Merge tag 'linux-can-fixes-for-4.16-20180314' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/mkl/linux-can

Marc Kleine-Budde says:

====================
pull-request: can 2018-03-14

this is a pull request of two patches for net/master.

Both patches are by Andri Yngvason and fix problems in the cc770 driver,
that show up quite fast on RT systems, but also on non RT setups.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 65 insertions, 40 deletions

diff --git a/drivers/net/can/cc770/cc770.c b/drivers/net/can/cc770/cc770.c
index 1e37313054f3..2743d82d4424 100644
--- a/drivers/net/can/cc770/cc770.c
+++ b/drivers/net/can/cc770/cc770.c
@@ -390,37 +390,23 @@ static int cc770_get_berr_counter(const struct net_device *dev,
         return 0;
 }
 
-static netdev_tx_t cc770_start_xmit(struct sk_buff *skb, struct net_device *dev)
+static void cc770_tx(struct net_device *dev, int mo)
 {
         struct cc770_priv *priv = netdev_priv(dev);
-        struct net_device_stats *stats = &dev->stats;
-        struct can_frame *cf = (struct can_frame *)skb->data;
-        unsigned int mo = obj2msgobj(CC770_OBJ_TX);
+        struct can_frame *cf = (struct can_frame *)priv->tx_skb->data;
         u8 dlc, rtr;
         u32 id;
         int i;
 
-        if (can_dropped_invalid_skb(dev, skb))
-                return NETDEV_TX_OK;
-
-        if ((cc770_read_reg(priv,
-                            msgobj[mo].ctrl1) & TXRQST_UNC) == TXRQST_SET) {
-                netdev_err(dev, "TX register is still occupied!\n");
-                return NETDEV_TX_BUSY;
-        }
-
-        netif_stop_queue(dev);
-
         dlc = cf->can_dlc;
         id = cf->can_id;
-        if (cf->can_id & CAN_RTR_FLAG)
-                rtr = 0;
-        else
-                rtr = MSGCFG_DIR;
+        rtr = cf->can_id & CAN_RTR_FLAG ? 0 : MSGCFG_DIR;
+
+        cc770_write_reg(priv, msgobj[mo].ctrl0,
+                        MSGVAL_RES | TXIE_RES | RXIE_RES | INTPND_RES);
         cc770_write_reg(priv, msgobj[mo].ctrl1,
                         RMTPND_RES | TXRQST_RES | CPUUPD_SET | NEWDAT_RES);
-        cc770_write_reg(priv, msgobj[mo].ctrl0,
-                        MSGVAL_SET | TXIE_SET | RXIE_RES | INTPND_RES);
+
         if (id & CAN_EFF_FLAG) {
                 id &= CAN_EFF_MASK;
                 cc770_write_reg(priv, msgobj[mo].config,
@@ -439,22 +425,30 @@ static netdev_tx_t cc770_start_xmit(struct sk_buff *skb, struct net_device *dev)
         for (i = 0; i < dlc; i++)
                 cc770_write_reg(priv, msgobj[mo].data[i], cf->data[i]);
 
-        /* Store echo skb before starting the transfer */
-        can_put_echo_skb(skb, dev, 0);
-
         cc770_write_reg(priv, msgobj[mo].ctrl1,
-                        RMTPND_RES | TXRQST_SET | CPUUPD_RES | NEWDAT_UNC);
+                        RMTPND_UNC | TXRQST_SET | CPUUPD_RES | NEWDAT_UNC);
+        cc770_write_reg(priv, msgobj[mo].ctrl0,
+                        MSGVAL_SET | TXIE_SET | RXIE_SET | INTPND_UNC);
+}
 
-        stats->tx_bytes += dlc;
+static netdev_tx_t cc770_start_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+        struct cc770_priv *priv = netdev_priv(dev);
+        unsigned int mo = obj2msgobj(CC770_OBJ_TX);
 
+        if (can_dropped_invalid_skb(dev, skb))
+                return NETDEV_TX_OK;
 
