[PATCH 3/6] can: sja1000: Add Quirks for RZ/N1 SJA1000 CAN controller

[Biju Das <biju.das.jz@xxxxxxxxxxxxxx>]

Chapter 6.5.16 of the RZ/N1 Peripheral Manual mentions the below
differences compared to the reference Philips SJA1000 device.

Handling of Transmitted Messages:
 * The CAN controller does not copy transmitted messages to the receive
   buffer, unlike the reference device.

Clock Divider Register:
 * This register is not supported

This patch adds device quirks to handle these differences.

Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
---
 drivers/net/can/sja1000/sja1000.c | 17 +++++++++++------
 drivers/net/can/sja1000/sja1000.h |  4 +++-
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/net/can/sja1000/sja1000.c b/drivers/net/can/sja1000/sja1000.c
index 2e7638f98cf1..49cf4fc4d896 100644
--- a/drivers/net/can/sja1000/sja1000.c
+++ b/drivers/net/can/sja1000/sja1000.c
@@ -183,8 +183,9 @@ static void chipset_init(struct net_device *dev)
 {
 	struct sja1000_priv *priv = netdev_priv(dev);
 
-	/* set clock divider and output control register */
-	priv->write_reg(priv, SJA1000_CDR, priv->cdr | CDR_PELICAN);
+	if (!(priv->flags & SJA1000_NO_CDR_REG_QUIRK))
+		/* set clock divider and output control register */
+		priv->write_reg(priv, SJA1000_CDR, priv->cdr | CDR_PELICAN);
 
 	/* set acceptance filter (accept all) */
 	priv->write_reg(priv, SJA1000_ACCC0, 0x00);
@@ -208,9 +209,11 @@ static void sja1000_start(struct net_device *dev)
 	if (priv->can.state != CAN_STATE_STOPPED)
 		set_reset_mode(dev);
 
-	/* Initialize chip if uninitialized at this stage */
-	if (!(priv->read_reg(priv, SJA1000_CDR) & CDR_PELICAN))
-		chipset_init(dev);
+	if (!(priv->flags & SJA1000_NO_CDR_REG_QUIRK)) {
+		/* Initialize chip if uninitialized at this stage */
+		if (!(priv->read_reg(priv, SJA1000_CDR) & CDR_PELICAN))
+			chipset_init(dev);
+	}
 
 	/* Clear error counters and error code capture */
 	priv->write_reg(priv, SJA1000_TXERR, 0x0);
@@ -652,12 +655,14 @@ static const struct net_device_ops sja1000_netdev_ops = {
 
 int register_sja1000dev(struct net_device *dev)
 {
+	struct sja1000_priv *priv = netdev_priv(dev);
 	int ret;
 
 	if (!sja1000_probe_chip(dev))
 		return -ENODEV;
 
-	dev->flags |= IFF_ECHO;	/* we support local echo */
+	if (!(priv->flags & SJA1000_NO_HW_LOOPBACK_QUIRK))
+		dev->flags |= IFF_ECHO;	/* we support local echo */
 	dev->netdev_ops = &sja1000_netdev_ops;
 
 	set_reset_mode(dev);
diff --git a/drivers/net/can/sja1000/sja1000.h b/drivers/net/can/sja1000/sja1000.h
index 9d46398f8154..d0b8ce3f70ec 100644
--- a/drivers/net/can/sja1000/sja1000.h
+++ b/drivers/net/can/sja1000/sja1000.h
@@ -145,7 +145,9 @@
 /*
  * Flags for sja1000priv.flags
  */
-#define SJA1000_CUSTOM_IRQ_HANDLER 0x1
+#define SJA1000_CUSTOM_IRQ_HANDLER	BIT(0)
+#define SJA1000_NO_CDR_REG_QUIRK	BIT(1)
+#define SJA1000_NO_HW_LOOPBACK_QUIRK	BIT(2)
 
 /*
  * SJA1000 private data structure
-- 
2.25.1