mtd: spinand: Handle the case where PROGRAM LOAD does not reset the cache

Looks like PROGRAM LOAD (AKA write cache) does not necessarily reset
the cache content to 0xFF (depends on vendor implementation), so we
must fill the page cache entirely even if we only want to program the
data portion of the page, otherwise we might corrupt the BBM or user
data previously programmed in OOB area.

Fixes: 7529df46 ("mtd: nand: Add core infrastructure to support SPI NANDs")
Reported-by: Stefan Roese <sr@denx.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <bbrezillon@kernel.org>
Tested-by: Stefan Roese <sr@denx.de>
Reviewed-by: Stefan Roese <sr@denx.de>
Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>

drivers/mtd/nand/spi/core.c

@@ -304,24 +304,30 @@ static int spinand_write_to_cache_op(struct spinand_device *spinand,
 	struct nand_device *nand = spinand_to_nand(spinand);
 	struct mtd_info *mtd = nanddev_to_mtd(nand);
 	struct nand_page_io_req adjreq = *req;
-	unsigned int nbytes = 0;
-	void *buf = NULL;
+	void *buf = spinand->databuf;
+	unsigned int nbytes;
 	u16 column = 0;
 	int ret;
 
-	memset(spinand->databuf, 0xff,
-	       nanddev_page_size(nand) +
-	       nanddev_per_page_oobsize(nand));
-
-	if (req->datalen) {
-		memcpy(spinand->databuf + req->dataoffs, req->databuf.out,
-		       req->datalen);
+	/*
+	 * Looks like PROGRAM LOAD (AKA write cache) does not necessarily reset
+	 * the cache content to 0xFF (depends on vendor implementation), so we
+	 * must fill the page cache entirely even if we only want to program
+	 * the data portion of the page, otherwise we might corrupt the BBM or
+	 * user data previously programmed in OOB area.
+	 */
+	nbytes = nanddev_page_size(nand) + nanddev_per_page_oobsize(nand);
+	memset(spinand->databuf, 0xff, nbytes);
 	adjreq.dataoffs = 0;
 	adjreq.datalen = nanddev_page_size(nand);
 	adjreq.databuf.out = spinand->databuf;
-		nbytes = adjreq.datalen;
-		buf = spinand->databuf;
-	}
+	adjreq.ooblen = nanddev_per_page_oobsize(nand);
+	adjreq.ooboffs = 0;
+	adjreq.oobbuf.out = spinand->oobbuf;
+
+	if (req->datalen)
+		memcpy(spinand->databuf + req->dataoffs, req->databuf.out,
+		       req->datalen);
 
 	if (req->ooblen) {
 		if (req->mode == MTD_OPS_AUTO_OOB)
@@ -332,14 +338,6 @@ static int spinand_write_to_cache_op(struct spinand_device *spinand,
 		else
 			memcpy(spinand->oobbuf + req->ooboffs, req->oobbuf.out,
 			       req->ooblen);
-
-		adjreq.ooblen = nanddev_per_page_oobsize(nand);
-		adjreq.ooboffs = 0;
-		nbytes += nanddev_per_page_oobsize(nand);
-		if (!buf) {
-			buf = spinand->oobbuf;
-			column = nanddev_page_size(nand);
-		}
 	}
 
 	spinand_cache_op_adjust_colum(spinand, &adjreq, &column);
@@ -370,8 +368,8 @@ static int spinand_write_to_cache_op(struct spinand_device *spinand,
 
 		/*
 		 * We need to use the RANDOM LOAD CACHE operation if there's
-		 * more than one iteration, because the LOAD operation resets
-		 * the cache to 0xff.
+		 * more than one iteration, because the LOAD operation might
+		 * reset the cache to 0xff.
 		 */
 		if (nbytes) {
 			column = op.addr.val;