AXI4 Target Interface Address Map

(Ask a Question)

This section shows the memory-mapped address offsets, sizes, and directions of all AXI4 Target interfaces. We will use the same example as in the AXI4 Initiator/Target Interface in the RTL Interface Report section to demonstrate:

#define SIZE 16

int top(int *arg1, int *arg2, int *arg3) {
#pragma HLS function top
#pragma HLS interface control          type(axi_target)
#pragma HLS interface argument(arg1)   type(axi_initiator) ptr_addr_interface(axi_target) num_elements(SIZE)
#pragma HLS interface argument(arg2)   type(axi_initiator) ptr_addr_interface(simple)     num_elements(SIZE)
#pragma HLS interface argument(arg3)   type(axi_target)                                   num_elements(SIZE)
    ...
}

====== 5. AXI4 Target Interface Address Map ======

Compatibility of HLS accelerator with reference SoC features: No.
SoC feature is only supported for PolarFire SoC Icicle Kit, and all accelerator interfaces need to be either axi_target or axi_initiator:
  - The interfaces of the following argument(s), global variable(s), and/or module control are not axi_target or axi_initiator:
    arg2 (pointer address interface).

+-----------------------------------------------------------------------------+
| Accelerator Function: top (Address Space Range: 0x80)                       |
+---------------------------------+----------------+--------------+-----------+
| Argument                        | Address Offset | Size [Bytes] | Direction |
+---------------------------------+----------------+--------------+-----------+
| Return Value                    | 0x00           | 8            | output    |
| Module Control                  | 0x08           | 4            | inout     |
| arg1 (pointer address register) | 0x10           | 4            | input**   |
| arg3                            | 0x40           | 64*          | output    |
+---------------------------------+----------------+--------------+-----------+

* On PolarFire SoC devices, it is recommended to use the PDMA engine for data transfer when the transfer size is bigger than 16KB, and use the memcpy driver functions when the transfer size is smaller than 16KB.
See memcpy and dma transfer driver functions in hls_output/accelerator_drivers/vector_add_soc_accelerator_driver.[h|cpp]

** The base pointer address of axi_initiator interface argument is an input to the accelerator. The actual direction of the argument can be different, depending on the read/write accesses through the pointer (or array/struct) argument in the C++ implementation.

Firstly, this section prints whether the top-level module is compatible with the SmartHLS-generated reference SoC (see SoC Features). For a top-level module to be compatible and thus can be integrated into the reference SoC, it needs to satisfy the following conditions:

The project has to be an Icicle_SoC project.
All interfaces of the top-level has to be either type(axi_target), or type(axi_initiator) ptr_addr_interface(axi_target). This includes the module control. This section will print out all the SoC incompatible interfaces. In this example, since arg2 has a simple pointer address interface, it is incompatible with the reference SoC.

If all interfaces are SoC-compatible, the report will print the default base address of the top-level module in the reference SoC instead e.g.

====== 5. AXI4 Target Interface Address Map ======

Compatibility of HLS accelerator with reference SoC features: Yes.
Default base address in reference SoC: 0x70000000.

Secondly, this section prints the table containing the memory-mapped address offset, size, and direction of all arguments using AXI4 Target.

In this example, since top() has an int return type which is non-void, the table will show a row for Return Value, which is always at offset 0x0, of size 8, and with output direction. For top-level functions that have void return type, there will be no Return Value row in the table.
Since the Module Control uses AXI4 Target, there will be a row for Module Control which is always at offset 0x8 (regardless of whether the return type is void or not), of size 4, and with inout direction. For top-level functions that have simple module control, there will be no Module Control row in the table.
arg1 is type(axi_initiator) ptr_addr_interface(axi_target), so there will be a row for the AXI4 Target pointer address register.
arg2 is type(axi_initiator) ptr_addr_interface(simple), so there will NOT be a row for it in this table because it doesn't use AXI4 Target pointer address register.
arg3 is type(axi_target) so there will be a row for the corresponding register/on-chip buffer.
Any arguments with other interface types will not appear in this table since they do not use AXI4 Target.

v2024.2

AXI4 Target Interface Address Map