mtd: nand: add support for BBT without OOB

The first (sixt) byte in the OOB area contains vendor's bad block
information. During identification of the NAND chip this information is
collected by scanning the complete chip.
The option NAND_USE_FLASH_BBT is used to store this information in a sector so
we don't have to scan the complete flash. Unfortunately the code stores
a marker in order to recognize the BBT in the OOB area. This will fail
if the OOB area is completely used for ECC.
This patch introduces the option NAND_USE_FLASH_BBT_NO_OOB which has to be
used with NAND_USE_FLASH_BBT. It will then store BBT on flash without
touching the OOB area. The BBT format on flash remains same except the
first page starts with the recognition pattern followed by the version byte.
This change was tested in nandsim and it looks good so far :)
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/nand/nand_bbt.c

@@ -13,23 +13,32 @@
  * Description:
  *
  * When nand_scan_bbt is called, then it tries to find the bad block table
- * depending on the options in the bbt descriptor(s). If a bbt is found
- * then the contents are read and the memory based bbt is created. If a
- * mirrored bbt is selected then the mirror is searched too and the
- * versions are compared. If the mirror has a greater version number
- * than the mirror bbt is used to build the memory based bbt.
+ * depending on the options in the BBT descriptor(s). If no flash based BBT
+ * (NAND_USE_FLASH_BBT) is specified then the device is scanned for factory
+ * marked good / bad blocks. This information is used to create a memory BBT.
+ * Once a new bad block is discovered then the "factory" information is updated
+ * on the device.
+ * If a flash based BBT is specified then the function first tries to find the
+ * BBT on flash. If a BBT is found then the contents are read and the memory
+ * based BBT is created. If a mirrored BBT is selected then the mirror is
+ * searched too and the versions are compared. If the mirror has a greater
+ * version number than the mirror BBT is used to build the memory based BBT.
  * If the tables are not versioned, then we "or" the bad block information.
- * If one of the bbt's is out of date or does not exist it is (re)created.
- * If no bbt exists at all then the device is scanned for factory marked
+ * If one of the BBTs is out of date or does not exist it is (re)created.
+ * If no BBT exists at all then the device is scanned for factory marked
  * good / bad blocks and the bad block tables are created.
  *
- * For manufacturer created bbts like the one found on M-SYS DOC devices
- * the bbt is searched and read but never created
+ * For manufacturer created BBTs like the one found on M-SYS DOC devices
+ * the BBT is searched and read but never created
  *
- * The autogenerated bad block table is located in the last good blocks
+ * The auto generated bad block table is located in the last good blocks
  * of the device. The table is mirrored, so it can be updated eventually.
- * The table is marked in the oob area with an ident pattern and a version
- * number which indicates which of both tables is more up to date.
+ * The table is marked in the OOB area with an ident pattern and a version
+ * number which indicates which of both tables is more up to date. If the NAND
+ * controller needs the complete OOB area for the ECC information then the
+ * option NAND_USE_FLASH_BBT_NO_OOB should be used: it moves the ident pattern
+ * and the version byte into the data area and the OOB area will remain
+ * untouched.
  *
  * The table uses 2 bits per block
  * 11b:		block is good
@@ -59,6 +68,16 @@
 #include <linux/delay.h>
 #include <linux/vmalloc.h>
 
+static int check_pattern_no_oob(uint8_t *buf, struct nand_bbt_descr *td)
+{
+	int ret;
+
+	ret = memcmp(buf, td->pattern, td->len);
+	if (!ret)
+		return ret;
+	return -1;
+}
+
 /**
  * check_pattern - [GENERIC] check if a pattern is in the buffer
  * @buf:	the buffer to search
@@ -77,6 +96,9 @@ static int check_pattern(uint8_t *buf, int len, int paglen, struct nand_bbt_desc
 	int i, end = 0;
 	uint8_t *p = buf;
 
+	if (td->options & NAND_BBT_NO_OOB)
+		return check_pattern_no_oob(buf, td);
+
 	end = paglen + td->offs;
 	if (td->options & NAND_BBT_SCANEMPTY) {
 		for (i = 0; i < end; i++) {
@@ -155,6 +177,25 @@ static int check_short_pattern(uint8_t *buf, struct nand_bbt_descr *td)
 	return 0;
 }
 
