flexcan: disable bus error interrupts for the i.MX28

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. So far
nobody could tell what Flexcan core version is available on what
Freescale SOC, apart from the i.MX6Q and P1010, and which bugs or
features are present on the various "hw_rev".

CC: Hui Wang <jason77.wang@gmail.com>
CC: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/can/flexcan.c

@@ -144,6 +144,10 @@
 
 #define FLEXCAN_MB_CODE_MASK		(0xf0ffffff)
 
+/* FLEXCAN hardware feature flags */
+#define FLEXCAN_HAS_V10_FEATURES	BIT(1) /* For core version >= 10 */
+#define FLEXCAN_HAS_BROKEN_ERR_STATE	BIT(2) /* Broken error state handling */
+
 /* Structure of the message buffer */
 struct flexcan_mb {
 	u32 can_ctrl;
@@ -178,7 +182,7 @@ struct flexcan_regs {
 };
 
 struct flexcan_devtype_data {
-	u32 hw_ver;	/* hardware controller version */
+	u32 features;	/* hardware controller features */
 };
 
 struct flexcan_priv {
@@ -197,11 +201,11 @@ 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 | FLEXCAN_HAS_BROKEN_ERR_STATE,
 };
 
 static const struct can_bittiming_const flexcan_bittiming_const = {
@@ -741,15 +745,19 @@ 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 +780,7 @@ 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 +962,7 @@ 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 */ },
 };