[PATCH 11/15] can: m_can: Batch acknowledge transmit events

[Markus Schneider-Pargmann]

Transmit events from the txe fifo can be batch acknowledged by
acknowledging the last read txe fifo item. This will save txe_count
writes which is important for peripheral chips.

Signed-off-by: Markus Schneider-Pargmann <msp@xxxxxxxxxxxx>
---
 drivers/net/can/m_can/m_can.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index 6179b9e815ed..347ba8e7d1b3 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -1019,7 +1019,9 @@ static int m_can_echo_tx_event(struct net_device *dev)
 	u32 txe_count = 0;
 	u32 m_can_txefs;
 	u32 fgi = 0;
+	int ack_fgi = -1;
 	int i = 0;
+	int err = 0;
 	unsigned int msg_mark;
 
 	struct m_can_classdev *cdev = netdev_priv(dev);
@@ -1034,21 +1036,18 @@ static int m_can_echo_tx_event(struct net_device *dev)
 	/* Get and process all sent elements */
 	for (i = 0; i < txe_count; i++) {
 		u32 txe, timestamp = 0;
-		int err;
 
 		/* get message marker, timestamp */
 		err = m_can_txe_fifo_read(cdev, fgi, 4, &txe);
 		if (err) {
 			netdev_err(dev, "TXE FIFO read returned %d\n", err);
-			return err;
+			break;
 		}
 
 		msg_mark = FIELD_GET(TX_EVENT_MM_MASK, txe);
 		timestamp = FIELD_GET(TX_EVENT_TXTS_MASK, txe) << 16;
 
-		/* ack txe element */
-		m_can_write(cdev, M_CAN_TXEFA, FIELD_PREP(TXEFA_EFAI_MASK,
-							  fgi));
+		ack_fgi = fgi;
 		fgi = (++fgi >= cdev->mcfg[MRAM_TXE].num ? 0 : fgi);
 		--cdev->tx_fifo_in_flight;
 
@@ -1056,7 +1055,11 @@ static int m_can_echo_tx_event(struct net_device *dev)
 		m_can_tx_update_stats(cdev, msg_mark, timestamp);
 	}
 
-	return 0;
+	if (ack_fgi != -1)
+		m_can_write(cdev, M_CAN_TXEFA, FIELD_PREP(TXEFA_EFAI_MASK,
+							  ack_fgi));
+
+	return err;
 }
 
 static irqreturn_t m_can_isr(int irq, void *dev_id)
-- 
2.38.1