[i.MX28 GPMI] problem overwriting all-0xff data in NAND

[LW@KARO-electronics.de (Lothar Waßmann)]

Hi,

Huang Shijie writes:
> Hi Lothar:
> > On Mon, Jul 18, 2011 at 03:13:27PM +0200, Lothar Wa?mann wrote:
> >> Hi,
> >>
> >> with the gpmi-nfc driver for imx28 from Shawn Guo on a TX28 I
> > To be clear, the author of gpmi-nfc driver is Huang Shijie (Cc-ed).
> >
> > Regards,
> > Shawn
> >
> >> encountered some problems with jffs2 when overwriting pages that have
> >> been written with 0xff (e.g. from padding from the file system image
> >> file).
> >>
> >> The problem is that the ECC info for an all-0xff block is not all-0xff
> >> and thus a newly erased block is different from a block that has been
> >> written with 0xff.
> >> If such a block is being altered (jffs2 thinking it can simply
> >> overwrite it without erasing first) the ECC information will be
> >> corrupted and will produce ECC errors upon read.
> >>
> >> The only remedy I can think of is to prevent empty pages from actually
> >> being written to flash, but leaving them in the erased state instead.
> Did you mean that:
> If the gpmi have to write a page which is full of 0xff,
> the gpmi driver should skip the writting, and leave the page in the 
> erased state.
> 
> Am I right?
> 
Exactly. But it seems others think this should be handled by userspace
tools rather than in the kernel driver.


Lothar Wa?mann
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