[WIP] MIF support

[tangxifan]

Is your feature request related to a problem? Please describe.
Memory Initialization File (MIF) is commonly used by FPGA design tools, to initialize Block RAM with proper values.

To enable such feature, both hardware and software support are required.

• The embedded RAM block should support initialization through dedicated protocols (Defer bitstream as the RAM size can be crazy big, like 36k-bit, causing large bitstream file sizes).
• The design tool supports MIF through which user can specify the initial values for part of or the whole RAM block at any location of an FPGA.
• The design tool can output testbenches (both full testbench and preconfigured testbench) which load MIF content and validate the process where RAMs are initialized.

Therefore, this requires hardware and software to be tightly co-integrated, which should be handled by the OpenFPGA framework.

Describe the solution you'd like

As stated, this task requires the following subtasks

• Develop the RTL for a RAM block which supports memory initialization, based on an existing one: link
• New command 'read_mif'
  • Option '--file' to specify the MIF file
  • This command should be called before 'link_arch'
  • This command can be called multiple times, enabling MIF data aggregation
• New command 'write_mif'
  • Option '--file' to specify the MIF file. If there are multiple MIF files as inputs, all their content will be outputted to the file

When MIF is enabled,

• the full testbench should include dedicated cycles before downloading bitstream.
• the preconfigured testbench should force bits to dedicated internal ports of BRAM block.

[tangxifan]

MIF file format

# This is a comment
# All the address and data in HEX format
// X 2 # Coordinates of the RAM block
// Y 1 # Coordinates of the RAM block
// ADDR_WIDTH 8
// DATA_WIDTH 32
# Address Data 
0x2000 0x0000000a
0x2001 0x00000000
0x2002 0x000007e8
0x20ff 0x00000688
//RAM_ID 46
//ID_WIDTH 8
//ADDR_WIDTH 8
//DATA_WIDTH 32
0x2e00 0x0000038f
0x2e01 0x00000020
0x2e02 0x000007ea
0x2ebc 0x000002fb

[treelin611]

I will try to migrate all commands related to mif first (read_mif, bind_mif, write_mif). Maybe later, we can then decide which one to keep and which one to delete.

[tangxifan]

I will try to migrate all commands related to mif first (read_mif, bind_mif, write_mif). Maybe later, we can then decide which one to keep and which one to delete.

Since this is going to be a breaking feature, the code changes will be big. My suggestion is to migrate one command each time. Keep each PR small so that we can review and merge fast.

[treelin611]

noted. I will create three prs for three commands.