can: kvaser_usb: Fix state handling upon BUS_ERROR events

While being in an ERROR_WARNING state, and receiving further
bus error events with error counters still in the ERROR_WARNING
range of 97-127 inclusive, the state handling code erroneously
reverts back to ERROR_ACTIVE.

Per the CAN standard, only revert to ERROR_ACTIVE when the
error counters are less than 96.

Moreover, in certain Kvaser models, the BUS_ERROR flag is
always set along with undefined bits in the M16C status
register. Thus use bitwise operators instead of full equality
for checking that register against bus errors.

Signed-off-by: Ahmed S. Darwish <ahmed.darwish@valeo.com>
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

1 files changed, 3 insertions, 4 deletions

diff --git a/drivers/net/can/usb/kvaser_usb.c b/drivers/net/can/usb/kvaser_usb.c
index 55407b9663a6..7af379ca861b 100644
--- a/drivers/net/can/usb/kvaser_usb.c
+++ b/drivers/net/can/usb/kvaser_usb.c
@@ -698,9 +698,7 @@ static void kvaser_usb_rx_error(const struct kvaser_usb *dev,
                 }
 
                 new_state = CAN_STATE_ERROR_PASSIVE;
-        }
-
-        if (status == M16C_STATE_BUS_ERROR) {
+        } else if (status & M16C_STATE_BUS_ERROR) {
                 if ((priv->can.state < CAN_STATE_ERROR_WARNING) &&
                     ((txerr >= 96) || (rxerr >= 96))) {
                         cf->can_id |= CAN_ERR_CRTL;
@@ -710,7 +708,8 @@ static void kvaser_usb_rx_error(const struct kvaser_usb *dev,
 
                         priv->can.can_stats.error_warning++;
                         new_state = CAN_STATE_ERROR_WARNING;
-                } else if (priv->can.state > CAN_STATE_ERROR_ACTIVE) {
+                } else if ((priv->can.state > CAN_STATE_ERROR_ACTIVE) &&
+                           ((txerr < 96) && (rxerr < 96))) {
                         cf->can_id |= CAN_ERR_PROT;
                         cf->data[2] = CAN_ERR_PROT_ACTIVE;