Reduce Kintex7 boot time when loading from flash

[unbtorsten]

write_cfgmem  -format bin -size 32 -interface SPIx4 -loadbit "up 0x00000000 $bitfile" -file "$binfile"

As per this command, we can see the quad mode is introduced during conversion from bitstream to binfile/mcsfile. So this is where we need to look to gain performance, rather than in the spiOverJtag Vivado settings

Originally posted by @unbtorsten and @jrrk2 in https://github.com/trabucayre/openFPGALoader/issues/181#issuecomment-1048059514

[unbtorsten]

Further input for reference:

At the same time, in order to speed up the FPGA loading the mcs file in QSPI Flash after power-on, we can configure the bit file to 4-wire mode (provided that your hardware must support 4-wire mode), and modify the loaded clock frequency to greatly speed up the FPGA The startup speed.

Source: https://www.ventronchip.com/news/Xilinx-FPGA-booting-from-QSPI-Flash(Bitstream-to-Flash-file-using-Vivado-RTL-program-alone).html

[unbtorsten]

Configuring the bitstream with the constraint

set_property CONFIG_MODE SPIx4 [current_design]

and generating it by use of Vivado seems to be equivalent to generating a binary as mentioned above:

write_cfgmem  -format bin -size 32 -interface SPIx4 -loadbit "up 0x00000000 $bitfile" -file "$binfile"

Either file (bitstream or binary) can be programmed by use of openFPGALoader with the commands

openFPGALoader -b genesys -f image.bit
openFPGALoader -b genesys -f image.bin

and yield short (not delayed) boot up times.

[jrrk2]

That’s good, but do we know what’s different between the x4 bitstream and the x1 bitstream in terms of fasm statements?

[unbtorsten]

That’s good, but do we know what’s different between the x4 bitstream and the x1 bitstream in terms of fasm statements?

I have not looked into that aspect. Just wanted to point out that this seems to be something that is/can be engraved into the bitstream configuration (and not just a binary stream).