[U-Boot] [PATCH] sunxi_nand_spl: Be smarter about where to look for backup u-boot.bin

[Ian Campbell <ijc+uboot@hellion.org.uk>]

On Tue, 2015-09-01 at 10:52 +0200, Hans de Goede wrote:
> Hi,
> 
> On 01-09-15 09:05, Ian Campbell wrote:
> > On Mon, 2015-08-31 at 17:42 +0200, Hans de Goede wrote:
> >> We know when u-boot is written to its own partition, in this case 
> the
> >> layout always is:
> >>
> >> eb 0 spl
> >> eb 1 spl-backup
> >> eb 2 u-boot
> >> eb 3 u-boot-backup
> >>
> >> eb: erase-block
> >
> > These are all the same size on this particular chip/all known sunxi
> > SoCs, right?
> 
> Nope, erase-block sizes is a property of the nand flash used, not of
> the SoC, so this can vary per board (and on some boards like the
> mk802 of which many production runs where done chances are it may
> vary between production runs...).

This is what I started out thinking but somehow convinced myself the
NAND was on the SoC itself... Partly because the division used in the
code below assumes some amount of uniformity (or at least some
relationship between the offset of eb2 and its size).

> >> So if we cannot load u-boot from its primary offset we know exactly where
> >> to look for it.
> >> +#else
> >> +> > 	> > /*
> >> +> > 	> >  * u-boot-dtb.bin on its own partition, do not use syndrome, u-boot
> >> +> > 	> >  * partition sits after 2 eraseblocks (spl, spl-backup), look for
> >> +> > 	> >  * backup u-boot 1 erase block further.
> >> +> > 	> >  */
> >> +> > 	> > const uint32_t boot_offsets[] = {
> >> +> > 	> > > 	> > CONFIG_SYS_NAND_U_BOOT_OFFS,
> >> +> > 	> > > 	> > CONFIG_SYS_NAND_U_BOOT_OFFS + CONFIG_SYS_NAND_U_BOOT_OFFS / 2,
> >> +> > 	> > };
> >> +> > 	> > const int syndrome = 0;
> >> +#endif
> >
> > The relationship between half of SYS_NAND_U_BOOT_OFFS and an erase
> > block here is a bit non-obvious in this context (the offset is 2 blocks
> > so one block is half that).
> >
> > Is there no suitable #define for the eb size which could be used here
> > (and ideally in the definition of U_BOOT_OFFS too)? Could we add one?
> 
> This is all still developing a bit some testing has shown that it is possible
> for u-boot.bin to suffer from non correctable ecc errors while it sits in
> a non bad erase block (looks like the erase block should actually be marked
> bad, but isn't). In cases like this it may help to write multiple copies of
> u-boot at 1MiB offsets (since u-boot will fit in 1 MiB) so maybe I need to
> revise this patch to use 1MiB offsets instead.

Sure.

> So for now we should probably just let this patch sit in my wip branch for a
> bit until we've a better handle on this.

OK.

> 
> Regards,
> 
> Hans
> 
> 
> 
> 
> 
> 
> 
> >
> > Ian.
> >
>