diff mbox series

[v3,06/16] can: m_can: Write transmit header and data in one transaction

Message ID 20230315110546.2518305-7-msp@baylibre.com
State New
Headers
Series can: m_can: Optimizations for m_can/tcan part 2 |

Commit Message

Markus Schneider-Pargmann March 15, 2023, 11:05 a.m. UTC 
  Combine header and data before writing to the transmit fifo to reduce
the overhead for peripheral chips.

Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
---
 drivers/net/can/m_can/m_can.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

Comments

Simon Horman March 16, 2023, 9:27 a.m. UTC | #1 
On Wed, Mar 15, 2023 at 12:05:36PM +0100, Markus Schneider-Pargmann wrote:
> Combine header and data before writing to the transmit fifo to reduce
> the overhead for peripheral chips.
> 
> Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>

Thanks for addressing my comments on v2.

> ---
>  drivers/net/can/m_can/m_can.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> index a5003435802b..35a2332464e5 100644
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -1681,6 +1681,8 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
>  		m_can_write(cdev, M_CAN_TXBAR, 0x1);
>  		/* End of xmit function for version 3.0.x */
>  	} else {
> +		char buf[TXB_ELEMENT_SIZE];
> +		u8 len_padded = DIV_ROUND_UP(cf->len, 4);
>  		/* Transmit routine for version >= v3.1.x */
>  
>  		txfqs = m_can_read(cdev, M_CAN_TXFQS);
> @@ -1720,12 +1722,11 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
>  		fifo_header.dlc = FIELD_PREP(TX_BUF_MM_MASK, putidx) |
>  			FIELD_PREP(TX_BUF_DLC_MASK, can_fd_len2dlc(cf->len)) |
>  			fdflags | TX_BUF_EFC;
> -		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_ID, &fifo_header, 2);
> -		if (err)
> -			goto out_fail;
> +		memcpy(buf, &fifo_header, 8);
> +		memcpy_and_pad(&buf[8], len_padded, &cf->data, cf->len, 0);

I'm probably missing something obvious here but I'm seeing:

* len_padded is the number of 4-byte words
* but the 2nd argument to memcpy_and_pad should be a length in bytes
* so perhaps it should be: len_padded * 4

>  
> -		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_DATA,
> -				       cf->data, DIV_ROUND_UP(cf->len, 4));
> +		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_ID,
> +				       buf, 2 + len_padded);

This part looks good to me :)

>  		if (err)
>  			goto out_fail;
>  
> -- 
> 2.39.2
>
Marc Kleine-Budde March 24, 2023, 6:32 p.m. UTC | #2 
On 15.03.2023 12:05:36, Markus Schneider-Pargmann wrote:
> Combine header and data before writing to the transmit fifo to reduce
> the overhead for peripheral chips.
> 
> Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> ---
>  drivers/net/can/m_can/m_can.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> index a5003435802b..35a2332464e5 100644
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -1681,6 +1681,8 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
>  		m_can_write(cdev, M_CAN_TXBAR, 0x1);
>  		/* End of xmit function for version 3.0.x */
>  	} else {
> +		char buf[TXB_ELEMENT_SIZE];

Can you create a proper struct that describes a single FIFO entry (id,
dlc, data)? Use that struct instead of the struct id_and_dlc
fifo_header.

> +		u8 len_padded = DIV_ROUND_UP(cf->len, 4);
>  		/* Transmit routine for version >= v3.1.x */
>  
>  		txfqs = m_can_read(cdev, M_CAN_TXFQS);
> @@ -1720,12 +1722,11 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
>  		fifo_header.dlc = FIELD_PREP(TX_BUF_MM_MASK, putidx) |
>  			FIELD_PREP(TX_BUF_DLC_MASK, can_fd_len2dlc(cf->len)) |
>  			fdflags | TX_BUF_EFC;
> -		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_ID, &fifo_header, 2);
> -		if (err)
> -			goto out_fail;
> +		memcpy(buf, &fifo_header, 8);
> +		memcpy_and_pad(&buf[8], len_padded, &cf->data, cf->len, 0);
>  
> -		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_DATA,
> -				       cf->data, DIV_ROUND_UP(cf->len, 4));
> +		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_ID,
> +				       buf, 2 + len_padded);
>  		if (err)
>  			goto out_fail;

