can: dev: Add support for limiting configured bitrate

Various CAN or CAN-FD IP may be able to run at a faster rate than
what the transceiver the CAN node is connected to. This can lead to
unexpected errors. However, CAN transceivers typically have fixed
limitations and provide no means to discover these limitations at
runtime. Therefore, add support for a can-transceiver node that
can be reused by other CAN peripheral drivers to determine for both
CAN and CAN-FD what the max bitrate that can be used. If the user
tries to configure CAN to pass these maximum bitrates it will throw
an error.

Also add support for reading bitrate_max via the netlink interface.

Reviewed-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
[nsekhar@ti.com: fix build error with !CONFIG_OF]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 365a8cc6240506ed165bc9141daf15ab29018541..cc94604b23e0275da9ac3fedb0f472b89479f29a 100644 (file)
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -27,6 +27,7 @@
 #include <linux/can/skb.h>
 #include <linux/can/netlink.h>
 #include <linux/can/led.h>
+#include <linux/of.h>
 #include <net/rtnetlink.h>
 
 #define MOD_DESC "CAN device driver interface"
@@ -814,6 +815,29 @@ int open_candev(struct net_device *dev)
 }
 EXPORT_SYMBOL_GPL(open_candev);
 
+#ifdef CONFIG_OF
+/* Common function that can be used to understand the limitation of
+ * a transceiver when it provides no means to determine these limitations
+ * at runtime.
+ */
+void of_can_transceiver(struct net_device *dev)
+{
+       struct device_node *dn;
+       struct can_priv *priv = netdev_priv(dev);
+       struct device_node *np = dev->dev.parent->of_node;
+       int ret;
+
+       dn = of_get_child_by_name(np, "can-transceiver");
+       if (!dn)
+               return;
+
+       ret = of_property_read_u32(dn, "max-bitrate", &priv->bitrate_max);
+       if ((ret && ret != -EINVAL) || (!ret && !priv->bitrate_max))
+               netdev_warn(dev, "Invalid value for transceiver max bitrate. Ignoring bitrate limit.\n");
+}
+EXPORT_SYMBOL_GPL(of_can_transceiver);
+#endif
+
 /*
  * Common close function for cleanup before the device gets closed.
  *
@@ -913,6 +937,13 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[],
                                        priv->bitrate_const_cnt);
                if (err)
                        return err;
+
+               if (priv->bitrate_max && bt.bitrate > priv->bitrate_max) {
+                       netdev_err(dev, "arbitration bitrate surpasses transceiver capabilities of %d bps\n",
+                                  priv->bitrate_max);
+                       return -EINVAL;
+               }
+
                memcpy(&priv->bittiming, &bt, sizeof(bt));
 
                if (priv->do_set_bittiming) {
@@ -997,6 +1028,13 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[],
                                        priv->data_bitrate_const_cnt);
                if (err)
                        return err;
+
+               if (priv->bitrate_max && dbt.bitrate > priv->bitrate_max) {
+                       netdev_err(dev, "canfd data bitrate surpasses transceiver capabilities of %d bps\n",
+                                  priv->bitrate_max);
+                       return -EINVAL;
+               }
+
                memcpy(&priv->data_bittiming, &dbt, sizeof(dbt));
 
                if (priv->do_set_data_bittiming) {
@@ -1064,6 +1102,7 @@ static size_t can_get_size(const struct net_device *dev)
        if (priv->data_bitrate_const)                           /* IFLA_CAN_DATA_BITRATE_CONST */
                size += nla_total_size(sizeof(*priv->data_bitrate_const) *
                                       priv->data_bitrate_const_cnt);
+       size += sizeof(priv->bitrate_max);                      /* IFLA_CAN_BITRATE_MAX */
 
        return size;
 }
@@ -1121,7 +1160,11 @@ static int can_fill_info(struct sk_buff *skb, const struct net_device *dev)
             nla_put(skb, IFLA_CAN_DATA_BITRATE_CONST,
                     sizeof(*priv->data_bitrate_const) *
                     priv->data_bitrate_const_cnt,
-                    priv->data_bitrate_const))
+                    priv->data_bitrate_const)) ||
+
+           (nla_put(skb, IFLA_CAN_BITRATE_MAX,
+                    sizeof(priv->bitrate_max),
+                    &priv->bitrate_max))
            )
 
                return -EMSGSIZE;

diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index 61f1cf2d9f440ce321e8a0f782a1003326aaf9ab..055aaf5ed9af38a839680c0570a8158db5e874b5 100644 (file)
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h
@@ -46,6 +46,7 @@ struct can_priv {
        unsigned int bitrate_const_cnt;
        const u32 *data_bitrate_const;
        unsigned int data_bitrate_const_cnt;
+       u32 bitrate_max;
        struct can_clock clock;
 
        enum can_state state;
@@ -166,6 +167,12 @@ void can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
 unsigned int can_get_echo_skb(struct net_device *dev, unsigned int idx);
 void can_free_echo_skb(struct net_device *dev, unsigned int idx);
 
+#ifdef CONFIG_OF
+void of_can_transceiver(struct net_device *dev);
+#else
+static inline void of_can_transceiver(struct net_device *dev) { }
+#endif
+
 struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf);
 struct sk_buff *alloc_canfd_skb(struct net_device *dev,
                                struct canfd_frame **cfd);

diff --git a/include/uapi/linux/can/netlink.h b/include/uapi/linux/can/netlink.h
index 96710e76d5cedad034f540bed21c706b6ff3f3a0..9f56fad4785b0b5a770b084355d863174868f1e3 100644 (file)
--- a/include/uapi/linux/can/netlink.h
+++ b/include/uapi/linux/can/netlink.h
@@ -132,6 +132,7 @@ enum {
        IFLA_CAN_TERMINATION_CONST,
        IFLA_CAN_BITRATE_CONST,
        IFLA_CAN_DATA_BITRATE_CONST,
+       IFLA_CAN_BITRATE_MAX,
        __IFLA_CAN_MAX
 };