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

[Ferruh Yigit]

On 1/29/2024 1:58 PM, lihuisong (C) wrote:
> 
> 在 2024/1/29 19:16, Ferruh Yigit 写道:
>> On 1/27/2024 1:52 AM, lihuisong (C) wrote:
>>> 在 2024/1/27 0:54, Ferruh Yigit 写道:
>>>> On 1/11/2024 6:25 AM, lihuisong (C) wrote:
>>>>> Hi Ferruh,
>>>>>
>>>>> 在 2023/11/23 19:56, lihuisong (C) 写道:
>>>>>> 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?
>>>>> Can you take a look at this discussion line again?
>>>>>
>>>>> Let's introduce a  RTE_ETH_DEV_PTP in dev->data->dev_flags to
>>>>> reveal if
>>>>> the device support PTP feature.
>>>>>
>>> Hi Ferruh,
>>>
>>> Thanks for taking your time to reply.
>>>
>>>> Hi Huisong,
>>>>
>>>> First let me try to summarize the discussion since it has been some
>>>> time.
>>>>
>>>> HW timer block can be used for Rx timestamp offload
>>>> (RTE_ETH_RX_OFFLOAD_TIMESTAMP) and/or PTP support, but they are two
>>>> different things.
>>>>
>>>> This patch uses 'RTE_ETH_RX_OFFLOAD_TIMESTAMP' capability for PTP
>>>> support, which is wrong.
>>>>
>>> correct.
>>>> After we agreed on above, your next question is to use 'dev_flag' to
>>>> report PTP capability.
>>>>
>>>> First, can you please describe what is the motivation to learn if HW
>>>> supports PTP or now, what is the benefit of knowing this.
>>> There are a couple of device which have the same driver on a platform or
>>> OS.
>>> But just allow one device to support or be responsible for PTP feature.
>>> The firmware will report a capability to tell the device if it is
>>> support PTP.
>>> But, currently, driver doesn't know how to report user which device
>>> support PTP feature.
>>>
>> Driver can hold a private data that records if PTP supported by the
>> device or not, and according this value PTP dev_ops can return error or
>> success.
>>
>> This may not be ideal but it lets user to know about the support status,
>> can this work?
> I don't think it is user friendly.
> Users know which port supports the PTP feature only when the API fails
> to be invoked, right?
> In addition, this is a common issue for all supported PTP device. So It
> is better to do this check in PMD.
>>
>>
>>> In addition, many drivers use RTE_LIBRTE_IEEE1588 to control PTP code
>>> flow.
>>> Whether the device supports PTP is irrelevant to this macro.
>>>
>> Yes, I guess because both features use same HW, there is confusion there.
>>
>>>> If we agree that there is a need to know the PTP capability,
>>>> question is
>>>> where to report this capability.
>>>>
>>>> Suggested 'dev_flags' is used for various things, some are internal
>>>> flags and some are status, I don't think overloading this variable is
>>>> not good idea.
>>> Yes, we need to consider  carefully.
>>>> Other option is an update 'rte_eth_dev_info_get()' for it but it has
>>>> the
>>>> same problem, this function is already overloaded with many different
>>>> things.
>>>>
>>>> We can have an API just to get PTP capability, but this will require a
>>>> new dev_ops, this can be an option but my concern is having a
>>>> capability
>>>> dev_ops for each feature create a mess in dev_ops.
>>>>
>>>> Perhaps we can have single get_capability() API, and it gets
>>>> features as
>>>> flags to return if that feature is supported or not, but this
>>>> requires a
>>>> wider discussion.
>>>>
>>>> Instead can we deduce the capability from PTP relevant dev_ops, if they
>>>> are implemented we can say it is supported? This doesn't require new
>>>> support.
>>> Thank you mentioning so many ways.
>>> For the end of advice, I don't think it is appropriate.
>>> Because we have to modify dynamically the pointer address of all PTP
>>> APIs in dev_ops on the above case.
>>>
>> I was thinking for the case application distinguish if PTP related
>> dev_ops set or not, but after your explanation I can see this won't help
>> for your case.
>> Because in your case PTP dev_ops implemented but some devices support it
>> and some don't, and you are looking for a way to distinguish it.
> Yes
>>
>>> How about we use rte_eth_dev_info.dev_capa to report PTP offload?
>>> This is specifically used to report "Non-offload capabilities" according
>>> to its document.
>>>
>> As mentioned above 'rte_eth_dev_info' is overloaded, I am for being more
>> cautious to expand it more.
>> Also I think it is a wider discussion if we want a capability reporting
>> in ethdev and where it should be.
> How about we send a RFC patch which use rte_eth_dev_info.dev_capa to
> report PTP offload and start to disscuss this issue?
>

Ack. Lets start discussion on top of a patch. Thanks.

> And add Thomas's patch [1] and this patch.
> 
> [1]https://patchwork.dpdk.org/project/dpdk/patch/20230203132810.14187-1-thomas@monjalon.net/
> 
>>
>> .