Re: [PATCH net-next RFC 8/9] net: dsa: mv88e6xxx: add rx/tx timestamping support

Richard Cochran
2017-10-08T15:29:18Z

On Thu, Sep 28, 2017 at 10:25:40AM -0500, Brandon Streiff wrote:
> +void mv88e6xxx_port_txtstamp(struct dsa_switch *ds, int port,
> + struct sk_buff *clone, unsigned int type)
> +{
> + struct mv88e6xxx_chip *chip = ds->priv;
> + struct mv88e6xxx_port_hwtstamp *ps = &chip->port_hwtstamp[port];
> +
> + if (!chip->info->ptp_support)
> + return;
> +
> + if (port < 0 || port >= mv88e6xxx_num_ports(chip))
> + goto out;
> +
> + if (unlikely(skb_shinfo(clone)->tx_flags & SKBTX_HW_TSTAMP) &&
> + mv88e6xxx_should_tstamp(chip, port, clone, type)) {
> + __be16 *seq_ptr = (__be16 *)(_get_ptp_header(clone, type) +
> + OFF_PTP_SEQUENCE_ID);
> +
> + if (!test_and_set_bit_lock(MV88E6XXX_HWTSTAMP_TX_IN_PROGRESS,
> + &ps->state)) {
> + ps->tx_skb = clone;
> + ps->tx_tstamp_start = jiffies;
> + ps->tx_seq_id = be16_to_cpup(seq_ptr);
> +
> + /* Fetching the timestamp is high-priority work because
> + * 802.1AS bounds the time for a response.

Can you please use this?

commit d9535cb7b7603aeb549c697ecdf92024e4d0a650
Author: Grygorii Strashko <grygorii.strashko@ti.com>
Date: Fri Jul 28 17:30:02 2017 -0500

ptp: introduce ptp auxiliary worker

Many PTP drivers required to perform some asynchronous or periodic work,
like periodically handling PHC counter overflow or handle delayed timestamp
for RX/TX network packets. In most of the cases, such work is implemented
using workqueues. Unfortunately, Kernel workqueues might introduce
significant delay in work scheduling under high system load and on -RT,
which could cause misbehavior of PTP drivers due to internal counter
overflow, for example, and there is no way to tune its execution policy and
priority manuallly.

Hence, The kthread_worker can be used insted of workqueues, as it create
separte named kthread for each worker and its its execution policy and
priority can be configured using chrt tool.

> + * No need to check result of queue_work(). ps->tx_skb
> + * check ensures work item is not pending (it may be
> + * waiting to exit)
> + */
> + queue_work(system_highpri_wq, &ps->tx_tstamp_work);
> + return;
> + }
> +
> + /* Otherwise we're already in progress... */
> + dev_dbg(chip->dev,
> + "p%d: tx timestamp already in progress, discarding",
> + port);
> + }
> +
> +out:
> + /* We don't need it after all. */
> + kfree_skb(clone);
> +}

Thanks,
Richard