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

[Po Liu <po.liu@nxp.com>]

Br,
Po Liu

> -----Original Message-----
> From: Murali Karicheri <m-karicheri2@ti.com>
> Sent: 2020年2月26日 1:59
> To: Po Liu <po.liu@nxp.com>; Vinicius Costa Gomes
> <vinicius.gomes@intel.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>; Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
> Subject: Re: [EXT] Re: [v1,net-next, 1/2] ethtool: add setting frame
> preemption of traffic classes
> 
> Caution: EXT Email
> 
> Hi Po,
> 
> On 02/21/2020 10:26 PM, Po Liu wrote:
> > 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:
> 
> It is Murali :)
> 
> > - Add config the fragment size, hold advance, release advance and
> > flags;
> 
>   - I believe hold advance, release advance values are read only
> 
> >      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."
>   - Couldn't understand the above? Could you please explain a bit more
>     on what you meant here?

Oh, I copy the original suggestion by you and other here. Just for more evaluation for next version.

> 
> Murali
> >     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
> 
> --
> Murali Karicheri
> Texas Instruments