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

Richard Cochran
2017-10-08T14:24:56Z

On Thu, Sep 28, 2017 at 10:25:40AM -0500, Brandon Streiff wrote:

> +static bool mv88e6xxx_should_tstamp(struct mv88e6xxx_chip *chip, int port,
> + struct sk_buff *skb, unsigned int type)
> +{
> + struct mv88e6xxx_port_hwtstamp *ps = &chip->port_hwtstamp[port];
> + u8 *ptp_hdr, *msgtype;
> + bool ret;
> +
> + if (port < 0 || port >= mv88e6xxx_num_ports(chip))
> + return false;
> +
> + ptp_hdr = _get_ptp_header(skb, type);
> + if (IS_ERR(ptp_hdr))
> + return false;
> +
> + if (unlikely(type & PTP_CLASS_V1))
> + msgtype = ptp_hdr + OFF_PTP_CONTROL;
> + else
> + msgtype = ptp_hdr;
> +
> + ret = test_bit(MV88E6XXX_HWTSTAMP_ENABLED, &ps->state);

This should be the first test, don't you think?

> + dev_dbg(chip->dev,
> + "p%d: PTP message classification 0x%x type 0x%x, tstamp? %d",
> + port, type, *msgtype, (int)ret);
> +
> + return ret;
> +}
> +
> +/* rxtstamp will be called in interrupt context so we don't to do
> + * anything like read PTP registers over SMI.
> + */
> +bool mv88e6xxx_port_rxtstamp(struct dsa_switch *ds, int port,
> + struct sk_buff *skb, unsigned int type)
> +{
> + struct mv88e6xxx_chip *chip = ds->priv;
> + struct skb_shared_hwtstamps *shhwtstamps;
> + __be32 *ptp_rx_ts;
> + u8 *ptp_hdr;
> + u32 raw_ts;
> + u64 ns;
> +
> + if (!chip->info->ptp_support)
> + return false;
> +
> + if (port < 0 || port >= mv88e6xxx_num_ports(chip))
> + return false;

This test is duplicated in mv88e6xxx_should_tstamp().

> + if (!mv88e6xxx_should_tstamp(chip, port, skb, type))
> + return false;
> +
> + shhwtstamps = skb_hwtstamps(skb);
> + memset(shhwtstamps, 0, sizeof(*shhwtstamps));
> +
> + /* Because we configured the arrival timestamper to put the counter
> + * into the 32-bit "reserved" field of the PTP header, we can retrieve
> + * the value from the packet directly instead of having to retrieve it
> + * via SMI.
> + */
> + ptp_hdr = _get_ptp_header(skb, type);
> + if (IS_ERR(ptp_hdr))
> + return false;
> + ptp_rx_ts = (__be32 *)(ptp_hdr + OFF_PTP_RESERVED);
> + raw_ts = __be32_to_cpu(*ptp_rx_ts);
> + ns = timecounter_cyc2time(&chip->tstamp_tc, raw_ts);
> + shhwtstamps->hwtstamp = ns_to_ktime(ns);
> +
> + dev_dbg(chip->dev, "p%d: rxtstamp %llx\n", port, ns);
> +
> + return false;
> +}
> +
> +static void mv88e6xxx_txtstamp_work(struct work_struct *ugly)
> +{
> + struct mv88e6xxx_port_hwtstamp *ps = container_of(
> + ugly, struct mv88e6xxx_port_hwtstamp, tx_tstamp_work);
> + struct mv88e6xxx_chip *chip = container_of(
> + ps, struct mv88e6xxx_chip, port_hwtstamp[ps->port_id]);
> + struct sk_buff *tmp_skb;
> + unsigned long tmp_tstamp_start;
> + int err;
> + u16 departure_block[4];
> + u16 tmp_seq_id;
> +
> + if (!test_bit(MV88E6XXX_HWTSTAMP_TX_IN_PROGRESS, &ps->state))
> + return;
> +
> + tmp_skb = ps->tx_skb;
> + tmp_seq_id = ps->tx_seq_id;
> + tmp_tstamp_start = ps->tx_tstamp_start;
> +
> + if (!tmp_skb)
> + return;
> +
> + mutex_lock(&chip->reg_lock);
> + err = mv88e6xxx_port_ptp_read(chip, ps->port_id,
> + MV88E6XXX_PORT_PTP_DEP_STS,
> + departure_block,
> + ARRAY_SIZE(departure_block));
> + mutex_unlock(&chip->reg_lock);
> +
> + if (err)
> + goto free_and_clear_skb;
> +
> + if (departure_block[0] & MV88E6XXX_PTP_TS_VALID) {

You can avoid the IfOk anti-pattern here. Make the test for !VALID
and move the 'else' block up.

