mtd: nand: Sync with Linux v4.6

Updates the NAND code to match Linux v4.6.  The previous sync was from
Linux v4.1 in commit d3963721d93fafa.

Note that none of the individual NAND drivers tracked Linux closely
enough to be synced themselves, other than manually applying a few
cross-tree changes.

Signed-off-by: Scott Wood <oss@buserror.net>
Tested-by: Heiko Schocher <hs@denx.de>

1 files changed, 228 insertions, 101 deletions

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 62e70a72aa..74c563c495 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -1,6 +1,4 @@
 /*
- *  drivers/mtd/nand.c
- *
  *  Overview:
  *   This is the generic MTD driver for NAND flash devices. It should be
  *   capable of working with almost all NAND chips currently available.
@@ -45,8 +43,6 @@
 #include <asm/io.h>
 #include <asm/errno.h>
 
-static bool is_module_text_address(unsigned long addr) {return 0;}
-
 /* Define default oob placement schemes for large and small page devices */
 static struct nand_ecclayout nand_oob_8 = {
 	.eccbytes = 3,
@@ -343,13 +339,12 @@ void nand_read_buf16(struct mtd_info *mtd, uint8_t *buf, int len)
  * nand_block_bad - [DEFAULT] Read bad block marker from the chip
  * @mtd: MTD device structure
  * @ofs: offset from device start
- * @getchip: 0, if the chip is already selected
  *
  * Check, if the block is bad.
  */
-static int nand_block_bad(struct mtd_info *mtd, loff_t ofs, int getchip)
+static int nand_block_bad(struct mtd_info *mtd, loff_t ofs)
 {
-	int page, chipnr, res = 0, i = 0;
+	int page, res = 0, i = 0;
 	struct nand_chip *chip = mtd_to_nand(mtd);
 	u16 bad;
 
@@ -358,15 +353,6 @@ static int nand_block_bad(struct mtd_info *mtd, loff_t ofs, int getchip)
 
 	page = (int)(ofs >> chip->page_shift) & chip->pagemask;
 
-	if (getchip) {
-		chipnr = (int)(ofs >> chip->chip_shift);
-
-		nand_get_device(mtd, FL_READING);
-
-		/* Select the NAND device */
-		chip->select_chip(mtd, chipnr);
-	}
-
 	do {
 		if (chip->options & NAND_BUSWIDTH_16) {
 			chip->cmdfunc(mtd, NAND_CMD_READOOB,
@@ -391,11 +377,6 @@ static int nand_block_bad(struct mtd_info *mtd, loff_t ofs, int getchip)
 		i++;
 	} while (!res && i < 2 && (chip->bbt_options & NAND_BBT_SCAN2NDPAGE));
 
-	if (getchip) {
-		chip->select_chip(mtd, -1);
-		nand_release_device(mtd);
-	}
-
 	return res;
 }
 
@@ -533,14 +514,12 @@ static int nand_block_isreserved(struct mtd_info *mtd, loff_t ofs)
  * nand_block_checkbad - [GENERIC] Check if a block is marked bad
  * @mtd: MTD device structure
  * @ofs: offset from device start
- * @getchip: 0, if the chip is already selected
  * @allowbbt: 1, if its allowed to access the bbt area
  *
  * Check, if the block is bad. Either by reading the bad block table or
  * calling of the scan function.
  */
-static int nand_block_checkbad(struct mtd_info *mtd, loff_t ofs, int getchip,
-			       int allowbbt)
+static int nand_block_checkbad(struct mtd_info *mtd, loff_t ofs, int allowbbt)
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
 
@@ -551,17 +530,22 @@ static int nand_block_checkbad(struct mtd_info *mtd, loff_t ofs, int getchip,
 	}
 
 	if (!chip->bbt)
-		return chip->block_bad(mtd, ofs, getchip);
+		return chip->block_bad(mtd, ofs);
 
 	/* Return info from the table */
 	return nand_isbad_bbt(mtd, ofs, allowbbt);
 }
 
-/* Wait for the ready pin, after a command. The timeout is caught later. */
+/**
+ * nand_wait_ready - [GENERIC] Wait for the ready pin after commands.
+ * @mtd: MTD device structure
+ *
+ * Wait for the ready pin after a command, and warn if a timeout occurs.
+ */
 void nand_wait_ready(struct mtd_info *mtd)
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
-	u32 timeo = (CONFIG_SYS_HZ * 20) / 1000;
+	u32 timeo = (CONFIG_SYS_HZ * 400) / 1000;
 	u32 time_start;
 
 	time_start = get_timer(0);
@@ -571,6 +555,9 @@ void nand_wait_ready(struct mtd_info *mtd)
 			if (chip->dev_ready(mtd))
 				break;
 	}
+
+	if (!chip->dev_ready(mtd))
+		pr_warn("timeout while waiting for chip to become ready\n");
 }
 EXPORT_SYMBOL_GPL(nand_wait_ready);
 
