[PATCH 09/15] can: m_can: Count read getindex in the driver

[Markus Schneider-Pargmann <msp@baylibre.com>]

The getindex gets increased by one every time. We can calculate the
correct getindex in the driver and avoid the additional reads of rxfs.

Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
---
 drivers/net/can/m_can/m_can.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index 27095a7254dd..02fd7fe4e9f8 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -477,19 +477,16 @@ static void m_can_receive_skb(struct m_can_classdev *cdev,
 	}
 }
 
-static int m_can_read_fifo(struct net_device *dev, u32 rxfs)
+static int m_can_read_fifo(struct net_device *dev, u32 fgi)
 {
 	struct net_device_stats *stats = &dev->stats;
 	struct m_can_classdev *cdev = netdev_priv(dev);
 	struct canfd_frame *cf;
 	struct sk_buff *skb;
 	struct id_and_dlc fifo_header;
-	u32 fgi;
 	u32 timestamp = 0;
 	int err;
 
-	/* calculate the fifo get index for where to read data */
-	fgi = FIELD_GET(RXFS_FGI_MASK, rxfs);
 	err = m_can_fifo_read(cdev, fgi, M_CAN_FIFO_ID, &fifo_header, 2);
 	if (err)
 		goto out_fail;
@@ -554,6 +551,9 @@ static int m_can_do_rx_poll(struct net_device *dev, int quota)
 	struct m_can_classdev *cdev = netdev_priv(dev);
 	u32 pkts = 0;
 	u32 rxfs;
+	u32 rx_count;
+	u32 fgi;
+	int i;
 	int err;
 
 	rxfs = m_can_read(cdev, M_CAN_RXF0S);
@@ -562,14 +562,17 @@ static int m_can_do_rx_poll(struct net_device *dev, int quota)
 		return 0;
 	}
 
-	while ((rxfs & RXFS_FFL_MASK) && (quota > 0)) {
-		err = m_can_read_fifo(dev, rxfs);
+	rx_count = FIELD_GET(RXFS_FFL_MASK, rxfs);
+	fgi = FIELD_GET(RXFS_FGI_MASK, rxfs);
+
+	for (i = 0; i < rx_count && quota > 0; ++i) {
+		err = m_can_read_fifo(dev, fgi);
 		if (err)
 			return err;
 
 		quota--;
 		pkts++;
-		rxfs = m_can_read(cdev, M_CAN_RXF0S);
+		fgi = (++fgi >= cdev->mcfg[MRAM_RXF0].num ? 0 : fgi);
 	}
 
 	return pkts;
-- 
2.38.1