> + struct skb_shared_hwtstamps shhwtstamps;
> + u64 ns;
> + u32 time_raw;
> + u16 status;
> +
> + /* We have the timestamp; go ahead and clear valid now */
> + mutex_lock(&chip->reg_lock);
> + mv88e6xxx_port_ptp_write(chip, ps->port_id,
> + MV88E6XXX_PORT_PTP_DEP_STS, 0);
> + mutex_unlock(&chip->reg_lock);
> +
> + status = departure_block[0] &
> + MV88E6XXX_PTP_TS_STATUS_MASK;
> + if (status != MV88E6XXX_PTP_TS_STATUS_NORMAL) {
> + dev_warn(chip->dev, "p%d: tx timestamp overrun\n",
> + ps->port_id);
> + goto free_and_clear_skb;
> + }
> +
> + if (departure_block[3] != tmp_seq_id) {
> + dev_warn(chip->dev, "p%d: unexpected sequence id\n",
> + ps->port_id);
> + goto free_and_clear_skb;
> + }
> +
> + memset(&shhwtstamps, 0, sizeof(shhwtstamps));
> + time_raw = ((u32)departure_block[2] << 16) |
> + departure_block[1];
> + ns = timecounter_cyc2time(&chip->tstamp_tc, time_raw);
> + shhwtstamps.hwtstamp = ns_to_ktime(ns);
> +
> + dev_dbg(chip->dev,
> + "p%d: txtstamp %llx status 0x%04x skb ID 0x%04x hw ID 0x%04x\n",
> + ps->port_id, ktime_to_ns(shhwtstamps.hwtstamp),
> + departure_block[0], tmp_seq_id, departure_block[3]);
> +
> + /* skb_complete_tx_timestamp() will free up the client to make
> + * another timestamp-able transmit. We have to be ready for it
> + * -- by clearing the ps->tx_skb "flag" -- beforehand.
> + */
> +
> + ps->tx_skb = NULL;
> + clear_bit_unlock(MV88E6XXX_HWTSTAMP_TX_IN_PROGRESS, &ps->state);
> +
> + skb_complete_tx_timestamp(tmp_skb, &shhwtstamps);
> +
> + } else {
> + if (time_is_before_jiffies(
> + tmp_tstamp_start + TX_TSTAMP_TIMEOUT)) {
> + dev_warn(chip->dev, "p%d: clearing tx timestamp hang\n",
> + ps->port_id);
> + goto free_and_clear_skb;
> + }
> +
> + /* The timestamp should be available quickly, while getting it
> + * is high priority and time bounded to only 10ms. A poll is
> + * warranted and this is the nicest way to realize it in a work
> + * item.
> + */
> + queue_work(system_highpri_wq, &ps->tx_tstamp_work);
> + }
> +
> + return;
> +
> +free_and_clear_skb:
> + ps->tx_skb = NULL;
> + clear_bit_unlock(MV88E6XXX_HWTSTAMP_TX_IN_PROGRESS, &ps->state);
> +
> + dev_kfree_skb_any(tmp_skb);
> +}
> +
> +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;

This test is duplicated in mv88e6xxx_should_tstamp().

> + if (unlikely(skb_shinfo(clone)->tx_flags & SKBTX_HW_TSTAMP) &&
> + mv88e6xxx_should_tstamp(chip, port, clone, type)) {

Please avoid the IfOk anti-pattern here as well.

> + __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.
> + *
> + * 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);

How about moving this logic should into the caller, letting the tx
callback return a code that tells whether the clone was accepted or
not?

> +}

Thanks,
Richard