input_gmio/output_gmio - 2024.1 English

AI Engine Kernel and Graph Programming Guide (UG1079)

Document ID
UG1079
Release Date
2024-05-30
Version
2024.1 English

This class represents the global memory (DDR) resource management and data transfer between AI Engine and global memory (DDR). The input_gmio object manages data transfer from global memory (DDR) to AI Engine or read from global memory (DDR) operation. The output_gmio object manages data transfer from AI Engine to global memory or write to global memory (DDR) operation.

Base Class Member Functions

static void* malloc(size_t size);
The malloc method allocates contiguous physical memory space and returns the corresponding virtual address. It accepts a parameter, size, to specify how many bytes to be allocated. If successful, the pointer to the allocated memory space is returned. nullptr is returned in the event of a failure.
static void free(void* address);
The free method frees memory space allocated by GMIO::malloc.
return_code wait();
The wait method blocks until all the previously issued transactions are complete. This method is only applicable for GMIO objects connected to AI Engine.
Note: The input_gmio and output_gmio classes are derived from GMIO base class. Functions malloc(), free(), and wait() are declared in the GMIO base class.

input_gmio Member Functions

create(std::string logical_name, size_t burst_length, size_t bandwidth);

The above port specification is used to connect DDR memory to AI Engine kernels. logical_name is the name of the port. The burst_length is the length of DDR memory burst transaction (can be 64, 128 or 256 bytes), and the bandwidth is the average expected throughput in MB/s.

create(size_t burst_length, size_t bandwidth);
The above port specification is used to connect DDR memory to AI Engine kernels. The burst_length is the length of DDR memory burst transaction (can be 64, 128 or 256 bytes), and the bandwidth is the average expected throughput in MB/s.
return_code gm2aie_nb(const void* address, size_t transaction_size);
The gm2aie_nb method initiates a DDR to AI Engine transfer. The memory space for the transaction is specified by the address pointer and the transaction_size parameter (in bytes). The transaction memory space needs to be within the total memory space allocated by the GMIO::malloc method. It is a non-blocking function in that it does not wait for the read transaction to complete.
return_code gm2aie(void* address, size_t transaction_size);

The gm2aie method is a blocking version of gm2aie_nb. It blocks until the AI Engine–DDR read transaction completes.

output_gmio Member Functions

create(std::string logical_name, size_t burst_length, size_t bandwidth);
The above port specification is used to connect AI Engine kernels to DDR memory. logical_name is the name of the port. The burst_length is the length of DDR memory burst transaction (can be 64, 128 or 256 bytes), and the bandwidth is the average expected throughput in MB/s.
create(size_t burst_length, size_t bandwidth);
The above port specification is used to connect AI Engine kernels to DDR memory. The burst_length is the length of DDR memory burst transaction (can be 64, 128 or 256 bytes), and the bandwidth is the average expected throughput in MB/s.
return_code aie2gm_nb(void* address, size_t transaction_size);
The aie2gm_nb method initiates an AI Engine to DDR transfer. The memory space for the transaction is specified by the address pointer and the transaction_size parameter (in bytes). The transaction memory space needs to be within the total memory space allocated by the GMIO::malloc method. It is a non-blocking function in that it does not wait for the write transaction to complete.
return_code aie2gm(void* address, size_t transaction_size);

The aie2gm method is a blocking version of aie2gm_nb. It blocks until the AI Engine–DDR write transaction completes.

Note: It is recommended using GMIO::malloc() and GMIO::free() to manage DDR memory resources.