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

Po Liu
2020-02-22T03:26:47Z

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.

Thanks！
>
>
> Cheers,
> --
> Vinicius