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SubjectRe: [PATCH v12 1/2] dt-bindings: media: Add Allwinner V3s Camera Sensor Interface (CSI)
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

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