interrupts = <GIC_SPI 84 IRQ_TYPE_LEVEL_HIGH>;
> +	clocks = <&ccu CLK_BUS_CSI>,
> +		 <&ccu CLK_CSI1_SCLK>,
> +		 <&ccu CLK_DRAM_CSI>;
> +	clock-names = "bus", "mod", "ram";
> +	resets = <&ccu RST_BUS_CSI>;
> +
> +	port {
> +		/* Parallel bus endpoint */
> +		csi1_ep: endpoint {
> +			remote-endpoint = <&adv7611_ep>;
> +			bus-width = <16>;
> +
> +			/* If hsync-active/vsync-active are missing,
> +			   embedded BT.656 sync is used */
> +			hsync-active = <0>; /* Active low */
> +			vsync-active = <0>; /* Active low */
> +			pclk-sample = <1>;  /* Rising */
> +		};
> +	};
> +};

-- 
Kind regards,

Sakari Ailus
sakari.ailus@...ux.intel.com