[U-Boot] where is the crc stored?

[U-Boot] where is the crc stored?

[John Stile]

What area of memory is the crc stored for a partition?
I would like to find some detailed documentation on the crc (how big is
it, where it is stored, how to invalidate to force the booting from a
second area).

[U-Boot] where is the crc stored?

[Wolfgang Denk]

Dear John Stile,

In message <1356114777.28896.92.camel@genx> you wrote:
> What area of memory is the crc stored for a partition?

Which sort of partitions are you talking here?

> I would like to find some detailed documentation on the crc (how big is
> it, where it is stored, how to invalidate to force the booting from a
> second area).

In general, erasing the whole region will usually work ;-)

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Q:  Why do mountain climbers rope themselves together?
A:  To prevent the sensible ones from going home.

[U-Boot] where is the crc stored?

[John Stile]

On Fri, 2012-12-21 at 20:54 +0100, Wolfgang Denk wrote:
> Dear John Stile,
> 
> In message <1356114777.28896.92.camel@genx> you wrote:
> > What area of memory is the crc stored for a partition?
> 
> Which sort of partitions are you talking here?

Maybe partition is the wrong word for a memory address region.

I am a total new-bee, but I have read there is a crc check in u-boot.

The crc check can result in a:
  Warning: Bad CRC, using default environment

The crc is considered during the bootcmd.

> > I would like to find some detailed documentation on the crc (how big is
> > it, where it is stored, how to invalidate to force the booting from a
> > second area).
> 
> In general, erasing the whole region will usually work ;-)
> 
> Best regards,
> 
> Wolfgang Denk
> 

I would like to know where this crc is stored.

I would like to know is it 8-bit, 16-bit, and 32-bit, or other.

[U-Boot] where is the crc stored?

[Wolfgang Denk]

Dear John Stile,

In message <1356125251.28896.119.camel@genx> you wrote:
>
> I am a total new-bee, but I have read there is a crc check in u-boot.

Actually there are several such checks, for several different
purposes.

> The crc check can result in a:
>   Warning: Bad CRC, using default environment

THis is when checking if there is a valid environment.  So we are
talkign about the CRC which protects the persistent environment copy.
The structure of this is defined in "include/environment.h", see
struct environment_s - as you can see, this is a CRC32.

> The crc is considered during the bootcmd.

No, this has absolutely nothing to do with bootcmd.

> I would like to know where this crc is stored.

In the first 4 bytes of the external representation of the
environment.

> I would like to know is it 8-bit, 16-bit, and 32-bit, or other.

32 bit.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
The ultimate barrier is one's viewpoint.
                        - Terry Pratchett, _The Dark Side of the Sun_