linux-kernel - [PATCH 08/18] can: m_can: Write transmit header and data in one transaction

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Message-Id: <20221221152537.751564-9-msp@baylibre.com>
Date:   Wed, 21 Dec 2022 16:25:27 +0100
From:   Markus Schneider-Pargmann <msp@...libre.com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>,
        Chandrasekar Ramakrishnan <rcsekar@...sung.com>,
        Wolfgang Grandegger <wg@...ndegger.com>
Cc:     Vincent MAILHOL <mailhol.vincent@...adoo.fr>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Markus Schneider-Pargmann <msp@...libre.com>
Subject: [PATCH 08/18] can: m_can: Write transmit header and data in one transaction

Combine header and data before writing to the transmit fifo to reduce
the overhead for peripheral chips.

Signed-off-by: Markus Schneider-Pargmann <msp@...libre.com>
---
 drivers/net/can/m_can/m_can.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index bcd3bcdc5123..9b5ad222aef7 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -1657,6 +1657,7 @@ 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];
 		/* Transmit routine for version >= v3.1.x */
 
 		txfqs = m_can_read(cdev, M_CAN_TXFQS);
@@ -1696,12 +1697,11 @@ 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(&buf[8], &cf->data, cf->len);
 
-		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, 8 + DIV_ROUND_UP(cf->len, 4));
 		if (err)
 			goto out_fail;
 
-- 
2.38.1