[U-Boot] [PATCH] wandboard: move environment partition farther from u-boot.img

[Otavio Salvador]

On Sat, Jul 9, 2016 at 9:42 AM, Alexey Brodkin
<Alexey.Brodkin at synopsys.com> wrote:
> Recently I started to notice that u-boot.img built for Wandboard
> by some toolchains becomes so large that it basically overlaps with
> U-Boot environment area on SD-card.
>
> According to
> http://wiki.wandboard.org/index.php/Boot-process#sdcard_boot_data_layout
> Wandboard's SD-card layout is as follows:
> ------------------------------>8---------------------------
> ==========================================================
> 1. 0x00000000           Reserved For MBR
> 2. 0x00000200   512     Secondary Image Table (optional)
> 3. 0x00000400   1024    uBoot Image (Starting From IVT)
> 4. 0x00060000   393216  start of uboot env (size:8k)
> 5. 0x00062000           end of uboot env
> 6. 0x00100000   1048576 Linux kernel start
> 7. 0x0076AC00   7777280 start of partition 1
> ------------------------------>8---------------------------
>
> So for U-Boot we have 383kB (392192 bytes).
>
> But in up to date U-Boot for Wandboard we build separately
>  a) SPL
>  b) u-boot.img
>
> which gives us a bit more detailed SD-card layout:
> ------------------------------>8---------------------------
> ==========================================================
> 1. 0x00000000           Reserved For MBR
> 2. 0x00000200   512     Secondary Image Table (optional)
> 3. 0x00000400   1024    SPL
> 4. 0x00011400   70656   u-boot.img
> 5. 0x00060000   393216  start of uboot env (size:8k)
> 6. 0x00062000           end of uboot env
> ...
> ------------------------------>8---------------------------
>
> From that layout we may calculate amount of space reserved for
> u-boot.img. It's just 315kb (322560 bytes).
>
> Now if I build U-Boot with Sourcery CodeBench ARM 2014.05 produced
> u-boot.img is already more than we expected
> (323840 bytes instead of "< 322560"):
> ------------------------------>8---------------------------
> ls -la u-boot.img
> -rw-rw-r-- 1 user user 323840 Jul  5 07:38 u-boot.img
> ------------------------------>8---------------------------
>
> Funny enough if I rebuild U-Boot with ARM toolchain available in
> my Fedora 23 distro u-boot.img becomes a little bit smaller:
> ------------------------------>8---------------------------
> ls -la u-boot.img
> -rw-rw-r-- 1 user user 322216 Jul  5 07:39 u-boot.img
> ------------------------------>8---------------------------
>
> What's worse this problem might not affect people most of the time
> because what happens people would just copy u-boot.img on SD-card and
> live in happiness with it... well until somebody attempts to save
> environment in U-Boot with "saveenv" command which will simply
> overwrite the very end of u-boot.img.
> That will lead to unusable SD-card until user dd u-boot.img on
> SD-card again.
>
> I may foresee this issue in the future to become more visible once we
> add more features in U-Boot for Wandboard or just existing code base
> becomes bulkier and people will consistently get larger u-boot.img
> files produced.
>
> IMHO there's an obvious solution for all that - just move U-Boot's env
> to the very end of the gap between U-Boot and the first real partition
> on the SD-card. This patch will follow
> 8fb9eea5653796 ("mx6sabre_common: Fix U-Boot corruption after 'saveenv'").
> So env is still not in the very end of the gap (obviously 256kb is way
> too much for U-Boot's env) but at least we have now the same
> partitioning for i.MX6 boards.
>
> Signed-off-by: Alexey Brodkin <abrodkin at synopsys.com>
> Cc: Fabio Estevam <fabio.estevam at nxp.com>
> Cc: Otavio Salvador <otavio at ossystems.com.br>
> Cc: Peter Robinson <pbrobinson at gmail.com>
> Cc: Tom Rini <trini at konsulko.com>
> Cc: Peter Korsgaard <peter at korsgaard.com>
> Cc: Wolfgang Denk <wd at denx.de>

Couldn't this be done on the common header?

-- 
Otavio Salvador                             O.S. Systems
http://www.ossystems.com.br        http://code.ossystems.com.br
Mobile: +55 (53) 9981-7854            Mobile: +1 (347) 903-9750