[MTD] dataflash OTP support

Now that we can tell when we have one of the newer DataFlash chips,
optionally expose the 128 bytes of OTP memory they provide.  Tested
on at45db642 revision B and D chips.

Switch mtdchar over to a generic HAVE_MTD_OTP flag instead of adding
another #ifdef for each type of chip whose driver has OTP support.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Bryan Wu <cooloney@kernel.org>
Cc: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

2 files changed, 210 insertions, 7 deletions

diff --git a/drivers/mtd/devices/Kconfig b/drivers/mtd/devices/Kconfig
index 9c613f06623..88f4df04746 100644
--- a/drivers/mtd/devices/Kconfig
+++ b/drivers/mtd/devices/Kconfig
@@ -59,6 +59,17 @@ config MTD_DATAFLASH
 	  Sometimes DataFlash chips are packaged inside MMC-format
 	  cards; at this writing, the MMC stack won't handle those.
 
+config MTD_DATAFLASH_OTP
+	bool "DataFlash OTP support (Security Register)"
+	depends on MTD_DATAFLASH
+	select HAVE_MTD_OTP
+	help
+	  Newer DataFlash chips (revisions C and D) support 128 bytes of
+	  one-time-programmable (OTP) data.  The first half may be written
+	  (once) with up to 64 bytes of data, such as a serial number or
+	  other key product data.  The second half is programmed with a
+	  unique-to-each-chip bit pattern at the factory.
+
 config MTD_M25P80
 	tristate "Support most SPI Flash chips (AT26DF, M25P, W25X, ...)"
 	depends on SPI_MASTER && EXPERIMENTAL
diff --git a/drivers/mtd/devices/mtd_dataflash.c b/drivers/mtd/devices/mtd_dataflash.c
index 8bd0dea6885..17c9b20dca8 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 @@ static int dataflash_write(struct mtd_info *mtd, loff_t to, size_t len,
 
 /* ......................................................................... */
 
+#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 @@ add_dataflash(struct spi_device *spi, char *name,
 	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 @@ add_dataflash(struct spi_device *spi, char *name,
 	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 @@ static int __devinit dataflash_probe(struct spi_device *spi)
 	 * 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