[PATCH] mtd: nand: gpmi: Use subpage reads only on suitable NAND chips

[Sascha Hauer]

On some NAND chips the driver uses a ECC size that is not dividable by
the number of chunks per page which means a single chunk cannot be read.
Disable the subpage feature for these NANDs. This is quite unfortunate
since the subpage feature really speeds up scanning NAND chips.

Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
 drivers/mtd/nand/nand_mxs.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/nand_mxs.c b/drivers/mtd/nand/nand_mxs.c
index a9c6e96..fd4e209 100644
--- a/drivers/mtd/nand/nand_mxs.c
+++ b/drivers/mtd/nand/nand_mxs.c
@@ -1392,14 +1392,16 @@ static int mxs_nand_probe(struct device_d *dev)
 	nand->ecc.size		= 512;
 	nand->ecc.strength	= 8;
 
-	nand->ecc.read_subpage = gpmi_ecc_read_subpage;
-	nand->options |= NAND_SUBPAGE_READ;
-
 	/* first scan to find the device and get the page size */
 	err = nand_scan_ident(mtd, 4, NULL);
 	if (err)
 		goto err2;
 
+	if ((13 * mxs_nand_get_ecc_strength(mtd->writesize, mtd->oobsize) % 8) == 0) {
+		nand->ecc.read_subpage = gpmi_ecc_read_subpage;
+		nand->options |= NAND_SUBPAGE_READ;
+	}
+
 	nand->options |= NAND_NO_SUBPAGE_WRITE;
 
 	/* second phase scan */
-- 
2.8.1