[RFC] mtd: nand: Preparatory patch for adding on-die ECC controller support. This patch adds NAND_ECC_HW_ON_DIE and all other changes to generic code.

[David Mosberger]

Pekon,

Before I go any further with this, could you confirm that what is
below is what you had in mind as far as the generic portion of the
patch is concerned.  If so, I'll go ahead and create the second,
Micron-specific part next.

Thanks,

  --david

PS: This patch adds a one-liner to of_mtd.c that I forgot about previously.

Signed-off-by: David Mosberger <davidm at egauge.net>
---
 drivers/mtd/nand/nand_base.c |   36 +++++++++++++++++++++++++++++++++---
 drivers/of/of_mtd.c          |    1 +
 include/linux/mtd/nand.h     |    7 +++++++
 3 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 5826da3..b94e2e9 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -3783,22 +3783,46 @@ EXPORT_SYMBOL(nand_scan_ident);
 int nand_scan_tail(struct mtd_info *mtd)
 {
 	int i;
+	u8 features[ONFI_SUBFEATURE_PARAM_LEN];
 	struct nand_chip *chip = mtd->priv;
 	struct nand_ecc_ctrl *ecc = &chip->ecc;
 	struct nand_buffers *nbuf;
 
+	if (chip->onfi_get_features(mtd, chip, ONFI_FEATURE_ADDR_OP_MODE,
+				    features) >= 0) {
+		if (features[0] & ONFI_FEATURE_OP_MODE_ENABLE_ON_DIE_ECC) {
+			/*
+			 * If the chip has on-die ECC enabled, we kind
+			 * of have to do the same...
+			 */
+			chip->ecc.mode = NAND_ECC_HW_ON_DIE;
+			pr_info("Using on-die ECC\n");
+		}
+	}
+
 	/* New bad blocks should be marked in OOB, flash-based BBT, or both */
 	BUG_ON((chip->bbt_options & NAND_BBT_NO_OOB_BBM) &&
 			!(chip->bbt_options & NAND_BBT_USE_FLASH));
 
 	if (!(chip->options & NAND_OWN_BUFFERS)) {
+		size_t on_die_bufsz = 0;
+
+		if (chip->ecc.mode == NAND_ECC_HW_ON_DIE)
+			on_die_bufsz = 2*(mtd->writesize + mtd->oobsize);
+
 		nbuf = kzalloc(sizeof(*nbuf) + mtd->writesize
-				+ mtd->oobsize * 3, GFP_KERNEL);
+				+ mtd->oobsize * 3 + on_die_bufsz, GFP_KERNEL);
 		if (!nbuf)
 			return -ENOMEM;
 		nbuf->ecccalc = (uint8_t *)(nbuf + 1);
 		nbuf->ecccode = nbuf->ecccalc + mtd->oobsize;
 		nbuf->databuf = nbuf->ecccode + mtd->oobsize;
+		if (chip->ecc.mode == NAND_ECC_HW_ON_DIE) {
+			nbuf->chkbuf = (nbuf->databuf + mtd->writesize
+					+ mtd->oobsize);
+			nbuf->rawbuf = (nbuf->chkbuf + mtd->writesize
+					+ mtd->oobsize);
+		}
 
 		chip->buffers = nbuf;
 	} else {
@@ -3956,6 +3980,7 @@ int nand_scan_tail(struct mtd_info *mtd)
 		ecc->strength = ecc->bytes * 8 / fls(8 * ecc->size);
 		break;
 
+	case NAND_ECC_HW_ON_DIE:
 	case NAND_ECC_NONE:
 		pr_warn("NAND_ECC_NONE selected by board driver. "
 			   "This is not recommended!\n");
@@ -4023,8 +4048,13 @@ int nand_scan_tail(struct mtd_info *mtd)
 	/* Invalidate the pagebuffer reference */
 	chip->pagebuf = -1;
 
-	/* Large page NAND with SOFT_ECC should support subpage reads */
-	if ((ecc->mode == NAND_ECC_SOFT) && (chip->page_shift > 9))
+	/*
+	 * Large page NAND with SOFT_ECC or on-die ECC should support
+	 * subpage reads.
+	 */
+	if (((ecc->mode == NAND_ECC_SOFT)
+	     || (chip->ecc.mode == NAND_ECC_HW_ON_DIE))
+	    && (chip->page_shift > 9))
 		chip->options |= NAND_SUBPAGE_READ;
 
 	/* Fill in remaining MTD driver data */
diff --git a/drivers/of/of_mtd.c b/drivers/of/of_mtd.c
index b7361ed..c844c84 100644
--- a/drivers/of/of_mtd.c
+++ b/drivers/of/of_mtd.c
@@ -23,6 +23,7 @@ static const char *nand_ecc_modes[] = {
 	[NAND_ECC_HW_SYNDROME]	= "hw_syndrome",
 	[NAND_ECC_HW_OOB_FIRST]	= "hw_oob_first",
 	[NAND_ECC_SOFT_BCH]	= "soft_bch",
+	[NAND_ECC_HW_ON_DIE]	= "hw_on_die",
 };
 
 /**
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 450d61e..a1cc980 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -115,6 +115,7 @@ typedef enum {
 	NAND_ECC_HW_SYNDROME,
 	NAND_ECC_HW_OOB_FIRST,
 	NAND_ECC_SOFT_BCH,
+	NAND_ECC_HW_ON_DIE,
 } nand_ecc_modes_t;
 
 /*
@@ -214,6 +215,10 @@ struct nand_chip;
 /* Vendor-specific feature address (Micron) */
 #define ONFI_FEATURE_ADDR_READ_RETRY	0x89
 
+/* Vendor-specific array operation mode (Micron) */
+#define ONFI_FEATURE_ADDR_OP_MODE	0x90
+#define ONFI_FEATURE_OP_MODE_ENABLE_ON_DIE_ECC		0x08
+
 /* ONFI subfeature parameters length */
 #define ONFI_SUBFEATURE_PARAM_LEN	4
 
@@ -516,6 +521,8 @@ struct nand_buffers {
 	uint8_t	*ecccalc;
 	uint8_t	*ecccode;
 	uint8_t *databuf;
+	uint8_t *chkbuf;
+	uint8_t *rawbuf;
 };
 
 /**
-- 
1.7.9.5