L4T R28.3 Dynamic change of csi lane number

Robotics & Edge Computing Jetson & Embedded Systems Jetson TX2
1

Hi all,

Is it possible to change, on the fly, the number of csi input lanes used?

Use case example:
Step 1- TX2 acquiring 1920x1080p25 video over 2-lane MIPI CSI.
Step 2- User send command to change input resolution acquisition to NTSC(720x480i60).
Step 3- TX2 reconfiguring itself (kernel driver or user space command) to aquire 720x480i60 video 1-lane MIPI CSI.

For 1920x1080p25 2-lane input, the csi configuration is set in device-tree like this:

host1x {
    vi@15700000 {
        num-channels = <1>;
        ports {
            #address-cells = <1>;
            #size-cells = <0>;
            port@0 {
                status = "okay";
                reg = <0>;
                csiconv_vi_in0: endpoint {
                    status = "okay";
                    csi-port = <0>;
                    bus-width = <2>;
                    remote-endpoint = <&csiconv_csi_out0>;
                };
            };
        };
    };

    nvcsi@150c0000 {
        num-channels = <2>;
        #address-cells = <1>;
        #size-cells = <0>;
        channel@0 {
            status = "okay";
            reg = <0>;
            ports {
                #address-cells = <1>;
                #size-cells = <0>;
                port@0 {
                    status = "okay";
                    reg = <0>;
                    csiconv_csi_in0: endpoint@0 {
                        status = "okay";
                        csi-port = <0>;
                        bus-width = <2>;
                        remote-endpoint = <&csiconv_out0>;
                    };
                };
                port@1 {
                    status = "okay";
                    reg = <1>;
                    csiconv_csi_out0: endpoint@1 {
                        status = "okay";
                        remote-endpoint = <&csiconv_vi_in0>;
                    };
                };
            };
        };
    };
};

...

i2c@3180000 {
    status = "okay";

    #address-cells = <1>;
    #size-cells = <0>;

    /* First input */
    csiconv@70 {
        status = "okay";
        compatible = "csiconv";
        reg = <0x70>;
        devnode = "video0";

        ...

        mode0 {
            num_lanes = "2";
            discontinuous_clk = "no";
            dpcm_enable = "false";
            cil_settletime = "0";
            dynamic_pixel_bit_depth = "16";
            csi_pixel_bit_depth = "16";
            mode_type = "yuv";
            pixel_phase = "uyvy";

            active_w = "1920";
            active_h = "1080";
            readout_orientation = "0";
            line_length = "2200";

            embedded_metadata_height = "0";
        };

        ports {
            #address-cells = <1>;
            #size-cells = <0>;

            port@0 {
                reg = <0>;
                csiconv_out0: endpoint {
                    csi-port = <0>;
                    bus-width = <2>;
                    remote-endpoint = <&csiconv_csi_in0>;
                };
            };
        };
    };
};

...

tcp: tegra-camera-platform {
    status = "okay";
    compatible = "nvidia, tegra-camera-platform";

    num_csi_lanes = <12>;
    max_lane_speed = <1500000>;
    min_bits_per_pixel = <8>;
    vi_peak_byte_per_pixel = <2>;
    vi_bw_margin_pct = <25>;
    max_pixel_rate = <408000>;
    isp_peak_byte_per_pixel = <2>;
    isp_bw_margin_pct = <25>;
    
    modules {
        module0 {
            status = "okay";
            badge = "csiconv_left_1111";
            position = "rear";
            orientation = "1";
            drivernode0 {
                status = "okay";
                /* Declare PCL support driver (classically known as guid)  */
                pcl_id = "v4l2_sensor";
                /* Driver's v4l2 device name */
                devname = "csiconv 2-0070";
                /* Declare the device-tree hierarchy to driver instance */
                proc-device-tree = "/proc/device-tree/i2c@3180000/csiconv_ef@70";
            };
        };
    };
};

I have looked different drivers/device-tree with several modes (mode0, mode1, etc.) but each mode have same number of lane.

From the device side, I have already implement methods to switch between 1, 2 and 4 lanes configuration.

My problem/question is about the capability of TX2 to reconfigure the lane number.
Q1 - First of all, is it possible?

Q2 - Is there an example? What is the tasks sequencing (reset DPHY, then NVCSI, etc.)?

Q3 - I think I should reconfigure or reset NVCSI and VI with the new parameters. How can I achieve this?

Q4 - How to send new parameters to NVCSI and VI?

Thanks

PS: It’s acceptable to have a video interruption during reconfiguration but I want to avoid TX2 restarting.

2

FYI, the device which generate MIPI CSI for TX2 isn’t able to generate 720x480i60 using 2-lane CSI (MIPI Clock is too slow for it).
That’s why I try to ‘dynamically’ change the number of CSI lane.

3

Sorry to tell don’t support dynamic lanes configure.
Why just use 4 lanes for all resolution?

4

Hi ShaneCCC,

Thanks for your answer.

As exposed in post #2, the device which generate MIPI CSI-2 data can’t generate data stream over 2 or 4 lanes for 720x480i60 because the mipi clock is too slow for the internal PLL (~54MHz).

In fact, it’s not a camera sensor, it’s an ADV748x.

I use it to grab two kind of video sources: (not at the same time, but alternately)

  • high definition digital video (1920x1080p25/30)
  • standard definition analog video (720x480i60)

Q1 - If I set 4-lanes in Device-Tree all the time, not depending which video input it is. What happens if the device send data only over 1 or 2 lanes? Is NVCSI able to catch and produce valid data to VI anyway?

Q2 - Is it possible to reset manually NVCSI and VI?

5

If the lanes number depend on the resolution you can try to modify the num_lanes in the modeX,
The NVCSI driver will load different mode(resolution) configure dynamically.

6

AurelienV, were you able to use mode in the dtsi to get it to switch lane count for different resolutions?