RE: [PATCH 1/2] media: dt-bindings: media: xilinx: Add Xilinx MIPI CSI-2 Rx Subsystem

[Vishal Sagar <vsagar@xilinx.com>]

Hi Rob,

Thanks for the review.

> -----Original Message-----
> From: Rob Herring [mailto:robh@kernel.org]
> Sent: Wednesday, June 13, 2018 1:34 AM
> To: Vishal Sagar <vishal.sagar@xilinx.com>
> Cc: Hyun Kwon <hyunk@xilinx.com>; laurent.pinchart@ideasonboard.com;
> michal.simek@xilinx.com; linux-media@vger.kernel.org;
> devicetree@vger.kernel.org; mark.rutland@arm.com; mchehab@kernel.org;
> linux-kernel@vger.kernel.org; hans.verkuil@cisco.com;
> sakari.ailus@linux.intel.com; Dinesh Kumar <dineshk@xilinx.com>; linux-arm-
> kernel@lists.infradead.org
> Subject: Re: [PATCH 1/2] media: dt-bindings: media: xilinx: Add Xilinx MIPI CSI-2
> Rx Subsystem
> 
> On Wed, May 30, 2018 at 12:24:43AM +0530, Vishal Sagar wrote:
> > Add bindings documentation for Xilinx MIPI CSI-2 Rx Subsystem.
> >
> > The Xilinx MIPI CSI-2 Rx Subsystem consists of a DPHY, CSI-2 Rx, an
> > optional I2C controller and an optional Video Format Bridge (VFB). The
> > active lanes can be configured at run time if enabled in the IP. The
> > DPHY register interface may also be enabled.
> >
> > Signed-off-by: Vishal Sagar <vishal.sagar@xilinx.com>
> > ---
> >  .../bindings/media/xilinx/xlnx,csi2rxss.txt        | 117
> +++++++++++++++++++++
> >  1 file changed, 117 insertions(+)
> >  create mode 100644
> Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.txt
> >
> > diff --git a/Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.txt
> b/Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.txt
> > new file mode 100644
> > index 0000000..31ed721
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/media/xilinx/xlnx,csi2rxss.txt
> > @@ -0,0 +1,117 @@
> > +
> > +Xilinx MIPI CSI2 Receiver Subsystem Device Tree Bindings
> > +--------------------------------------------------------
> > +
> > +The Xilinx MIPI CSI2 Receiver Subsystem is used to capture MIPI CSI2 traffic
> > +from compliant camera sensors and send the output as AXI4 Stream video
> data
> > +for image processing.
> > +
> > +The subsystem consists of a MIPI DPHY in slave mode which captures the
> > +data packets. This is passed along the MIPI CSI2 Rx IP which extracts the
> > +packet data. This data is taken in by the Video Format Bridge (VFB),
> > +if selected, and converted into AXI4 Stream video data at selected
> > +pixels per clock as per AXI4-Stream Video IP and System Design UG934.
> > +
> > +For more details, please refer to PG232 MIPI CSI-2 Receiver Subsystem.
> >
> +https://www.xilinx.com/support/documentation/ip_documentation/mipi_csi
> 2_rx_subsystem/v3_0/pg232-mipi-csi2-rx.pdf
> > +
> > +Required properties:
> > +
> > +- compatible: Must contain "xlnx,mipi-csi2-rx-subsystem-2.0" or
> > +  "xlnx,mipi-csi2-rx-subsystem-3.0"
> > +
> > +- reg: Physical base address and length of the registers set for the device.
> > +
> > +- interrupt-parent: specifies the phandle to the parent interrupt controller
> > +
> > +- interrupts: Property with a value describing the interrupt number.
> > +
> > +- xlnx,max-lanes: Maximum active lanes in the design.
> 
> There's already a property defined in video-interfaces.txt to limit
> lanes.
> 

Ok I will use the standard data-lanes and remove this.

> > +
> > +- xlnx,vc: Virtual Channel, specifies virtual channel number to be filtered.
> > +  If this is 4 then all virtual channels are allowed.
> > +
> > +- xlnx,csi-pxl-format: This denotes the CSI Data type selected in hw design.
> > +  Packets other than this data type (except for RAW8 and User defined data
> > +  types) will be filtered out. Possible values are RAW6, RAW7, RAW8, RAW10,
> > +  RAW12, RAW14, RGB444, RGB555, RGB565, RGB666, RGB888 and
> YUV4228bit.
> 
> This should be standard property.

I don't see a standard property for the CSI pixel formats.
Do you mean media bus formats?

