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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 09:13:00 +0100
jacopo mondi <jacopo@jmondi.org> wrote:

> Hi Yong,
>
> On Fri, Nov 23, 2018 at 04:01:17PM +0800, Yong wrote:
> > 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.
>
> Well, BT.565 sync mode applies to parallel data transmission busses as
> BT.601 sync mode does... I don't want to bikeshed on terms though, I'm
> sorry...
>
> I would have write here:
>
> hsync-active : Required when using explicit HSYNC synchronism
> signal. Default valuse is "high"/"low".
> vsync-active : Required when using explicit VSYNC synchronism
> signal. Default valuse is "high"/"low".
> When both vsync-active and hsync-active are omitted BT.565 implicit
> synchronization mode is used.
>
> To avoid confusing people already confused as I am :)
>
> I got this patch is already in, right? Feel free to ignore my comment or
> either send an incremental patch if you think it is appropriate.
>

As Laurent's mentioned in this thread, this is a problem in
Documentation/devicetree/bindings/media/video-interfaces.txt in the
first place. And he said he'll try to submit a patch for
video-interfaces.txt.

Thanks,
Yong

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