mtd: cfi_cmdset_0002: Add support for writing OTP memory

This patch adds support for writing the one time programmable (OTP)
memory of Micron M29EW devices.
Signed-off-by: Christian Riesch <christian.riesch@omicron.at>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/chips/cfi_cmdset_0002.c

@@ -67,6 +67,8 @@ static int cfi_amdstd_read_fact_prot_reg(struct mtd_info *, loff_t, size_t,
 					 size_t *, u_char *);
 static int cfi_amdstd_read_user_prot_reg(struct mtd_info *, loff_t, size_t,
 					 size_t *, u_char *);
+static int cfi_amdstd_write_user_prot_reg(struct mtd_info *, loff_t, size_t,
+					  size_t *, u_char *);
 
 static int cfi_amdstd_panic_write(struct mtd_info *mtd, loff_t to, size_t len,
 				  size_t *retlen, const u_char *buf);
@@ -530,6 +532,7 @@ struct mtd_info *cfi_cmdset_0002(struct map_info *map, int primary)
 	mtd->_read_fact_prot_reg = cfi_amdstd_read_fact_prot_reg;
 	mtd->_get_fact_prot_info = cfi_amdstd_get_fact_prot_info;
 	mtd->_get_user_prot_info = cfi_amdstd_get_user_prot_info;
+	mtd->_write_user_prot_reg = cfi_amdstd_write_user_prot_reg;
 	mtd->flags   = MTD_CAP_NORFLASH;
 	mtd->name    = map->name;
 	mtd->writesize = 1;
@@ -1257,6 +1260,40 @@ static int cfi_amdstd_secsi_read (struct mtd_info *mtd, loff_t from, size_t len,
 	return ret;
 }
 
+static int __xipram do_write_oneword(struct map_info *map, struct flchip *chip,
+				     unsigned long adr, map_word datum,
+				     int mode);
+
+static int do_otp_write(struct map_info *map, struct flchip *chip, loff_t adr,
+			size_t len, u_char *buf)
+{
+	int ret;
+	while (len) {
+		unsigned long bus_ofs = adr & ~(map_bankwidth(map)-1);
+		int gap = adr - bus_ofs;
+		int n = min_t(int, len, map_bankwidth(map) - gap);
+		map_word datum;
+
+		if (n != map_bankwidth(map)) {
+			/* partial write of a word, load old contents */
+			otp_enter(map, chip, bus_ofs, map_bankwidth(map));
+			datum = map_read(map, bus_ofs);
+			otp_exit(map, chip, bus_ofs, map_bankwidth(map));
+		}
+
+		datum = map_word_load_partial(map, datum, buf, gap, n);
+		ret = do_write_oneword(map, chip, bus_ofs, datum, FL_OTP_WRITE);
+		if (ret)
+			return ret;
+
+		adr += n;
+		buf += n;
+		len -= n;
+	}
+
+	return 0;
+}
+
 static int cfi_amdstd_otp_walk(struct mtd_info *mtd, loff_t from, size_t len,
 			       size_t *retlen, u_char *buf,
 			       otp_op_t action, int user_regs)
@@ -1400,7 +1437,17 @@ static int cfi_amdstd_read_user_prot_reg(struct mtd_info *mtd, loff_t from,
 				   buf, do_read_secsi_onechip, 1);
 }
 
-static int __xipram do_write_oneword(struct map_info *map, struct flchip *chip, unsigned long adr, map_word datum)
+static int cfi_amdstd_write_user_prot_reg(struct mtd_info *mtd, loff_t from,
+					  size_t len, size_t *retlen,
+					  u_char *buf)
+{
+	return cfi_amdstd_otp_walk(mtd, from, len, retlen, buf,
+				   do_otp_write, 1);
+}
+
+static int __xipram do_write_oneword(struct map_info *map, struct flchip *chip,
+				     unsigned long adr, map_word datum,
+				     int mode)
 {
 	struct cfi_private *cfi = map->fldrv_priv;
 	unsigned long timeo = jiffies + HZ;
@@ -1421,7 +1468,7 @@ static int __xipram do_write_oneword(struct map_info *map, struct flchip *chip,
 	adr += chip->start;
 