Marc
Markus Schneider-Pargmann June 19, 2023, 11:46 a.m. UTC | #3 
Hi Simon,

On Thu, Mar 16, 2023 at 10:27:41AM +0100, Simon Horman wrote:
> On Wed, Mar 15, 2023 at 12:05:36PM +0100, Markus Schneider-Pargmann wrote:
> > Combine header and data before writing to the transmit fifo to reduce
> > the overhead for peripheral chips.
> > 
> > Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> 
> Thanks for addressing my comments on v2.
> 
> > ---
> >  drivers/net/can/m_can/m_can.c | 11 ++++++-----
> >  1 file changed, 6 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> > index a5003435802b..35a2332464e5 100644
> > --- a/drivers/net/can/m_can/m_can.c
> > +++ b/drivers/net/can/m_can/m_can.c
> > @@ -1681,6 +1681,8 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
> >  		m_can_write(cdev, M_CAN_TXBAR, 0x1);
> >  		/* End of xmit function for version 3.0.x */
> >  	} else {
> > +		char buf[TXB_ELEMENT_SIZE];
> > +		u8 len_padded = DIV_ROUND_UP(cf->len, 4);
> >  		/* Transmit routine for version >= v3.1.x */
> >  
> >  		txfqs = m_can_read(cdev, M_CAN_TXFQS);
> > @@ -1720,12 +1722,11 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
> >  		fifo_header.dlc = FIELD_PREP(TX_BUF_MM_MASK, putidx) |
> >  			FIELD_PREP(TX_BUF_DLC_MASK, can_fd_len2dlc(cf->len)) |
> >  			fdflags | TX_BUF_EFC;
> > -		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_ID, &fifo_header, 2);
> > -		if (err)
> > -			goto out_fail;
> > +		memcpy(buf, &fifo_header, 8);
> > +		memcpy_and_pad(&buf[8], len_padded, &cf->data, cf->len, 0);
> 
> I'm probably missing something obvious here but I'm seeing:
> 
> * len_padded is the number of 4-byte words
> * but the 2nd argument to memcpy_and_pad should be a length in bytes
> * so perhaps it should be: len_padded * 4

Thank you Simon for all the reviews, finally some time to continue on
this:

Thanks for pointing this out. I updated my script used for testing so I
catch something like this the next time. I will be using
TXB_ELEMENT_SIZE - 8 to reflect the buffer size and the 8 byte offset.

Best,
Markus

> 
> >  
> > -		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_DATA,
> > -				       cf->data, DIV_ROUND_UP(cf->len, 4));
> > +		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_ID,
> > +				       buf, 2 + len_padded);
> 
> This part looks good to me :)
> 
> >  		if (err)
> >  			goto out_fail;
> >  
> > -- 
> > 2.39.2
> >
diff mbox series

Patch

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index a5003435802b..35a2332464e5 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -1681,6 +1681,8 @@  static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
 		m_can_write(cdev, M_CAN_TXBAR, 0x1);
 		/* End of xmit function for version 3.0.x */
 	} else {
+		char buf[TXB_ELEMENT_SIZE];
+		u8 len_padded = DIV_ROUND_UP(cf->len, 4);
 		/* Transmit routine for version >= v3.1.x */
 
 		txfqs = m_can_read(cdev, M_CAN_TXFQS);
@@ -1720,12 +1722,11 @@  static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
 		fifo_header.dlc = FIELD_PREP(TX_BUF_MM_MASK, putidx) |
 			FIELD_PREP(TX_BUF_DLC_MASK, can_fd_len2dlc(cf->len)) |
 			fdflags | TX_BUF_EFC;
-		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_ID, &fifo_header, 2);
-		if (err)
-			goto out_fail;
+		memcpy(buf, &fifo_header, 8);
+		memcpy_and_pad(&buf[8], len_padded, &cf->data, cf->len, 0);
 
-		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_DATA,
-				       cf->data, DIV_ROUND_UP(cf->len, 4));
+		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_ID,
+				       buf, 2 + len_padded);
 		if (err)
 			goto out_fail;