[PATCH v5 6/6] mtd: rawnand: micron: detect forced on-die ECC

[Chris Packham]

Some Micron NAND chips have on-die ECC forceably enabled. The detect
these based on chip ID as there seems to be no other way of
distinguishing these chips from those that have optional support for
on-die ECC.

When a chip with mandatory on-die ECC is detected change the current ECC
mode to on-die.

Signed-off-by: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx>
---

Notes:
    Changes in v4:
    - New
    Changes in v5:
    - fail if on-die ECC is mandatory and the current ecc.mode is not
      NAND_ECC_ON_DIE.

 drivers/mtd/nand/raw/nand_micron.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/nand_micron.c b/drivers/mtd/nand/raw/nand_micron.c
index f83053562925..35fa6880a799 100644
--- a/drivers/mtd/nand/raw/nand_micron.c
+++ b/drivers/mtd/nand/raw/nand_micron.c
@@ -255,6 +255,14 @@ enum {
 	MICRON_ON_DIE_MANDATORY,
 };
 
+/*
+ * These parts are known to have on-die ECC forceably enabled
+ */
+static u8 micron_on_die_ecc[] = {
+	0xd1, /* MT29F1G08ABAFA */
+	0xa1, /* MT29F1G08ABBFA */
+};
+
 /*
  * Try to detect if the NAND support on-die ECC. To do this, we enable
  * the feature, and read back if it has been enabled as expected. We
@@ -269,6 +277,11 @@ static int micron_supports_on_die_ecc(struct nand_chip *chip)
 {
 	u8 feature[ONFI_SUBFEATURE_PARAM_LEN] = { 0, };
 	int ret;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(micron_on_die_ecc); i++)
+		if (chip->id.data[1] == micron_on_die_ecc[i])
+			return MICRON_ON_DIE_MANDATORY;
 
 	if (!chip->parameters.onfi.version)
 		return MICRON_ON_DIE_UNSUPPORTED;
@@ -322,7 +335,8 @@ static int micron_nand_init(struct nand_chip *chip)
 
 	ondie = micron_supports_on_die_ecc(chip);
 
-	if (ondie == MICRON_ON_DIE_MANDATORY) {
+	if (ondie == MICRON_ON_DIE_MANDATORY &&
+	    chip->ecc.mode != NAND_ECC_ON_DIE) {
 		pr_err("On-die ECC forcefully enabled, not supported\n");
 		return -EINVAL;
 	}
-- 
2.17.1