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

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Date:   Sat, 22 Feb 2020 03:26:40 +0000
From:   Po Liu <po.liu@....com>
To:     Vinicius Costa Gomes <vinicius.gomes@...el.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>,
        Murali Karicheri <m-karicheri2@...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,


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.

Thanks！
> 
> 
> Cheers,
> --
> Vinicius