[PATCH 3/3] can: at91_can: make can_id of mailbox 0 configurable

[Marc Kleine-Budde <mkl@pengutronix.de>]

Due to a chip bug (errata 50.2.6.3 & 50.3.5.3 in
"AT91SAM9263 Preliminary 6249H-ATARM-27-Jul-09") the contents of mailbox
0 may be send under certain conditions (even if disabled or in rx mode).

The workaround in the errata suggests not to use the mailbox and load it
with a unused identifier.

This patch implements the second part of the workaround. A sysfs entry
"mb0_id" is introduced. While the interface is down it can be used to
configure the can_id of mailbox 0. The default value id 0x7ff.

In order to use an extended can_id add the CAN_EFF_FLAG (0x80000000U)
to the can_id. Example:

- standard id 0x7ff:
echo 0x7ff      > /sys/class/net/can0/mb0_id

- extended if 0x1fffffff:
echo 0x9fffffff > /sys/class/net/can0/mb0_id

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/at91_can.c |   90 ++++++++++++++++++++++++++++++++++++++++---
 1 files changed, 83 insertions(+), 7 deletions(-)

diff --git a/drivers/net/can/at91_can.c b/drivers/net/can/at91_can.c
index 16e45a5..2532b96 100644
--- a/drivers/net/can/at91_can.c
+++ b/drivers/net/can/at91_can.c
@@ -30,6 +30,7 @@
 #include <linux/module.h>
 #include <linux/netdevice.h>
 #include <linux/platform_device.h>
+#include <linux/rtnetlink.h>
 #include <linux/skbuff.h>
 #include <linux/spinlock.h>
 #include <linux/string.h>
@@ -169,6 +170,8 @@ struct at91_priv {
 
 	struct clk		*clk;
 	struct at91_can_data	*pdata;
+
+	canid_t			mb0_id;
 };
 
 static struct can_bittiming_const at91_bittiming_const = {
@@ -221,6 +224,18 @@ static inline void set_mb_mode(const struct at91_priv *priv, unsigned int mb,
 	set_mb_mode_prio(priv, mb, mode, 0);
 }
 
+static inline u32 at91_can_id_to_reg_mid(canid_t can_id)
+{
+	u32 reg_mid;
+
+	if (can_id & CAN_EFF_FLAG)
+		reg_mid = (can_id & CAN_EFF_MASK) | AT91_MID_MIDE;
+	else
+		reg_mid = (can_id & CAN_SFF_MASK) << 18;
+
+	return reg_mid;
+}
+
 /*
  * Swtich transceiver on or off
  */
@@ -234,6 +249,7 @@ static void at91_setup_mailboxes(struct net_device *dev)
 {
 	struct at91_priv *priv = netdev_priv(dev);
 	unsigned int i;
+	u32 reg_mid;
 
 	/*
 	 * Due to a chip bug (errata 50.2.6.3 & 50.3.5.3) the first
@@ -242,8 +258,13 @@ static void at91_setup_mailboxes(struct net_device *dev)
 	 * overwrite option. The overwrite flag indicates a FIFO
 	 * overflow.
 	 */
-	for (i = 0; i < AT91_MB_RX_FIRST; i++)
+	reg_mid = at91_can_id_to_reg_mid(priv->mb0_id);
+	for (i = 0; i < AT91_MB_RX_FIRST; i++) {
 		set_mb_mode(priv, i, AT91_MB_MODE_DISABLED);
+		at91_write(priv, AT91_MID(i), reg_mid);
+		at91_write(priv, AT91_MCR(i), 0x0);	/* clear dlc */
+	}
+
 	for (i = AT91_MB_RX_FIRST; i < AT91_MB_RX_LAST; i++)
 		set_mb_mode(priv, i, AT91_MB_MODE_RX);
 	set_mb_mode(priv, AT91_MB_RX_LAST, AT91_MB_MODE_RX_OVRWR);
@@ -378,12 +399,7 @@ static netdev_tx_t at91_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		netdev_err(dev, "BUG! TX buffer full when queue awake!\n");
 		return NETDEV_TX_BUSY;
 	}
-
-	if (cf->can_id & CAN_EFF_FLAG)
-		reg_mid = (cf->can_id & CAN_EFF_MASK) | AT91_MID_MIDE;
-	else
-		reg_mid = (cf->can_id & CAN_SFF_MASK) << 18;
-
+	reg_mid = at91_can_id_to_reg_mid(cf->can_id);
 	reg_mcr = ((cf->can_id & CAN_RTR_FLAG) ? AT91_MCR_MRTR : 0) |
 		(cf->can_dlc << 16) | AT91_MCR_MTCR;
 
@@ -1047,6 +1063,64 @@ static const struct net_device_ops at91_netdev_ops = {
 	.ndo_start_xmit	= at91_start_xmit,
 };
 
+static ssize_t at91_sysfs_show_mb0_id(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct at91_priv *priv = netdev_priv(to_net_dev(dev));
+
+	if (priv->mb0_id & CAN_EFF_FLAG)
+		return snprintf(buf, PAGE_SIZE, "0x%08x\n", priv->mb0_id);
+	else
+		return snprintf(buf, PAGE_SIZE, "0x%03x\n", priv->mb0_id);
+}
+
+static ssize_t at91_sysfs_set_mb0_id(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct net_device *ndev = to_net_dev(dev);
+	struct at91_priv *priv = netdev_priv(ndev);
+	unsigned long can_id;
+	ssize_t ret;
+	int err;
+
+	rtnl_lock();
+
+	if (ndev->flags & IFF_UP) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	err = strict_strtoul(buf, 0, &can_id);
+	if (err) {
+		ret = err;
+		goto out;
+	}
+
+	if (can_id & CAN_EFF_FLAG)
+		can_id &= CAN_EFF_MASK | CAN_EFF_FLAG;
+	else
+		can_id &= CAN_SFF_MASK;
+
+	priv->mb0_id = can_id;
+	ret = count;
+
+ out:
+	rtnl_unlock();
+	return ret;
+}
+
+static DEVICE_ATTR(mb0_id, S_IWUGO | S_IRUGO,
+	at91_sysfs_show_mb0_id, at91_sysfs_set_mb0_id);
+
+static struct attribute *at91_sysfs_attrs[] = {
+	&dev_attr_mb0_id.attr,
+	NULL,
+};
+
+static struct attribute_group at91_sysfs_attr_group = {
+	.attrs = at91_sysfs_attrs,
+};
+
 static int __devinit at91_can_probe(struct platform_device *pdev)
 {
 	struct net_device *dev;
@@ -1092,6 +1166,7 @@ static int __devinit at91_can_probe(struct platform_device *pdev)
 	dev->netdev_ops	= &at91_netdev_ops;
 	dev->irq = irq;
 	dev->flags |= IFF_ECHO;
+	dev->sysfs_groups[0] = &at91_sysfs_attr_group;
 
 	priv = netdev_priv(dev);
 	priv->can.clock.freq = clk_get_rate(clk);
@@ -1103,6 +1178,7 @@ static int __devinit at91_can_probe(struct platform_device *pdev)
 	priv->dev = dev;
 	priv->clk = clk;
 	priv->pdata = pdev->dev.platform_data;
+	priv->mb0_id = 0x7ff;
 
 	netif_napi_add(dev, &priv->napi, at91_poll, AT91_NAPI_WEIGHT);
 
-- 
1.7.2.3