NovuFPGA driver README

Novu

• This README describes the structure and design of PCI-e driver for NovuFPGA, and HOW-TO-RUN instructions
• PCI-e driver git: link

Main commit

• Please goto git link to find commit info, eg. comments, and hash. So you can use git checkout <commit_hash> to switch to particular commit. PLEASE make clean before checkout/checkin!
• The Stable commit used for Demo (May 03, 2017) : ba66.
  
  • This has a bug for double free in pci_close, may cause segment_fault.
  • This user-space API, read_result can only read 4MB from DDR (Given premise that result is always < 4MB)
• The latest commit for development (Dec 15, 2017) : 5f23.
  
  • This fixed the bug for double free in pci_close.
  • This user-space API, read_result can read any size from DDR.

Implementation

The FPGA driver has 2 parts: Kernel-space driver + User-space driver

Kernel-space Driver

• pci_skel.[c/h]: This is the kernel driver core file. It defined APIs to do these operations:

  1. IOCTL_CMD_READ_REG
  2. IOCTL_CMD_WRITE_REG
  3. IOCTL_CMD_DMA_READ_BUF
  4. IOCTL_CMD_DMA_WRITE_BUF
  5. IOCTL_CMD_DMA_READ_RESULT: DEPRECATED
  6. IOCTL_CMD_EXECUTE_NPU: NEW CMD

• The DMA is limit by the kmalloc size, which is restricted by linux kernel to 4MB. So the kernel-space driver's DMA_READ_BUF, DMA_WRITE_BUF can R/W 4MB each instruction.

User-space driver

• Pcie.[c/h]: This is the user driver core file, It defined APIs for application to call so as to R/W memory, and start NPU. Notice: ALL user-space API need to call kernel-space driver in between open/close clause. The best practice is to use user-space driver on large block memory block to compensate the over-head.

• The main API:

  1. set_write_mem: this function calls the kernel API: DMA_WRITE_BUF to write ANY size of user space memory into FPGA's DDR space, 4MB each time in the do...while loop.
  2. set_read_mem
  3. read_result this function is DEPRECATED
  4. execute_npu this is the function to call instead of read_result, this function is blocking to trigger NPU to finish and wait for it to finish. Please call set_read_mem to read result from DDR.

• Test/vgg2_test.c: This is the example test to show the use of User-space driver to interact with FPGA.

  • Notice the use of execute_npu & set_read_mem.
  • after its run, simply do python dif.py to verify the bin output with ofm.bin