+/**
+ * add_marker_len - compute the length of the marker in data area
+ * @td:		BBT descriptor used for computation
+ *
+ * The length will be 0 if the markeris located in OOB area.
+ */
+static u32 add_marker_len(struct nand_bbt_descr *td)
+{
+	u32 len;
+
+	if (!(td->options & NAND_BBT_NO_OOB))
+		return 0;
+
+	len = td->len;
+	if (td->options & NAND_BBT_VERSION)
+		len++;
+	return len;
+}
+
 /**
  * read_bbt - [GENERIC] Read the bad block table starting from page
  * @mtd:	MTD device structure
@@ -176,13 +217,24 @@ static int read_bbt(struct mtd_info *mtd, uint8_t *buf, int page, int num,
 	loff_t from;
 	int bits = td->options & NAND_BBT_NRBITS_MSK;
 	uint8_t msk = (uint8_t) ((1 << bits) - 1);
+	u32 marker_len;
 	int reserved_block_code = td->reserved_block_code;
 
 	totlen = (num * bits) >> 3;
+	marker_len = add_marker_len(td);
 	from = ((loff_t) page) << this->page_shift;
 
 	while (totlen) {
 		len = min(totlen, (size_t) (1 << this->bbt_erase_shift));
+		if (marker_len) {
+			/*
+			 * In case the BBT marker is not in the OOB area it
+			 * will be just in the first page.
+			 */
+			len -= marker_len;
+			from += marker_len;
+			marker_len = 0;
+		}
 		res = mtd->read(mtd, from, len, &retlen, buf);
 		if (res < 0) {
 			if (retlen != len) {
@@ -260,10 +312,26 @@ static int read_abs_bbt(struct mtd_info *mtd, uint8_t *buf, struct nand_bbt_desc
 	return 0;
 }
 
+/*
+ * BBT marker is in the first page, no OOB.
+ */
+static int scan_read_raw_data(struct mtd_info *mtd, uint8_t *buf, loff_t offs,
+			 struct nand_bbt_descr *td)
+{
+	size_t retlen;
+	size_t len;
+
+	len = td->len;
+	if (td->options & NAND_BBT_VERSION)
+		len++;
+
+	return mtd->read(mtd, offs, len, &retlen, buf);
+}
+
 /*
  * Scan read raw data from flash
  */
-static int scan_read_raw(struct mtd_info *mtd, uint8_t *buf, loff_t offs,
+static int scan_read_raw_oob(struct mtd_info *mtd, uint8_t *buf, loff_t offs,
 			 size_t len)
 {
 	struct mtd_oob_ops ops;
@@ -296,6 +364,15 @@ static int scan_read_raw(struct mtd_info *mtd, uint8_t *buf, loff_t offs,
 	return 0;
 }
 
+static int scan_read_raw(struct mtd_info *mtd, uint8_t *buf, loff_t offs,
+			 size_t len, struct nand_bbt_descr *td)
+{
+	if (td->options & NAND_BBT_NO_OOB)
+		return scan_read_raw_data(mtd, buf, offs, td);
+	else
+		return scan_read_raw_oob(mtd, buf, offs, len);
+}
+
 /*
  * Scan write data with oob to flash
  */
@@ -314,6 +391,15 @@ static int scan_write_bbt(struct mtd_info *mtd, loff_t offs, size_t len,
 	return mtd->write_oob(mtd, offs, &ops);
 }
 
+static u32 bbt_get_ver_offs(struct mtd_info *mtd, struct nand_bbt_descr *td)
+{
+	u32 ver_offs = td->veroffs;
+
+	if (!(td->options & NAND_BBT_NO_OOB))
+		ver_offs += mtd->writesize;
+	return ver_offs;
+}
+
 /**
  * read_abs_bbts - [GENERIC] Read the bad block table(s) for all chips starting at a given page
  * @mtd:	MTD device structure
@@ -333,8 +419,8 @@ static int read_abs_bbts(struct mtd_info *mtd, uint8_t *buf,
 	/* Read the primary version, if available */
 	if (td->options & NAND_BBT_VERSION) {
 		scan_read_raw(mtd, buf, (loff_t)td->pages[0] << this->page_shift,
-			      mtd->writesize);
-		td->version[0] = buf[mtd->writesize + td->veroffs];
+			      mtd->writesize, td);
+		td->version[0] = buf[bbt_get_ver_offs(mtd, td)];
 		printk(KERN_DEBUG "Bad block table at page %d, version 0x%02X\n",
 		       td->pages[0], td->version[0]);
 	}
@@ -342,8 +428,8 @@ static int read_abs_bbts(struct mtd_info *mtd, uint8_t *buf,
 	/* Read the mirror version, if available */
 	if (md && (md->options & NAND_BBT_VERSION)) {
 		scan_read_raw(mtd, buf, (loff_t)md->pages[0] << this->page_shift,
-			      mtd->writesize);
-		md->version[0] = buf[mtd->writesize + md->veroffs];
+			      mtd->writesize, td);
+		md->version[0] = buf[bbt_get_ver_offs(mtd, md)];
 		printk(KERN_DEBUG "Bad block table at page %d, version 0x%02X\n",
 		       md->pages[0], md->version[0]);
 	}
@@ -359,7 +445,7 @@ static int scan_block_full(struct mtd_info *mtd, struct nand_bbt_descr *bd,
 {
 	int ret, j;
 