-        /*
-         * HM: We had some cases of repeated IRQs so make sure the
-         * INT is acknowledged I know it's already further up, but
-         * doing again fixed the issue
-         */
-        cc770_write_reg(priv, msgobj[mo].ctrl0,
-                        MSGVAL_UNC | TXIE_UNC | RXIE_UNC | INTPND_RES);
+        netif_stop_queue(dev);
+
+        if ((cc770_read_reg(priv,
+                            msgobj[mo].ctrl1) & TXRQST_UNC) == TXRQST_SET) {
+                netdev_err(dev, "TX register is still occupied!\n");
+                return NETDEV_TX_BUSY;
+        }
+
+        priv->tx_skb = skb;
+        cc770_tx(dev, mo);
 
         return NETDEV_TX_OK;
 }
@@ -680,19 +674,47 @@ static void cc770_tx_interrupt(struct net_device *dev, unsigned int o)
         struct cc770_priv *priv = netdev_priv(dev);
         struct net_device_stats *stats = &dev->stats;
         unsigned int mo = obj2msgobj(o);
+        struct can_frame *cf;
+        u8 ctrl1;
+
+        ctrl1 = cc770_read_reg(priv, msgobj[mo].ctrl1);
 
-        /* Nothing more to send, switch off interrupts */
         cc770_write_reg(priv, msgobj[mo].ctrl0,
                         MSGVAL_RES | TXIE_RES | RXIE_RES | INTPND_RES);
-        /*
-         * We had some cases of repeated IRQ so make sure the
-         * INT is acknowledged
+        cc770_write_reg(priv, msgobj[mo].ctrl1,
+                        RMTPND_RES | TXRQST_RES | MSGLST_RES | NEWDAT_RES);
+
+        if (unlikely(!priv->tx_skb)) {
+                netdev_err(dev, "missing tx skb in tx interrupt\n");
+                return;
+        }
+
+        if (unlikely(ctrl1 & MSGLST_SET)) {
+                stats->rx_over_errors++;
+                stats->rx_errors++;
+        }
+
+        /* When the CC770 is sending an RTR message and it receives a regular
+         * message that matches the id of the RTR message, it will overwrite the
+         * outgoing message in the TX register. When this happens we must
+         * process the received message and try to transmit the outgoing skb
+         * again.
          */
-        cc770_write_reg(priv, msgobj[mo].ctrl0,
-                        MSGVAL_UNC | TXIE_UNC | RXIE_UNC | INTPND_RES);
+        if (unlikely(ctrl1 & NEWDAT_SET)) {
+                cc770_rx(dev, mo, ctrl1);
+                cc770_tx(dev, mo);
+                return;
+        }
 
-        stats->tx_packets++;
+        can_put_echo_skb(priv->tx_skb, dev, 0);
         can_get_echo_skb(dev, 0);
+
+        cf = (struct can_frame *)priv->tx_skb->data;
+        stats->tx_bytes += cf->can_dlc;
+        stats->tx_packets++;
+
+        priv->tx_skb = NULL;
+
         netif_wake_queue(dev);
 }
 
@@ -804,6 +826,7 @@ struct net_device *alloc_cc770dev(int sizeof_priv)
         priv->can.do_set_bittiming = cc770_set_bittiming;
         priv->can.do_set_mode = cc770_set_mode;
         priv->can.ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES;
+        priv->tx_skb = NULL;
 
         memcpy(priv->obj_flags, cc770_obj_flags, sizeof(cc770_obj_flags));
 
diff --git a/drivers/net/can/cc770/cc770.h b/drivers/net/can/cc770/cc770.h
index a1739db98d91..95752e1d1283 100644
--- a/drivers/net/can/cc770/cc770.h
+++ b/drivers/net/can/cc770/cc770.h
@@ -193,6 +193,8 @@ struct cc770_priv {
         u8 cpu_interface;       /* CPU interface register */
         u8 clkout;              /* Clock out register */
         u8 bus_config;          /* Bus conffiguration register */
+
+        struct sk_buff *tx_skb;
 };
 
 struct net_device *alloc_cc770dev(int sizeof_priv);