[RFC PATCH v2 07/12] mtd: rawnand: ams-delta: Set port direction once per transfer

Janusz Krzysztofik
2018-08-06T22:29:13Z

In its current shape, the driver sets data port direction before each
byte read/write operation, even during multi-byte transfers. Since
performance of the driver is completely not acceptable on Amstrad Delta
after it has been converted to GPIO bitbang, try to improve things a
bit by setting the port direction only on first byte of each transfer.

Resulting performance on Amstrad Delta is still far from acceptable.

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
---
drivers/mtd/nand/raw/ams-delta.c | 58 ++++++++++++++++++++++++++++++++--------
1 file changed, 47 insertions(+), 11 deletions(-)

diff --git a/drivers/mtd/nand/raw/ams-delta.c b/drivers/mtd/nand/raw/ams-delta.c
index 78996ddf82e0..d02c48c013e8 100644
--- a/drivers/mtd/nand/raw/ams-delta.c
+++ b/drivers/mtd/nand/raw/ams-delta.c
@@ -69,6 +69,30 @@ static const struct mtd_partition partition_info[] = {
.size = 3 * SZ_256K },
};

+static void ams_delta_write_commit(struct ams_delta_nand *priv)
+{
+ gpiod_set_value(priv->gpiod_nwe, 0);
+ ndelay(40);
+ gpiod_set_value(priv->gpiod_nwe, 1);
+}
+
+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);
+ struct gpio_descs *data_gpiods = priv->data_gpiods;
+ unsigned long bits = byte;
+ int i, value_array[data_gpiods->ndescs];
+
+ for (i = 0; i < data_gpiods->ndescs; i++)
+ value_array[i] = test_bit(i, &bits);
+
+ gpiod_set_raw_array_value(data_gpiods->ndescs, data_gpiods->desc,
+ value_array);
+
+ ams_delta_write_commit(priv);
+}
+
static void ams_delta_write_byte(struct mtd_info *mtd, u_char byte)
{
struct nand_chip *this = mtd_to_nand(mtd);
@@ -81,12 +105,10 @@ static void ams_delta_write_byte(struct mtd_info *mtd, u_char byte)
gpiod_direction_output_raw(data_gpiods->desc[i],
test_bit(i, &bits));

- gpiod_set_value(priv->gpiod_nwe, 0);
- ndelay(40);
- gpiod_set_value(priv->gpiod_nwe, 1);
+ ams_delta_write_commit(priv);
}

-static u_char ams_delta_read_byte(struct mtd_info *mtd)
+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);
@@ -94,9 +116,6 @@ static u_char ams_delta_read_byte(struct mtd_info *mtd)
unsigned long bits = 0;
int i, value_array[data_gpiods->ndescs];

- for (i = 0; i < data_gpiods->ndescs; i++)
- gpiod_direction_input(data_gpiods->desc[i]);
-
gpiod_set_value(priv->gpiod_nre, 0);
ndelay(40);

@@ -112,21 +131,38 @@ static u_char ams_delta_read_byte(struct mtd_info *mtd)
return bits;
}

+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);
+ struct gpio_descs *data_gpiods = priv->data_gpiods;
+ int i;
+
+ for (i = 0; i < data_gpiods->ndescs; i++)
+ gpiod_direction_input(data_gpiods->desc[i]);
+
+ 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