On 10/29/20 2:33 AM, Hans Verkuil wrote:
On 29/10/2020 02:48, Sowjanya Komatineni wrote:
Hi Sakari,
Missed to add you to below patch series for HDMI2CSI bridge support
https://patchwork.kernel.org/project/linux-media/cover/1603768763-25590-1-git-send-email-skomatineni@xxxxxxxxxx/
Patch-10 of this series is for x8 capture from HDMI2CSI bridge.
Would like to get your suggestion on x8 gang/combined ports capture implementation.
Tegra VI/CSI don't have native x8. HDMI2CSI bridges uses dual ports with split image on to each port.
So on Tegra side at SW level we can use dual ports as gang where both ports are simultaneously programmed for combined image capture.
Currently v2 patches use bus-width with V4L2 parallel bus type for this x8 gang mode implementation.
So, driver parses endpoint and if bus type is parallel (for x8), it uses v4l2_ep.bus.parallel.bus_width other wise (x4 and below) it uses
v4l2_ep.bus.mipi_csi2.num_data_lanes for getting lanes from DT.
x8 is not from native HW and current v2 version does not explicitly add 2nd port in device tree and driver uses consecutive ports as
combined capture for same video device node.
From offline discussion with Hans, looks like its better to explicitly specify both ports used as gang/combined capture in device tree on
Tegra side and bridge side also will expose both TX ports.
Current CSI driver implementation uses max 2 media pads port@0 as Sink and port@1 as Source. So can add 2nd endpoint in sink node and source
nodes.
Below is tc358840 and csi device node change to explicitly add second source.
With this, VI/CSI driver can be updated to use second port only for identifying total combined ports for capture.
My understanding is there is no need for creating media links for 2nd port as both ports together are used as combined ports by the Tegra
driver during streaming for the same csi subdev and video device nodes.
In my opinion both links should be shown in the media controller topology.
Basically these are just independent CSI ports (two independent TX ports on
the tc358840 and two independent RX ports on the Tegra SoC side), that are
combined afterwards into a single video stream.
While this is an HDMI receiver, it is conceivable to have two sensors instead
that combine to a single 3D side-by-side image. In that case each CSI port on
the Tegra goes to a separate sensor. You want to model this.
Regards,
Hans
With 2 ports (used as combined ports on Tegra side), as they all are for
the same subdev and video device, exposing 2nd port and creating media
links will create 2 source pads and 2 sink pads.
Subdev will be same for both 2 source pads. I am trying to understand
the usage of creating media links for 2nd port which is used as combined
port with side-by-side capture thru VI for same video device node.
Please provide your suggestions/comments on this so I can take care of exposing both combined ports in v3.
tc358840@1f {
...
...
ports {
#address-cells = <1>;
#size-cells = <0>;
port@0 {
reg = <0>;
tc358840_out0: endpoint {
link-frequencies = /bits/ 64 <297000000>;
clock-lanes = <0>;
data-lanes = <1 2 3 4>;
remote-endpoint = <&tc358840_csi_in0>;
};
};
port@1 {
reg = <1>;
tc358840_out1: endpoint {
link-frequencies = /bits/ 64 <297000000>;
clock-lanes = <0>;
data-lanes = <1 2 3 4>;
remote-endpoint = <&tc358840_csi_in1>;
};
};
};
};
csi_chan: channel@2 {
reg = <2> /* CSI Port No */
..
..
ports {
/* port@0 always for Sink pads */
port@0 {
reg = <0>; /* Media Pad-0 (Sink) */
tc358840_csi_in0: endpoint@0 {
reg = <0>;
data-lanes = <1 2 3 4>;
remote-endpoint = <&tc358840_tx0>;
};
tc358840_csi_in1: endpoint@1 {
reg = <1>;
data-lanes = <1 2 3 4>;
remote-endpoint = <&tc358840_tx1>;
};
}
/* port@1 always Source pads */
port@1 {
reg = <1>; /* Media Pad-1 (Source) */
tc358840_csi_in0: endpoint@0 {
reg = <0>;
remote-endpoint = <&tc358840_vi_in0>;
};
tc358840_csi_in0: endpoint@1 {
reg = <1>;
remote-endpoint = <&tc358840_vi_in1>;
};
}
}
}
Thanks
Sowjanya
