mtd: spi-nor: Prepare the introduction of a new locking mechanism

This commit alone just introduces two new "prepare and lock" pairs of
helpers which do the exact same thing as before. They will soon be
improved in a followup commit which actually brings the logic, but I
figured out it was more readable to do it this way.

One new pair is suffixed _pe which stands for "program and erase" and
hence is being called by spi_nor_write() and spi_nor_erase().

The other pair is suffixed _rd which stands for "read" and hence is
being called by spi_nor_read().

One note however, these extra helpers will need to know the operation
range, so they come with two new parameters to define it. Otherwise
there is no functional change.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20230328154105.448540-6-miquel.raynal@bootlin.comSigned-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>

drivers/mtd/spi-nor/core.c

@@ -1086,6 +1086,7 @@ static void spi_nor_unprep(struct spi_nor *nor)
 		nor->controller_ops->unprepare(nor);
 }
 
+/* Generic helpers for internal locking and serialization */
 int spi_nor_prep_and_lock(struct spi_nor *nor)
 {
 	int ret;
@@ -1106,6 +1107,48 @@ void spi_nor_unlock_and_unprep(struct spi_nor *nor)
 	spi_nor_unprep(nor);
 }
 
+/* Internal locking helpers for program and erase operations */
+static int spi_nor_prep_and_lock_pe(struct spi_nor *nor, loff_t start, size_t len)
+{
+	int ret;
+
+	ret = spi_nor_prep(nor);
+	if (ret)
+		return ret;
+
+	mutex_lock(&nor->lock);
+
+	return 0;
+}
+
+static void spi_nor_unlock_and_unprep_pe(struct spi_nor *nor, loff_t start, size_t len)
+{
+	mutex_unlock(&nor->lock);
+
+	spi_nor_unprep(nor);
+}
+
+/* Internal locking helpers for read operations */
+static int spi_nor_prep_and_lock_rd(struct spi_nor *nor, loff_t start, size_t len)
+{
+	int ret;
+
+	ret = spi_nor_prep(nor);
+	if (ret)
+		return ret;
+
+	mutex_lock(&nor->lock);
+
+	return 0;
+}
+
+static void spi_nor_unlock_and_unprep_rd(struct spi_nor *nor, loff_t start, size_t len)
+{
+	mutex_unlock(&nor->lock);
+
+	spi_nor_unprep(nor);
+}
+
 static u32 spi_nor_convert_addr(struct spi_nor *nor, loff_t addr)
 {
 	if (!nor->params->convert_addr)
@@ -1459,7 +1502,7 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
 	addr = instr->addr;
 	len = instr->len;
 
-	ret = spi_nor_prep_and_lock(nor);
+	ret = spi_nor_prep_and_lock_pe(nor, instr->addr, instr->len);
 	if (ret)
 		return ret;
 
@@ -1522,7 +1565,7 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
 	ret = spi_nor_write_disable(nor);
 
 erase_err:
-	spi_nor_unlock_and_unprep(nor);
+	spi_nor_unlock_and_unprep_pe(nor, instr->addr, instr->len);
 
 	return ret;
 }
@@ -1715,11 +1758,13 @@ static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len,
 			size_t *retlen, u_char *buf)
 {
 	struct spi_nor *nor = mtd_to_spi_nor(mtd);
+	loff_t from_lock = from;
+	size_t len_lock = len;
 	ssize_t ret;
 
 	dev_dbg(nor->dev, "from 0x%08x, len %zd\n", (u32)from, len);
 
-	ret = spi_nor_prep_and_lock(nor);
+	ret = spi_nor_prep_and_lock_rd(nor, from_lock, len_lock);
 	if (ret)
 		return ret;
 
@@ -1746,7 +1791,8 @@ static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len,
 	ret = 0;
 
 read_err:
-	spi_nor_unlock_and_unprep(nor);
+	spi_nor_unlock_and_unprep_rd(nor, from_lock, len_lock);
+
 	return ret;
 }
 
@@ -1765,7 +1811,7 @@ static int spi_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
 
 	dev_dbg(nor->dev, "to 0x%08x, len %zd\n", (u32)to, len);
 
-	ret = spi_nor_prep_and_lock(nor);
+	ret = spi_nor_prep_and_lock_pe(nor, to, len);
 	if (ret)
 		return ret;
 
@@ -1807,7 +1853,8 @@ static int spi_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
 	}
 
 write_err:
-	spi_nor_unlock_and_unprep(nor);
+	spi_nor_unlock_and_unprep_pe(nor, to, len);
+
 	return ret;
 }