mtd: fsl-quadspi: return amount of data read/written or error

Return amount of data read/written or error as read(2)/write(2) does.
Signed-off-by: Michal Suchanek <hramrach@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/spi-nor/fsl-quadspi.c

@@ -618,7 +618,7 @@ static inline void fsl_qspi_invalid(struct fsl_qspi *q)
 	qspi_writel(q, reg, q->iobase + QUADSPI_MCR);
 }
 
-static int fsl_qspi_nor_write(struct fsl_qspi *q, struct spi_nor *nor,
+static ssize_t fsl_qspi_nor_write(struct fsl_qspi *q, struct spi_nor *nor,
 				u8 opcode, unsigned int to, u32 *txbuf,
 				unsigned count, size_t *retlen)
 {
@@ -647,8 +647,11 @@ static int fsl_qspi_nor_write(struct fsl_qspi *q, struct spi_nor *nor,
 	/* Trigger it */
 	ret = fsl_qspi_runcmd(q, opcode, to, count);
 
-	if (ret == 0 && retlen)
-		*retlen += count;
+	if (ret == 0) {
+		if (retlen)
+			*retlen += count;
+		return count;
+	}
 
 	return ret;
 }
@@ -860,6 +863,8 @@ static int fsl_qspi_write_reg(struct spi_nor *nor, u8 opcode, u8 *buf, int len)
 	} else if (len > 0) {
 		ret = fsl_qspi_nor_write(q, nor, opcode, 0,
 					(u32 *)buf, len, NULL);
+		if (ret > 0)
+			return 0;
 	} else {
 		dev_err(q->dev, "invalid cmd %d\n", opcode);
 		ret = -EINVAL;
@@ -873,12 +878,12 @@ static ssize_t fsl_qspi_write(struct spi_nor *nor, loff_t to,
 {
 	struct fsl_qspi *q = nor->priv;
 
-	fsl_qspi_nor_write(q, nor, nor->program_opcode, to,
+	ssize_t ret = fsl_qspi_nor_write(q, nor, nor->program_opcode, to,
 				(u32 *)buf, len, retlen);
 
 	/* invalid the data in the AHB buffer. */
 	fsl_qspi_invalid(q);
-	return 0;
+	return ret;
 }
 
 static ssize_t fsl_qspi_read(struct spi_nor *nor, loff_t from,
@@ -925,7 +930,7 @@ static ssize_t fsl_qspi_read(struct spi_nor *nor, loff_t from,
 		len);
 
 	*retlen += len;
-	return 0;
+	return len;
 }
 
 static int fsl_qspi_erase(struct spi_nor *nor, loff_t offs)