NAND flash Write protection

[kasi viswanathan]

Hi Miquel Raynal,

Thanks for sharing the information. It is very useful.


On Mon, May 10, 2021 at 1:29 PM Miquel Raynal <miquel.raynal at bootlin.com> wrote:
>
> Hi kasi,
>
> kasi viswanathan <kviswanathan.83 at gmail.com> wrote on Sat, 8 May 2021
> 09:49:58 +0530:
>
> > Hi all,
> >
> > In one of our current boards we are using Micron NAND flash of Size 512MB.
> > Sometimes the first page (4k) gets corrupted and the board gets bricked.
>
> I think this is your real issue. I am not sure trying to lock the flash
> is the right thing to focus on, understanding why it gets bricked seems
> more legitimate to me.
>
> > We have stored the bootloader at this location.
> >
> > As a preventive measure we have added read-only and lock flags in the dtb entry.
> >
> > My query is, Is it possible to lock a particular block of NAND flash
> > memory in linux ?
>
> I don't think this capability really belongs to Linux. The right
> question is, is your NAND flash capable of that? I know that Macronix
> flashes have a specific additional lock/unlock feature that is
> upstream, but there is no Micron support for that yet. You can add it
> though if it exists with Micron's devices through the
> ->{lock,unlock}_area() hooks.
>
> > I understood after googling that a specific H/W pin support is needed
> > to achieve this "Power-Up  Read  Enable,  Lock/Unlock  Enable(PRL)"
>
> There is indeed a WP (Write Protect) pin which prevents writes and
> erasures over the entire chip that you can use to protect the content
> of your chip. But that won't work if you use eg. UBIFS on top of it as
> it will need write access at some point.
>
> Thanks,
> Miquèl