@@ -871,15 +858,13 @@ static void panic_nand_wait(struct mtd_info *mtd, struct nand_chip *chip,
  * @mtd: MTD device structure
  * @chip: NAND chip structure
  *
- * Wait for command done. This applies to erase and program only. Erase can
- * take up to 400ms and program up to 20ms according to general NAND and
- * SmartMedia specs.
+ * Wait for command done. This applies to erase and program only.
  */
 static int nand_wait(struct mtd_info *mtd, struct nand_chip *chip)
 {
 
-	int status, state = chip->state;
-	unsigned long timeo = (state == FL_ERASING ? 400 : 20);
+	int status;
+	unsigned long timeo = 400;
 
 	led_trigger_event(nand_led_trigger, LED_FULL);
 
@@ -912,6 +897,135 @@ static int nand_wait(struct mtd_info *mtd, struct nand_chip *chip)
 	return status;
 }
 
+#define BITS_PER_BYTE 8
+
+/**
+ * nand_check_erased_buf - check if a buffer contains (almost) only 0xff data
+ * @buf: buffer to test
+ * @len: buffer length
+ * @bitflips_threshold: maximum number of bitflips
+ *
+ * Check if a buffer contains only 0xff, which means the underlying region
+ * has been erased and is ready to be programmed.
+ * The bitflips_threshold specify the maximum number of bitflips before
+ * considering the region is not erased.
+ * Note: The logic of this function has been extracted from the memweight
+ * implementation, except that nand_check_erased_buf function exit before
+ * testing the whole buffer if the number of bitflips exceed the
+ * bitflips_threshold value.
+ *
+ * Returns a positive number of bitflips less than or equal to
+ * bitflips_threshold, or -ERROR_CODE for bitflips in excess of the
+ * threshold.
+ */
+static int nand_check_erased_buf(void *buf, int len, int bitflips_threshold)
+{
+	const unsigned char *bitmap = buf;
+	int bitflips = 0;
+	int weight;
+
+	for (; len && ((uintptr_t)bitmap) % sizeof(long);
+	     len--, bitmap++) {
+		weight = hweight8(*bitmap);
+		bitflips += BITS_PER_BYTE - weight;
+		if (unlikely(bitflips > bitflips_threshold))
+			return -EBADMSG;
+	}
+
+	for (; len >= 4; len -= 4, bitmap += 4) {
+		weight = hweight32(*((u32 *)bitmap));
+		bitflips += 32 - weight;
+		if (unlikely(bitflips > bitflips_threshold))
+			return -EBADMSG;
+	}
+
+	for (; len > 0; len--, bitmap++) {
+		weight = hweight8(*bitmap);
+		bitflips += BITS_PER_BYTE - weight;
+		if (unlikely(bitflips > bitflips_threshold))
+			return -EBADMSG;
+	}
+
+	return bitflips;
+}
+
+/**
+ * nand_check_erased_ecc_chunk - check if an ECC chunk contains (almost) only
+ *				 0xff data
+ * @data: data buffer to test
+ * @datalen: data length
+ * @ecc: ECC buffer
+ * @ecclen: ECC length
+ * @extraoob: extra OOB buffer
+ * @extraooblen: extra OOB length
+ * @bitflips_threshold: maximum number of bitflips
+ *
+ * Check if a data buffer and its associated ECC and OOB data contains only
+ * 0xff pattern, which means the underlying region has been erased and is
+ * ready to be programmed.
+ * The bitflips_threshold specify the maximum number of bitflips before
+ * considering the region as not erased.
+ *
+ * Note:
+ * 1/ ECC algorithms are working on pre-defined block sizes which are usually
+ *    different from the NAND page size. When fixing bitflips, ECC engines will
+ *    report the number of errors per chunk, and the NAND core infrastructure
+ *    expect you to return the maximum number of bitflips for the whole page.
+ *    This is why you should always use this function on a single chunk and
+ *    not on the whole page. After checking each chunk you should update your
+ *    max_bitflips value accordingly.
+ * 2/ When checking for bitflips in erased pages you should not only check
+ *    the payload data but also their associated ECC data, because a user might
+ *    have programmed almost all bits to 1 but a few. In this case, we
+ *    shouldn't consider the chunk as erased, and checking ECC bytes prevent
+ *    this case.
+ * 3/ The extraoob argument is optional, and should be used if some of your OOB
+ *    data are protected by the ECC engine.
+ *    It could also be used if you support subpages and want to attach some
+ *    extra OOB data to an ECC chunk.
+ *
+ * Returns a positive number of bitflips less than or equal to
+ * bitflips_threshold, or -ERROR_CODE for bitflips in excess of the
+ * threshold. In case of success, the passed buffers are filled with 0xff.
+ */
+int nand_check_erased_ecc_chunk(void *data, int datalen,
+				void *ecc, int ecclen,
+				void *extraoob, int extraooblen,
+				int bitflips_threshold)
+{
+	int data_bitflips = 0, ecc_bitflips = 0, extraoob_bitflips = 0;
+
+	data_bitflips = nand_check_erased_buf(data, datalen,
+					      bitflips_threshold);
+	if (data_bitflips < 0)
+		return data_bitflips;
+
+	bitflips_threshold -= data_bitflips;
+
+	ecc_bitflips = nand_check_erased_buf(ecc, ecclen, bitflips_threshold);
+	if (ecc_bitflips < 0)
+		return ecc_bitflips;
+
+	bitflips_threshold -= ecc_bitflips;
+
+	extraoob_bitflips = nand_check_erased_buf(extraoob, extraooblen,
+						  bitflips_threshold);
+	if (extraoob_bitflips < 0)
+		return extraoob_bitflips;
+
+	if (data_bitflips)
+		memset(data, 0xff, datalen);
+
+	if (ecc_bitflips)
+		memset(ecc, 0xff, ecclen);
+
+	if (extraoob_bitflips)
+		memset(extraoob, 0xff, extraooblen);
+
+	return data_bitflips + ecc_bitflips + extraoob_bitflips;
+}
+EXPORT_SYMBOL(nand_check_erased_ecc_chunk);
+
 /**
  * nand_read_page_raw - [INTERN] read raw page data without ecc
  * @mtd: mtd info structure
@@ -1103,6 +1217,16 @@ static int nand_read_subpage(struct mtd_info *mtd, struct nand_chip *chip,
 
