[PATCH RFC 2/2] dt-bindings: add binding documentation for Allwinner CSI

[Yong]

On Fri, 30 Jun 2017 11:41:50 +0800
Chen-Yu Tsai <wens at csie.org> wrote:

> On Fri, Jun 30, 2017 at 5:19 AM, Rob Herring <robh at kernel.org> wrote:
> > On Tue, Jun 27, 2017 at 07:07:34PM +0800, Yong Deng wrote:
> >> Add binding documentation for Allwinner CSI.
> >
> > For the subject:
> >
> > dt-bindings: media: Add Allwinner Camera Sensor Interface (CSI)
> >
> > "binding documentation" is redundant.

OK.

> >
> >>
> >> Signed-off-by: Yong Deng <yong.deng at magewell.com>
> >> ---
> >>  .../devicetree/bindings/media/sunxi-csi.txt        | 51 ++++++++++++++++++++++
> >>  1 file changed, 51 insertions(+)
> >>  create mode 100644 Documentation/devicetree/bindings/media/sunxi-csi.txt
> >>
> >> diff --git a/Documentation/devicetree/bindings/media/sunxi-csi.txt b/Documentation/devicetree/bindings/media/sunxi-csi.txt
> >> new file mode 100644
> >> index 0000000..770be0e
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/media/sunxi-csi.txt
> >> @@ -0,0 +1,51 @@
> >> +Allwinner V3s Camera Sensor 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
> >> +    * ahb: 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
> >> +
> >> +- ports: A ports node with endpoint definitions as defined in
> >> +  Documentation/devicetree/bindings/media/video-interfaces.txt. The
> >> +  first port should be the input endpoints, the second one the outputs
> >
> > Is there more than one endpoint for each port? If so, need to define
> > that numbering too.

I made a mistake here.
"The first port should be the input endpoints, the second one the outputs"
is wrong and redundant.

> 
> It is possible to have multiple camera sensors connected to the same
> bus. Think front and back cameras on a cell phone or tablet.
> 
> I don't think any kind of numbering makes much sense though. The
> system is free to use just one sensor at a time, or use many with
> some time multiplexing scheme. What might matter to the end user
> is where the camera is placed. But using the position or orientation
> as a numbering scheme might not work well either. Someone may end
> up using two sensors with the same orientation for stereoscopic
> vision.

It is! But multiple sensors can't be working on the same bus 
simultaneously. So, the driver should have capability to switch
input device. But my driver does not support switching between 
multiple camera sensors for now! The driver only pickup the first
valid one. Maybe it's a feature to implement in the future.

Maybe like this:
- port: A port node with endpoint definitions as defined in
  Documentation/devicetree/bindings/media/video-interfaces.txt.
  A CSI have only one port. But you can define multiple endpoint
  under the port. The driver will pick up the first valid one.

> 
> >
> >> +
> >> +Example:
> >> +
> >> +     csi1: csi at 01cb4000 {
> >> +             compatible = "allwinner,sun8i-v3s-csi";
> >> +             reg = <0x01cb4000 0x1000>;
> 
> Yong, the address range size is 0x4000, including the CCI (I2C)
> controller at offset 0x3000. You should also consider this in
> the device tree binding, and the driver.
> 
> ChenYu

For V3s, the reg range <0x01cb0000 0x4000> of CSI0 have 4 module:
  * <0x01cb0000 0x1000>	-- CSI0
  * <0x01cb1000 0x1000>	-- MIPI-CSI
  * <0x01cb2000 0x1000>	-- MIPI-DPHY
  * <0x01cb3000 0x1000>	-- CCI
the reg range <0x01cb4000 0x4000> of CSI1 have 1 module:
  * <0x01cb4000 0x1000>	-- CSI1

And, I think the CCI, MIPI-CSI, MIPI-DPHY should have their own
device tree binding and driver.

> 
> >> +             interrupts = <GIC_SPI 84 IRQ_TYPE_LEVEL_HIGH>;
> >> +             clocks = <&ccu CLK_BUS_CSI>,
> >> +                      <&ccu CLK_CSI1_SCLK>,
> >> +                      <&ccu CLK_DRAM_CSI>;
> >> +             clock-names = "ahb", "mod", "ram";
> >> +             resets = <&ccu RST_BUS_CSI>;
> >> +
> >> +             port {
> >> +                     #address-cells = <1>;
> >> +                     #size-cells = <0>;
> >> +
> >> +                     /* Parallel bus endpoint */
> >> +                     csi1_0: endpoint at 0 {
> >> +                             reg = <0>;
> >
> > Don't need this and everything associated with it for a single endpoint.

Like this?
            csi1_ep: endpoint {
                remote-endpoint = <&adv7611_ep>;
                bus-width = <16>;
                data-shift = <0>;
    
                /* If hsync-active/vsync-active are missing,
                   embedded BT.656 sync is used */
                hsync-active = <0>; /* Active low */
                vsync-active = <0>; /* Active low */
                data-active = <1>;  /* Active high */
                pclk-sample = <1>;  /* Rising */
            };

The property "remote" should be "remote-endpoint".
Is there a mistake in video-interfaces.txt's example?

> >
> >> +                             remote = <&adv7611_1>;
> >> +                             bus-width = <16>;
> >> +                             data-shift = <0>;
> >> +
> >> +                             /* If hsync-active/vsync-active are missing,
> >> +                                embedded BT.656 sync is used */
> >> +                             hsync-active = <0>; /* Active low */
> >> +                             vsync-active = <0>; /* Active low */
> >> +                             data-active = <1>;  /* Active high */
> >> +                             pclk-sample = <1>;  /* Rising */
> >> +                     };
> >> +             };
> >> +     };
> >> +
> >> --
> >> 1.8.3.1
> >>
> >> --
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