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

[Murali Karicheri]

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@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;
> > > ÂÂÂÂ 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."Â "Better not to using the traffic class 
> > > concept."
> > > ÂÂÂ 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
> > > ÂÂ 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.
> >
> > > Thanksï
> > > > Cheers,
> > > > --
> > > > Vinicius

--
Murali Karicheri
Texas Instruments