mcp2515: Change interrupt to TRIGGER_LOW

The MCP2515 datasheet clearly describes a level-triggered interrupt
pin. Therefore the receiving interrupt controller must also be
configured for level-triggered operation otherwise there is a danger
of a missed interrupt condition blocking all subsequent interrupts.

The ONESHOT flag ensures that the interrupt is masked until the
threaded interrupt handler exits.

See: #2175
     #2263

Signed-off-by: Phil Elwell <[email protected]>

Author: Phil Elwell

arch/arm/boot/dts/overlays/mcp2515-can0-overlay.dts

@@ -60,7 +60,7 @@
                 pinctrl-0 = <&can0_pins>;
                 spi-max-frequency = <10000000>;
                 interrupt-parent = <&gpio>;
-                interrupts = <25 0x2>;
+                interrupts = <25 8>; /* IRQF_TRIGGER_LOW */
                 clocks = <&can0_osc>;
             };
         };

arch/arm/boot/dts/overlays/mcp2515-can1-overlay.dts

@@ -60,7 +60,7 @@
                 pinctrl-0 = <&can1_pins>;
                 spi-max-frequency = <10000000>;
                 interrupt-parent = <&gpio>;
-                interrupts = <25 0x2>;
+                interrupts = <25 8>; /* IRQF_TRIGGER_LOW */
                 clocks = <&can1_osc>;
             };
         };

drivers/net/can/spi/mcp251x.c

@@ -936,7 +936,7 @@ static int mcp251x_open(struct net_device *net)
 {
 	struct mcp251x_priv *priv = netdev_priv(net);
 	struct spi_device *spi = priv->spi;
-	unsigned long flags = IRQF_ONESHOT | IRQF_TRIGGER_FALLING;
+	unsigned long flags = IRQF_TRIGGER_LOW;
 	int ret;
 
 	ret = open_candev(net);