linux-kernel - Re: pxa3xx_nand times out in 4.14 with JFFS2

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Message-ID: <20171217190746.2a61232c@bbrezillon>
Date:   Sun, 17 Dec 2017 19:07:46 +0100
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Willy Tarreau <w@....eu>
Cc:     Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: pxa3xx_nand times out in 4.14 with JFFS2

On Sun, 17 Dec 2017 17:23:42 +0100
Willy Tarreau <w@....eu> wrote:

> On Sun, Dec 17, 2017 at 12:53:36PM -0300, Ezequiel Garcia wrote:
> > If not too much to ask, this is the test that I believe is needed.
> > You seem to have a setup ready, hence why I'm asking you, if
> > possible, to give it a shot.
> > 
> > (1) Scrub the BBT from the NAND. Or scrub the whole NAND.
> > You cannot do this from the kernel, it needs to be done from the bootloader.
> > 
> > (2) Mark a couple blocks as bad using the OOB -- AFAICR, there
> > was a command to do this in the bootloader.
> > 
> > (3) Boot, let Linux create the BBT and see if it catches the bad blocks.  
> 
> Are the current boot loaders safe regarding the scrub operation ? I'm
> asking because that's how I bricked my mirabox a few years ago when
> trying to mark a bad block from u-boot :-/  If someone has a good
> knowledge of these commands to limit the risk and helps me only playing
> with a small part at the end of the flash (or in the unused area) I'd
> prefer it :-)
> 
> > This would guarantee that devices with factory bad blocks,
> > (and no BBT), would be OK with this patch.  
> 
> I see. I'm fine with trying provided I have reasonably good assurance
> that I won't have to go through the kwboot pain again :-/

There's a easy test you can do without scrubing the NAND:
1/ comment the nand-on-flash-bbt property in your DT (this will trigger
   a full scan)
2/ from u-boot (before booting the kernel), erase a block that you know
   contains nothing important
3/ during the kernel scan, make sure this block is not reported as bad