mtd: rawnand: micron: Fix on-die ECC detection logic

Basing the "mandatory on-die" detection on ID byte 2 does not work,
because Micron has plenty of NANDs using the same device ID code, and
not all of them have forcibly enabled on-die ECC.

Since the "Array Operation" feature does not provide the "ECC
enabled/disabled" bit when the ECC can't be disabled, let's try to use
the "ECC enabled/disabled" bit in the READ_ID bytes.

It seems that this bit is dynamically updated on NANDs where on-die ECC
can freely be enabled/disabled, so let's hope it stays at one when we
have a NAND with on-die ECC forcibly enabled.

Fixes: 51f3b3970a8c ("mtd: rawnand: micron: detect forced on-die ECC")
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Tested-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

diff --git a/drivers/mtd/nand/raw/nand_micron.c b/drivers/mtd/nand/raw/nand_micron.c
index d30bd4d..d85bb4d 100644 (file)
--- a/drivers/mtd/nand/raw/nand_micron.c
+++ b/drivers/mtd/nand/raw/nand_micron.c
@@ -196,6 +196,9 @@ enum {
        MICRON_ON_DIE_MANDATORY,
 };
 
+#define MICRON_ID_INTERNAL_ECC_MASK    GENMASK(1, 0)
+#define MICRON_ID_ECC_ENABLED          BIT(7)
+
 /*
  * 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
@@ -208,7 +211,7 @@ enum {
  */
 static int micron_supports_on_die_ecc(struct nand_chip *chip)
 {
-       u8 feature[ONFI_SUBFEATURE_PARAM_LEN] = { 0, };
+       u8 id[5];
        int ret;
 
        if (!chip->parameters.onfi.version)
@@ -217,26 +220,37 @@ static int micron_supports_on_die_ecc(struct nand_chip *chip)
        if (chip->bits_per_cell != 1)
                return MICRON_ON_DIE_UNSUPPORTED;
 
+       /*
+        * We only support on-die ECC of 4/512 or 8/512
+        */
+       if  (chip->ecc_strength_ds != 4 && chip->ecc_strength_ds != 8)
+               return MICRON_ON_DIE_UNSUPPORTED;
+
+       /* 0x2 means on-die ECC is available. */
+       if (chip->id.len != 5 ||
+           (chip->id.data[4] & MICRON_ID_INTERNAL_ECC_MASK) != 0x2)
+               return MICRON_ON_DIE_UNSUPPORTED;
+
        ret = micron_nand_on_die_ecc_setup(chip, true);
        if (ret)
                return MICRON_ON_DIE_UNSUPPORTED;
 
-       ret = nand_get_features(chip, ONFI_FEATURE_ON_DIE_ECC, feature);
-       if (ret < 0)
-               return ret;
+       ret = nand_readid_op(chip, 0, id, sizeof(id));
+       if (ret)
+               return MICRON_ON_DIE_UNSUPPORTED;
 
-       if ((feature[0] & ONFI_FEATURE_ON_DIE_ECC_EN) == 0)
+       if (!(id[4] & MICRON_ID_ECC_ENABLED))
                return MICRON_ON_DIE_UNSUPPORTED;
 
        ret = micron_nand_on_die_ecc_setup(chip, false);
        if (ret)
                return MICRON_ON_DIE_UNSUPPORTED;
 
-       ret = nand_get_features(chip, ONFI_FEATURE_ON_DIE_ECC, feature);
-       if (ret < 0)
-               return ret;
+       ret = nand_readid_op(chip, 0, id, sizeof(id));
+       if (ret)
+               return MICRON_ON_DIE_UNSUPPORTED;
 
-       if (feature[0] & ONFI_FEATURE_ON_DIE_ECC_EN)
+       if (id[4] & MICRON_ID_ECC_ENABLED)
                return MICRON_ON_DIE_MANDATORY;
 
        /*