-	ret = scan_read_raw(mtd, buf, offs, readlen);
+	ret = scan_read_raw_oob(mtd, buf, offs, readlen);
 	if (ret)
 		return ret;
 
@@ -466,6 +552,8 @@ static int create_bbt(struct mtd_info *mtd, uint8_t *buf,
 	for (i = startblock; i < numblocks;) {
 		int ret;
 
+		BUG_ON(bd->options & NAND_BBT_NO_OOB);
+
 		if (bd->options & NAND_BBT_SCANALLPAGES)
 			ret = scan_block_full(mtd, bd, from, buf, readlen,
 					      scanlen, len);
@@ -547,11 +635,12 @@ static int search_bbt(struct mtd_info *mtd, uint8_t *buf, struct nand_bbt_descr
 			loff_t offs = (loff_t)actblock << this->bbt_erase_shift;
 
 			/* Read first page */
-			scan_read_raw(mtd, buf, offs, mtd->writesize);
+			scan_read_raw(mtd, buf, offs, mtd->writesize, td);
 			if (!check_pattern(buf, scanlen, mtd->writesize, td)) {
 				td->pages[i] = actblock << blocktopage;
 				if (td->options & NAND_BBT_VERSION) {
-					td->version[i] = buf[mtd->writesize + td->veroffs];
+					offs = bbt_get_ver_offs(mtd, td);
+					td->version[i] = buf[offs];
 				}
 				break;
 			}
@@ -735,6 +824,21 @@ static int write_bbt(struct mtd_info *mtd, uint8_t *buf,
 			memset(&buf[offs], 0xff, (size_t) (numblocks >> sft));
 			ooboffs = len + (pageoffs * mtd->oobsize);
 
+		} else if (td->options & NAND_BBT_NO_OOB) {
+			ooboffs = 0;
+			offs = td->len;
+			/* the version byte */
+			if (td->options & NAND_BBT_VERSION)
+				offs++;
+			/* Calc length */
+			len = (size_t) (numblocks >> sft);
+			len += offs;
+			/* Make it page aligned ! */
+			len = ALIGN(len, mtd->writesize);
+			/* Preset the buffer with 0xff */
+			memset(buf, 0xff, len);
+			/* Pattern is located at the begin of first page */
+			memcpy(buf, td->pattern, td->len);
 		} else {
 			/* Calc length */
 			len = (size_t) (numblocks >> sft);
@@ -773,7 +877,9 @@ static int write_bbt(struct mtd_info *mtd, uint8_t *buf,
 		if (res < 0)
 			goto outerr;
 
-		res = scan_write_bbt(mtd, to, len, buf, &buf[len]);
+		res = scan_write_bbt(mtd, to, len, buf,
+				td->options & NAND_BBT_NO_OOB ? NULL :
+				&buf[len]);
 		if (res < 0)
 			goto outerr;
 
@@ -983,6 +1089,49 @@ static void mark_bbt_region(struct mtd_info *mtd, struct nand_bbt_descr *td)
 	}
 }
 
+/**
+ * verify_bbt_descr - verify the bad block description
+ * @bd:			the table to verify
+ *
+ * This functions performs a few sanity checks on the bad block description
+ * table.
+ */
+static void verify_bbt_descr(struct mtd_info *mtd, struct nand_bbt_descr *bd)
+{
+	struct nand_chip *this = mtd->priv;
+	u32 pattern_len = bd->len;
+	u32 bits = bd->options & NAND_BBT_NRBITS_MSK;
+	u32 table_size;
+
+	if (!bd)
+		return;
+	BUG_ON((this->options & NAND_USE_FLASH_BBT_NO_OOB) &&
+			!(this->options & NAND_USE_FLASH_BBT));
+	BUG_ON(!bits);
+
+	if (bd->options & NAND_BBT_VERSION)
+		pattern_len++;
+
+	if (bd->options & NAND_BBT_NO_OOB) {
+		BUG_ON(!(this->options & NAND_USE_FLASH_BBT));
+		BUG_ON(!(this->options & NAND_USE_FLASH_BBT_NO_OOB));
+		BUG_ON(bd->offs);
+		if (bd->options & NAND_BBT_VERSION)
+			BUG_ON(bd->veroffs != bd->len);
+		BUG_ON(bd->options & NAND_BBT_SAVECONTENT);
+	}
+
+	if (bd->options & NAND_BBT_PERCHIP)
+		table_size = this->chipsize >> this->bbt_erase_shift;
+	else
+		table_size = mtd->size >> this->bbt_erase_shift;
+	table_size >>= 3;
+	table_size *= bits;
+	if (bd->options & NAND_BBT_NO_OOB)
+		table_size += pattern_len;
+	BUG_ON(table_size > (1 << this->bbt_erase_shift));
+}
+
 /**
  * nand_scan_bbt - [NAND Interface] scan, find, read and maybe create bad block table(s)
  * @mtd:	MTD device structure
@@ -1024,6 +1173,8 @@ int nand_scan_bbt(struct mtd_info *mtd, struct nand_bbt_descr *bd)
 		}
 		return res;
 	}
+	verify_bbt_descr(mtd, td);
+	verify_bbt_descr(mtd, md);
 
