[U-Boot] SPI flash writing

[Mike Frysinger <vapier@gentoo.org>]

On Tuesday 13 March 2012 14:25:07 Gerlando Falauto wrote:
> As it turned out, our update procedure:
> 
> sf probe 0;sf erase 0 50000;sf write ${load_addr_r} 0 ${filesize}
> 
> mistakenly expects a maximum size of 0x50000 (327680) bytes for
> u-boot.kwb. Sadly, the latest u-boot trunk results in a binary size for
> that board which is dangerously close to that limit. Hence, after adding
> some innocent lines of code, the update procedure could brick the board
> (for no evident reason and with no error message whatsoever) if the
> binary size crosses that boundary.

sounds like you should define CONFIG_BOARD_SIZE_LIMIT.  this will turn it from 
a runtime failure into a build time failure as u-boot will do size checking on 
the image for you.

>  From what I can understand, writing into a sector which has not been
> erased first is an acceptable behaviour of the flash interface, it will
> just set to zero whatever bits are not zero already, without reporting
> any error whatsoever.

correct

> 1) a "+" syntax to the "sf update" command so it can be used with
> ${filesize} as a parameter, and/or some "read,replace,erase,overwrite"
> block mechanism for the last (incomplete) block

"+len" is already in there for erase, so it'd be trivial to add to the update 
command.  feel free to post a patch and i'd be happy to review/merge.

> 2) an out-of-boundary-check againts the flash size so at least a warning
> is issued when you use too big a size value

i'm not sure about this.  if you want to do size checking, then enable the 
hush shell and do it in a script.

> 3) a command line option ("sf write -v" and/or to "sf update -v"), or an
> entirely new command (like "sf writeverify", "sf updateverify") to read
> back after writing so to double-check what really ended up being written
> to the flash before it's too late.

i don't think our other flash interfaces have a verify command, so this would 
be a general question -- the spi flash interface shouldn't diverge if we don't 
want this in general.  then again, this too would be a fairly simple thing to 
write in a hush script.
-mike
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