linux-kernel - Re: [PATCH net] net: sparx5: fix reconfiguration of PCS on link mode change

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Date: Fri, 5 Apr 2024 21:05:23 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Daniel Machon <daniel.machon@...rochip.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Lars Povlsen <lars.povlsen@...rochip.com>,
	Steen Hegelund <Steen.Hegelund@...rochip.com>,
	UNGLinuxDriver@...rochip.com,
	Bjarni Jonasson <bjarni.jonasson@...rochip.com>,
	netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: sparx5: fix reconfiguration of PCS on link mode
 change

On Fri, Apr 05, 2024 at 07:45:56PM +0000, Daniel Machon wrote:
> Hi Russel,
> 
> > It does change conf.autoneg slightly in that this will always be true
> > for SGMII, but will only be true for Autoneg + 802.3z modes.
> > 
> > As far as your code change goes, it looks correct to me, but I think
> > it's fixing a bug that goes back long before the commit you have
> > identified.
> 
> Just to be clear - by commit do you mean the phylink change or the commit
> referenced in the fixes tag?

I think the bug technically exists prior to the phylink change if
there is any possibility that the link may switch between inband
and a non-inband mode. (e.g. as a result of inserting a SFP module.)

> > However, I think there's another issue here which is more relevant to
> > the problem you describe in your commit message. If you look at
> > port_conf_has_changed(), you will notice that it fails to compare
> > conf.inband, and thus fails to notice any change in the setting of
> > that configuration item. This will result in sparx5_port_pcs_set()
> > not even being called if only conf.inband changes state.
> > 
> > Thus, changing from in-band to out-of-band or vice versa won't have
> > any effect if this is the only change that occurs, and this also
> > exists prior to my change.
> 
> Yes. I agree this is an issue that deserves a fix - separate from this
> one I would think.

Agreed, thanks.

-- 
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