Hi,
On 08/10/2017 10:29 AM, Marc Kleine-Budde wrote:
> 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);
That works
>
>> +
>> + if (max_bitrate > 0) {
>> + priv->max_bitrate = max_bitrate;
>> + priv->is_bitrate_limited = true;
>
> Do we need is_bitrate_limited...
No.
>
>> + } 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?
Yes
Thanks for reviewing and for your feedback.
>
> 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
>
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