Re: [EXT] Re: [v1,net-next, 1/2] ethtool: add setting frame preemption of traffic classes

[Murali Karicheri <m-karicheri2@ti.com>]

Hi Vinicius,

On 03/12/2020 07:34 PM, Vinicius Costa Gomes wrote:
> Hi,
> 
> Po Liu <po.liu@nxp.com> writes:
> 
>> Hi Vinicius,
>>
>>
>> Br,
>> Po Liu
>>
>>> -----Original Message-----
>>> From: Vinicius Costa Gomes <vinicius.gomes@intel.com>
>>> Sent: 2020年2月22日 5:44
>>> To: Po Liu <po.liu@nxp.com>; davem@davemloft.net;
>>> hauke.mehrtens@intel.com; gregkh@linuxfoundation.org; allison@lohutok.net;
>>> tglx@linutronix.de; hkallweit1@gmail.com; saeedm@mellanox.com;
>>> andrew@lunn.ch; f.fainelli@gmail.com; alexandru.ardelean@analog.com;
>>> jiri@mellanox.com; ayal@mellanox.com; pablo@netfilter.org; linux-
>>> kernel@vger.kernel.org; netdev@vger.kernel.org
>>> Cc: simon.horman@netronome.com; Claudiu Manoil
>>> <claudiu.manoil@nxp.com>; Vladimir Oltean <vladimir.oltean@nxp.com>;
>>> Alexandru Marginean <alexandru.marginean@nxp.com>; Xiaoliang Yang
>>> <xiaoliang.yang_1@nxp.com>; Roy Zang <roy.zang@nxp.com>; Mingkai Hu
>>> <mingkai.hu@nxp.com>; Jerry Huang <jerry.huang@nxp.com>; Leo Li
>>> <leoyang.li@nxp.com>; Po Liu <po.liu@nxp.com>
>>> Subject: [EXT] Re: [v1,net-next, 1/2] ethtool: add setting frame preemption of
>>> traffic classes
>>>
>>> Caution: EXT Email
>>>
>>> Hi,
>>>
>>> Po Liu <po.liu@nxp.com> writes:
>>>
>>>> IEEE Std 802.1Qbu standard defined the frame preemption of port
>>>> traffic classes. This patch introduce a method to set traffic classes
>>>> preemption. Add a parameter 'preemption' in struct
>>>> ethtool_link_settings. The value will be translated to a binary, each
>>>> bit represent a traffic class. Bit "1" means preemptable traffic
>>>> class. Bit "0" means express traffic class.  MSB represent high number
>>>> traffic class.
>>>>
>>>> If hardware support the frame preemption, driver could set the
>>>> ethernet device with hw_features and features with NETIF_F_PREEMPTION
>>>> when initializing the port driver.
>>>>
>>>> User can check the feature 'tx-preemption' by command 'ethtool -k
>>>> devname'. If hareware set preemption feature. The property would be a
>>>> fixed value 'on' if hardware support the frame preemption.
>>>> Feature would show a fixed value 'off' if hardware don't support the
>>>> frame preemption.
>>>>
>>>> Command 'ethtool devname' and 'ethtool -s devname preemption N'
>>>> would show/set which traffic classes are frame preemptable.
>>>>
>>>> Port driver would implement the frame preemption in the function
>>>> get_link_ksettings() and set_link_ksettings() in the struct ethtool_ops.
>>>>
>>>
>>> Any updates on this series? If you think that there's something that I could help,
>>> just tell.
>>
>> Sorry for the long time not involve the discussion. I am focus on other tsn code for tc flower.
>> If you can take more about this preemption serial, that would be good.
>>
>> I summary some suggestions from Marali Karicheri and Ivan Khornonzhuk and by you and also others:
>> - Add config the fragment size, hold advance, release advance and flags;
>>      My comments about the fragment size is in the Qbu spec limit the fragment size " the minimum non-final fragment size is 64,
>> 128, 192, or 256 octets " this setting would affect the guardband setting for Qbv. But the ethtool setting could not involve this issues but by the taprio side.
>> - " Furthermore, this setting could be extend for a serial setting for mac and traffic class."  "Better not to using the traffic class concept."
>>     Could adding a serial setting by "ethtool --preemption xxx" or other name. I don' t think it is good to involve in the queue control since queues number may bigger than the TC number.
>> - The ethtool is the better choice to configure the preemption
>>    I agree.
> 
> Just a quick update. I was able to dedicate some time to this, and have
> something aproaching RFC-quality, but it needs more testing.
> 
Great! I have got my frame preemption working on my SoC. Currently I am
using some defaults. I test it by using statistics provided by the
SoC. I will be able to integrate and test your patch using my internal
version and will include it in my patch to upstream once I am ready.

Regards,

Murali
> So, question, what were you using for testing this? Anything special?
> 
> And btw, thanks for the summary of the discussion.
> 
>>
>> Thanks！
>>>
>>>
>>> Cheers,
>>> --
>>> Vinicius
> 
> 

-- 
Murali Karicheri
Texas Instruments