[PATCH v3 5/7] mtd: rawnand: ams-delta: Set port direction when needed

[Janusz Krzysztofik]

In its current shape, the driver sets data port direction before each
byte read/write operation, even during multi-byte transfers.  Improve
performance of the driver by setting the port direction only when
needed.

This optimisation will become particularly important as soon as
planned conversion of the driver to GPIO API for data I/O will be
implemented.

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@xxxxxxxxx>
---
 drivers/mtd/nand/raw/ams-delta.c | 59 ++++++++++++++++++++++++++++++++--------
 1 file changed, 47 insertions(+), 12 deletions(-)

diff --git a/drivers/mtd/nand/raw/ams-delta.c b/drivers/mtd/nand/raw/ams-delta.c
index 09d6901fc94d..5f9180fe4f8b 100644
--- a/drivers/mtd/nand/raw/ams-delta.c
+++ b/drivers/mtd/nand/raw/ams-delta.c
@@ -45,6 +45,7 @@ struct ams_delta_nand {
 	struct gpio_desc	*gpiod_ale;
 	struct gpio_desc	*gpiod_cle;
 	void __iomem		*io_base;
+	bool			data_in;
 };
 
 /*
@@ -72,50 +73,83 @@ static const struct mtd_partition partition_info[] = {
 	  .size		=  3 * SZ_256K },
 };
 
-static void ams_delta_write_byte(struct mtd_info *mtd, u_char byte)
+static void ams_delta_write_next_byte(struct mtd_info *mtd, u_char byte)
 {
 	struct nand_chip *this = mtd_to_nand(mtd);
 	struct ams_delta_nand *priv = nand_get_controller_data(this);
-	void __iomem *io_base = priv->io_base;
 
-	writew(0, io_base + OMAP_MPUIO_IO_CNTL);
 	writew(byte, this->IO_ADDR_W);
+
 	gpiod_set_value(priv->gpiod_nwe, 0);
 	ndelay(40);
 	gpiod_set_value(priv->gpiod_nwe, 1);
 }
 
-static u_char ams_delta_read_byte(struct mtd_info *mtd)
+static void ams_delta_write_byte(struct mtd_info *mtd, u_char byte)
 {
-	u_char res;
 	struct nand_chip *this = mtd_to_nand(mtd);
 	struct ams_delta_nand *priv = nand_get_controller_data(this);
 	void __iomem *io_base = priv->io_base;
 
+	if (priv->data_in) {
+		writew(0, io_base + OMAP_MPUIO_IO_CNTL);
+		priv->data_in = false;
+	}
+
+	ams_delta_write_next_byte(mtd, byte);
+}
+
+static u_char ams_delta_read_next_byte(struct mtd_info *mtd)
+{
+	struct nand_chip *this = mtd_to_nand(mtd);
+	struct ams_delta_nand *priv = nand_get_controller_data(this);
+	u_char res;
+
 	gpiod_set_value(priv->gpiod_nre, 0);
 	ndelay(40);
-	writew(~0, io_base + OMAP_MPUIO_IO_CNTL);
+
 	res = readw(this->IO_ADDR_R);
+
 	gpiod_set_value(priv->gpiod_nre, 1);
 
 	return res;
 }
 
+static u_char ams_delta_read_byte(struct mtd_info *mtd)
+{
+	struct nand_chip *this = mtd_to_nand(mtd);
+	struct ams_delta_nand *priv = nand_get_controller_data(this);
+	void __iomem *io_base = priv->io_base;
+
+	if (!priv->data_in) {
+		writew(~0, io_base + OMAP_MPUIO_IO_CNTL);
+		priv->data_in = true;
+	}
+
+	return ams_delta_read_next_byte(mtd);
+}
+
 static void ams_delta_write_buf(struct mtd_info *mtd, const u_char *buf,
 				int len)
 {
-	int i;
+	int i = 0;
+
+	if (len > 0)
+		ams_delta_write_byte(mtd, buf[i++]);
 
-	for (i=0; i<len; i++)
-		ams_delta_write_byte(mtd, buf[i]);
+	while (i < len)
+		ams_delta_write_next_byte(mtd, buf[i++]);
 }
 
 static void ams_delta_read_buf(struct mtd_info *mtd, u_char *buf, int len)
 {
-	int i;
+	int i = 0;
+
+	if (len > 0)
+		buf[i++] = ams_delta_read_byte(mtd);
 
-	for (i=0; i<len; i++)
-		buf[i] = ams_delta_read_byte(mtd);
+	while (i < len)
+		buf[i++] = ams_delta_read_next_byte(mtd);
 }
 
 /*
@@ -269,6 +303,7 @@ static int ams_delta_init(struct platform_device *pdev)
 		dev_err(&pdev->dev, "data GPIO request failed: %d\n", err);
 		goto out_mtd;
 	}
+	priv->data_in = true;
 
 	/* Scan to find existence of the device */
 	err = nand_scan(mtd, 1);
-- 
2.16.4