netdev - Re: [PATCH v2 net-next 1/1] net: dsa: hellcreek: Add TAPRIO offloading support

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Date:   Wed, 20 Jan 2021 16:50:39 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Kurt Kanzenbach <kurt@...utronix.de>
Cc:     Vladimir Oltean <olteanv@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next 1/1] net: dsa: hellcreek: Add TAPRIO
 offloading support

On Wed, 20 Jan 2021 08:18:15 +0100 Kurt Kanzenbach wrote:
> >> +	/* Schedule periodic schedule check */
> >> +	schedule_delayed_work(&hellcreek_port->schedule_work,
> >> +			      HELLCREEK_SCHEDULE_PERIOD);  
> >
> > Why schedule this work every 2 seconds rather than scheduling it
> > $start_time - 8 sec + epsilon?  
> 
> The two seconds are taken from the programming guide. That's why I used
> it.
> 
> The PTP frequency starts to matter for large deltas. In theory the
> rescheduling period can be increased [1]. Should I adjust it? 

I see, makes sense. You can leave it as is, please just add a comment
next to the definition saying that the exact value is not important we
just want it to be low enough to no suffer from clock freq error.