Commit 812270e5 authored by Matt Kline's avatar Matt Kline Committed by Marc Kleine-Budde
Browse files

can: m_can: Batch FIFO writes during CAN transmit 

Give FIFO writes the same treatment as reads to avoid fixed costs of
individual transfers on a slow bus (e.g., tcan4x5x).

Link: https://lore.kernel.org/r/20210817050853.14875-4-matt@bitbashing.io


Signed-off-by: default avatarMatt Kline <matt@bitbashing.io>
Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
parent 1aa6772f

drivers/net/can/m_can/m_can.c

+26 −35
Original line number Diff line number Diff line
@@ -279,7 +279,7 @@ enum m_can_reg { 
/* Message RAM Elements */

#define M_CAN_FIFO_ID		0x0

#define M_CAN_FIFO_DLC		0x4

#define M_CAN_FIFO_DATA(n)	(0x8 + ((n) << 2))

#define M_CAN_FIFO_DATA		0x8



/* Rx Buffer Element */

/* R0 */
@@ -514,7 +514,7 @@ static int m_can_read_fifo(struct net_device *dev, u32 rxfs) 
		if (fifo_header.dlc & RX_BUF_BRS)

			cf->flags |= CANFD_BRS;



		err = m_can_fifo_read(cdev, fgi, M_CAN_FIFO_DATA(0),

		err = m_can_fifo_read(cdev, fgi, M_CAN_FIFO_DATA,

				      cf->data, DIV_ROUND_UP(cf->len, 4));

		if (err)

			goto out_fail;
@@ -1588,8 +1588,9 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev) 
	struct canfd_frame *cf = (struct canfd_frame *)cdev->tx_skb->data;

	struct net_device *dev = cdev->net;

	struct sk_buff *skb = cdev->tx_skb;

	u32 id, dlc, cccr, fdflags;

	int i, err;

	struct id_and_dlc fifo_header;

	u32 cccr, fdflags;

	int err;

	int putidx;



	cdev->tx_skb = NULL;
@@ -1597,33 +1598,29 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev) 
	/* Generate ID field for TX buffer Element */

	/* Common to all supported M_CAN versions */

	if (cf->can_id & CAN_EFF_FLAG) {

		id = cf->can_id & CAN_EFF_MASK;

		id |= TX_BUF_XTD;

		fifo_header.id = cf->can_id & CAN_EFF_MASK;

		fifo_header.id |= TX_BUF_XTD;

	} else {

		id = ((cf->can_id & CAN_SFF_MASK) << 18);

		fifo_header.id = ((cf->can_id & CAN_SFF_MASK) << 18);

	}



	if (cf->can_id & CAN_RTR_FLAG)

		id |= TX_BUF_RTR;

		fifo_header.id |= TX_BUF_RTR;



	if (cdev->version == 30) {

		netif_stop_queue(dev);



		/* message ram configuration */

		err = m_can_fifo_write(cdev, 0, M_CAN_FIFO_ID, &id, 1);

		if (err)

			goto out_fail;

		fifo_header.dlc = can_fd_len2dlc(cf->len) << 16;



		dlc = can_fd_len2dlc(cf->len) << 16;

		err = m_can_fifo_write(cdev, 0, M_CAN_FIFO_DLC, &dlc, 1);

		/* Write the frame ID, DLC, and payload to the FIFO element. */

		err = m_can_fifo_write(cdev, 0, M_CAN_FIFO_ID, &fifo_header, 2);

		if (err)

			goto out_fail;



		for (i = 0; i < cf->len; i += 4) {

			err = m_can_fifo_write(cdev, 0, M_CAN_FIFO_DATA(i / 4), cf->data + i, 1);

		err = m_can_fifo_write(cdev, 0, M_CAN_FIFO_DATA,

				       cf->data, DIV_ROUND_UP(cf->len, 4));

		if (err)

			goto out_fail;

		}



		can_put_echo_skb(skb, dev, 0, 0);
@@ -1667,10 +1664,11 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev) 
		/* get put index for frame */

		putidx = FIELD_GET(TXFQS_TFQPI_MASK,

				   m_can_read(cdev, M_CAN_TXFQS));

		/* Write ID Field to FIFO Element */

		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_ID, &id, 1);

		if (err)

			goto out_fail;



		/* Construct DLC Field, with CAN-FD configuration.

		 * Use the put index of the fifo as the message marker,

		 * used in the TX interrupt for sending the correct echo frame.

		 */



		/* get CAN FD configuration of frame */

		fdflags = 0;
@@ -1680,24 +1678,17 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev) 
				fdflags |= TX_BUF_BRS;

		}



		/* Construct DLC Field. Also contains CAN-FD configuration

		 * use put index of fifo as message marker

		 * it is used in TX interrupt for

		 * sending the correct echo frame

		 */

		dlc = FIELD_PREP(TX_BUF_MM_MASK, putidx) |

		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_DLC, &dlc, 1);

		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_ID, &fifo_header, 2);

		if (err)

			goto out_fail;



		for (i = 0; i < cf->len; i += 4) {

			err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_DATA(i / 4),

					       cf->data + i, 1);

		err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_DATA,

				       cf->data, DIV_ROUND_UP(cf->len, 4));

		if (err)

			goto out_fail;

		}



		/* Push loopback echo.

		 * Will be looped back on TX interrupt based on message marker