 		stat = chip->ecc.correct(mtd, p,
 			&chip->buffers->ecccode[i], &chip->buffers->ecccalc[i]);
+		if (stat == -EBADMSG &&
+		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
+			/* check for empty pages with bitflips */
+			stat = nand_check_erased_ecc_chunk(p, chip->ecc.size,
+						&chip->buffers->ecccode[i],
+						chip->ecc.bytes,
+						NULL, 0,
+						chip->ecc.strength);
+		}
+
 		if (stat < 0) {
 			mtd->ecc_stats.failed++;
 		} else {
@@ -1152,6 +1276,15 @@ static int nand_read_page_hwecc(struct mtd_info *mtd, struct nand_chip *chip,
 		int stat;
 
 		stat = chip->ecc.correct(mtd, p, &ecc_code[i], &ecc_calc[i]);
+		if (stat == -EBADMSG &&
+		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
+			/* check for empty pages with bitflips */
+			stat = nand_check_erased_ecc_chunk(p, eccsize,
+						&ecc_code[i], eccbytes,
+						NULL, 0,
+						chip->ecc.strength);
+		}
+
 		if (stat < 0) {
 			mtd->ecc_stats.failed++;
 		} else {
@@ -1204,6 +1337,15 @@ static int nand_read_page_hwecc_oob_first(struct mtd_info *mtd,
 		chip->ecc.calculate(mtd, p, &ecc_calc[i]);
 
