[PATCH v4 5/5] mtd: rawnand: micron: Micron SLC NAND filling block

[Bean Huo <huobean@xxxxxxxxx>]

From: Bean Huo <beanhuo@xxxxxxxxxx>

On some legacy planar 2D Micron NAND devices when a block erase command
is issued, occasionally even though a block erase operation completes and
returns a pass status, the flash block may not be completely erased.
Subsequent operations to this block on very rare cases can result in subtle
failures or corruption. These extremely rare cases should nevertheless be
considered. These rare occurrences have been observed on partially written
blocks.

To avoid this rare occurrence, we should make sure that at least 15 pages
have been programmed to a block before it is erased. In case we find that
less than 15 pages have been programmed, we will rewrite first 15 pages of
block.

Signed-off-by: Bean Huo <beanhuo@xxxxxxxxxx>
---
 drivers/mtd/nand/raw/nand_micron.c | 102 +++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)

diff --git a/drivers/mtd/nand/raw/nand_micron.c b/drivers/mtd/nand/raw/nand_micron.c
index b3485b0995ad..c5fd9e60f46d 100644
--- a/drivers/mtd/nand/raw/nand_micron.c
+++ b/drivers/mtd/nand/raw/nand_micron.c
@@ -36,6 +36,9 @@
 #define NAND_ECC_STATUS_1_3_CORRECTED	BIT(4)
 #define NAND_ECC_STATUS_7_8_CORRECTED	(BIT(4) | BIT(3))
 
+#define MICRON_SHALLOW_ERASE_MIN_PAGE 15
+#define MICRON_PAGE_MASK_TRIGGER GENMASK(MICRON_SHALLOW_ERASE_MIN_PAGE, 0)
+
 struct nand_onfi_vendor_micron {
 	u8 two_plane_read;
 	u8 read_cache;
@@ -64,6 +67,7 @@ struct micron_on_die_ecc {
 
 struct micron_nand {
 	struct micron_on_die_ecc ecc;
+	u16 *writtenp;
 };
 
 static int micron_nand_setup_read_retry(struct nand_chip *chip, int retry_mode)
@@ -429,6 +433,93 @@ static int micron_supports_on_die_ecc(struct nand_chip *chip)
 	return MICRON_ON_DIE_SUPPORTED;
 }
 
+static int micron_nand_pre_erase(struct nand_chip *chip, u32 eraseblock)
+{
+	struct micron_nand *micron = nand_get_manufacturer_data(chip);
+	struct mtd_info *mtd = nand_to_mtd(chip);
+	u8 last_page = MICRON_SHALLOW_ERASE_MIN_PAGE - 1;
+	u32 page;
+	u8 *data_buf;
+	int ret, i;
+
+	data_buf = nand_get_data_buf(chip);
+	WARN_ON(!data_buf);
+
+	if (likely(micron->writtenp[eraseblock] & BIT(last_page)))
+		return 0;
+
+	page = eraseblock << (chip->phys_erase_shift - chip->page_shift);
+
+	if (unlikely(micron->writtenp[eraseblock] == 0)) {
+		ret = nand_read_page_raw(chip, data_buf, 1, page + last_page);
+		if (ret)
+			return ret; /* Read error */
+		ret = nand_check_is_erased_page(chip, data_buf, true);
+		if (!ret)
+			return 0;
+	}
+
+	memset(data_buf, 0x00, mtd->writesize);
+
+	for (i = 0; i < MICRON_SHALLOW_ERASE_MIN_PAGE; i++) {
+		ret = nand_write_page_raw(chip, data_buf, false, page + i);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int micron_nand_post_erase(struct nand_chip *chip, u32 eraseblock)
+{
+	struct micron_nand *micron = nand_get_manufacturer_data(chip);
+
+	if (!micron)
+		return -EINVAL;
+
+	micron->writtenp[eraseblock] = 0;
+
+	return 0;
+}
+
+static int micron_nand_write_oob(struct nand_chip *chip, loff_t to,
+				 struct mtd_oob_ops *ops)
+{
+	struct micron_nand *micron = nand_get_manufacturer_data(chip);
+	u32 eb_sz = nanddev_eraseblock_size(&chip->base);
+	u32 p_sz = nanddev_page_size(&chip->base);
+	u32 ppeb = nanddev_pages_per_eraseblock(&chip->base);
+	u32 nb_p_tot = ops->len / p_sz;
+	u32 first_eb = DIV_ROUND_DOWN_ULL(to, eb_sz);
+	u32 first_p = DIV_ROUND_UP_ULL(to - (first_eb * eb_sz), p_sz);
+	u32 nb_eb = DIV_ROUND_UP_ULL(first_p + nb_p_tot, ppeb);
+	u32 remaining_p, eb, nb_p;
+	int ret;
+
+	ret = nand_write_oob_nand(chip, to, ops);
+
+	if (ret || ops->len != ops->retlen)
+		return ret;
+
+	/* Mark the last pages of the first erase block to write */
+	nb_p = min(nb_p_tot, ppeb - first_p);
+	micron->writtenp[first_eb] |= GENMASK(first_p + nb_p, 0) &
+					MICRON_PAGE_MASK_TRIGGER;
+	remaining_p = nb_p_tot - nb_p;
+
+	/* Mark all the pages of all "in-the-middle" erase blocks */
+	for (eb = first_eb + 1; eb < first_eb + nb_eb - 1; eb++) {
+		micron->writtenp[eb] |= MICRON_PAGE_MASK_TRIGGER;
+		remaining_p -= ppeb;
+	}
+
+	/* Mark the first pages of the last erase block to write */
+	if (remaining_p)
+		micron->writtenp[eb] |= GENMASK(remaining_p - 1, 0) &
+					MICRON_PAGE_MASK_TRIGGER;
+		return 0;
+}
+
 static int micron_nand_init(struct nand_chip *chip)
 {
 	struct mtd_info *mtd = nand_to_mtd(chip);
@@ -515,6 +606,17 @@ static int micron_nand_init(struct nand_chip *chip)
 		}
 	}
 
+	if (nand_is_slc(chip)) {
+		micron->writtenp = kcalloc(nanddev_neraseblocks(&chip->base),
+					   sizeof(u16), GFP_KERNEL);
+		if (!micron->writtenp)
+			goto err_free_manuf_data;
+
+		chip->ops.write_oob = micron_nand_write_oob;
+		chip->ops.pre_erase = micron_nand_pre_erase;
+		chip->ops.post_erase = micron_nand_post_erase;
+	}
+
 	return 0;
 
 err_free_manuf_data:
-- 
2.17.1


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