linux-kernel - RE: [EXT] Re: [PATCH v2 RFC net-next 08/18] net: mvpp2: add FCA periodic timer configurations

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Date:   Mon, 25 Jan 2021 07:15:40 +0000
From:   Stefan Chulski <stefanc@...vell.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "thomas.petazzoni@...tlin.com" <thomas.petazzoni@...tlin.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Nadav Haklai <nadavh@...vell.com>,
        Yan Markman <ymarkman@...vell.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "mw@...ihalf.com" <mw@...ihalf.com>,
        "atenart@...nel.org" <atenart@...nel.org>
Subject: RE: [EXT] Re: [PATCH v2 RFC net-next 08/18] net: mvpp2: add FCA
 periodic timer configurations

> > >
> > > --------------------------------------------------------------------
> > > -- On Sun, Jan 24, 2021 at 01:43:57PM +0200, stefanc@...vell.com
> > > wrote:
> > > > +/* Set Flow Control timer x140 faster than pause quanta to ensure
> > > > +that link
> > > > + * partner won't send taffic if port in XOFF mode.
> > >
> > > Can you explain more why 140 times faster is desirable here? Why 140
> > > times and not, say, 10 times faster? Where does this figure come
> > > from, and what is the reasoning? Is there a switch that requires it?
> >
> > I tested with 140.
> > Actually regarding to spec each quanta should be equal to 512 bit times.
> > In 10G bit time is 0.1ns.
> 
> And if the link has been negotiated to 10Mbps? Or is the clock already scaled
> to the link speed?
> 
>        Andrew

Currently its static, probably I can add function that reconfigure timer during runtime(based on link speed).
Should it be part of this series or add it afterwards?

Regards,
Stefan.