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Date:   Tue, 17 Nov 2020 13:08:51 +0100
From:   Jacopo Mondi <jacopo@jmondi.org>
To:     Eugen.Hristev@microchip.com
Cc:     linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
        devicetree@vger.kernel.org, robh+dt@kernel.org,
        sakari.ailus@iki.fi, laurent.pinchart@ideasonboard.com
Subject: Re: [PATCH v5 1/3] dt-bindings: media: atmel: csi2dc: add bindings
 for microchip csi2dc
Message-ID: <20201117120851.ra7f2szm3cqgnfaw@uno.localdomain>
References: <20201112133437.372475-1-eugen.hristev@microchip.com>
 <20201117103702.2h77qvh7ebqx4yaq@uno.localdomain>
 <812d92e6-e595-7cf0-b1a4-3eded08bf737@microchip.com>
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In-Reply-To: <812d92e6-e595-7cf0-b1a4-3eded08bf737@microchip.com>
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Hi Eugen,

On Tue, Nov 17, 2020 at 11:14:18AM +0000, Eugen.Hristev@microchip.com wrote:
> On 17.11.2020 12:37, Jacopo Mondi wrote:
> > Hi again,
> >
> > On Thu, Nov 12, 2020 at 03:34:35PM +0200, Eugen Hristev wrote:
> >> Add bindings documentation for Microchip CSI2 Demultiplexer controller.
> >>
> >> CSI2DC is a demultiplexer from Synopsys IDI interface specification to
> >> parallel interface connection or direct memory access.
> >>
> >> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
> >> ---
> >> Changes in v5:
> >> - modified bindings as per Rob Herring review
> >>
> >> Changes in v4:
> >> - Removed property for inter-line-delay and for clock continuous/non-continuous
> >> - Removed virtual channel by reg for second endpoint
> >>
> >> Changes in v3:
> >> - Removed some text from description, as it was explained in the schema
> >> - fixed other things as per Rob's review
> >> - moved some text inside the schema, like the clock description
> >>
> >> Changes in v2:
> >> - fixed warnings reported by dt_binding_check
> >>
> >>   .../bindings/media/microchip,csi2dc.yaml      | 119 ++++++++++++++++++
> >>   1 file changed, 119 insertions(+)
> >>   create mode 100644 Documentation/devicetree/bindings/media/microchip,csi2dc.yaml
> >>
> >> diff --git a/Documentation/devicetree/bindings/media/microchip,csi2dc.yaml b/Documentation/devicetree/bindings/media/microchip,csi2dc.yaml
> >> new file mode 100644
> >> index 000000000000..e79f0d6ba9db
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/media/microchip,csi2dc.yaml
> >> @@ -0,0 +1,119 @@
> >> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >> +%YAML 1.2
> >> +---
> >> +$id: http://devicetree.org/schemas/media/microchip,csi2dc.yaml#
> >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >> +
> >> +title: Microchip CSI2 Demux Controller (CSI2DC)
> >> +
> >> +maintainers:
> >> +  - Eugen Hristev <eugen.hristev@microchip.com>
> >> +
> >> +description:
> >> +  CSI2DC - Camera Serial Interface 2 Demux Controller
> >> +
> >> +  CSI2DC is a hardware block that receives incoming data from an IDI interface
> >> +  and filters packets based on their data type and virtual channel identifier,
> >> +  then converts the byte stream into a cross clock domain to a pixel stream
> >> +  to a parallel interface that can be read by a sensor controller.
> >> +
> >> +  CSI2DC provides two pipes, one video pipe and one data pipe. Video pipe
> >> +  is connected to a sensor controller and the data pipe is accessible
> >> +  as a DMA slave port to a DMA controller.
> >> +
> >> +  CSI2DC supports a single 'port' node as a source pad with Synopsys 32-bit
> >> +  IDI interface. The connected endpoint must be a IDI interface compatible
> >> +  device (like Synopsys CSI2HOST) , that can provide 32-bit IDI interface
> >> +  connection as sink pad.
> >> +  For media entity and endpoints please refer to the bindings defined in
> >> +  Documentation/devicetree/bindings/media/video-interfaces.txt.
> >> +  For Synopsys IDI interface please refer to
> >> +  Documentation/devicetree/bindings/media/snps,dw-csi-plat.txt
> >
> > Is it me or this file doesn't exists on the most recent media/master
> > and on v5.10-rc4 ?
>
> Hi Jacopo,
>
> Thanks for reviewing this patch.
> You are right. As I said at some point during the review, actually this
> controller has an input the IDI interface which is not currently in
> kernel. There is a patch series that adds the Synopsys platform driver,
> but nobody worked on it anymore and I use it for testing my driver.
> You can see the last version that was sent here:
>
> https://patchwork.linuxtv.org/project/linux-media/patch/1560280855-18085-2-git-send-email-luis.oliveira@synopsys.com/
>
>
> I sent this series to understand how to improve and how to get my driver
> in kernel, but indeed there are holes, especially this input type of bus
> which is not in the subsystem either.
>
> So how would you suggest to move forward ? Remove the reference to the
> synopsys binding and just leave 'IDI interface' which is undocumented ?

