can: sja1000: Add support for CAN_CTRLMODE_LOOPBACK

This adds support for hardware loopback in SJA1000 by utilising its self
reception request (SRR) feature. Upon SRR the message is transmitted and
received simultaneously, meaning you can't have hardware loopback
without actually sending a message to the CAN bus in case of SJA1000.

Signed-off-by: Nikita Edward Baruzdin <nebaruzdin@gmail.com>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/sja1000/sja1000.c b/drivers/net/can/sja1000/sja1000.c
index f31499a32d7dcf4fde4eb1a0864af4f15bfb6118..45400d9aeedbcffc2500026574034945d143b018 100644 (file)
--- a/drivers/net/can/sja1000/sja1000.c
+++ b/drivers/net/can/sja1000/sja1000.c
@@ -278,6 +278,7 @@ static netdev_tx_t sja1000_start_xmit(struct sk_buff *skb,
        uint8_t dlc;
        canid_t id;
        uint8_t dreg;
+       u8 cmd_reg_val = 0x00;
        int i;
 
        if (can_dropped_invalid_skb(dev, skb))
@@ -312,9 +313,14 @@ static netdev_tx_t sja1000_start_xmit(struct sk_buff *skb,
        can_put_echo_skb(skb, dev, 0);
 
        if (priv->can.ctrlmode & CAN_CTRLMODE_ONE_SHOT)
-               sja1000_write_cmdreg(priv, CMD_TR | CMD_AT);
+               cmd_reg_val |= CMD_AT;
+
+       if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK)
+               cmd_reg_val |= CMD_SRR;
        else
-               sja1000_write_cmdreg(priv, CMD_TR);
+               cmd_reg_val |= CMD_TR;
+
+       sja1000_write_cmdreg(priv, cmd_reg_val);
 
        return NETDEV_TX_OK;
 }
@@ -622,9 +628,11 @@ struct net_device *alloc_sja1000dev(int sizeof_priv)
        priv->can.do_set_bittiming = sja1000_set_bittiming;
        priv->can.do_set_mode = sja1000_set_mode;
        priv->can.do_get_berr_counter = sja1000_get_berr_counter;
-       priv->can.ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES |
-               CAN_CTRLMODE_BERR_REPORTING | CAN_CTRLMODE_LISTENONLY |
-               CAN_CTRLMODE_ONE_SHOT;
+       priv->can.ctrlmode_supported = CAN_CTRLMODE_LOOPBACK |
+                                      CAN_CTRLMODE_LISTENONLY |
+                                      CAN_CTRLMODE_3_SAMPLES |
+                                      CAN_CTRLMODE_ONE_SHOT |
+                                      CAN_CTRLMODE_BERR_REPORTING;
 
        spin_lock_init(&priv->cmdreg_lock);