Hello,
sorry for stepping in late....
On 08/10/2017 02:59 AM, Franklin S Cooper Jr wrote:
> 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.
>
> Signed-off-by: Franklin S Cooper Jr <fcooper@xxxxxx>
> ---
> Version 4 changes:
> Used can-transceiver instead of fixed-transceiver.
>
> drivers/net/can/dev.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/can/dev.h | 5 +++++
> 2 files changed, 55 insertions(+)
>
> diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
> index 365a8cc..372108f 100644
> --- 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 +815,39 @@ 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;
> + unsigned int max_bitrate;
> + int ret;
> +
> + np = dev->dev.parent->of_node;
> +
> + dn = of_get_child_by_name(np, "can-transceiver");
> + if (!dn)
> + return;
> +
> + max_bitrate = 0;
> + ret = of_property_read_u32(dn, "max-bitrate", &max_bitrate);
IIRC the last argument is only modified in case of no error, so what about:
ret = of_property_read_u32(dn, "max-bitrate",
&priv->max_bitrate);
> +
> + if (max_bitrate > 0) {
> + priv->max_bitrate = max_bitrate;
> + priv->is_bitrate_limited = true;
Do we need is_bitrate_limited...
> + } else if (ret != -EINVAL) {
> + netdev_warn(dev, "Invalid value for transceiver max bitrate\n");
> + }
> +}
> +EXPORT_SYMBOL(of_can_transceiver);
> +#endif
> +
> /*
> * Common close function for cleanup before the device gets closed.
> *
> @@ -913,6 +947,14 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[],
> priv->bitrate_const_cnt);
> if (err)
> return err;
> +
> + if (priv->is_bitrate_limited &&
> + bt.bitrate > priv->max_bitrate) {
...can we just use priv->max_bitrate?
if (priv->max_bitrate && bt.bitrate > priv->max_bitrate)
> + netdev_err(dev, "arbitration bitrate surpasses transceiver capabilities of %d bps\n",
> + priv->max_bitrate);
> + return -EINVAL;
> + }
> +
> memcpy(&priv->bittiming, &bt, sizeof(bt));
>
> if (priv->do_set_bittiming) {
> @@ -997,6 +1039,14 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[],
> priv->data_bitrate_const_cnt);
> if (err)
> return err;
> +
> + if (priv->is_bitrate_limited &&
> + dbt.bitrate > priv->max_bitrate) {
> + netdev_err(dev, "canfd data bitrate surpasses transceiver capabilities of %d bps\n",
> + priv->max_bitrate);
> + return -EINVAL;
> + }
> +
> memcpy(&priv->data_bittiming, &dbt, sizeof(dbt));
>
> if (priv->do_set_data_bittiming) {
> diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
> index 141b05a..5519f59 100644
> --- a/include/linux/can/dev.h
> +++ b/include/linux/can/dev.h
> @@ -47,6 +47,9 @@ struct can_priv {
> unsigned int data_bitrate_const_cnt;
> struct can_clock clock;
>
> + unsigned int max_bitrate;
> + bool is_bitrate_limited;
> +
> enum can_state state;
>
> /* CAN controller features - see include/uapi/linux/can/netlink.h */
> @@ -165,6 +168,8 @@ 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);
>
> +void of_can_transceiver(struct net_device *dev);
> +
> 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);
>
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Industrial Linux Solutions | Phone: +49-231-2826-924 |
Vertretung West/Dortmund | Fax: +49-5121-206917-5555 |
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