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 3/18/20 10:07 AM, Murali Karicheri wrote:
> 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.
> 
Any progress on your side for a patch for the support?

I have posted my EST offload series for AM65x CPSW to netdev list today
at

https://marc.info/?l=linux-netdev&m=158937640015582&w=2
https://marc.info/?l=linux-netdev&m=158937639515579&w=2
https://marc.info/?l=linux-netdev&m=158937638315573&w=2

Next on my list of things to do is the IET FPE support for which I need
to have ethtool interface to allow configuring the express/preemptible
queues and feature enable/disable. Currently I am using a ethtool
priv-flags and some defaults. If you can post a patch, I will be able
to integrate and test it on AM65x CPSW driver and provide my comments/
Tested-by:

Regards,

Murali

> 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