3.6.4.1. Resource Tables

3.6.4.1.1. When are resource tables used?

PRU cores must be initialized by an outside source. There are 3 different ways to initialize a PRU and load the PRU firmware:

  1. Code Composer Studio (CCS)

  2. A processor core running Linux

  3. A processor core running RTOS or bare metal (i.e., NORTOS)

PRU resource tables are only used if the PRU firmware is loaded by a processor core running Linux. If the processor core is running Linux kernel 5.4 or earlier, then resource tables are used differently than if the processor core is running Linux kernel 5.10 or later.

Examples of different resource tables can be found in the PRU Software Support Package (PSSP). The PSSP can be found:

  • In the Processor SDK Linux under example-applications/pru-icss-x.x.x

  • At the PSSP git repo

3.6.4.1.2. Linux kernel 5.10 or later

If the PRU firmware is loaded by a core running Linux kernel 5.10 or later, then resource tables are only used if the PRU project uses RPMsg to communicate with the Linux core.

For Linux kernel 5.10 or later, INTC configuration is passed to the Linux RemoteProc driver in a separate INTC map file. For more information on the INTC map file, reference INTC Configuration.

Note

PSSP projects for Linux 5.4 or earlier have different resource tables than PSSP projects for Linux 5.10 or later. Check the tag on your PSSP to make sure you are using PSSP v6.0.0 or later.

Does the PRU project use RPMsg?

  • Yes –> A resource table is required. Refer to the example resource table at <PSSP_PATH>/examples/<processor>/xxx_RPMsg_Echo_InterruptX

  • No –> If the PRU project does not use RPMsg, then a resource table is not required. Do not include a resource table in the PRU project. If there are references to a resource table in the linker command file and the firmware, then remove those references. A sample project with no resource table is at <PSSP_PATH>/examples/<processor>/xxx_Halt

3.6.4.1.3. Linux kernel 5.4 or earlier

Resource tables are required if the PRU firmware is loaded by a core running Linux kernel 5.4 or earlier.

Note

PSSP projects for Linux 5.4 or earlier have different resource tables than PSSP projects for Linux 5.10 or later. Check the tag on your PSSP to make sure you are using PSSP v5.9.0 or earlier.

Does the PRU project use RPMsg?

  • Yes –> Refer to the example resource table at <PSSP_PATH>/examples/<processor>/xxx_RPMsg_Echo_InterruptX

  • No –>

    • Does the PRU project configure the INTC?

      • Yes –> Refer to the AM335x example at <PSSP_PATH>/examples/am335x/PRU_Direct_Connect0

      • No –> If the project does not use RPMsg, or configure the INTC, then use an empty resource table. Refer to the example resource table at <PSSP_PATH>/examples/<processor>/xxx_Halt