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

["lihuisong (C)" <lihuisong@huawei.com>]

在 2023/11/2 7:39, Ferruh Yigit 写道:
> On 10/20/2023 4:58 AM, lihuisong (C) wrote:
>> 在 2023/9/21 19:17, Hemant Agrawal 写道:
>>> HI Ferruh,
>>>
>>>> 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"?
>>>>
>>>>>> 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.
>>>>>>> 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.
>>> [Hemant] In case of dpaa2, we need to enable HW timestamp for PTP. In
>>> the current dpaa2 driver
>>> If the code is compiled with, RTE_LIBRTE_IEEE1588, we are enabling the
>>> HW timestamp
>>> Otherwise, we are only enabling it when the TIMESTAMP offload is
>>> selected.
>>>
>>> We added patch in ptpclient earlier to pass the timestamp offload,
>>> however later we also updated the driver to do it by default.
>>>
>>>
>> It is a little mess for PTP and RTE_LIBRTE_IEEE1588 to use.
>> Actually, whether PTP code is compiled should not depended on this macro
>> RTE_LIBRTE_IEEE1588.
>>
> There is already a patch by Thomas to remove RTE_LIBRTE_IEEE1588 [1],
> agree that this functionality needs some attention.
>
> Removing RTE_LIBRTE_IEEE1588 impact drivers, that is what holding us back.
+1 remove the compile macro RTE_LIBRTE_IEEE1588.
And hns3 had beed removed it.
>
>
> [1]
> https://patchwork.dpdk.org/project/dpdk/patch/20230203132810.14187-1-thomas@monjalon.net/
>
>> If there is a capability, it will be perfect, no matter whether it is
>> TIMESTAMP offload.
>> What do you think, Ferruh?
>>
> Difficulty is to know when to enable HW timestamp, and for some drivers
> this may change the descriptor format (to include timestamp), so driver
> should set correct datapath functions for this case.
Yes, to get Rx timestamp of PTP packet from descriptor for many NIC.
>
> We know when a HW timer is required, it is required for PTP protocol and
> required for TIMESTAMP offload.
TIMESTAMP offload may be unnecessary for some NIC which don't get Rx 
timestamp from descriptor(But, IMO, like this hardware is very rare.).
>
> What do you think to dynamically enable it for PTP when
> 'rte_eth_timesync_enable()' API called, and for TIMESTAMP offload when
> the offload is enabled.
Agree above.
At least, this can make sure all NIC can enable PTP feature.
> If this works, now new configuration item or offload is required, what
> do you think?
The new capability item is required to know if the port support PTP feature.
so application can enable/disable PTP based on this capability.
>
>>>>> 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?
>>>>
>>>>
>>>>>> 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(-)
>>>>>>>
>>>>>> .
> .