> 
> > +
> > +- xlnx,axis-tdata-width: AXI Stream width, This denotes the AXI Stream width.
> > +  It depends on Data type chosen, Video Format Bridge enabled/disabled and
> > +  pixels per clock. If VFB is disabled then its value is either 0x20 (32 bit)
> > +  or 0x40(64 bit) width.
> > +
> > +- xlnx,video-format, xlnx,video-width: Video format and width, as defined in
> > +  video.txt.
> 
> This doc needs to define what are valid values.
> 

Ok. The valid values list will be added in next revision.

> Why do you need this on both ports? Can there be a conversion in this
> block? At least for the MIPI CSI interface part, this should be a common
> property. Not sure offhand if we have defined one. We have for parallel
> interfaces.
> 
> And 'width' doesn't seem like the right term for what this is defined to
> be.
> 

This is put on both ports to keep it consistent with other drivers.
The video-format values are specific to Xilinx. 
The width here means bit per component.

> > +
> > +- port: Video port, using the DT bindings defined in ../video-interfaces.txt.
> 
> port is not a property. It goes in its own section. And port properties
> should be under it.

I will update this in next version.

> 
> > +  The CSI 2 Rx Subsystem has a two ports, one input port for connecting to
> > +  camera sensor and other is output port.
> 
> Need be specific port #0 is ?? and port #1 is ??.
> 

Right. I will describe them in the next version correctly.
0 will be sink pad and 1 will source pad.

> > +
> > +- data-lanes: The number of data lanes through which CSI2 Rx Subsystem is
> > +  connected to the camera sensor as per video-interfaces.txt
> 
> Why do you need both this and max-lanes?

I didn't know more and added both. I will keep this.

> 
> > +
> > +Optional properties:
> > +
> > +- xlnx,en-active-lanes: Enable Active lanes configuration in Protocol
> > +  Configuration Register.
> > +
> > +- xlnx,dphy-present: This is equivalent to whether DPHY register interface is
> > +  enabled or not.
> > +
> > +- xlnx,iic-present: This shows whether subsystem's IIC is present or not. This
> > +  affects the base address of the DPHY.
> 
> Perhaps you should break up reg into ranges for each submodule (or make
> the DPHY a separate node and use the phy binding.
> 

Ok I will break the range into 2 parts and access DPHY accordingly.

Regards
Vishal Sagar

> > +
> > +- xlnx,vfb: Video Format Bridge, Denotes if Video Format Bridge is selected
> > +  so that output is as per AXI stream documented in UG934.
> > +
> > +- xlnx,ppc: Pixels per clock, Number of pixels to be transferred per pixel
> > +  clock. This is valid only if xlnx,vfb property is present.
> > +
> > +Example:
> > +
> > +       csiss_1: csiss@a0020000 {
> > +               compatible = "xlnx,mipi-csi2-rx-subsystem-3.0";
> > +               reg = <0x0 0xa0020000 0x0 0x20000>;
> > +               interrupt-parent = <&gic>;
> > +               interrupts = <0 95 4>;
> > +
> > +               xlnx,max-lanes = <0x4>;
> > +               xlnx,en-active-lanes;
> > +               xlnx,dphy-present;
> > +               xlnx,iic-present;
> > +               xlnx,vc = <0x4>;
> > +               xlnx,csi-pxl-format = "RAW8";
> > +               xlnx,vfb;
> > +               xlnx,ppc = <0x4>;
> > +               xlnx,axis-tdata-width = <0x20>;
> > +
> > +               ports {
> > +                       #address-cells = <1>;
> > +                       #size-cells = <0>;
> > +
> > +                       port@0 {
> > +                               reg = <0>;
> > +
> > +                               xlnx,video-format = <XVIP_VF_YUV_422>;
> > +                               xlnx,video-width = <8>;
> > +                               csiss_out: endpoint {
> > +                                       remote-endpoint = <&vcap_csiss_in>;
> > +                               };
> > +                       };
> > +                       port@1 {
> > +                               reg = <1>;
> > +
> > +                               xlnx,video-format = <XVIP_VF_YUV_422>;
> > +                               xlnx,video-width = <8>;
> > +
> > +                               csiss_in: endpoint {
> > +                                       data-lanes = <1 2 3 4>;
> > +                                       /* MIPI CSI2 Camera handle */
> > +                                       remote-endpoint = <&vs2016_out>;
> > +                               };
> > +
> > +                       };
> > +
> > +               };
> > +       };
> > --
> > 2.7.4
> >
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