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

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Message-ID: <20240503085026.GH3927860@ragnatech.se>
Date: Fri, 3 May 2024 10:50:26 +0200
From: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
To: Arnd Bergmann <arnd@...db.de>, Simon Horman <horms@...nel.org>
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 <netdev@...r.kernel.org>,
	Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [net-next] net: ethernet: rtsn: Add support for Renesas
 Ethernet-TSN

Hi Arnd and Simon,

Thanks for your comments.

On 2024-04-18 21:03:51 +0200, Arnd Bergmann wrote:
> On Thu, Apr 18, 2024, at 20:32, Simon Horman wrote:
> >
> > Hi Niklas,
> >
> > I think that the use of __iowbm() means that this will not
> > compile for many architectures: grep indicates it
> > is only defined for arm, arm64, and arc.
> >
> > Perhaps COMPILE_TEST should be qualified somehow?
> 
> 
> >> +	/* Re-enable TX/RX interrupts */
> >> +	spin_lock_irqsave(&priv->lock, flags);
> >> +	rtsn_ctrl_data_irq(priv, true);
> >> +	__iowmb();
> >> +	spin_unlock_irqrestore(&priv->lock, flags);
> 
> I think this needs a comment anyway: what is this trying
> to serialize?
> 
> The arm64 __iowmb() usually tries to ensure that a memory
> write to a coherent buffer is complete before a following
> writel() is sent to the bus, but this one appears to be
> after the writel() where it has no effect because the
> transaction may still be in flight on the bus after it
> has left the store buffer.

Indeed, this is a leftover from development. Thanks for catching it, 
will drop for v2.

> 
>       Arnd

-- 
Kind Regards,
Niklas Söderlund