 		stat = chip->ecc.correct(mtd, p, &ecc_code[i], NULL);
+		if (stat == -EBADMSG &&
+		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
+			/* check for empty pages with bitflips */
+			stat = nand_check_erased_ecc_chunk(p, eccsize,
+						&ecc_code[i], eccbytes,
+						NULL, 0,
+						chip->ecc.strength);
+		}
+
 		if (stat < 0) {
 			mtd->ecc_stats.failed++;
 		} else {
@@ -1231,6 +1373,7 @@ static int nand_read_page_syndrome(struct mtd_info *mtd, struct nand_chip *chip,
 	int i, eccsize = chip->ecc.size;
 	int eccbytes = chip->ecc.bytes;
 	int eccsteps = chip->ecc.steps;
+	int eccpadbytes = eccbytes + chip->ecc.prepad + chip->ecc.postpad;
 	uint8_t *p = buf;
 	uint8_t *oob = chip->oob_poi;
 	unsigned int max_bitflips = 0;
@@ -1250,19 +1393,29 @@ static int nand_read_page_syndrome(struct mtd_info *mtd, struct nand_chip *chip,
 		chip->read_buf(mtd, oob, eccbytes);
 		stat = chip->ecc.correct(mtd, p, oob, NULL);
 
-		if (stat < 0) {
-			mtd->ecc_stats.failed++;
-		} else {
-			mtd->ecc_stats.corrected += stat;
-			max_bitflips = max_t(unsigned int, max_bitflips, stat);
-		}
-
 		oob += eccbytes;
 
 		if (chip->ecc.postpad) {
 			chip->read_buf(mtd, oob, chip->ecc.postpad);
 			oob += chip->ecc.postpad;
 		}
+
+		if (stat == -EBADMSG &&
+		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
+			/* check for empty pages with bitflips */
+			stat = nand_check_erased_ecc_chunk(p, chip->ecc.size,
+							   oob - eccpadbytes,
+							   eccpadbytes,
+							   NULL, 0,
+							   chip->ecc.strength);
+		}
+
+		if (stat < 0) {
+			mtd->ecc_stats.failed++;
+		} else {
+			mtd->ecc_stats.corrected += stat;
+			max_bitflips = max_t(unsigned int, max_bitflips, stat);
+		}
 	}
 
 	/* Calculate remaining oob bytes */
@@ -1361,8 +1514,7 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
 	int ret = 0;
 	uint32_t readlen = ops->len;
 	uint32_t oobreadlen = ops->ooblen;
-	uint32_t max_oobsize = ops->mode == MTD_OPS_AUTO_OOB ?
-		mtd->oobavail : mtd->oobsize;
+	uint32_t max_oobsize = mtd_oobavail(mtd, ops);
 
 	uint8_t *bufpoi, *oob, *buf;
 	int use_bufpoi;
@@ -1712,10 +1864,7 @@ static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
 
 	stats = mtd->ecc_stats;
 
-	if (ops->mode == MTD_OPS_AUTO_OOB)
-		len = chip->ecc.layout->oobavail;
-	else
-		len = mtd->oobsize;
+	len = mtd_oobavail(mtd, ops);
 
 	if (unlikely(ops->ooboffs >= len)) {
 		pr_debug("%s: attempt to start read outside oob\n",
@@ -1845,8 +1994,7 @@ out:
  * Not for syndrome calculating ECC controllers, which use a special oob layout.
  */
 static int nand_write_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
-				const uint8_t *buf, int oob_required,
-				int page)
+			       const uint8_t *buf, int oob_required, int page)
 {
 	chip->write_buf(mtd, buf, mtd->writesize);
 	if (oob_required)
@@ -1861,6 +2009,7 @@ static int nand_write_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
  * @chip: nand chip info structure
  * @buf: data buffer
  * @oob_required: must write chip->oob_poi to OOB
+ * @page: page number to write
  *
  * We need a special oob layout and handling even when ECC isn't checked.
  */
@@ -1907,8 +2056,8 @@ static int nand_write_page_raw_syndrome(struct mtd_info *mtd,
  * @page: page number to write
  */
 static int nand_write_page_swecc(struct mtd_info *mtd, struct nand_chip *chip,
-				  const uint8_t *buf, int oob_required,
-				  int page)
+				 const uint8_t *buf, int oob_required,
+				 int page)
 {
 	int i, eccsize = chip->ecc.size;
 	int eccbytes = chip->ecc.bytes;
@@ -2029,6 +2178,7 @@ static int nand_write_subpage_hwecc(struct mtd_info *mtd,
  * @chip: nand chip info structure
  * @buf: data buffer
  * @oob_required: must write chip->oob_poi to OOB
+ * @page: page number to write
  *
  * The hw generator calculates the error syndrome automatically. Therefore we
  * need a special oob layout and handling.
@@ -2103,7 +2253,7 @@ static int nand_write_page(struct mtd_info *mtd, struct nand_chip *chip,
 						  oob_required, page);
 	else if (subpage)
 		status = chip->ecc.write_subpage(mtd, chip, offset, data_len,
-						  buf, oob_required, page);
+						 buf, oob_required, page);
 	else
 		status = chip->ecc.write_page(mtd, chip, buf, oob_required,
 					      page);
@@ -2145,7 +2295,6 @@ static int nand_write_page(struct mtd_info *mtd, struct nand_chip *chip,
  * @oob: oob data buffer
  * @len: oob data write length
  * @ops: oob ops structure
- * @page: page number to write
  */
 static uint8_t *nand_fill_oob(struct mtd_info *mtd, uint8_t *oob, size_t len,
 			      struct mtd_oob_ops *ops)
@@ -2214,8 +2363,7 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
 	uint32_t writelen = ops->len;
 
