[PATCH] Add support for Macronix NAND randomizer

[Mason Yang]

Macronix NANDs support randomizer operation for user data scrambled,
which can be enabled with a SET_FEATURE.

User data written to the NAND device without randomizer is still readable
after randomizer function enabled.
The penalty of randomizer are NOP = 1 instead of NOP = 4 and more time period
is needed in program operation and entering deep power-down mode.
i.e., tPROG 300us to 340us(randomizer enabled)

If subpage write not available with hardware ECC, for example,
NAND chip options NAND_NO_SUBPAGE_WRITE be set in driver and
randomizer function is recommended for high-reliability.
Driver checks byte 167 of Vendor Blocks in ONFI parameter page table
to see if this high-reliability function is supported.

Signed-off-by: Mason Yang <masonccyang@xxxxxxxxxxx>
---
 drivers/mtd/nand/raw/nand_macronix.c | 54 ++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/drivers/mtd/nand/raw/nand_macronix.c b/drivers/mtd/nand/raw/nand_macronix.c
index 58511ae..b8b5bcb 100644
--- a/drivers/mtd/nand/raw/nand_macronix.c
+++ b/drivers/mtd/nand/raw/nand_macronix.c
@@ -11,6 +11,13 @@
 #define MACRONIX_READ_RETRY_BIT BIT(0)
 #define MACRONIX_NUM_READ_RETRY_MODES 6
 
+#define MACRONIX_RANDOMIZER_BIT BIT(1)
+#define ONFI_FEATURE_ADDR_MXIC_RANDOMIZER 0xB0
+#define MACRONIX_RANDOMIZER_ENPGM BIT(0)
+#define MACRONIX_RANDOMIZER_RANDEN BIT(1)
+#define MACRONIX_RANDOMIZER_RANDOPT BIT(2)
+#define MACRONIX_RANDOMIZER_MODE_EXIT 0
+
 struct nand_onfi_vendor_macronix {
 	u8 reserved;
 	u8 reliability_func;
@@ -29,6 +36,42 @@ static int macronix_nand_setup_read_retry(struct nand_chip *chip, int mode)
 	return nand_set_features(chip, ONFI_FEATURE_ADDR_READ_RETRY, feature);
 }
 
+static void macronix_nand_randomizer_check_enable(struct nand_chip *chip)
+{
+	u8 feature[ONFI_SUBFEATURE_PARAM_LEN];
+	int ret;
+
+	ret = nand_get_features(chip, ONFI_FEATURE_ADDR_MXIC_RANDOMIZER,
+				feature);
+	if (feature[0]) {
+		pr_info("Macronix NAND randomizer enabled:0x%x\n", feature[0]);
+		return;
+	}
+
+	feature[0] = MACRONIX_RANDOMIZER_ENPGM | MACRONIX_RANDOMIZER_RANDEN |
+		     MACRONIX_RANDOMIZER_RANDOPT;
+	ret = nand_set_features(chip, ONFI_FEATURE_ADDR_MXIC_RANDOMIZER,
+				feature);
+	if (ret)
+		goto err;
+
+	feature[0] = 0x0;
+	ret = nand_prog_page_op(chip, 0, 0, feature, 1);
+	if (ret)
+		goto err;
+
+	feature[0] = MACRONIX_RANDOMIZER_MODE_EXIT;
+	ret = nand_set_features(chip, ONFI_FEATURE_ADDR_MXIC_RANDOMIZER,
+				feature);
+	if (ret)
+		goto err;
+
+	pr_info("Macronix NAND randomizer enable ok\n");
+	return;
+err:
+	pr_err("Macronix NAND randomizer enable failed\n");
+}
+
 static void macronix_nand_onfi_init(struct nand_chip *chip)
 {
 	struct nand_parameters *p = &chip->parameters;
@@ -38,6 +81,17 @@ static void macronix_nand_onfi_init(struct nand_chip *chip)
 		return;
 
 	mxic = (struct nand_onfi_vendor_macronix *)p->onfi->vendor;
+	if (chip->options & NAND_NO_SUBPAGE_WRITE &&
+	    mxic->reliability_func & MACRONIX_RANDOMIZER_BIT) {
+		if (p->supports_set_get_features) {
+			bitmap_set(p->set_feature_list,
+				   ONFI_FEATURE_ADDR_MXIC_RANDOMIZER, 1);
+			bitmap_set(p->get_feature_list,
+				   ONFI_FEATURE_ADDR_MXIC_RANDOMIZER, 1);
+			macronix_nand_randomizer_check_enable(chip);
+		}
+	}
+
 	if ((mxic->reliability_func & MACRONIX_READ_RETRY_BIT) == 0)
 		return;
 
-- 
1.9.1