[U-Boot-Users] CFI support for flash with hardware write-protect.

[U-Boot-Users] CFI support for flash with hardware write-protect.

[Edward Jubenville]

We have a built a custom board with onboard flash and using CFI.  Our design
supports a jumper that enables hardware write-protection on the flash, but
u-boot will not come up with the jumper installed.  It fails due to code in
drivers/cfi_flash.c that must write a command word to detect the flash
configuration.

Is there an elegant way to override the CFI discovery process, prefilling
flash_info[] with the details of our flash hardware?  Our board will boot if
we hardcode our flash settings and bypass auto-detection, but I was
wondering if somebody has a patch to cfi_flash.c to do it through
configuration parameters.

In case you are wondering, we cannot use software write-protect because our
equipment must conform with a security directive from the U.S. Department of
Defense, paraphrased:
	"There shall be no user-modifiable, non-removable, persistent storage."
The onboard flash cannot be removed from the unit, and therefore may not be
allowed to be written by an operator (e.g., by stopping in u-boot).  Forcing
somebody to disassemble the unit to switch a jumper is apparently acceptable
to the security guys.

Thanks,

Ed Jubenville

[U-Boot-Users] CFI support for flash with hardware write-protect.

[Stefan Roese]

Hi Ed,

On Friday 29 June 2007, Edward Jubenville wrote:
> We have a built a custom board with onboard flash and using CFI.  Our
> design supports a jumper that enables hardware write-protection on the
> flash, but u-boot will not come up with the jumper installed.  It fails due
> to code in drivers/cfi_flash.c that must write a command word to detect the
> flash configuration.
>
> Is there an elegant way to override the CFI discovery process, prefilling
> flash_info[] with the details of our flash hardware?

No, there is no elegant method for this right now. But I'm wondering why your 
board crashes upon writes. You seem to have disabled writes in the chip 
selects, correct? Why did you have to do this?

Best regards,
Stefan

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