 	uint32_t oobwritelen = ops->ooblen;
-	uint32_t oobmaxlen = ops->mode == MTD_OPS_AUTO_OOB ?
-				mtd->oobavail : mtd->oobsize;
+	uint32_t oobmaxlen = mtd_oobavail(mtd, ops);
 
 	uint8_t *oob = ops->oobbuf;
 	uint8_t *buf = ops->datbuf;
@@ -2404,10 +2552,7 @@ static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
 	pr_debug("%s: to = 0x%08x, len = %i\n",
 			 __func__, (unsigned int)to, (int)ops->ooblen);
 
-	if (ops->mode == MTD_OPS_AUTO_OOB)
-		len = chip->ecc.layout->oobavail;
-	else
-		len = mtd->oobsize;
+	len = mtd_oobavail(mtd, ops);
 
 	/* Do not allow write past end of page */
 	if ((ops->ooboffs + ops->ooblen) > len) {
@@ -2597,7 +2742,7 @@ int nand_erase_nand(struct mtd_info *mtd, struct erase_info *instr,
 
 		/* Check if we have a bad block, we do not erase bad blocks! */
 		if (!instr->scrub && nand_block_checkbad(mtd, ((loff_t) page) <<
-					chip->page_shift, 0, allowbbt)) {
+					chip->page_shift, allowbbt)) {
 			pr_warn("%s: attempt to erase a bad block at page 0x%08x\n",
 				    __func__, page);
 			instr->state = MTD_ERASE_FAILED;
@@ -2684,7 +2829,20 @@ static void nand_sync(struct mtd_info *mtd)
  */
 static int nand_block_isbad(struct mtd_info *mtd, loff_t offs)
 {
-	return nand_block_checkbad(mtd, offs, 1, 0);
+	struct nand_chip *chip = mtd_to_nand(mtd);
+	int chipnr = (int)(offs >> chip->chip_shift);
+	int ret;
+
+	/* Select the NAND device */
+	nand_get_device(mtd, FL_READING);
+	chip->select_chip(mtd, chipnr);
+
+	ret = nand_block_checkbad(mtd, offs, 0);
+
+	chip->select_chip(mtd, -1);
+	nand_release_device(mtd);
+
+	return ret;
 }
 
 /**
@@ -2756,9 +2914,6 @@ static int nand_onfi_get_features(struct mtd_info *mtd, struct nand_chip *chip,
 		return -EINVAL;
 #endif
 
-	/* clear the sub feature parameters */
-	memset(subfeature_param, 0, ONFI_SUBFEATURE_PARAM_LEN);
-
 	chip->cmdfunc(mtd, NAND_CMD_GET_FEATURES, addr, -1);
 	for (i = 0; i < ONFI_SUBFEATURE_PARAM_LEN; ++i)
 		*subfeature_param++ = chip->read_byte(mtd);
@@ -3491,7 +3646,7 @@ static struct nand_flash_dev *nand_get_flash_type(struct mtd_info *mtd,
 			if (find_full_id_nand(mtd, chip, type, id_data, &busw))
 				goto ident_done;
 		} else if (*dev_id == type->dev_id) {
-				break;
+			break;
 		}
 	}
 
@@ -3514,10 +3669,7 @@ static struct nand_flash_dev *nand_get_flash_type(struct mtd_info *mtd,
 
 	chip->chipsize = (uint64_t)type->chipsize << 20;
 
