mtd: rawnand: sunxi: Update OOB layout to match hardware

When using the hardware ECC engine, the OOB data is made available in
the NFC_REG_USER_DATA registers, as one 32-bit word per ECC step. Any
additional bytes are only accessible through raw reads and software
descrambling. For efficiency, and to match the vendor driver, ignore
these extra bytes when using hardware ECC.

Note that until commit 34569d8 ("mtd: rawnand: sunxi: Fix the size
of the last OOB region"), this extra free area was reported with length
zero, so this is not a functional change for any stable kernel user.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230204143520.9682-2-samuel@sholland.org

Author: smaeul

drivers/mtd/nand/raw/sunxi_nand.c

@@ -1604,6 +1604,13 @@ static int sunxi_nand_ooblayout_free(struct mtd_info *mtd, int section,
 		return 0;
 	}
 
+	/*
+	 * The controller does not provide access to OOB bytes
+	 * past the end of the ECC data.
+	 */
+	if (section == ecc->steps && ecc->engine_type == NAND_ECC_ENGINE_TYPE_ON_HOST)
+		return -ERANGE;
+
 	oobregion->offset = section * (ecc->bytes + 4);
 
 	if (section < ecc->steps)