[PATCH v3 0/2] ethdev: add the check for PTP capability

[lihuisong (C)]

在 2023/11/2 7:39, Ferruh Yigit 写道:
> timesync_read_rx_timestamp
> On 9/21/2023 12:59 PM, lihuisong (C) wrote:
>> add ice & igc maintainers
>>
>> 在 2023/9/21 19:06, Ferruh Yigit 写道:
>>> On 9/21/2023 11:02 AM, lihuisong (C) wrote:
>>>> Hi Ferruh,
>>>>
>>>> Sorry for my delay reply because of taking a look at all PMDs
>>>> implementation.
>>>>
>>>>
>>>> 在 2023/9/16 1:46, Ferruh Yigit 写道:
>>>>> On 8/17/2023 9:42 AM, Huisong Li wrote:
>>>>>>    From the first version of ptpclient, it seems that this example
>>>>>> assume that
>>>>>> the PMDs support the PTP feature and enable PTP by default. Please see
>>>>>> commit ab129e9065a5 ("examples/ptpclient: add minimal PTP client")
>>>>>> which are introduced in 2015.
>>>>>>
>>>>>> And two years later, Rx HW timestamp offload was introduced to
>>>>>> enable or
>>>>>> disable PTP feature in HW via rte_eth_rxmode. Please see
>>>>>> commit 42ffc45aa340 ("ethdev: add Rx HW timestamp capability").
>>>>>>
>>>>> Hi Huisong,
>>>>>
>>>>> As far as I know this offload is not for PTP.
>>>>> PTP and TIMESTAMP are different.
>>>> If TIMESTAMP offload cannot stand for PTP, we may need to add one new
>>>> offlaod for PTP.
>>>>
>>> Can you please detail what is "PTP offload"?
>>>
>> It indicates whether the device supports PTP or enable  PTP feature.
>>
> We have 'rte_eth_timesync_enable()' and 'rte_eth_timesync_disable()'
> APIs to control PTP support.
No, this is just to control it.
we still need to like a device capablity to report application if the 
port support to call this API, right?
>
> But when mention from "offload", it is something device itself does.
>
> PTP is a protocol (IEEE 1588), and used to synchronize clocks.
> What I get is protocol can be parsed by networking stack and it can be
> used by application to synchronize clock.
>
> When you are refer to "PTP offload", does it mean device (NIC)
> understands the protocol and parse it to synchronize device clock with
> other devices?
Good point. PTP offload is unreasonable.
But the capablity is required indeed.
What do you think of introducing a RTE_ETH_DEV_PTP in 
dev->data->dev_flags for PTP feature?
>
>
> We have 'rte_eth_timesync_*()' APIs, my understanding is application
> parses the PTP protocol, and it may use this information to configure
> NIC to synchronize its clock, but it may also use PTP provided
> information to sync any other clock. Is this understanding correct?
>
>
>> If TIMESTAMP offload is not for PTP, I don't know what the point of this
>> offload independent existence is.
>>
> TIMESTAMP offload request device to add timestamp to mbuf in ingress,
> and use mbuf timestamp to schedule packet for egress.
Agree.
>
> Technically this time-stamping can be done by driver, but if offload
> set, HW timestamp is used for it.
>
> Rx timestamp can be used for various reasons, like debugging and
> performance/latency analyses, etc..
>
>
>>>>> PTP is a protocol for time sync.
>>>>> Rx TIMESTAMP offload is to ask HW to add timestamp to mbuf.
>>>> Yes.
>>>> But a lot of PMDs actually depand on HW to report Rx timestamp releated
>>>> information
>>>> because of reading Rx timestamp of PTP SYNC packet in read_rx_timestamp
>>>> API.
>>>>
>>> HW support may be required for PTP but this doesn't mean timestamp
>>> offload is used.
>> understand.
>>>>>> And then about four years later, ptpclient enable Rx timestamp offload
>>>>>> because some PMDs require this offload to enable. Please see
>>>>>> commit 7a04a4f67dca ("examples/ptpclient: enable Rx timestamp
>>>>>> offload").
>>>>>>
>>>>> dpaa2 seems using TIMESTAMP offload and PTP together, hence they
>>>>> updated
>>>>> ptpclient sample to set TIMESTAMP offload.
>>>> There are many PMDs doing like this, such as ice, igc, cnxk, dpaa2, hns3
>>>> and so on.
>>>>
>>> Can you please point the ice & igc code, cc'ing their maintainers, we
>>> can look together?
>> *-->igc code:*
>>
>> Having following codes in igc_recv_scattered_pkts():
>>
>>          if (rxq->offloads & RTE_ETH_RX_OFFLOAD_TIMESTAMP) {
>>              uint32_t *ts = rte_pktmbuf_mtod_offset(first_seg,
>>                      uint32_t *, -IGC_TS_HDR_LEN);
>>              rxq->rx_timestamp = (uint64_t)ts[3] * NSEC_PER_SEC +
>>                      ts[2];
>>              rxm->timesync = rxq->queue_id;
>>          }
>> Note：this rxm->timesync will be used in timesync_read_rx_timestamp()
>>
> Above code requires TIMESTAMP offload to set timesync, but this
> shouldn't be a requirement. Usage seems mixed.
