[RFC] imx21ads nand boot

[Alessandro Rubini]

> I tried getting barebox MX21ADS to boot from NAND, but I can't get
> it to work.
> 
> Any clues, anyone ?


> +	ldmia	r0!, {r3-r9}		/* copy from source address [r0]    */
> +	stmia	r1!, {r3-r9}		/* copy to   target address [r1]    */

This is 7 registers, so 28 bytes at a time. So you copy
28, 56, .... 2044, 2072

I don't know what happens when you access memory over the end of
the SRAM area. Maybe it fires a data abort or something like that?

I'd use 4 registers instead of 7, but it might well not be the problem

> +	cmp	r0, r2			/* until source end addreee [r2]    */
> +	ble	copy_loop

"blt" would be better, because when it is equal you are done. Or using
4 registers will not prevent the extra accesses.

> +	ldr	pc, =1f			/* Jump to SDRAM                    */
> +1:
> +	bl	nand_boot		/* Load barebox from NAND Flash     */
> +

Finally, you should ensure the literary pool is within the first 2kB.
I'd place ".ltorg" before the "1:", or would check the disassembly.

Hope this helps, but it may well not help

/alessandro, who has an mx21ads looking at him but also real work to deliver