diff --git a/drivers/mtd/devices/mtd_dataflash.c b/drivers/mtd/devices/mtd_dataflash.c
index 8bd0dea..17c9b20 100644
--- a/drivers/mtd/devices/mtd_dataflash.c
+++ b/drivers/mtd/devices/mtd_dataflash.c
@@ -80,7 +80,8 @@
  */
 #define OP_READ_ID		0x9F
 #define OP_READ_SECURITY	0x77
-#define OP_WRITE_SECURITY	0x9A	/* OTP bits */
+#define OP_WRITE_SECURITY_REVC	0x9A
+#define OP_WRITE_SECURITY	0x9B	/* revision D */
 
 
 struct dataflash {
@@ -451,16 +452,192 @@
 
 /* ......................................................................... */
 
+#ifdef CONFIG_MTD_DATAFLASH_OTP
+
+static int dataflash_get_otp_info(struct mtd_info *mtd,
+		struct otp_info *info, size_t len)
+{
+	/* Report both blocks as identical:  bytes 0..64, locked.
+	 * Unless the user block changed from all-ones, we can't
+	 * tell whether it's still writable; so we assume it isn't.
+	 */
+	info->start = 0;
+	info->length = 64;
+	info->locked = 1;
+	return sizeof(*info);
+}
+
+static ssize_t otp_read(struct spi_device *spi, unsigned base,
+		uint8_t *buf, loff_t off, size_t len)
+{
+	struct spi_message	m;
+	size_t			l;
+	uint8_t			*scratch;
+	struct spi_transfer	t;
+	int			status;
+
+	if (off > 64)
+		return -EINVAL;
+
+	if ((off + len) > 64)
+		len = 64 - off;
+	if (len == 0)
+		return len;
+
+	spi_message_init(&m);
+
+	l = 4 + base + off + len;
+	scratch = kzalloc(l, GFP_KERNEL);
+	if (!scratch)
+		return -ENOMEM;
+
+	/* OUT: OP_READ_SECURITY, 3 don't-care bytes, zeroes
+	 * IN:  ignore 4 bytes, data bytes 0..N (max 127)
+	 */
+	scratch[0] = OP_READ_SECURITY;
+
+	memset(&t, 0, sizeof t);
+	t.tx_buf = scratch;
+	t.rx_buf = scratch;
+	t.len = l;
+	spi_message_add_tail(&t, &m);
+
+	dataflash_waitready(spi);
+
+	status = spi_sync(spi, &m);
+	if (status >= 0) {
+		memcpy(buf, scratch + 4 + base + off, len);
+		status = len;
+	}
+
+	kfree(scratch);
+	return status;
+}
+
+static int dataflash_read_fact_otp(struct mtd_info *mtd,
+		loff_t from, size_t len, size_t *retlen, u_char *buf)
+{
+	struct dataflash	*priv = (struct dataflash *)mtd->priv;
+	int			status;
+
+	/* 64 bytes, from 0..63 ... start at 64 on-chip */
+	mutex_lock(&priv->lock);
+	status = otp_read(priv->spi, 64, buf, from, len);
+	mutex_unlock(&priv->lock);
+
+	if (status < 0)
+		return status;
+	*retlen = status;
+	return 0;
+}
+
+static int dataflash_read_user_otp(struct mtd_info *mtd,
+		loff_t from, size_t len, size_t *retlen, u_char *buf)
+{
+	struct dataflash	*priv = (struct dataflash *)mtd->priv;
+	int			status;
+
+	/* 64 bytes, from 0..63 ... start at 0 on-chip */
+	mutex_lock(&priv->lock);
+	status = otp_read(priv->spi, 0, buf, from, len);
+	mutex_unlock(&priv->lock);
+
+	if (status < 0)
+		return status;
+	*retlen = status;
+	return 0;
+}
+
+static int dataflash_write_user_otp(struct mtd_info *mtd,
+		loff_t from, size_t len, size_t *retlen, u_char *buf)
+{
+	struct spi_message	m;
+	const size_t		l = 4 + 64;
+	uint8_t			*scratch;
+	struct spi_transfer	t;
+	struct dataflash	*priv = (struct dataflash *)mtd->priv;
+	int			status;
+
+	if (len > 64)
+		return -EINVAL;
+
+	/* Strictly speaking, we *could* truncate the write ... but
+	 * let's not do that for the only write that's ever possible.
+	 */
+	if ((from + len) > 64)
+		return -EINVAL;
+
+	/* OUT: OP_WRITE_SECURITY, 3 zeroes, 64 data-or-zero bytes
+	 * IN:  ignore all
+	 */
+	scratch = kzalloc(l, GFP_KERNEL);
+	if (!scratch)
+		return -ENOMEM;
+	scratch[0] = OP_WRITE_SECURITY;
+	memcpy(scratch + 4 + from, buf, len);
+
+	spi_message_init(&m);
+
+	memset(&t, 0, sizeof t);
+	t.tx_buf = scratch;
+	t.len = l;
+	spi_message_add_tail(&t, &m);
+
+	/* Write the OTP bits, if they've not yet been written.
+	 * This modifies SRAM buffer1.
+	 */
+	mutex_lock(&priv->lock);
+	dataflash_waitready(priv->spi);
+	status = spi_sync(priv->spi, &m);
+	mutex_unlock(&priv->lock);
+
+	kfree(scratch);
+
+	if (status >= 0) {
+		status = 0;
+		*retlen = len;
+	}
+	return status;
+}
+
+static char *otp_setup(struct mtd_info *device, char revision)
+{
+	device->get_fact_prot_info = dataflash_get_otp_info;
+	device->read_fact_prot_reg = dataflash_read_fact_otp;
+	device->get_user_prot_info = dataflash_get_otp_info;
+	device->read_user_prot_reg = dataflash_read_user_otp;
+
+	/* rev c parts (at45db321c and at45db1281 only!) use a
+	 * different write procedure; not (yet?) implemented.
+	 */
+	if (revision > 'c')
+		device->write_user_prot_reg = dataflash_write_user_otp;
+
+	return ", OTP";
+}
+
+#else
+
+static char *otp_setup(struct mtd_info *device)
+{
+	return " (OTP)";
+}
+
+#endif
+
+/* ......................................................................... */
+
 /*
  * Register DataFlash device with MTD subsystem.
  */
 static int __devinit
-add_dataflash(struct spi_device *spi, char *name,
-		int nr_pages, int pagesize, int pageoffset)
+add_dataflash_otp(struct spi_device *spi, char *name,
+		int nr_pages, int pagesize, int pageoffset, char revision)
 {
 	struct dataflash		*priv;
 	struct mtd_info			*device;
 	struct flash_platform_data	*pdata = spi->dev.platform_data;
+	char				*otp_tag = "";
 
