Re: [PATCH] ARM: dts: omap3-igep00x0: Fix nand ECC to maintain backward compatibility.

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Dear Gupta, Pekon,

On Mon, 2 Dec 2013 16:13:56 +0000, Gupta, Pekon wrote:

> Yes, at-least OMAP3 arch u-boot should still supports 'nandecc'.
> The infrastructure is still in place, however the command 'nandecc' is
> deprecated in newer versions.
> References in mainline u-boot: 
> arch/arm/cpu/armv7/omap3/board.c  @@do_switch_ecc()
> driver/mtd/nand/omap_gpmc.c @@omap_nand_switch_ecc()
> 
> So with minor hacks, you should be able to bring-back 'nandecc'.

So in short, what it means is that indeed the fact of switching to BCH8
on the kernel side is really breaking things, because U-Boot users now
have the choice between:

 * Configuring U-Boot to use Hamming ECC, and be able to reflash their
   SPL, but not their filesystem images.

 * Configuring U-Boot to use BCH8, and be able to reflash their
   filesystem images, but not their SPL.

Seems a little bit annoying for users, no?

> But for all these, images need to be flashed from u-boot. As kernel
> cannot switch ecc-schemes on-the-fly.

Which as I was saying, is a bit of shame. There is technically nothing
that makes the ECC scheme something that needs to be applied globally
on the entire flash. And we see real practical cases where being able
to specify a different ECC scheme per partition would make sense: when
the ROM code uses a weaker ECC scheme than the one used for most other
partitions.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com