>
>> *-->ice code:*
>>
>> #ifndef RTE_LIBRTE_ICE_16BYTE_RX_DESC
>>          if (ice_timestamp_dynflag > 0 &&
>>              (rxq->offloads & RTE_ETH_RX_OFFLOAD_TIMESTAMP)) {
>>              rxq->time_high =
>>                 rte_le_to_cpu_32(rxd.wb.flex_ts.ts_high);
>>              if (unlikely(is_tsinit)) {
>>                  ts_ns = ice_tstamp_convert_32b_64b(hw, ad, 1,
>> rxq->time_high);
>>                  rxq->hw_time_low = (uint32_t)ts_ns;
>>                  rxq->hw_time_high = (uint32_t)(ts_ns >> 32);
>>                  is_tsinit = false;
>>              } else {
>>                  if (rxq->time_high < rxq->hw_time_low)
>>                      rxq->hw_time_high += 1;
>>                  ts_ns = (uint64_t)rxq->hw_time_high << 32 | rxq->time_high;
>>                  rxq->hw_time_low = rxq->time_high;
>>              }
>>              rxq->hw_time_update = rte_get_timer_cycles() /
>>                           (rte_get_timer_hz() / 1000);
>>              *RTE_MBUF_DYNFIELD(rxm,
>>                         (ice_timestamp_dynfield_offset),
>>                         rte_mbuf_timestamp_t *) = ts_ns;
>>              pkt_flags |= ice_timestamp_dynflag;
>>          }
>>
>>          if (ad->ptp_ena && ((rxm->packet_type & RTE_PTYPE_L2_MASK) ==
>>              RTE_PTYPE_L2_ETHER_TIMESYNC)) {
>>              rxq->time_high =
>>                 rte_le_to_cpu_32(rxd.wb.flex_ts.ts_high);
>>              rxm->timesync = rxq->queue_id;
>>              pkt_flags |= RTE_MBUF_F_RX_IEEE1588_PTP;
>>          }
>> #endif
>>
>> Note: rxm->timesync and rxq->time_high will be used in
>> timesync_read_rx_timestamp()
>>
> This usage looks good, if TIMESTAMP offload enabled mbuf dynamic field
> and flag set accordingly.
hns3 also implemented PTP as ice did.
>
> And if PTP enabled, and PTP packet type detected relevant flag set in
> mbuf, and timesyc value set to use later for 'timesync_read_rx_timestamp()'.
Yes.
>
>
> Although above usage looks correct, I can see in 'ice_timesync_enable()'
> TIMESTAMP offload is used requirement to enable timesync.
> TIMESTAMP offload seems used as way to enable HW timestamp, as Hemant
> mentioned what is done is dpaa2.
>
>
>>>
>>>>> We need to clarify dpaa2 usage.
>>>>>
>>>>>> By all the records, this is more like a process of perfecting PTP
>>>>>> feature.
>>>>>> Not all network adaptors support PTP feature. So adding the check for
>>>>>> PTP
>>>>>> capability in ethdev layer is necessary.
>>>>>>
>>>>> Nope, as PTP (IEEE1588/802.1AS) implemented as dev_ops, and ops already
>>>>> checked, so no additional check is needed.
>>>> But only having dev_ops about PTP doesn't satisfy the use of this
>>>> feature.
>>>> For example,
>>>> there are serveal network ports belonged to a driver on one OS, and only
>>>> one port support PTP function.
>>>> So driver needs one *PTP* offload.
>>>>> We just need to clarify TIMESTAMP offload and PTP usage and find out
>>>>> what is causing confusion.
>>>> Yes it is a little bit confusion.
>>>> There are two kinds of implementation:
>>>> A： ixgbe and txgbe (it seems that their HW is similar) don't need
>>>> TIMESTAMP offload，and only use dev_ops to finish PTP feature.
>>>> B:  saving "Rx timestamp related information" from Rx description when
>>>> receive PTP SYNC packet and
>>>>       report it in read_rx_timestamp API.
>>>> For case B, most of driver use TIMESTAMP offload to decide if driver
>>>> save "Rx timestamp related information.
>>>> What do you think about this, Ferruh?
>>>>> I would be great if you can help on clarification, and update
>>>>> documentation or API comments, or what ever required, for this.
>>>> ok
>>>>>> ---
>>>>>> v3:
>>>>>>     - patch [2/3] for hns3 has been applied and so remove it.
>>>>>>     - ops pointer check is closer to usage.
>>>>>>
>>>>>> Huisong Li (2):
>>>>>>      examples/ptpclient: add the check for PTP capability
>>>>>>      ethdev: add the check for the valitity of timestamp offload
>>>>>>
>>>>>>     examples/ptpclient/ptpclient.c |  5 +++
>>>>>>     lib/ethdev/rte_ethdev.c        | 57
>>>>>> +++++++++++++++++++++++++++++++++-
>>>>>>     2 files changed, 61 insertions(+), 1 deletion(-)
>>>>>>
>>>>> .
>>> .
> .