[U-Boot-Users] Question about CFG_ENV_ADDR during RAMBOOT
wd at denx.de
Fri May 25 01:46:45 CEST 2007
In message <030501c79e4e$862cf740$0302a8c0 at atmel.com> you wrote:
> > What exactly do you mean by "checksum write"? The currently used
> > "cp.b" interface doesn't do anything like this either, or does it?
> No but a way to common error is that the kernel is too large to fit into
> its allocated area and when the file system is written it overwwrites
> the end
> of the kernel.
> In my branch, I can set an environment variable crccheck=1
> and if set, any cp.b to dataflash will add a checksum at the end.
> Any cp.b from dataflash will again compute the checksum
> and compare vs the checksum at the end.
Why would that be needed? The U-Boot image itself is protected by a
CRC32 checksum (by two, actually), so any such corruption will be
detected automatically whenever you try to boot such an image.
> Saves me a lot of confusing linux boot errors.
Of course checksums are very useful - but we already have them?
> > * That would be a two step procedure, like currently used for other
> > storage devices:
> > - Copy from dataflash to memory
> > - compare two memory areas
> If I wanted to wear down my fingers by typing a lot of things,
> I would have choosen a career as a COBOL programmer.
U-Boot follows good old Unix philosophy here: prvode small and simple
tools that implemnt just one task, but this reliably and efficiently,
and provide ways to combine these tools easily to bigger things. Of
course it is trivial to combine these steps into one "command" for
> Your suggestion has the unwanted side effect that you destroy the SDRAM
> in the process, and you have to keep in mind where you put intermediate
Well, the same is stru for your current implementation, which also
needs some buffers in RAM. The only difference is size and locatioon
of the buffers. U-Boot usually remembers the "last used" image
address, you normally you don't need to remember much. If in doubt,
> Since dataflash sectors are 256 kB, and you should avoid putting
> in the same sector as u-boot, code size is of much less importance than
> ease of use.
Primarily it's not a question of code size, but of interfaces.
> It is very important to reduce typing to a minimum.
This is not one of my primary targets. It's not even very high on my
> >> * list dataflash contents
> > What exactly do you mean here? Do you have any such function
> > currently?
What exactly does it do?
> It should be possible to remove any code accessing parallel flash,
> so the memory commands only access SDRAM.
> Many boards do not have any parallel flash, and this code will just
> bloat the binary.
"Many" is probably not correct if you look at the total of nearly 400
board configurations in the public U-Boot tree. But I agree that
support for NOR flash should be configurable like other features,
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