Hi Albert,
On Sun, Jan 30, 2011 at 10:36:17AM +0100, Albert ARIBAUD wrote:
Hi Simon :)
Le 29/01/2011 18:00, Simon Guinot a écrit :
Hi,
I am looking to add U-Boot support for the LaCie Network Space v2 board.
The SoC is a Kirkwood 88F6281_A0 and the boot device is a Macronix SPI flash (MX25L4005A). My problem is that the embedded stock U-Boot (1.1.4 version patched by Marvell and LaCie) enable write protection for the SPI flash. Then, after an U-Boot update, turn off this protection is needed to allow saving U-Boot environment.
It is not clear for me how to proceed. Disable the write protection from the board setup code could be an idea but a problem is that the SPI flash API don't export any helpful method... Maybe I should add one ?
An another idea is disabling the write protection anyway while initializing the flash (from the low level macronix driver). It is quite straightforward but I don't know if a flash driver is allowed to do that. After all, a flash could be protected for some good reasons.
My last idea is doing nothing and let an another piece of software handle the problem...
Thanks in advance for advices.
My personal take: let users of the board do their own mistakes and thus, do not protect the Flash, *except* for U-Boot itself.
So, if SPI Flash protection is possible on block or sector levels, protect the blocks/sectors where U-Boot is located, including the environment.
For a Macronix SPI flash, the status register export 3 bits (or 4 depending the model and size) to configure the block protection.
Here is the protect area map for a MX25L4005A 4Mb flash:
bit 2 1 0 | protect level ____________|_______________ 0 0 0 | none 0 0 1 | block 7 0 1 0 | block 6-7 0 1 1 | block 4-7 1 * * | all
As you can figure, deal with a per block protection in a generic way is not easy..
Saveenv should unprotect and re-protect the environment sector/block.
If I understand well, macronix_{erase,write}() are called from either "saveenv" or "spi erase/write" commands and the low level macronix functions don't have any flash map knowledge. Then, leave protect or not a flash sector after a write/erase operation is not an easy decision.
Maybe the status register protection can be configured during the board initialization ? after all, the required flash informations (as device size, u-boot and environment localization) are available within the board setup code.
As for the kernel and rootfs... You can either leave them unprotected or protected.
As a side note, the Macronix Linux driver (m25p80) don't deal either with the block protect bits.
Simon
PS: some pointers about this project:
git : http://git.lacie-nas.org/u-boot-lacie.git (branch netspace_v2)
You should keep this branch based on u-boot/master generally, and on u-boot-arm/master right now because it has the most recent ARM commits.
OK, done :)
Simon