[FRC] [PATCH] MTD: nand_base.c: Enable support for Samsung E-die SLC NAND

[David Jander]

Samsung E-die SLC NAND doesn't support partial writes anymore and there
seems to be no other way of detecting this than looking at bits 0 & 1
of the 5th ID byte. Those bits were "reserved" and 00 for all older
chips. On E-die chips, "01" seems to indicate 21nm feature size. This
patch assumes that all later revisions (if they will ever come) will have
this characteristic as well and disables sub-page writes in this case.

Signed-off-by: David Jander <david at protonic.nl>
---
 drivers/mtd/nand/nand_base.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 41167e9..e68e0c7 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -3468,6 +3468,16 @@ static void nand_decode_ext_id(struct mtd_info *mtd, struct nand_chip *chip,
 			mtd->oobsize = 32 * mtd->writesize >> 9;
 		}
 
+		/*
+		 * Samsung E-die SLC NAND doesn't support partial writes
+		 * anymore. The only way to distinguish this die-revision
+		 * is by checking bits 0 and 1 of id_data[4], which seem
+		 * to indicate feature size (previous => 00, 21nm => 01).
+		 */
+		if (id_data[0] == NAND_MFR_SAMSUNG && nand_is_slc(chip) &&
+				(id_data[4] & 0x03) /* 21nm or newer */) {
+			chip->options |= NAND_NO_SUBPAGE_WRITE;
+		}
 	}
 }
 
-- 
1.9.1