Hi,

In addition to what Stefan described about ME descriptors, there is also BIOS CNTL register, that if BIOS
enables it, you will not be able to write to flash using flashrom.

Refer to: 

Intel® C600 Series Chipset and
Intel® X79 Express Chipset

BIOS_CNTL—BIOS Control Register
(LPC I/F—D31:F0)

---
Rich


On Tue, Aug 12, 2014 at 3:07 PM, Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at> wrote:
On Tue, 12 Aug 2014 12:15:53 -0400 (EDT)
wenw@adiengineering.com wrote:

> 0x54: 0x000f0000 FREG0: Warning: Flash Descriptor region (0x00000000-0x0000ffff) is read-only.
> 0x58: 0x07ff0200 FREG1: BIOS region (0x00200000-0x007fffff) is read-write.

Hello Wen,

it seems like this bogus kind of descriptor layout becomes popular. Let
me explain in case you don't understand: The descriptor region in the
first 4kB of the flash chip - similar to a partition table - defines
(among other things) which parts of the flash chip are used for what
components. Usually all addresses of the flas chip are covered by this
but sometimes vendor forget to do this properly - or do have no use for
it.

The problem (for flashrom) is that the Intel SPI controllers forbid
accesses to addresses that are not covered by the descriptor regions -
like 0x00010000 to 0x001FFFFF in this case, which is almost a quarter
of the flash chip - but flashrom tries to read the whole chip
nevertheless (for good reasons).

So flashrom works more or less as expected on that board as far as you
have tested it. That result is probably not very useful to you, but
fine with me for now... :)

If you want to be able to write to the BIOS region, you
will also need my layout patches (they are also on github), and also
set the read_all_first variable in doit() in flashrom.c to 0.
I'd welcome such further tests of course but please be prepared for
recovery if need be.

I have included Marc from Sage because I guess he may be able to tell
us about the reason for this.
--
Kind regards/Mit freundlichen Grüßen, Stefan Tauner

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