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Date:   Wed, 6 Dec 2023 19:58:02 +0100
From:   Maxime Chevallier <maxime.chevallier@bootlin.com>
To:     "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc:     Daniel Golle <daniel@makrotopia.org>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
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        Conor Dooley <conor+dt@kernel.org>,
        Chunfeng Yun <chunfeng.yun@mediatek.com>,
        Vinod Koul <vkoul@kernel.org>,
        Kishon Vijay Abraham I <kishon@kernel.org>,
        Felix Fietkau <nbd@nbd.name>, John Crispin <john@phrozen.org>,
        Sean Wang <sean.wang@mediatek.com>,
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Subject: Re: [RFC PATCH v2 5/8] net: pcs: add driver for MediaTek USXGMII
 PCS
Message-ID: <20231206195802.5d2562e7@device.home>
In-Reply-To: <ZXC2MFn7pVX/KNmJ@shell.armlinux.org.uk>
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        <3cd8af5e44554c2db2d7898494ee813967206bd9.1701826319.git.daniel@makrotopia.org>
        <20231206105838.069ae288@device.home>
        <ZXC2MFn7pVX/KNmJ@shell.armlinux.org.uk>
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On Wed, 6 Dec 2023 17:58:08 +0000
"Russell King (Oracle)" <linux@armlinux.org.uk> wrote:

> On Wed, Dec 06, 2023 at 10:58:38AM +0100, Maxime Chevallier wrote:
> > On Wed, 6 Dec 2023 01:44:38 +0000
> > Daniel Golle <daniel@makrotopia.org> wrote:  
> > > +	/* Read USXGMII link status */
> > > +	state->link = FIELD_GET(RG_PCS_RX_LINK_STATUS,
> > > +				mtk_r32(mpcs, RG_PCS_RX_STATUS0));
> > > +
> > > +	/* Continuously repeat re-configuration sequence until link comes up */
> > > +	if (!state->link) {
> > > +		mtk_usxgmii_pcs_config(pcs, mpcs->neg_mode,
> > > +				       state->interface, NULL, false);
> > > +		return;  
> > 
> > .pcs_get_state() isn't called only for link state polling,but also when querying
> > the link state from ethtool, from phylink_ethtool_ksettings_get().
> > 
> > As mtk_usxgmii_pcs_config triggers a pcs reset and reconfiguration, won't this disrupt
> > the link ?   
> 
> Highly likely if there's a race, but note that mtk_usxgmii_pcs_config()
> only gets called if the link is *down*. I guess some IPs need a bit of
> kicking to work properly.
> 
Ah right that's true, it should be OK then.

Thanks,

Maxime