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

Janusz Krzysztofik
2018-07-18T23:57:05Z

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@gmail.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