netdev - Re: [net-next,v4] net: ethernet: rtsn: Add support for Renesas Ethernet-TSN

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Message-ID: <20240509220720.GN1385281@ragnatech.se>
Date: Fri, 10 May 2024 00:07:20 +0200
From: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
To: Andrew Lunn <andrew@...n.ch>
Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org
Subject: Re: [net-next,v4] net: ethernet: rtsn: Add support for Renesas
 Ethernet-TSN

On 2024-05-09 23:12:43 +0200, Andrew Lunn wrote:
> > +	/* Link verification */
> > +	rtsn_modify(priv, MLVC, MLVC_PLV, MLVC_PLV);
> > +	ret = rtsn_reg_wait(priv, MLVC, MLVC_PLV, 0);
> > +	if (ret)
> > +		return ret;
> 
> What is link verification?

It's a part of the TSN capabilities, it verifies if the link is capable 
of preemption. AFIK it's described in IEEE802.1Qbu Frame Preemption 
Protocol.

For this device in particular, this register writes enables the Link 
Verification process. Which in turn allows the IP to transmitting Verify 
frames, which if replied too with a valid Reply frame by the other node 
lets the IP know the link supports preemption.

-- 
Kind Regards,
Niklas Söderlund