 	priv = kzalloc(sizeof *priv, GFP_KERNEL);
 	if (!priv)
@@ -489,8 +666,12 @@
 	device->write = dataflash_write;
 	device->priv = priv;
 
-	dev_info(&spi->dev, "%s (%d KBytes) pagesize %d bytes\n",
-			name, DIV_ROUND_UP(device->size, 1024), pagesize);
+	if (revision >= 'c')
+		otp_tag = otp_setup(device, revision);
+
+	dev_info(&spi->dev, "%s (%d KBytes) pagesize %d bytes%s\n",
+			name, DIV_ROUND_UP(device->size, 1024),
+			pagesize, otp_tag);
 	dev_set_drvdata(&spi->dev, priv);
 
 	if (mtd_has_partitions()) {
@@ -519,6 +700,14 @@
 	return add_mtd_device(device) == 1 ? -ENODEV : 0;
 }
 
+static inline int __devinit
+add_dataflash(struct spi_device *spi, char *name,
+		int nr_pages, int pagesize, int pageoffset)
+{
+	return add_dataflash_otp(spi, name, nr_pages, pagesize,
+			pageoffset, 0);
+}
+
 struct flash_info {
 	char		*name;
 
@@ -664,13 +853,16 @@
 	 * Try to detect dataflash by JEDEC ID.
 	 * If it succeeds we know we have either a C or D part.
 	 * D will support power of 2 pagesize option.
+	 * Both support the security register, though with different
+	 * write procedures.
 	 */
 	info = jedec_probe(spi);
 	if (IS_ERR(info))
 		return PTR_ERR(info);
 	if (info != NULL)
-		return add_dataflash(spi, info->name, info->nr_pages,
-				 info->pagesize, info->pageoffset);
+		return add_dataflash_otp(spi, info->name, info->nr_pages,
+				info->pagesize, info->pageoffset,
+				(info->flags & SUP_POW2PS) ? 'd' : 'c');
 
 	/*
 	 * Older chips support only legacy commands, identifing