Question about `bios_flash_offset` in `targets/kosagi_fomu.py`
See original GitHub issueIn the kosagi_fomu.py
file the --bios-flash-offset
argument has a default of 0x60000
but the flash function disregards its bios_flash_offset
argument and always places the bios at 0x0020000
. I would have thought this was a bug but using the file I can successfully boot into bios while leaving the bios_flash_offset
value at 0x60000
. I could be missing something, why does this work?
https://github.com/litex-hub/litex-boards/blob/4b48f15265c902dc2931809444b5eb803023d0b5/litex_boards/targets/kosagi_fomu.py#L120-L161
Issue Analytics
- State:
- Created 2 years ago
- Comments:6 (6 by maintainers)
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Thanks @xobs, I indeed wanted to have confirmation of the offset introduced by the DFU programmer (ie that a write at 0 is physically localed at
0x4_0000
in the SPI Flash).In this target, we are relying on DFU for the flashing and then using XiP for the BIOS, so we just need to handle this offset which is now the case.
With Foboot, it doesn’t matter /where/ the BIOS goes since:
The program that it jumps to is usually located at offset
0x4_0000
from the start of flash, or address0x2004_0000
in memory-mapped RAM (SPI is mapped XIP at `0x2000_0000). See https://github.com/im-tomu/foboot/blob/master/doc/FLASHLAYOUT.md for the flash layout – I wish we had memory maps generated as part of the documentation.I’m not sure what the situation is with this command, since I’ve never used this to prepare an image. However, if you’re loading a bitstream from SPI flash, then indeed it will be located on the flash chip at offset
0x4_0000
.