IVC

Inter VM Communication provides interfaces to communicate between chip processors through memory channel. The only channel supported in the current distribution is the echo channel. The echo channel demonstrates:

• How to establish the IVC channel.
• How IVC communication works in the kernel.
• How IVC communication works in the Freertos code.

AGX Xavier

1. The current IVC channel are described in the device tree repository. You must run source_sync.sh to get the dtsi file. After running source_sync.sh, the file is located at Linux_for_Tegra/sources/hardware/nvidia/soc/t19x/kernel-dts/tegra194-soc/tegra194-aon.dtsi
2. To add/remove or enable/disable the channels in linux kernel, you must update the device tree entries in the above dtsi file. The following code shows how to enable the IVC echo channel:

                   };
           };
    
   +       aon_echo {
   +               compatible = "nvidia,tegra186-aon-ivc-echo";
   +               mboxes = <&aon 0>;
   +               status = "okay";
   +       };
   +
           aondbg {
                   compatible = "nvidia,tegra186-aondbg";
                   mboxes = <&aon 1>;

3. Compile the device tree and copy the dtb file to Linux_for_Tegra/dtb/ directory.
4. Rebuild the device tree and reflash the board by referencing the instructions in the Building the Kernel section of the Linux Developer Guide.
5. Build the SPE application, and copy the output to ${L4T}/bootloader/spe_t194.bin.

AGX Orin

1. The current IVC channel are described in the device tree repository. You must run source_sync.sh to get the dtsi file. After running source_sync.sh, the file is located at Linux_for_Tegra/sources/hardware/nvidia/soc/t23x/kernel-dts/tegra234-soc/tegra234-aon.dtsi
2. To add/remove or enable/disable the channels in linux kernel, you must update the device tree entries in the above dtsi file. The following code shows how to enable the IVC echo channel:

           aon_echo {
                   compatible = "nvidia,tegra186-aon-ivc-echo";
                   mboxes = <&aon 1>;
   -               status = "disabled";
   +               status = "okay";
           };

3. Compile the device tree and copy the dtb file to Linux_for_Tegra/dtb/ directory.
4. Rebuild the device tree and reflash the board by referencing the instructions in the Building the Kernel section of the Linux Developer Guide.
5. Build the SPE application, and copy the output to ${L4T}/bootloader/spe_t234.bin.

How to test

From the Linux kernel side, the /sys/devices/platform/aon_echo/data_channel node is used to communicate with AON after enabling echo channel as mentioned above. Messages sent to AON through this channel are echoed back to CCPLEX.

ubuntu@jetson:~$ sudo su -c 'echo tegra > /sys/devices/platform/aon_echo/data_channel'
ubuntu@jetson:~$ cat /sys/devices/platform/aon_echo/data_channel
tegra
ubuntu@jetson:~$

Sources

The echo channel ivc code in the current firmware resides at:

rt-aux-cpu-demo-fsp/app/ivc-echo-task.c

And the channel descriptions are at:

rt-aux-cpu-demo-fsp/platform/ivc-channel-ids.c