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

[Murali Karicheri]

Hi Vinicius,

On 03/12/2020 07:34 PM, Vinicius Costa Gomes wrote:
> Hi,
>
> Po Liu <po.liu@xxxxxxx> writes:
>
> > Hi Vinicius,
> >
> >
> > Br,
> > Po Liu
> >
> > > -----Original Message-----
> > > From: Vinicius Costa Gomes <vinicius.gomes@xxxxxxxxx>
> > > Sent: 2020å2æ22æ 5:44
> > > To: Po Liu <po.liu@xxxxxxx>; davem@xxxxxxxxxxxxx;
> > > hauke.mehrtens@xxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; allison@xxxxxxxxxxx;
> > > tglx@xxxxxxxxxxxxx; hkallweit1@xxxxxxxxx; saeedm@xxxxxxxxxxxx;
> > > andrew@xxxxxxx; f.fainelli@xxxxxxxxx; alexandru.ardelean@xxxxxxxxxx;
> > > jiri@xxxxxxxxxxxx; ayal@xxxxxxxxxxxx; pablo@xxxxxxxxxxxxx; linux-
> > > kernel@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx
> > > Cc: simon.horman@xxxxxxxxxxxxx; Claudiu Manoil
> > > <claudiu.manoil@xxxxxxx>; Vladimir Oltean <vladimir.oltean@xxxxxxx>;
> > > Alexandru Marginean <alexandru.marginean@xxxxxxx>; Xiaoliang Yang
> > > <xiaoliang.yang_1@xxxxxxx>; Roy Zang <roy.zang@xxxxxxx>; Mingkai Hu
> > > <mingkai.hu@xxxxxxx>; Jerry Huang <jerry.huang@xxxxxxx>; Leo Li
> > > <leoyang.li@xxxxxxx>; Po Liu <po.liu@xxxxxxx>
> > > Subject: [EXT] Re: [v1,net-next, 1/2] ethtool: add setting frame preemption of
> > > traffic classes
> > >
> > > Caution: EXT Email
> > >
> > > Hi,
> > >
> > > Po Liu <po.liu@xxxxxxx> 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.

Regards,

Murali
> So, question, what were you using for testing this? Anything special?
>
> And btw, thanks for the summary of the discussion.
>
> > Thanksï
> > > Cheers,
> > > --
> > > Vinicius

--
Murali Karicheri
Texas Instruments