[PATCH v3 3/6] can: sja1000: Add Quirk for RZ/N1 SJA1000 CAN controller

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

As per Chapter 6.5.16 of the RZ/N1 Peripheral Manual, The SJA1000
CAN controller does not support Clock Divider Register compared to
the reference Philips SJA1000 device.

This patch adds a device quirk to handle this difference.

Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
---
v2->v3:
 * No Change
v1->v2:
 * Updated commit description
 * Removed the quirk macro SJA1000_NO_HW_LOOPBACK_QUIRK
 * Added prefix SJA1000_QUIRK_* for quirk macro.
---
 drivers/net/can/sja1000/sja1000.c | 13 ++++++++-----
 drivers/net/can/sja1000/sja1000.h |  3 ++-
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/net/can/sja1000/sja1000.c b/drivers/net/can/sja1000/sja1000.c
index 2e7638f98cf1..e9c55f5aa3c3 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_QUIRK_NO_CDR_REG))
+		/* 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_QUIRK_NO_CDR_REG)) {
+		/* 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);
diff --git a/drivers/net/can/sja1000/sja1000.h b/drivers/net/can/sja1000/sja1000.h
index 9d46398f8154..7f736f1df547 100644
--- a/drivers/net/can/sja1000/sja1000.h
+++ b/drivers/net/can/sja1000/sja1000.h
@@ -145,7 +145,8 @@
 /*
  * Flags for sja1000priv.flags
  */
-#define SJA1000_CUSTOM_IRQ_HANDLER 0x1
+#define SJA1000_CUSTOM_IRQ_HANDLER	BIT(0)
+#define SJA1000_QUIRK_NO_CDR_REG	BIT(1)
 
 /*
  * SJA1000 private data structure
-- 
2.25.1