The AM62ax processors have Cortex-R5F and C7x DSP subsystems in addition to a Quad core Cortex-A53 subsystem. Please refer to the AM62ax Technical Reference Manual for details.
This article is geared toward AM62ax users that are running Linux on the Cortex A53 cores. The goal is to help users understand how to establish IPC communication with the C7x DSP and R5F cores.
There are many facets to this task: building, loading, debugging, memory sharing, etc. This article intends to take incremental steps toward understanding all of those pieces.
Prerequisites
- Processor SDK Linux for AM62ax |__SDK_DOWNLOAD_URL__|.
- Processor SDK MCU+ for AM62ax
Note
Please be sure that you have the same version number for both Processor SDK RTOS and Linux.
Please refer to the MCU+SDK documentation, section "Developer Guides" -> "Understanding inter-processor communication (IPC)" for IPC architecture and builds.
AM62ax SOC's have multiple processor cores - Cortex-A53, Cortex-R5F and DSP cores. The A53 typically runs a HLOS like Linux/Android. The C7x and R5F remote cores run No-OS or RTOS (FreeRTOS etc). In normal operation, the boot loader (U-Boot/SPL) boots and loads the A53 with the HLOS. The A53 then boots the C7x and R5F cores.
The wakeup R5F firmware runs device manager software (SciServer) along with vision apps application.
The wakeup R5F firmware is integrated as part of tispl.bin binary and is started early in the boot process by u-boot R5 SPL right after DDR initialization.
The figure below illustrates how the Remoteproc/RPMsg driver from the ARM Linux kernel communicates with the IPC driver on a remote processors (e.g. R5F) running RTOS.
In order to setup IPC on remote cores, we provide some pre-built examples in the SDK package that can be run from ARM Linux.
The remoteproc driver is hard-coded to look for specific files when loading the R5F and C7x cores. Here are the files it looks for on an AM62ax device:
+------------------+-----------------+----------------------+----------------------+ | Core Name | RemoteProc Name | Description | Firmware File Name | +==================+=================+======================+======================+ | C7x | 7e000000.c7x | C7x core | am62a-c71_0-fw | +------------------+-----------------+----------------------+----------------------+ | R5F | 79000000.r5f | R5F core(MCU domain) | am62a-mcu-r5f0_0-fw | +------------------+-----------------+----------------------+----------------------+
Generally on a target file system the above files are soft linked to the intended executable FW files:
root@am62axx-evm:~# ls -l /lib/firmware/ lrwxrwxrwx 1 root root 60 Feb 2 2023 am62a-c71_0-fw -> /lib/firmware/pdk-ipc/ipc_echo_test_c7x_1_release_strip.xe71 lrwxrwxrwx 1 root root 41 Feb 2 2023 am62a-mcu-r5f0_0-fw -> /lib/firmware/pdk-ipc/am62a-mcu-r5f0_0-fw
For updating wakeup (DM) R5F firmware binary, tispl.bin needs to be recompiled with the new firmware binary as mentioned below :
- Go to linux installer and replace the existing R5F wakeup (DM) firmware binary with the new one
host# cp <path_to_new_fw_binary>/ipc_echo_testb_freertos_mcu1_0_release.xer5f <path_to_linux_installer>/board-support/prebuilt-images/ipc_echo_testb_mcu1_0_release_strip.xer5f
- Recompile u-boot to regenerate tispl.bin using the top level makefile.
host# make u-boot
Please refer to Top-Level Makefile for more details on Top Level makefile.
- Replace the updated tispl.bin containing new R5F firmware binary in the boot partition of sdcard and reboot
host# sudo cp board-support/u-boot_build/a53/tispl.bin /media/$USER/boot
To reload a remote core with new executables, please follow the below steps.
First, identify the remotproc node associated with the remote core:
root@am62axx-evm:~# head /sys/class/remoteproc/remoteproc*/name ==> /sys/class/remoteproc/remoteproc0/name <== 7e000000.dsp ==> /sys/class/remoteproc/remoteproc1/name <== 79000000.r5f ==> /sys/class/remoteproc/remoteproc2/name <== 78000000.r5f
Then, use the sysfs interface to stop the remote core. For example, to stop the C71x
root@am62axx-evm:~# echo stop > /sys/class/remoteproc/remoteproc0/state [ 61.497327] remoteproc remoteproc0: stopped remote processor 7e000000.dsp
If needed, update the firmware symbolic link to point to a new firmware:
root@am62xx-evm:/lib/firmware# ln -sf /lib/firmware/pdk-ipc/ipc_echo_test_c7x_1_release_strip.xe71 am62a-c71_0-fw
Finally, use the sysfs interface to start the remote core:
root@am62axx-evm:~# echo start > /sys/class/remoteproc/remoteproc0/state [ 66.768814] remoteproc remoteproc0: powering up 7e000000.dsp [ 66.776893] remoteproc remoteproc0: Booting fw image am62a-c71_0-fw, size 2100144 [ 66.785144] k3-dsp-rproc 7e000000.dsp: booting DSP core using boot addr = 0x9a000000 [ 66.836110] remoteproc0#vdev0buffer: assigned reserved memory node c7x-dma-memory@99800000 [ 66.845052] virtio_rpmsg_bus virtio2: rpmsg host is online [ 66.850813] virtio_rpmsg_bus virtio2: creating channel ti.ipc4.ping-pong addr 0xd [ 66.851203] remoteproc0#vdev0buffer: registered virtio2 (type 7) [ 66.858507] virtio_rpmsg_bus virtio2: creating channel rpmsg_chrdev addr 0xe [ 66.864574] remoteproc remoteproc0: remote processor 7e000000.dsp is now up
Note
The RemoteProc driver does not support a graceful shutdown of R5 and DSP cores in the current Linux Processor SDK. For now, it is recommended to reboot the board when loading new binaries into an R5F or DSP core.
