[PATCH 1/2] mtd: rawnand: vf610_nfc: fix reads on chips with more than 64 bytes of OOB

[Mehmet Fide <mehmet.fide@gmail.com>]

From: Mehmet Fide <mehmet.fide@screeningeagle.com>

The driver only implements the 64-byte OOB 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 therefore transfers writesize + the chip's full OOB size, so
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.

Clamp the memory organization as well so the driver's 64-byte layout
stays in effect, and log the truncation once, as it decides which
on-flash layout the system uses.

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
Fixes: a7ab085d7c16 ("mtd: rawnand: Initialize the nand_device object")
Cc: stable@vger.kernel.org
Signed-off-by: Mehmet Fide <mehmet.fide@screeningeagle.com>
---
 drivers/mtd/nand/raw/vf610_nfc.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/vf610_nfc.c b/drivers/mtd/nand/raw/vf610_nfc.c
index 9940681810cf..f27ef2b0884d 100644
--- a/drivers/mtd/nand/raw/vf610_nfc.c
+++ b/drivers/mtd/nand/raw/vf610_nfc.c
@@ -771,8 +771,14 @@ static int vf610_nfc_attach_chip(struct nand_chip *chip)
 	}
 
 	/* Only 64 byte ECC layouts known */
-	if (mtd->oobsize > 64)
+	if (mtd->oobsize > 64) {
+		dev_info(nfc->dev,
+			 "using 64 of %d OOB bytes, ECC layout is unchanged\n",
+			 mtd->oobsize);
 		mtd->oobsize = 64;
+		/* nand_scan_tail() restores mtd->oobsize from the memorg */
+		nanddev_get_memorg(&chip->base)->oobsize = 64;
+	}
 
 	/* Use default large page ECC layout defined in NAND core */
 	mtd_set_ooblayout(mtd, nand_get_large_page_ooblayout());
-- 
2.54.0