[PATCH v6 1/6] net: can: flexcan: enable loopback mode in flexcan

[Pankaj Bansal <pankaj.bansal@xxxxxxx>]

Self reception disbale bit needs to be cleared for loopback mode
to work in flexcan.

Signed-off-by: Pankaj Bansal <pankaj.bansal@xxxxxxx>
---

Notes:
    V6:
    - Added comment that the self reception bit is needed for loopback mode,
      but not documented.
    V5:
    - New patch

 drivers/net/can/flexcan.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index 8ab77c583c32..297d0914303f 100644
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -933,10 +933,9 @@ static int flexcan_chip_start(struct net_device *dev)
 	 * set max mailbox number
 	 */
 	reg_mcr = priv->read(&regs->mcr);
-	reg_mcr &= ~FLEXCAN_MCR_MAXMB(0xff);
+	reg_mcr &= ~(FLEXCAN_MCR_MAXMB(0xff) | FLEXCAN_MCR_SRX_DIS);
 	reg_mcr |= FLEXCAN_MCR_FRZ | FLEXCAN_MCR_HALT | FLEXCAN_MCR_SUPV |
-		FLEXCAN_MCR_WRN_EN | FLEXCAN_MCR_SRX_DIS | FLEXCAN_MCR_IRMQ |
-		FLEXCAN_MCR_IDAM_C;
+		FLEXCAN_MCR_WRN_EN | FLEXCAN_MCR_IRMQ | FLEXCAN_MCR_IDAM_C;
 
 	if (priv->devtype_data->quirks & FLEXCAN_QUIRK_USE_OFF_TIMESTAMP) {
 		reg_mcr &= ~FLEXCAN_MCR_FEN;
@@ -945,6 +944,13 @@ static int flexcan_chip_start(struct net_device *dev)
 		reg_mcr |= FLEXCAN_MCR_FEN |
 			FLEXCAN_MCR_MAXMB(priv->tx_mb_idx);
 	}
+	/* NOTE: In loopback mode, the CAN_MCR[SRXDIS] cannot be asserted
+	 * because this will impede the self reception of a transmitted message.
+	 * This is not documented in earlier versions of flexcan block guide.
+	 */
+	if (likely(!(priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK)))
+		reg_mcr |= FLEXCAN_MCR_SRX_DIS;
+
 	netdev_dbg(dev, "%s: writing mcr=0x%08x", __func__, reg_mcr);
 	priv->write(reg_mcr, &regs->mcr);
 
-- 
2.17.1