mmm, I see... I was hoping it was a simple CSI-2 tx :)

The Synopsys proposed bindings do not tell much as they don't describe
the csi2host output port. I would just mention "Synopsys IDI
compatible interface" without mentioning a file that cannot be
accessed :)

Thanks
   j

>
> Eugen
>
> >
> >> +
> >> +  CSI2DC supports one 'port' node as sink pad with parallel interface. This is
> >> +  called video pipe.
> >> +  This port has an 'endpoint' can then be used as a source pad for another
> >> +  controller (next in pipeline).
> >> +  Please refer to the bindings defined in
> >> +  Documentation/devicetree/bindings/media/video-interfaces.txt.
> >> +
> >> +  CSI2DC also supports direct access to the data through AHB, via DMA channel,
> >> +  called data pipe.
> >> +  Because of this, the sink 'port' child node (second) is not mandatory.
> >> +  If the sink 'port' child node is missing, only data pipe is available.
> >> +
> >> +properties:
> >> +  compatible:
> >> +    const: microchip,sama7g5-csi2dc
> >> +
> >> +  reg:
> >> +    maxItems: 1
> >> +
> >> +  clocks:
> >> +    maxItems: 2
> >> +
> >> +  clock-names:
> >> +    description:
> >> +      CSI2DC must have two clocks to function correctly. One clock is the
> >> +      peripheral clock for the inside functionality of the hardware block.
> >> +      This is named 'pclk'. The second clock must be the cross domain clock,
> >> +      in which CSI2DC will perform clock crossing. This clock must be fed
> >> +      by the next controller in pipeline, which usually is a sensor controller.
> >> +      Normally this clock should be given by this sensor controller who
> >> +      is also a clock source. This clock is named 'scck', sensor controller clock.
> >> +    items:
> >> +      - const: pclk
> >> +      - const: scck
> >> +
> >> +  ports:
> >> +    type: object
> >> +    description:
> >> +      List of ports
> >> +
> >> +    properties:
> >> +      port@0:
> >> +        type: object
> >> +        description:
> >> +          Input port node, single endpoint describing the input pad.
> >> +      port@1:
> >> +        type: object
> >> +        description:
> >> +          Output port node, single endpoint, describing the output pad.
> >> +
> >> +additionalProperties: false
> >> +
> >> +required:
> >> +  - compatible
> >> +  - reg
> >> +  - clocks
> >> +  - clock-names
> >> +  - ports
> >> +
> >> +examples:
> >> +  - |
> >> +    csi2dc@e1404000 {
> >> +        compatible = "microchip,sama7g5-csi2dc";
> >> +        reg = <0xe1404000 0x500>;
> >> +        clocks = <&pclk>, <&scck>;
> >> +        clock-names = "pclk", "scck";
> >> +
> >> +        ports {
> >> +               #address-cells = <1>;
> >> +               #size-cells = <0>;
> >> +               port@0 {
> >> +                       reg = <0>; /* must be 0, first child port */
> >> +                       csi2dc_in: endpoint { /* input from IDI interface */
> >> +                               remote-endpoint = <&csi2host_out>;
> >> +                       };
> >> +               };
> >> +
> >> +               port@1 {
> >> +                       reg = <1>; /* must be 1, second child port */
> >> +                       csi2dc_out: endpoint {
> >> +                               remote-endpoint = <&xisc_in>; /* output to sensor controller */
> >> +                       };
> >> +               };
> >> +        };
> >> +    };
> >> +
> >> +...
> >> --
> >> 2.25.1
> >>
>