My R500 board has a AT25DF321 chip (confirmed -- read the chip) and is detected. Reads never produce the same output. I've tried these SPI speeds: 2048, 4096, 32768. No slower speed is able to detect the chip.
Write output example:
flashrom on Linux 5.10.17-v7+ (armv7l)
flashrom is free software, get the source code at https://flashrom.org
Using clock_gettime for delay loops (clk_id: 1, resolution: 1ns).
Found Atmel flash chip "AT25DF321" (4096 kB, SPI) on linux_spi.
Reading old flash chip contents... done.
Erasing and writing flash chip... FAILED at 0x0001d000! Expected=0xff, Found=0x48, failed byt
Reading current flash chip contents... done. Looking for another erase function.
Verifying flash... FAILED at 0x00010200! Expected=0x4c, Found=0x05, failed byte count from 0x00000000-0x003fffff: 0x36eea
Your flash chip is in an unknown state.
Please report this on IRC at chat.freenode.net (channel #flashrom) or
mail firstname.lastname@example.org, thanks!
this is not a libreboot issue. however, you can come to the IRC channel and request support with whatever flashing hardware you use.