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

Paul Kocialkowski
2022-02-14T16:18:30Z

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Hi Laurent,

Thanks for the review and the follow-up questions!

On Mon 07 Feb 22, 17:51, Laurent Pinchart wrote:
> Hi Paul,
>
> Thank you for the patch.
>
> 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@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@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@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@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@0
> > + - required:
> > + - port@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.

> 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.

Thanks,

Paul

> > +
> > +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@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@0 {
> > + reg = <0>;
> > +
> > + isp_in_csi0: endpoint {
> > + remote-endpoint = <&csi0_out_isp>;
> > + };
> > + };
> > + };
> > + };
> > +
> > +...
>
> --
> Regards,
>
> Laurent Pinchart

--
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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