Making changes sticky across reboots

[Lanthade]

Is there a way to make FPGA changes sticky across reboots/power cycles? For instance I always have to manually set color space to ycrcb on each power up.

[bunnie]

I'd recommend using a startup script to run the command, e.g. something similar to

echo "your custom command" > /dev/ttyS0

inside a .sh file that is sequenced by systemd to run a bit after the power-on.

The only possible gotcha is if /dev/ttyS0 is not configured for 115200 baud, if that seems to be the case I can help search for the incantation to set the baud rate before you do that.

[Lanthade]

Got it. I'd vote for a feature request to accomplish this on the FPGA board if that's possible in the future. It just strikes me as more reliable. Thanks!

[bunnie]

That's a possibility. I don't think write capabilities are built into the litex SPI block that the FPGA is using, so it might be hard to burn in, but I'll leave this issue open so I can keep that in mind for the next dev cycle.

[mithro]

@bunnie - LiteX BIOS has a demo on how to write to the SPI flash -> https://github.com/enjoy-digital/litex/blob/master/litex/soc/software/libbase/spiflash.c

https://github.com/enjoy-digital/litex/blob/d905521185fada6fe246e546384eb19e6188e030/litex/soc/software/bios/main.c#L181-L221

#if (defined CSR_SPIFLASH_BASE && defined SPIFLASH_PAGE_SIZE)
static void fw(char *addr, char *value, char *count)
{
    char *c;
    unsigned int addr2;
    unsigned int value2;
    unsigned int count2;
    unsigned int i;

    if((*addr == 0) || (*value == 0)) {
        printf("fw <offset> <value> [count]\n");
        return;
    }
    addr2 = strtoul(addr, &c, 0);
    if(*c != 0) {
        printf("incorrect offset\n");
        return;
    }
    value2 = strtoul(value, &c, 0);
    if(*c != 0) {
        printf("incorrect value\n");
        return;
    }
    if(*count == 0) {
        count2 = 1;
    } else {
        count2 = strtoul(count, &c, 0);
        if(*c != 0) {
            printf("incorrect count\n");
            return;
        }
    }
    for (i=0;i<count2;i++) write_to_flash(addr2 + i * 4, (unsigned char *)&value2, 4);
}

static void fe(void)
{
    erase_flash();
    printf("flash erased\n");
}
#endif