imx6 nand: dbbt version/layout

Middelschulte, Leif Leif.Middelschulte at
Fri Jun 11 08:16:40 PDT 2021

Am Montag, dem 03.05.2021 um 14:32 +0200 schrieb Sascha Hauer:
> Hi Leif,
Hi Sascha,

> On Thu, Apr 22, 2021 at 12:13:59PM +0000, Middelschulte, Leif wrote:
> > Hi,
> >
> > I'm in the process of fixing up imx-kobs to support
> > - boot configuration dumps
> > - boot stream extracts/updates
> > on iMX6QDL using the GPMI-NAND interface, as provided by some more
> > "recent" kernels.
> >
> > I updated barebox on the NAND flash storage using another instance of
> > barebox. Now it turns out that the dbbt version used (i.e. written)
> > by
> > barebox and supported by imx-kobs (as it was) is not documented in
> > the
> > i.MX6 QDL reference manual.
> > Barebox uses[0] DBBT version 0x1000000, while the reference manual
> > describes (i.MX6DQRM Rev 3., section layout version 0x1.
> It's stored in big endian. Just endianess swap 0x01000000 and you have
> your 0x00000001.
Thank you for explaining the quite obvious, my bad.  :)

On another note though: Barebox writes[0] and verifies[1] ' BCF' and
'TBBD' in the BCB.

The most recent manual (IMX6DQRM rev. 6)* states the following though:
- FCB FingerPrint "FCB ": also given as 0x20424346, which is ' BCF' in
- DBBT FingerPrint "DBBT": also given as 0x44424254, which is 'DBBT' in
Notice how the value is reversed in the first case, while it is not in
the second.

Other tools, such as imx-kobs, seem to use[2] the value given in the
reference manual for the DBBT.

Since the ROM seems to boot either way, finding "the correct"
Fingerprint might be nitpicking, besides the verification (write skip).



*CAUTION: Older versions of the IMX6DQRM state even other hex values
for the FCB fingerprint (i.e. the ascii equivalent of ` BCN`).

> >
> > Besides that, the reference manual apparently does not describe the
> > field `BBMarkerPhysicalOffsetInSpareData` at the end of the FCB
> > structure. Yet again, imx-kobs and barebox are reading/writing it.
> barebox doesn't actively sets the value to anything else than 0x0. I
> have no idea if and how the ROM interprets this value. Indeed the name
> of the field seems to be inconsistent to the reference manual.
Never mind this.
> Regards,
>   Sascha
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Kind regards

Leif Middelschulte
Software Development

KLS Martin GmbH + Co. KG
A company of the KLS Martin Group
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