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

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

Hi,

with the gpmi-nfc driver for imx28 from Shawn Guo on a TX28 I
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.

Any comments?


Lothar Wa?mann
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