Addressing Kernels in Bare-metal Applications - 2021.2 English

Versal ACAP AI Engine Programming Environment User Guide (UG1076)

Document ID
UG1076
ft:locale
English (United States)
Release Date
2021-12-17
Version
2021.2 English

For bare-metal applications, when addressing the PL kernels from the embedded application, you must use the control registers, or read and write to the kernel at the appropriate base address and offset as it is implemented in hardware. Looking at the application discussed earlier, the embedded application can deliver data to the MM2S kernel, to introduce it to the AI Engine graph for the Interpolator and Classifier kernels, and read data from the S2MM kernel to continue processing in the embedded application. In this case, address the MM2S and S2MM kernels as they are implemented in the PL region of the fixed platform.

The main.cpp of the example shows the #define statements for the kernel base address and the address offset for specific registers. For example:

#define MM2S_BASE XPAR_MM2S_S_AXI_CONTROL_BASEADDR
#define S2MM_BASE XPAR_S2MM_S_AXI_CONTROL_BASEADDR

#define MEM_OFFSET 0x10
#define SIZE_OFFSET 0x1C
#define CTRL_OFFSET 0x0

To determine the address and offsets for the kernels, examine some of the files in the fixed platform. The location of the base address for the implemented kernels is located in the fixed platform xparameters.h file, that is located in the <platform_name>/standalone_domain/bspinclude/include folder. For the example design, use the following entries in xparameters.h to determine the base addresses of these kernels.

/* Definitions for peripheral MM2S */
#define XPAR_MM2S_S_AXI_CONTROL_BASEADDR 0xA4020000
#define XPAR_MM2S_S_AXI_CONTROL_HIGHADDR 0xA402FFFF

/* Definitions for peripheral S2MM */
#define XPAR_S2MM_S_AXI_CONTROL_BASEADDR 0xA4030000
#define XPAR_S2MM_S_AXI_CONTROL_HIGHADDR 0xA403FFFF
Note: The xparameters.h file is generated and addressing is dynamic. It is best to reference the address macros for kernels than to hard code them.

The location of the address offset is located in the <kernel_driver>_hw.h file of the _x/<kernel>/<kernel>/<kernel>/solution/impl/ip/drivers/<kernel>_v1_0/src folder of the compiled kernel produced by the Vitis™ compiler. For example, the MM2S kernel driver, xmm2s_mm2s_hw.h displays the following data.

#define XMM2S_MM2S_CONTROL_ADDR_AP_CTRL    0x00
#define XMM2S_MM2S_CONTROL_ADDR_GIE        0x04
#define XMM2S_MM2S_CONTROL_ADDR_IER        0x08
#define XMM2S_MM2S_CONTROL_ADDR_ISR        0x0c
#define XMM2S_MM2S_CONTROL_ADDR_MEM_V_DATA 0x10
#define XMM2S_MM2S_CONTROL_BITS_MEM_V_DATA 64
#define XMM2S_MM2S_CONTROL_ADDR_SIZE_DATA  0x1c
#define XMM2S_MM2S_CONTROL_BITS_SIZE_DATA  32

Use these offsets when reading or writing to the kernels. For instance, from the example application main.cpp file use the following to write to the memory location.

Xil_Out32(MM2S_BASE + MEM_OFFSET, (uint32_t) memAddr);