linux-kernel - [RFC PATCH 3/8] mtd: rawnand: ams-delta: Set port direction once per transfer

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Date:   Thu, 19 Jul 2018 01:57:05 +0200
From:   Janusz Krzysztofik <jmkrzyszt@...il.com>
To:     Boris Brezillon <boris.brezillon@...tlin.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Tony Lindgren <tony@...mide.com>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        linux-mtd@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-omap@...r.kernel.org,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
        Janusz Krzysztofik <jmkrzyszt@...il.com>
Subject: [RFC PATCH 3/8] mtd: rawnand: ams-delta: Set port direction once per transfer

In its current shape, the driver sets data port direction before each
byte read/write operation, even during multi-byte transfers.  Optimize
that by setting the port direction only on first byte of each transfer.

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@...il.com>
---
 drivers/mtd/nand/raw/ams-delta.c | 42 ++++++++++++++++++++++++++++++----------
 1 file changed, 32 insertions(+), 10 deletions(-)

diff --git a/drivers/mtd/nand/raw/ams-delta.c b/drivers/mtd/nand/raw/ams-delta.c
index 6ac38e9cfa1a..dfefcd79b420 100644
--- a/drivers/mtd/nand/raw/ams-delta.c
+++ b/drivers/mtd/nand/raw/ams-delta.c
@@ -72,50 +72,72 @@ 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;
 
+	writew(0, io_base + OMAP_MPUIO_IO_CNTL);
+
+	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;
+
+	writew(~0, io_base + OMAP_MPUIO_IO_CNTL);
+
+	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;
 
-	for (i=0; i<len; i++)
-		ams_delta_write_byte(mtd, buf[i]);
+	if (len > 0)
+		ams_delta_write_byte(mtd, buf[0]);
+	for (i = 1; i < len; i++)
+		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;
 
-	for (i=0; i<len; i++)
-		buf[i] = ams_delta_read_byte(mtd);
+	if (len > 0)
+		buf[0] = ams_delta_read_byte(mtd);
+	for (i = 1; i < len; i++)
+		buf[i] = ams_delta_read_next_byte(mtd);
 }
 
 /*
-- 
2.16.4