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Date:   Fri, 23 Nov 2018 16:01:17 +0800
From:   Yong <yong.deng@magewell.com>
To:     jacopo mondi <jacopo@jmondi.org>
Cc:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Maxime Ripard <maxime.ripard@bootlin.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Chen-Yu Tsai <wens@csie.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "David S. Miller" <davem@davemloft.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Hans Verkuil <hans.verkuil@cisco.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Jacopo Mondi <jacopo+renesas@jmondi.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Todor Tomov <todor.tomov@linaro.org>,
        linux-media@vger.kernel.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-sunxi@googlegroups.com,
        Sakari Ailus <sakari.ailus@linux.intel.com>
Subject: Re: [PATCH v12 1/2] dt-bindings: media: Add Allwinner V3s Camera
 Sensor Interface (CSI)
Message-Id: <20181123160117.7eed41aac3e7e31e4e6d98be@magewell.com>
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        <308184907.pMD7ZDI2dr@avalon>
        <20181123074514.GB6788@w540>
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Hi jacopo,

On Fri, 23 Nov 2018 08:45:14 +0100
jacopo mondi <jacopo@jmondi.org> wrote:

> Hi Yong,
> 
> On Tue, Oct 30, 2018 at 03:06:24PM +0200, Laurent Pinchart wrote:
> > Hi Yong,
> >
> > Thank you for the patch.
> >
> > On Tuesday, 30 October 2018 10:12:23 EET Yong Deng wrote:
> > > Add binding documentation for Allwinner V3s CSI.
> > >
> > > Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
> > > Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > > Reviewed-by: Rob Herring <robh@kernel.org>
> > > Signed-off-by: Yong Deng <yong.deng@magewell.com>
> >
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >
> > > ---
> > >  .../devicetree/bindings/media/sun6i-csi.txt        | 56 +++++++++++++++++++
> > >  1 file changed, 56 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..443e18c181b3
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/media/sun6i-csi.txt
> > > @@ -0,0 +1,56 @@
> > > +Allwinner V3s Camera Sensor Interface
> > > +-------------------------------------
> > > +
> > > +Allwinner V3s SoC features a CSI module(CSI1) with 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
> > > +
> > > +The 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.
> > > +
> > > +Endpoint node properties for CSI
> > > +---------------------------------
> > > +See the video-interfaces.txt for a detailed description of these
> > > properties. +- 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)
> > > +- hsync-active		: (required; parallel-only)
> > > +- vsync-active		: (required; parallel-only)
> > > +
> > > +Example:
> > > +
> > > +csi1: csi@1cb4000 {
> > > +	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 */
> 
> Am I confused? The properties description defines [v|h]sync-active as
> required, but the example reports that they can be omitted to use
> BT.656 synchronization.
> 
> Which one of the following is correct?
> 1) [h|v]sync-active are mandatory: no BT.656 support can be selected.
> 2) [h|v]sync-active are optional, and if not specified BT.656 is
>    selected.
> 3) I am confused.
>
 
hsync-active		: (required; parallel-only)
vsync-active		: (required; parallel-only)

Here, parallel means seperate sync signal, BT.656 means embedded sync
signal. Kernel use these two properties to detect if the bus type is 
parallel or Bt656. So [h|v]sync-active are mandatory only if your bus
type is parallel and must not be specified if your bus type is Bt656.

Thanks,
Yong