[PATCH v2 0/3] can: provide GPIO based termination

@@ -15,6 +15,7 @@
 #include <linux/can/dev.h>
 #include <linux/can/skb.h>
 #include <linux/can/led.h>
+#include <linux/gpio/consumer.h>
 #include <linux/of.h>
 
 #define MOD_DESC "CAN device driver interface"

@@ -400,10 +401,57 @@ void close_candev(struct net_device *dev)
 }
 EXPORT_SYMBOL_GPL(close_candev);
 
+static int can_set_termination(struct net_device *ndev, u16 term)
+{
+	struct can_priv *priv = netdev_priv(ndev);
+	int set;
+
+	if (term == priv->termination_gpio_ohms[CAN_TERMINATION_GPIO_ENABLED])
+		set = 1;
+	else
+		set = 0;
+
+	gpiod_set_value(priv->termination_gpio, set);
+
+	return 0;
+}
+
+static int can_get_termination(struct net_device *ndev)
+{
+	struct can_priv *priv = netdev_priv(ndev);
+	struct device *dev = ndev->dev.parent;
+	struct gpio_desc *gpio;
+	u16 term;
+	int ret;
+
+	/* Disabling termination by default is the safe choice: Else if many
+	 * bus participants enable it, no communication is possible at all.
+	 */
+	gpio = devm_gpiod_get_optional(dev, "termination", GPIOD_OUT_LOW);
+	if (IS_ERR(gpio))
+		return dev_err_probe(dev, PTR_ERR(gpio),
+				     "Cannot get termination-gpios\n");
+
+	ret = device_property_read_u16(dev, "termination-ohms", &term);
+	if (ret)
+		return ret;
+
+	priv->termination_const_cnt = ARRAY_SIZE(priv->termination_gpio_ohms);
+	priv->termination_const = priv->termination_gpio_ohms;
+	priv->termination_gpio = gpio;
+	priv->termination_gpio_ohms[CAN_TERMINATION_GPIO_DISABLED] =
+		CAN_TERMINATION_DISABLED;
+	priv->termination_gpio_ohms[CAN_TERMINATION_GPIO_ENABLED] = term;
+	priv->do_set_termination = can_set_termination;
+
+	return 0;
+}
+
 /* Register the CAN network device */
 int register_candev(struct net_device *dev)
 {
 	struct can_priv *priv = netdev_priv(dev);
+	int err;
 
 	/* Ensure termination_const, termination_const_cnt and
 	 * do_set_termination consistency. All must be either set or

@@ -419,6 +467,12 @@ int register_candev(struct net_device *dev)
 	if (!priv->data_bitrate_const != !priv->data_bitrate_const_cnt)
 		return -EINVAL;
 
+	if (!priv->termination_const) {
+		err = can_get_termination(dev);
+		if (err)
+			return err;
+	}
+
 	dev->rtnl_link_ops = &can_link_ops;
 	netif_carrier_off(dev);
 

@@ -32,6 +32,12 @@ enum can_mode {
 	CAN_MODE_SLEEP
 };
 
+enum can_termination_gpio {
+	CAN_TERMINATION_GPIO_DISABLED = 0,
+	CAN_TERMINATION_GPIO_ENABLED,
+	CAN_TERMINATION_GPIO_MAX,
+};
+
 /*
  * CAN common private data
  */

@@ -55,6 +61,8 @@ struct can_priv {
 	unsigned int termination_const_cnt;
 	const u16 *termination_const;
 	u16 termination;
+	struct gpio_desc *termination_gpio;
+	u16 termination_gpio_ohms[CAN_TERMINATION_GPIO_MAX];
 
 	enum can_state state;
 

@@ -119,6 +119,9 @@ properties:
     minimum: 0
     maximum: 2
 
+  termination-gpios: true
+  termination-ohms: true
+
 required:
   - compatible
   - reg

@@ -148,3 +151,17 @@ examples:
         fsl,stop-mode = <&gpr 0x34 28>;
         fsl,scu-index = /bits/ 8 <1>;
     };
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/gpio/gpio.h>
+
+    can@2090000 {
+        compatible = "fsl,imx6q-flexcan";
+        reg = <0x02090000 0x4000>;
+        interrupts = <0 110 IRQ_TYPE_LEVEL_HIGH>;
+        clocks = <&clks 1>, <&clks 2>;
+        clock-names = "ipg", "per";
+        fsl,stop-mode = <&gpr 0x34 28>;
+        termination-gpios = <&gpio1 0 GPIO_ACTIVE_LOW>;
+        termination-ohms = /bits/ 16 <150>;
+    };

@@ -13,6 +13,15 @@ properties:
   $nodename:
     pattern: "^can(@.*)?$"
 
+  termination-gpios:
+    description: GPIO pin to enable CAN bus termination.
+
+  termination-ohms:
+    description: The resistance value of the CAN bus termination resistor.
+    $ref: /schemas/types.yaml#/definitions/uint16-array
+    minimum: 1
+    maximum: 65535
+
 additionalProperties: true
 
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