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

Message ID 20180806222918.12644-8-jmkrzyszt@gmail.com
State New
Headers show
Series
  • [RFC,v2,01/12] mtd: rawnand: ams-delta: Assign mtd->dev.parent, not mtd->owner
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Commit Message

Janusz Krzysztofik Aug. 6, 2018, 10:29 p.m.
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(-)

Comments

Boris Brezillon Aug. 7, 2018, 6:57 p.m. | #1
On Tue,  7 Aug 2018 00:29:13 +0200
Janusz Krzysztofik <jmkrzyszt@gmail.com> wrote:

> 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);
>  }

I'd suggest a slightly different approach where the data pins
direction state is stored in the the priv struct and only changed when
required. This way you just have to add a test in
ams_delta_read/write_byte().
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Janusz Krzysztofik Aug. 8, 2018, 4:55 p.m. | #2
Hi Boris,

On Tuesday, August 7, 2018 8:57:52 PM CEST Boris Brezillon wrote:
> On Tue,  7 Aug 2018 00:29:13 +0200
> Janusz Krzysztofik <jmkrzyszt@gmail.com> wrote:
> 
> > 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.
> ...
> I'd suggest a slightly different approach where the data pins
> direction state is stored in the the priv struct and only changed when
> required. This way you just have to add a test in
> ams_delta_read/write_byte().

Good idea, I'm going to use it, thanks.

Once done, may I also move that one earlier in the series so that it can be 
applied while our discussion on GPIO bitmap changes still continues?

Thanks,
Janusz




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Miquel Raynal Aug. 8, 2018, 5:42 p.m. | #3
Hi Janusz,

Janusz Krzysztofik <jmkrzyszt@gmail.com> wrote on Wed, 08 Aug 2018
18:55:35 +0200:

> Hi Boris,
> 
> On Tuesday, August 7, 2018 8:57:52 PM CEST Boris Brezillon wrote:
> > On Tue,  7 Aug 2018 00:29:13 +0200
> > Janusz Krzysztofik <jmkrzyszt@gmail.com> wrote:
> >   
> > > 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.  
> > ...
> > I'd suggest a slightly different approach where the data pins
> > direction state is stored in the the priv struct and only changed when
> > required. This way you just have to add a test in
> > ams_delta_read/write_byte().  
> 
> Good idea, I'm going to use it, thanks.
> 
> Once done, may I also move that one earlier in the series so that it can be 
> applied while our discussion on GPIO bitmap changes still continues?

I think I may answer on his behalf: yes! You can move the GPIO bitmap
changes at the end of the series, checking that you never break the
bisectability. Then I could apply the major changes and let us iterate
on the GPIO bitmap stuff only.

Thanks,
Miquèl
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Patch

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);
 }
 
 /*