Handling bus locking of CFI Flash devices

Thomas De Schampheleire patrickdepinguin at gmail.com
Thu Nov 29 10:39:26 EST 2012

On Fri, Nov 23, 2012 at 7:34 PM, Thomas De Schampheleire
<patrickdepinguin at gmail.com> wrote:
> Hi,
> I have an embedded PowerPC system with a CFI Flash located on the local bus.
> Additionally, there is a control device with a 'flash-write-protect'
> feature. By default, no writes can happen to the flash device on the
> local bus, unless the flash-write-protect bit is cleared.
> This also means that detection of the flash chip using CFI commands
> will fail by default, as this incurs write operations to the bus.
> Note that this flash-write-protect is different from the standard
> flash 'lock/unlock' feature. The former is implemented on a specific
> control logic chip of the board, while the latter is part of the flash
> chip/controller itself.
> My question is: what is the best way to handle this flash-write-protect bit?
> Right now, I am simply clearing the bit before booting the kernel,
> which means that all write access to the flash is allowed. While this
> works, it completely bypasses the protection feature.
> Is there already a place in the MTD subsystem to handle such a
> flash-write-protect bit, for example a hook that can be implemented
> for a particular board?
> If not, how do you suggest I proceed?

Any feedback on this issue?


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