System memory is carved out for each remote processor core for IPC and for the remote processor's code/data section needs. The default memory carveouts (DMA pools) are shown below.
See the devicetree bindings documentation for more details: :ti-linux-kernel-binding:`remoteproc/ti,k3-r5f-rproc.yaml`
+------------------+--------------------+---------+----------------------------+ | Memory Section | Physical Address | Size | Description | +==================+====================+=========+============================+ | C7x Pool | 0x99800000 | 1MB | IPC (Virtio/Vring buffers) | +------------------+--------------------+---------+----------------------------+ | C7x Pool | 0x99900000 | 31MB | C7x externel code/data mem | +------------------+--------------------+---------+----------------------------+ | R5F(mcu) Pool | 0x9b800000 | 1MB | IPC (Virtio/Vring buffers) | +------------------+--------------------+---------+----------------------------+ | R5F(mcu) Pool | 0x9b900000 | 15MB | R5F externel code/data mem | +------------------+--------------------+---------+----------------------------+ | R5F(wkup) Pool | 0x9c800000 | 1MB | IPC (Virtio/Vring buffers) | +------------------+--------------------+---------+----------------------------+ | R5F(wkup) Pool | 0x9c900000 | 30MB | R5F externel code/data mem | +------------------+--------------------+---------+----------------------------+ root@am62axx-evm:/lib/firmware# dmesg | grep Reserved [ 0.000000] Reserved memory: created DMA memory pool at 0x0000000099800000, size 1 MiB [ 0.000000] Reserved memory: created DMA memory pool at 0x0000000099900000, size 30 MiB [ 0.000000] Reserved memory: created DMA memory pool at 0x000000009b800000, size 1 MiB [ 0.000000] Reserved memory: created DMA memory pool at 0x000000009b900000, size 15 MiB [ 0.000000] Reserved memory: created DMA memory pool at 0x000000009c800000, size 1 MiB [ 0.000000] Reserved memory: created DMA memory pool at 0x000000009c900000, size 30 MiB [ 0.000000] Reserved memory: created DMA memory pool at 0x00000000a0300000, size 32 MiB [ 0.000000] Reserved memory: created DMA memory pool at 0x00000000ae300000, size 288 MiB [ 0.000000] cma: Reserved 512 MiB at 0x00000000dd000000
Note
The reserved memory sizes listed above are provided as a reference only and subject to change between releases. For latest memory reservations, please refer to the kernel device tree repository : 'https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/arch/arm64/boot/dts/ti/k3-am62a7-sk.dts?h=ti-linux-6.12.y'
By default the first 1MB of each pool is used for the Virtio and Vring buffers used to communicate with the remote processor core. The remaining carveout is used for the remote core external memory (program code, data, etc).
Note
The resource table entity (which describes the system resources needed by the remote processor) needs to be at the beginning of the remote processor external memory section.
For details on how to adjust the sizes and locations of the remote core pool carveouts, please see section :ref:`changing_the_memory_map`.
The address and size of the DMA memory carveouts needs to match with the MCU M4F and R5F external memory section sizes in their respective linker mapfiles.
arch/arm64/boot/dts/ti/k3-am62a7-sk.dts
reserved-memory {
#address-cells = <2>;
#size-cells = <2>;
ranges;
wkup_r5fss0_core0_dma_memory_region: r5f-dma-memory@9c800000 {
compatible = "shared-dma-pool";
reg = <0x00 0x9c800000 0x00 0x100000>;
no-map;
};
wkup_r5fss0_core0_memory_region: r5f-dma-memory@9c900000 {
compatible = "shared-dma-pool";
reg = <0x00 0x9c900000 0x00 0x01e00000>;
no-map;
};
mcu_r5fss0_core0_dma_memory_region: r5f-dma-memory@9b800000 {
compatible = "shared-dma-pool";
reg = <0x00 0x9b800000 0x00 0x100000>;
no-map;
};
mcu_r5fss0_core0_memory_region: r5f-dma-memory@9b900000 {
compatible = "shared-dma-pool";
reg = <0x00 0x9b900000 0x00 0x0f00000>;
no-map;
};
c7x_0_dma_memory_region: c7x-dma-memory@99800000 {
compatible = "shared-dma-pool";
reg = <0x00 0x99800000 0x00 0x100000>;
no-map;
};
c7x_0_memory_region: c7x-memory@99900000 {
compatible = "shared-dma-pool";
reg = <0x00 0x99900000 0x00 0x01efffff>;
no-map;
};
};
Warning
Be careful not to overlap carveouts!
Note
The reserved memory sizes listed above are provided as a reference only and subject to change between releases. For latest memory reservations, please refer to the kernel device tree repository : 'https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/arch/arm64/boot/dts/ti/k3-am62a7-sk.dts?h=ti-linux-6.12.y'