mtd: rawnand: vf610_nfc: fix reads on chips with more than 64 bytes of OOB

The controller transfers 64 spare bytes per page and the driver only
implements the matching 64-byte ECC layout, so attach_chip() shrinks
mtd->oobsize when the chip provides more. That clamp does not survive:
nand_scan_tail() runs nanddev_init() after ->attach_chip(), and it
restores mtd->oobsize from the memory organization, which still holds
the value detected from the chip. The driver then transfers writesize
plus the chip's full OOB size, the hardware ECC parity ends up at a
different offset than the layout the controller was set up for, and
every ECC-protected read fails with -EBADMSG.

Measured on a Colibri VF61 (MX30LF4G28AC, 2048-byte pages, 112 bytes of
OOB): with the clamp lost, UBI cannot read the erase counter headers of
the pages U-Boot has just written, and the on-flash bad block table
written by an older kernel reads back with ECC errors, so the board
does not boot. Kernels before commit a7ab085d7c16 ("mtd: rawnand:
Initialize the nand_device object") are not affected because nothing
overwrote the clamp there, which is why the same chip works with a v4.4
kernel and with U-Boot, whose copy of this driver has no memory
organization to restore the value from. Edward Karpicz reported that
the clamp no longer takes effect on this chip; see the link below.

Instead of modifying the memory organization, keep the detected OOB
size and give the driver its own mtd_ooblayout_ops: the same layout the
NAND core uses for large pages, but computed on the first 64 OOB bytes
instead of the whole OOB, so the ECC bytes stay where U-Boot and the
old kernels put them. The data paths transfer writesize plus those 64
bytes, as the controller always has.

Since mtd->oobsize now reports the chip's real spare size, fill the
tail of oob_poi with 0xff after the 64 transferred bytes on ECC page
reads: the core may copy the full mtd->oobsize from it, which would
otherwise expose whatever the buffer held before. 0xff also matches
what a raw read returns from flash, since the write path only ever
programs the first 64 spare bytes.

Reported-by: Edward Karpicz <webmaster@toradex.com>
Link: https://community.toradex.com/t/colibri-vf50-vf61-on-the-current-bsp-mainline-u-boot-v2026-07-and-linux-6-18-lts/30735
Suggested-by: Miquel Raynal <miquel.raynal@bootlin.com>
Fixes: a7ab085d7c16 ("mtd: rawnand: Initialize the nand_device object")
Cc: stable@vger.kernel.org
Signed-off-by: Mehmet Fide <mehmet.fide@screeningeagle.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

0 files changed, 0 insertions, 0 deletions