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

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Date:   Wed, 13 May 2020 10:55:47 -0400
From:   Murali Karicheri <m-karicheri2@...com>
To:     Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        Po Liu <po.liu@....com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "hauke.mehrtens@...el.com" <hauke.mehrtens@...el.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "allison@...utok.net" <allison@...utok.net>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "saeedm@...lanox.com" <saeedm@...lanox.com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "alexandru.ardelean@...log.com" <alexandru.ardelean@...log.com>,
        "jiri@...lanox.com" <jiri@...lanox.com>,
        "ayal@...lanox.com" <ayal@...lanox.com>,
        "pablo@...filter.org" <pablo@...filter.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "simon.horman@...ronome.com" <simon.horman@...ronome.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Alexandru Marginean <alexandru.marginean@....com>,
        Xiaoliang Yang <xiaoliang.yang_1@....com>,
        Roy Zang <roy.zang@....com>, Mingkai Hu <mingkai.hu@....com>,
        Jerry Huang <jerry.huang@....com>, Leo Li <leoyang.li@....com>,
        Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
Subject: Re: [EXT] Re: [v1,net-next, 1/2] ethtool: add setting frame
 preemption of traffic classes

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@....com> writes:
>>
>>> Hi Vinicius,
>>>
>>>
>>> Br,
>>> Po Liu
>>>
>>>> -----Original Message-----
>>>> From: Vinicius Costa Gomes <vinicius.gomes@...el.com>
>>>> Sent: 2020年2月22日 5:44
>>>> To: Po Liu <po.liu@....com>; davem@...emloft.net;
>>>> hauke.mehrtens@...el.com; gregkh@...uxfoundation.org; 
>>>> allison@...utok.net;
>>>> tglx@...utronix.de; hkallweit1@...il.com; saeedm@...lanox.com;
>>>> andrew@...n.ch; f.fainelli@...il.com; alexandru.ardelean@...log.com;
>>>> jiri@...lanox.com; ayal@...lanox.com; pablo@...filter.org; linux-
>>>> kernel@...r.kernel.org; netdev@...r.kernel.org
>>>> Cc: simon.horman@...ronome.com; Claudiu Manoil
>>>> <claudiu.manoil@....com>; Vladimir Oltean <vladimir.oltean@....com>;
>>>> Alexandru Marginean <alexandru.marginean@....com>; Xiaoliang Yang
>>>> <xiaoliang.yang_1@....com>; Roy Zang <roy.zang@....com>; Mingkai Hu
>>>> <mingkai.hu@....com>; Jerry Huang <jerry.huang@....com>; Leo Li
>>>> <leoyang.li@....com>; Po Liu <po.liu@....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@....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