 	/* Allocate a temporary buffer for one eraseblock incl. oob */
 	len = (1 << this->bbt_erase_shift);
@@ -1167,6 +1318,26 @@ static struct nand_bbt_descr bbt_mirror_descr = {
 	.pattern = mirror_pattern
 };
 
+static struct nand_bbt_descr bbt_main_no_bbt_descr = {
+	.options = NAND_BBT_LASTBLOCK | NAND_BBT_CREATE | NAND_BBT_WRITE
+		| NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP
+		| NAND_BBT_NO_OOB,
+	.len = 4,
+	.veroffs = 4,
+	.maxblocks = 4,
+	.pattern = bbt_pattern
+};
+
+static struct nand_bbt_descr bbt_mirror_no_bbt_descr = {
+	.options = NAND_BBT_LASTBLOCK | NAND_BBT_CREATE | NAND_BBT_WRITE
+		| NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP
+		| NAND_BBT_NO_OOB,
+	.len = 4,
+	.veroffs = 4,
+	.maxblocks = 4,
+	.pattern = mirror_pattern
+};
+
 #define BBT_SCAN_OPTIONS (NAND_BBT_SCANLASTPAGE | NAND_BBT_SCAN2NDPAGE | \
 		NAND_BBT_SCANBYTE1AND6)
 /**
@@ -1237,9 +1408,14 @@ int nand_default_bbt(struct mtd_info *mtd)
 	if (this->options & NAND_USE_FLASH_BBT) {
 		/* Use the default pattern descriptors */
 		if (!this->bbt_td) {
+			if (this->options & NAND_USE_FLASH_BBT_NO_OOB) {
+				this->bbt_td = &bbt_main_no_bbt_descr;
+				this->bbt_md = &bbt_mirror_no_bbt_descr;
+			} else {
 				this->bbt_td = &bbt_main_descr;
 				this->bbt_md = &bbt_mirror_descr;
 			}
+		}
 		if (!this->badblock_pattern) {
 			this->badblock_pattern = (mtd->writesize > 512) ? &largepage_flashbased : &smallpage_flashbased;
 		}

include/linux/mtd/bbm.h

@@ -102,6 +102,8 @@ struct nand_bbt_descr {
 #define NAND_BBT_SCANBYTE1AND6 0x00100000
 /* The nand_bbt_descr was created dynamicaly and must be freed */
 #define NAND_BBT_DYNAMICSTRUCT 0x00200000
+/* The bad block table does not OOB for marker */
+#define NAND_BBT_NO_OOB		0x00400000
 
 /* The maximum number of blocks to scan for a bbt */
 #define NAND_BBT_SCAN_MAXBLOCKS	4

include/linux/mtd/nand.h

@@ -206,8 +206,10 @@ typedef enum {
 #define NAND_CHIPOPTIONS_MSK	(0x0000ffff & ~NAND_NO_AUTOINCR)
 
 /* Non chip related options */
-/* Use a flash based bad block table. This option is passed to the
- * default bad block table function. */
+/*
+ * Use a flash based bad block table. OOB identifier is saved in OOB area.
+ * This option is passed to the default bad block table function.
+ */
 #define NAND_USE_FLASH_BBT	0x00010000
 /* This option skips the bbt scan during initialization. */
 #define NAND_SKIP_BBTSCAN	0x00020000
@@ -216,6 +218,11 @@ typedef enum {
 #define NAND_OWN_BUFFERS	0x00040000
 /* Chip may not exist, so silence any errors in scan */
 #define NAND_SCAN_SILENT_NODEV	0x00080000
+/*
+ * If passed additionally to NAND_USE_FLASH_BBT then BBT code will not touch
+ * the OOB area.
+ */
+#define NAND_USE_FLASH_BBT_NO_OOB	0x00100000
 
 /* Options set by nand scan */
 /* Nand scan has allocated controller struct */