[PATCH v2 61/66] dt-bindings: media: Add Allwinner A31 ISP bindings documentation

[Laurent Pinchart]

Hi Paul,

On Mon, Feb 14, 2022 at 05:18:07PM +0100, Paul Kocialkowski wrote:
> On Mon 07 Feb 22, 17:51, Laurent Pinchart wrote:
> > On Sat, Feb 05, 2022 at 07:54:24PM +0100, Paul Kocialkowski wrote:
> > > This introduces YAML bindings documentation for the Allwinner A31 Image
> > > Signal Processor (ISP).
> > > 
> > > Signed-off-by: Paul Kocialkowski <paul.kocialkowski at bootlin.com>
> > > ---
> > >  .../media/allwinner,sun6i-a31-isp.yaml        | 117 ++++++++++++++++++
> > >  1 file changed, 117 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml
> > > 
> > > diff --git a/Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml b/Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml
> > > new file mode 100644
> > > index 000000000000..2d87022c43ce
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/media/allwinner,sun6i-a31-isp.yaml
> > > @@ -0,0 +1,117 @@
> > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/media/allwinner,sun6i-a31-isp.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Allwinner A31 Image Signal Processor Driver (ISP) Device Tree Bindings
> > > +
> > > +maintainers:
> > > +  - Paul Kocialkowski <paul.kocialkowski at bootlin.com>
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - allwinner,sun6i-a31-isp
> > > +      - allwinner,sun8i-v3s-isp
> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +
> > > +  interrupts:
> > > +    maxItems: 1
> > > +
> > > +  clocks:
> > > +    items:
> > > +      - description: Bus Clock
> > > +      - description: Module Clock
> > > +      - description: DRAM Clock
> > 
> > That's interesting, does the ISP have a dedicated DRAM ?
> 
> It doesn't, it actually uses the main DRAM with the "mbus" interconnect.
> The clock is probably for the DMA engine.
> 
> > > +
> > > +  clock-names:
> > > +    items:
> > > +      - const: bus
> > > +      - const: mod
> > > +      - const: ram
> > > +
> > > +  resets:
> > > +    maxItems: 1
> > > +
> > > +  ports:
> > > +    $ref: /schemas/graph.yaml#/properties/ports
> > > +
> > > +    properties:
> > > +      port at 0:
> > > +        $ref: /schemas/graph.yaml#/$defs/port-base
> > > +        description: CSI0 input port
> > > +
> > > +        properties:
> > > +          reg:
> > > +            const: 0
> > > +
> > > +          endpoint:
> > > +            $ref: video-interfaces.yaml#
> > > +            unevaluatedProperties: false
> > 
> > If no other property than remote-endpoint are allowed, I'd write
> > 
> >           endpoint:
> >             $ref: video-interfaces.yaml#
> > 	    remote-endpoint: true
> >             additionalProperties: false
> > 
> > Same below.
> > 
> > > +
> > > +        additionalProperties: false
> > > +
> > > +      port at 1:
> > > +        $ref: /schemas/graph.yaml#/$defs/port-base
> > > +        description: CSI1 input port
> > > +
> > > +        properties:
> > > +          reg:
> > > +            const: 0
> > 
> > This should be 1.
> 
> Correct, thanks!
> 
> > > +
> > > +          endpoint:
> > > +            $ref: video-interfaces.yaml#
> > > +            unevaluatedProperties: false
> > > +
> > > +        additionalProperties: false
> > > +
> > > +    anyOf:
> > > +      - required:
> > > +        - port at 0
> > > +      - required:
> > > +        - port at 1
> > 
> > As ports are an intrinsic property of the ISP, both should be required,
> > but they don't have to be connected.
> 
> Well the ISP does have the ability to source from either CSI0 and CSI1
> but I don't really get the point of declaring both ports when only one
> of the two controllers is present.

If it's within an SoC I don't mind too much. What I usually insist on is
declaring all ports even when no external devices are connected on the
board. It may however be easier to implement things on the driver side
when all the ports are declared, even for internal devices. I won't
insist either way here.

> > By the way, how do you select at runtime which CSI-2 RX the ISP gets its
> > image stream from ? Is it configured through registers of the ISP ?
> 
> Actually what the ISP gets is fully dependent on what is received by the
> CSI controller it is connected to (which can be the mipi csi-2 controller
> or its direct parallel pins), so the configuration happens on the CSI side.

OK, then how do you select at runtime which CSI the ISP gets its image
stream from ? :-)

> > > +
> > > +required:
> > > +  - compatible
> > > +  - reg
> > > +  - interrupts
> > > +  - clocks
> > > +  - clock-names
> > > +  - resets
> > > +
> > > +additionalProperties: false
> > > +
> > > +examples:
> > > +  - |
> > > +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> > > +    #include <dt-bindings/clock/sun8i-v3s-ccu.h>
> > > +    #include <dt-bindings/reset/sun8i-v3s-ccu.h>
> > > +
> > > +    isp: isp at 1cb8000 {
> > > +        compatible = "allwinner,sun8i-v3s-isp";
> > > +        reg = <0x01cb8000 0x1000>;
> > > +        interrupts = <GIC_SPI 83 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>;
> > > +
> > > +        ports {
> > > +            #address-cells = <1>;
> > > +            #size-cells = <0>;
> > > +
> > > +            port at 0 {
> > > +                reg = <0>;
> > > +
> > > +                isp_in_csi0: endpoint {
> > > +                    remote-endpoint = <&csi0_out_isp>;
> > > +                };
> > > +            };
> > > +        };
> > > +    };
> > > +
> > > +...

-- 
Regards,

Laurent Pinchart