[PATCH v5 6/8] net: can: c_can: Disable pins when CAN interface is down

[Roger Quadros <rogerq@ti.com>]

DRA7 CAN IP suffers from a problem which causes it to be prevented
from fully turning OFF (i.e. stuck in transition) if the module was
disabled while there was traffic on the CAN_RX line.

To work around this issue we select the SLEEP pin state by default
on probe and use the DEFAULT pin state on CAN up and back to the
SLEEP pin state on CAN down.

Signed-off-by: Roger Quadros <rogerq@ti.com>
---
 drivers/net/can/c_can/c_can.c | 37 +++++++++++++++++++++++++++++++++++++
 drivers/net/can/c_can/c_can.h |  1 +
 2 files changed, 38 insertions(+)

diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c
index 8e78bb4..c80cb3d 100644
--- a/drivers/net/can/c_can/c_can.c
+++ b/drivers/net/can/c_can/c_can.c
@@ -35,6 +35,7 @@
 #include <linux/list.h>
 #include <linux/io.h>
 #include <linux/pm_runtime.h>
+#include <linux/pinctrl/consumer.h>
 
 #include <linux/can.h>
 #include <linux/can/dev.h>
@@ -587,6 +588,21 @@ static int c_can_chip_config(struct net_device *dev)
 	return c_can_set_bittiming(dev);
 }
 
+/*
+ * Selects the pinctrl state specified in the name.
+ */
+static void c_can_pinctrl_select_state(struct c_can_priv *priv,
+				      const char *name)
+{
+	if (!IS_ERR(priv->pinctrl)) {
+		struct pinctrl_state *s;
+
+		s = pinctrl_lookup_state(priv->pinctrl, name);
+		if (!IS_ERR(s))
+			pinctrl_select_state(priv->pinctrl, s);
+	}
+}
+
 static int c_can_start(struct net_device *dev)
 {
 	struct c_can_priv *priv = netdev_priv(dev);
@@ -603,6 +619,8 @@ static int c_can_start(struct net_device *dev)
 
 	priv->can.state = CAN_STATE_ERROR_ACTIVE;
 
+	/* activate pins */
+	c_can_pinctrl_select_state(priv, PINCTRL_STATE_DEFAULT);
 	return 0;
 }
 
@@ -611,6 +629,9 @@ static void c_can_stop(struct net_device *dev)
 	struct c_can_priv *priv = netdev_priv(dev);
 
 	c_can_irq_control(priv, false);
+
+	/* deactivate pins */
+	c_can_pinctrl_select_state(priv, PINCTRL_STATE_SLEEP);
 	priv->can.state = CAN_STATE_STOPPED;
 }
 
@@ -1244,6 +1265,22 @@ int register_c_can_dev(struct net_device *dev)
 	struct c_can_priv *priv = netdev_priv(dev);
 	int err;
 
+	priv->pinctrl = devm_pinctrl_get(dev->dev.parent);
+	if (!IS_ERR(priv->pinctrl)) {
+		struct pinctrl_state *s;
+
+		/* Deactivate pins to prevent DRA7 DCAN IP from being
+		 * stuck in transition when module is disabled.
+		 * Pins are activated in c_can_start() and deactivated
+		 * in c_can_stop()
+		 */
+		s = pinctrl_lookup_state(priv->pinctrl, PINCTRL_STATE_SLEEP);
+		if (!IS_ERR(s))
+			pinctrl_select_state(priv->pinctrl, s);
+	} else {
+		netdev_dbg(dev, "failed to get pinctrl\n");
+	}
+
 	c_can_pm_runtime_enable(priv);
 
 	dev->flags |= IFF_ECHO;	/* we support local echo */
diff --git a/drivers/net/can/c_can/c_can.h b/drivers/net/can/c_can/c_can.h
index c6715ca..3cedf48 100644
--- a/drivers/net/can/c_can/c_can.h
+++ b/drivers/net/can/c_can/c_can.h
@@ -210,6 +210,7 @@ struct c_can_priv {
 	u32 comm_rcv_high;
 	u32 rxmasked;
 	u32 dlc[C_CAN_MSG_OBJ_TX_NUM];
+	struct pinctrl *pinctrl;
 };
 
 struct net_device *alloc_c_can_dev(void);
-- 
1.8.3.2