can: m_can: Disable and ignore ELO interrupt

With the design of this driver, this condition is often triggered.
However, the counter that this interrupt indicates an overflow is never
read either, so overflowing is harmless.

On my system, when a CAN bus starts flapping up and down, this locks up
the whole system with lots of interrupts and printks.

Specifically, this interrupt indicates the CEL field of ECR has
overflowed. All reads of ECR mask out CEL.

Fixes: e0d1f481 ("can: m_can: add Bosch M_CAN controller support")
Link: https://lore.kernel.org/all/20211129222628.7490-1-brian.silverman@bluerivertech.com
Cc: stable@vger.kernel.org
Signed-off-by: Brian Silverman <brian.silverman@bluerivertech.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/m_can.c

@@ -204,16 +204,16 @@ enum m_can_reg {
 
 /* Interrupts for version 3.0.x */
 #define IR_ERR_LEC_30X	(IR_STE	| IR_FOE | IR_ACKE | IR_BE | IR_CRCE)
-#define IR_ERR_BUS_30X	(IR_ERR_LEC_30X | IR_WDI | IR_ELO | IR_BEU | \
-			 IR_BEC | IR_TOO | IR_MRAF | IR_TSW | IR_TEFL | \
-			 IR_RF1L | IR_RF0L)
+#define IR_ERR_BUS_30X	(IR_ERR_LEC_30X | IR_WDI | IR_BEU | IR_BEC | \
+			 IR_TOO | IR_MRAF | IR_TSW | IR_TEFL | IR_RF1L | \
+			 IR_RF0L)
 #define IR_ERR_ALL_30X	(IR_ERR_STATE | IR_ERR_BUS_30X)
 
 /* Interrupts for version >= 3.1.x */
 #define IR_ERR_LEC_31X	(IR_PED | IR_PEA)
-#define IR_ERR_BUS_31X      (IR_ERR_LEC_31X | IR_WDI | IR_ELO | IR_BEU | \
-			 IR_BEC | IR_TOO | IR_MRAF | IR_TSW | IR_TEFL | \
-			 IR_RF1L | IR_RF0L)
+#define IR_ERR_BUS_31X      (IR_ERR_LEC_31X | IR_WDI | IR_BEU | IR_BEC | \
+			 IR_TOO | IR_MRAF | IR_TSW | IR_TEFL | IR_RF1L | \
+			 IR_RF0L)
 #define IR_ERR_ALL_31X	(IR_ERR_STATE | IR_ERR_BUS_31X)
 
 /* Interrupt Line Select (ILS) */
@@ -810,8 +810,6 @@ static void m_can_handle_other_err(struct net_device *dev, u32 irqstatus)
 {
 	if (irqstatus & IR_WDI)
 		netdev_err(dev, "Message RAM Watchdog event due to missing READY\n");
-	if (irqstatus & IR_ELO)
-		netdev_err(dev, "Error Logging Overflow\n");
 	if (irqstatus & IR_BEU)
 		netdev_err(dev, "Bit Error Uncorrected\n");
 	if (irqstatus & IR_BEC)