-	if (!type->pagesize && chip->init_size) {
-		/* Set the pagesize, oobsize, erasesize by the driver */
-		busw = chip->init_size(mtd, chip, id_data);
-	} else if (!type->pagesize) {
+	if (!type->pagesize) {
 		/* Decode parameters from extended ID */
 		nand_decode_ext_id(mtd, chip, id_data, &busw);
 	} else {
@@ -3621,7 +3773,6 @@ ident_done:
  * This is the first phase of the normal nand_scan() function. It reads the
  * flash ID and sets up MTD fields accordingly.
  *
- * The mtd->owner field must be set to the module of the caller.
  */
 int nand_scan_ident(struct mtd_info *mtd, int maxchips,
 		    struct nand_flash_dev *table)
@@ -3797,7 +3948,7 @@ int nand_scan_tail(struct mtd_info *mtd)
 			ecc->write_oob = nand_write_oob_std;
 		if (!ecc->read_subpage)
 			ecc->read_subpage = nand_read_subpage;
-		if (!ecc->write_subpage)
+		if (!ecc->write_subpage && ecc->hwctl && ecc->calculate)
 			ecc->write_subpage = nand_write_subpage_hwecc;
 
 	case NAND_ECC_HW_SYNDROME:
@@ -3875,10 +4026,8 @@ int nand_scan_tail(struct mtd_info *mtd)
 		}
 
 		/* See nand_bch_init() for details. */
-		ecc->bytes = DIV_ROUND_UP(
-				ecc->strength * fls(8 * ecc->size), 8);
-		ecc->priv = nand_bch_init(mtd, ecc->size, ecc->bytes,
-					       &ecc->layout);
+		ecc->bytes = 0;
+		ecc->priv = nand_bch_init(mtd);
 		if (!ecc->priv) {
 			pr_warn("BCH ECC initialization failed!\n");
 			BUG();
@@ -3913,11 +4062,11 @@ int nand_scan_tail(struct mtd_info *mtd)
 	 * The number of bytes available for a client to place data into
 	 * the out of band area.
 	 */
-	ecc->layout->oobavail = 0;
-	for (i = 0; ecc->layout->oobfree[i].length
-			&& i < ARRAY_SIZE(ecc->layout->oobfree); i++)
-		ecc->layout->oobavail += ecc->layout->oobfree[i].length;
-	mtd->oobavail = ecc->layout->oobavail;
+	mtd->oobavail = 0;
+	if (ecc->layout) {
+		for (i = 0; ecc->layout->oobfree[i].length; i++)
+			mtd->oobavail += ecc->layout->oobfree[i].length;
+	}
 
 	/* ECC sanity check: warn if it's too weak */
 	if (!nand_ecc_strength_good(mtd))
@@ -4002,18 +4151,6 @@ int nand_scan_tail(struct mtd_info *mtd)
 }
 EXPORT_SYMBOL(nand_scan_tail);
 
-/*
- * is_module_text_address() isn't exported, and it's mostly a pointless
- * test if this is a module _anyway_ -- they'd have to try _really_ hard
- * to call us from in-kernel code if the core NAND support is modular.
- */
-#ifdef MODULE
-#define caller_is_module() (1)
-#else
-#define caller_is_module() \
-	is_module_text_address((unsigned long)__builtin_return_address(0))
-#endif
-
 /**
  * nand_scan - [NAND Interface] Scan for the NAND device
  * @mtd: MTD device structure
@@ -4021,19 +4158,12 @@ EXPORT_SYMBOL(nand_scan_tail);
  *
  * This fills out all the uninitialized function pointers with the defaults.
  * The flash ID is read and the mtd/chip structures are filled with the
- * appropriate values. The mtd->owner field must be set to the module of the
- * caller.
+ * appropriate values.
  */
 int nand_scan(struct mtd_info *mtd, int maxchips)
 {
 	int ret;
 
-	/* Many callers got this wrong, so check for it for a while... */
-	if (!mtd->owner && caller_is_module()) {
-		pr_crit("%s called with NULL mtd->owner!\n", __func__);
-		BUG();
-	}
-
 	ret = nand_scan_ident(mtd, maxchips, NULL);
 	if (!ret)
 		ret = nand_scan_tail(mtd);
@@ -4041,9 +4171,6 @@ int nand_scan(struct mtd_info *mtd, int maxchips)
 }
 EXPORT_SYMBOL(nand_scan);
 
-module_init(nand_base_init);
-module_exit(nand_base_exit);
-
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Steven J. Hill <sjhill@realitydiluted.com>");
 MODULE_AUTHOR("Thomas Gleixner <tglx@linutronix.de>");