[PATCH v2] flexcan: disable bus error interrupts for the i.MX28

[Wolfgang Grandegger <wg@grandegger.com>]

Due to a bug in most Flexcan cores, the bus error interrupt needs
to be enabled. Otherwise we don't get any error warning or passive
interrupts. This is _not_ necessary for the i.MX28 and this patch
disables bus error interrupts if "berr-reporting" is not requested.
This avoids bus error flooding, which might harm, especially on
low-end systems.

To handle such quirks of the Flexcan cores, a hardware feature flag
has been introduced, also replacing the "hw_ver" variable. We got
some version info about what Flexcan core version is available on
what Freescale SOC which have been summarized as comment.

Changes since v1:

- add known version info and hw bugs as comment
- remove FLEXCAN_HAS_BROKEN_ERR_STATE for i.MX6Q

CC: Hui Wang <jason77.wang@gmail.com>
CC: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
---
 drivers/net/can/flexcan.c |   42 ++++++++++++++++++++++++++++++++----------
 1 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index c5f1431..f07128b 100644
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -144,6 +144,23 @@
 
 #define FLEXCAN_MB_CODE_MASK		(0xf0ffffff)
 
+/*
+ * FLEXCAN hardware feature flags
+ *
+ * Below is some version info we got:
+ *    SOC   Version   IP-Version  Glitch-  [TR]WRN_INT
+ *                                Filter?   connected?
+ *   MX25  FlexCAN2  03.00.00.00     no         no
+ *   MX28  FlexCAN2  03.00.04.00    yes        yes
+ *   MX35  FlexCAN2  03.00.00.00     no         no
+ *   MX53  FlexCAN2  03.00.00.00    yes         no
+ *   MX6s  FlexCAN3  10.00.12.00     ?         yes
+ *
+ * Some SOCs do not have the RX_WARN & TX_WARN interrupt line connected.
+ */
+#define FLEXCAN_HAS_V10_FEATURES	BIT(1) /* For core version >= 10 */
+#define FLEXCAN_HAS_BROKEN_ERR_STATE	BIT(2) /* [TR]WRN_INT not connected */
+
 /* Structure of the message buffer */
 struct flexcan_mb {
 	u32 can_ctrl;
@@ -178,7 +195,7 @@ struct flexcan_regs {
 };
 
 struct flexcan_devtype_data {
-	u32 hw_ver;	/* hardware controller version */
+	u32 features;	/* hardware controller features */
 };
 
 struct flexcan_priv {
@@ -197,11 +214,11 @@ struct flexcan_priv {
 };
 
 static struct flexcan_devtype_data fsl_p1010_devtype_data = {
-	.hw_ver = 3,
+	.features = FLEXCAN_HAS_BROKEN_ERR_STATE,
 };
-
+static struct flexcan_devtype_data fsl_imx28_devtype_data;
 static struct flexcan_devtype_data fsl_imx6q_devtype_data = {
-	.hw_ver = 10,
+	.features = FLEXCAN_HAS_V10_FEATURES,
 };
 
 static const struct can_bittiming_const flexcan_bittiming_const = {
@@ -741,15 +758,19 @@ static int flexcan_chip_start(struct net_device *dev)
 	 * enable tx and rx warning interrupt
 	 * enable bus off interrupt
 	 * (== FLEXCAN_CTRL_ERR_STATE)
-	 *
-	 * _note_: we enable the "error interrupt"
-	 * (FLEXCAN_CTRL_ERR_MSK), too. Otherwise we don't get any
-	 * warning or bus passive interrupts.
 	 */
 	reg_ctrl = flexcan_read(&regs->ctrl);
 	reg_ctrl &= ~FLEXCAN_CTRL_TSYN;
 	reg_ctrl |= FLEXCAN_CTRL_BOFF_REC | FLEXCAN_CTRL_LBUF |
-		FLEXCAN_CTRL_ERR_STATE | FLEXCAN_CTRL_ERR_MSK;
+		FLEXCAN_CTRL_ERR_STATE;
+	/*
+	 * enable the "error interrupt" (FLEXCAN_CTRL_ERR_MSK),
+	 * on most Flexcan cores, too. Otherwise we don't get
+	 * any error warning or passive interrupts.
+	 */
+	if (priv->devtype_data->features & FLEXCAN_HAS_BROKEN_ERR_STATE ||
+	    priv->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING)
+		reg_ctrl |= FLEXCAN_CTRL_ERR_MSK;
 
 	/* save for later use */
 	priv->reg_ctrl_default = reg_ctrl;
@@ -772,7 +793,7 @@ static int flexcan_chip_start(struct net_device *dev)
 	flexcan_write(0x0, &regs->rx14mask);
 	flexcan_write(0x0, &regs->rx15mask);
 
-	if (priv->devtype_data->hw_ver >= 10)
+	if (priv->devtype_data->features & FLEXCAN_HAS_V10_FEATURES)
 		flexcan_write(0x0, &regs->rxfgmask);
 
 	flexcan_transceiver_switch(priv, 1);
@@ -954,6 +975,7 @@ static void __devexit unregister_flexcandev(struct net_device *dev)
 
 static const struct of_device_id flexcan_of_match[] = {
 	{ .compatible = "fsl,p1010-flexcan", .data = &fsl_p1010_devtype_data, },
+	{ .compatible = "fsl,imx28-flexcan", .data = &fsl_imx28_devtype_data, },
 	{ .compatible = "fsl,imx6q-flexcan", .data = &fsl_imx6q_devtype_data, },
 	{ /* sentinel */ },
 };
-- 
1.7.7.6