 	mutex_lock(&chip->mutex);
-	ret = get_chip(map, chip, adr, FL_WRITING);
+	ret = get_chip(map, chip, adr, mode);
 	if (ret) {
 		mutex_unlock(&chip->mutex);
 		return ret;
@@ -1430,6 +1477,9 @@ static int __xipram do_write_oneword(struct map_info *map, struct flchip *chip,
 	pr_debug("MTD %s(): WRITE 0x%.8lx(0x%.8lx)\n",
 	       __func__, adr, datum.x[0] );
 
+	if (mode == FL_OTP_WRITE)
+		otp_enter(map, chip, adr, map_bankwidth(map));
+
 	/*
 	 * Check for a NOP for the case when the datum to write is already
 	 * present - it saves time and works around buggy chips that corrupt
@@ -1446,12 +1496,13 @@ static int __xipram do_write_oneword(struct map_info *map, struct flchip *chip,
 	XIP_INVAL_CACHED_RANGE(map, adr, map_bankwidth(map));
 	ENABLE_VPP(map);
 	xip_disable(map, chip, adr);
+
  retry:
 	cfi_send_gen_cmd(0xAA, cfi->addr_unlock1, chip->start, map, cfi, cfi->device_type, NULL);
 	cfi_send_gen_cmd(0x55, cfi->addr_unlock2, chip->start, map, cfi, cfi->device_type, NULL);
 	cfi_send_gen_cmd(0xA0, cfi->addr_unlock1, chip->start, map, cfi, cfi->device_type, NULL);
 	map_write(map, datum, adr);
-	chip->state = FL_WRITING;
+	chip->state = mode;
 
 	INVALIDATE_CACHE_UDELAY(map, chip,
 				adr, map_bankwidth(map),
@@ -1460,7 +1511,7 @@ static int __xipram do_write_oneword(struct map_info *map, struct flchip *chip,
 	/* See comment above for timeout value. */
 	timeo = jiffies + uWriteTimeout;
 	for (;;) {
-		if (chip->state != FL_WRITING) {
+		if (chip->state != mode) {
 			/* Someone's suspended the write. Sleep */
 			DECLARE_WAITQUEUE(wait, current);
 
@@ -1500,6 +1551,8 @@ static int __xipram do_write_oneword(struct map_info *map, struct flchip *chip,
 	}
 	xip_enable(map, chip, adr);
  op_done:
+	if (mode == FL_OTP_WRITE)
+		otp_exit(map, chip, adr, map_bankwidth(map));
 	chip->state = FL_READY;
 	DISABLE_VPP(map);
 	put_chip(map, chip, adr);
@@ -1555,7 +1608,7 @@ static int cfi_amdstd_write_words(struct mtd_info *mtd, loff_t to, size_t len,
 		tmp_buf = map_word_load_partial(map, tmp_buf, buf, i, n);
 
 		ret = do_write_oneword(map, &cfi->chips[chipnum],
-				       bus_ofs, tmp_buf);
+				       bus_ofs, tmp_buf, FL_WRITING);
 		if (ret)
 			return ret;
 
@@ -1579,7 +1632,7 @@ static int cfi_amdstd_write_words(struct mtd_info *mtd, loff_t to, size_t len,
 		datum = map_word_load(map, buf);
 
 		ret = do_write_oneword(map, &cfi->chips[chipnum],
-				       ofs, datum);
+				       ofs, datum, FL_WRITING);
 		if (ret)
 			return ret;
 
@@ -1622,7 +1675,7 @@ static int cfi_amdstd_write_words(struct mtd_info *mtd, loff_t to, size_t len,
 		tmp_buf = map_word_load_partial(map, tmp_buf, buf, 0, len);
 
 		ret = do_write_oneword(map, &cfi->chips[chipnum],
-				ofs, tmp_buf);
+				       ofs, tmp_buf, FL_WRITING);
 		if (ret)
 			return ret;