can: ti_hecc: add fifo overflow error reporting

When the rx FIFO overflows the ti_hecc would silently drop them since
the overwrite protection is enabled for all mailboxes. So disable it for
the lowest priority mailbox and return a proper error value when receive
message lost is set. Drop the message itself in that case, since it
might be partially updated.

Signed-off-by: Jeroen Hofstee <jhofstee@victronenergy.com>
Acked-by: Jeroen Hofstee <jhofstee@victronenergy.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/ti_hecc.c b/drivers/net/can/ti_hecc.c
index 6ea29126c60be03f59ce3b8b10c70f9d7bcfbeae..b12fd0bd489d6d5a894a3c578344c7cdecec6f0a 100644 (file)
--- a/drivers/net/can/ti_hecc.c
+++ b/drivers/net/can/ti_hecc.c
@@ -73,6 +73,7 @@ MODULE_VERSION(HECC_MODULE_VERSION);
  */
 #define HECC_MAX_RX_MBOX       (HECC_MAX_MAILBOXES - HECC_MAX_TX_MBOX)
 #define HECC_RX_FIRST_MBOX     (HECC_MAX_MAILBOXES - 1)
+#define HECC_RX_LAST_MBOX      (HECC_MAX_TX_MBOX)
 
 /* TI HECC module registers */
 #define HECC_CANME             0x0     /* Mailbox enable */
@@ -82,7 +83,7 @@ MODULE_VERSION(HECC_MODULE_VERSION);
 #define HECC_CANTA             0x10    /* Transmission acknowledge */
 #define HECC_CANAA             0x14    /* Abort acknowledge */
 #define HECC_CANRMP            0x18    /* Receive message pending */
-#define HECC_CANRML            0x1C    /* Remote message lost */
+#define HECC_CANRML            0x1C    /* Receive message lost */
 #define HECC_CANRFP            0x20    /* Remote frame pending */
 #define HECC_CANGAM            0x24    /* SECC only:Global acceptance mask */
 #define HECC_CANMC             0x28    /* Master control */
@@ -385,8 +386,15 @@ static void ti_hecc_start(struct net_device *ndev)
        /* Enable tx interrupts */
        hecc_set_bit(priv, HECC_CANMIM, BIT(HECC_MAX_TX_MBOX) - 1);
 
-       /* Prevent message over-write & Enable interrupts */
-       hecc_write(priv, HECC_CANOPC, HECC_SET_REG);
+       /* Prevent message over-write to create a rx fifo, but not for
+        * the lowest priority mailbox, since that allows detecting
+        * overflows instead of the hardware silently dropping the
+        * messages.
+        */
+       mbx_mask = ~BIT(HECC_RX_LAST_MBOX);
+       hecc_write(priv, HECC_CANOPC, mbx_mask);
+
+       /* Enable interrupts */
        if (priv->use_hecc1int) {
                hecc_write(priv, HECC_CANMIL, HECC_SET_REG);
                hecc_write(priv, HECC_CANGIM, HECC_CANGIM_DEF_MASK |
@@ -531,6 +539,7 @@ static unsigned int ti_hecc_mailbox_read(struct can_rx_offload *offload,
 {
        struct ti_hecc_priv *priv = rx_offload_to_priv(offload);
        u32 data, mbx_mask;
+       int ret = 1;
 
        mbx_mask = BIT(mbxno);
        data = hecc_read_mbx(priv, mbxno, HECC_CANMID);
@@ -552,9 +561,26 @@ static unsigned int ti_hecc_mailbox_read(struct can_rx_offload *offload,
        }
 
        *timestamp = hecc_read_stamp(priv, mbxno);
+
+       /* Check for FIFO overrun.
+        *
+        * All but the last RX mailbox have activated overwrite
+        * protection. So skip check for overrun, if we're not
+        * handling the last RX mailbox.
+        *
+        * As the overwrite protection for the last RX mailbox is
+        * disabled, the CAN core might update while we're reading
+        * it. This means the skb might be inconsistent.
+        *
+        * Return an error to let rx-offload discard this CAN frame.
+        */
+       if (unlikely(mbxno == HECC_RX_LAST_MBOX &&
+                    hecc_read(priv, HECC_CANRML) & mbx_mask))
+               ret = -ENOBUFS;
+
        hecc_write(priv, HECC_CANRMP, mbx_mask);
 
-       return 1;
+       return ret;
 }
 
 static int ti_hecc_error(struct net_device *ndev, int int_status,
@@ -884,7 +910,7 @@ static int ti_hecc_probe(struct platform_device *pdev)
 
        priv->offload.mailbox_read = ti_hecc_mailbox_read;
        priv->offload.mb_first = HECC_RX_FIRST_MBOX;
-       priv->offload.mb_last = HECC_MAX_TX_MBOX;
+       priv->offload.mb_last = HECC_RX_LAST_MBOX;
        err = can_rx_offload_add_timestamp(ndev, &priv->offload);
        if (err) {
                dev_err(&pdev->dev, "can_rx_offload_add_timestamp() failed\n");