11.4. How To Take Care Of Remote Core Memory Map Updates¶
11.4.1. Introduction¶
The use of DDR memory for remote core firmware image needs to be accounted for on the A72 side running QNX. Whenever there are updates to the memory usage by the PSDK RTOS, we would need to take care of the below on the PSDK QNX side.
Note
See the file ${PSDK_RTOS_PATH}/vision_apps/platform/j721e/rtos/system_memory_map.html for memory map used by Vision App Remote Core Images.
Make sure QNX Kernel is aware of the usage so that these regions of memory is reserved for remote core use only.
The QNX IPC resource manager used for communication between processors in a multi-processor environment need to be aware of the VRING memory to be used to communicate with the remote cores.
The Shared Memory Allocator resource manager (shmemallocator) make use of shared memory region that need to be in-sync with the remote core usage.
11.4.2. PSDK QNX memory map updates¶
11.4.2.1. Memory Carveout entry to QNX Startup¶
Memory sections with pre-defined physical addresses must be set aside in the QNX BSP IFS build file so that the memory is not given to other programs and can be used solely by the remote cores
Specify a section to be set aside by modifying the startup line to use the “-r” option. For example, to reserve 0x30000000 bytes, at physical address 0xA0000000, on QNX BSP, the build file the arguments would be (highlighted below):
-r0xA0000000,0x30000000,1
For J721E QNX BSP standalone BSP with U-boot loaded DM and no other remote core image loaded would required 16MB of carveout reserved at address 0xA0000000.
[+keeplinked] startup-j721e-evm -v -r0xA0000000,0x1000000,1
For J721E QNX BSP with U-boot loaded DM and Vision Apps remote core images loaded would required carevout as below. The same carveout can be specified when loading the EthFW or IPC ECHO TEST remote core images though their requirements may be lesser.
[+keeplinked] startup-j721e-evm -v -r0xA0000000,0x60000000,1 -r0x880000000,0x10000000,1
11.4.2.2. IPC VRING memory resource¶
The QNX IPC resource manager is used for communication between processors in a multi-processor environment. The QNX IPC resource manager needs to be aware of the VRING memory to be used by remote cores. This is specified by the VRING_BASE_ADDRESS define in the tiipc_mgr_private.h file of QNX IPC resource manager source code.
Note
See the file ${PSDK_QNX_PATH}/qnx/resmgr/ipc_qnx_rsmgr/resmgr/src/tiipc_mgr_private.h for VRING_BASE_ADDRESS address used.