netdev - Re: [PATCH] net: phy: mscc: enable MAC SerDes autonegotiation

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Date:   Sun, 27 Mar 2022 14:00:12 +0530
From:   Raag Jadav <raagjadav@...il.com>
To:     Siddharth Vadapalli <s-vadapalli@...com>
Cc:     "Russell King (Oracle)" <linux@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Steen Hegelund <steen.hegelund@...rochip.com>,
        Bjarni Jonasson <bjarni.jonasson@...rochip.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: phy: mscc: enable MAC SerDes autonegotiation

On Thu, Mar 24, 2022 at 03:36:02PM +0530, Siddharth Vadapalli wrote:
> Hi Raag,
> 
> On 26/02/22 12:53, Raag Jadav wrote:
> > On Thu, Feb 24, 2022 at 10:48:57AM +0000, Russell King (Oracle) wrote:
> >> Sorry for the late comment on this patch.
> >>
> >> On Sat, Feb 05, 2022 at 12:14:52PM +0530, Raag Jadav wrote:
> >>> +static int vsc85xx_config_inband_aneg(struct phy_device *phydev, bool enabled)
> >>> +{
> >>> +	int rc;
> >>> +	u16 reg_val = 0;
> >>> +
> >>> +	if (enabled)
> >>> +		reg_val = MSCC_PHY_SERDES_ANEG;
> >>> +
> >>> +	mutex_lock(&phydev->lock);
> >>> +
> >>> +	rc = phy_modify_paged(phydev, MSCC_PHY_PAGE_EXTENDED_3,
> >>> +			      MSCC_PHY_SERDES_PCS_CTRL, MSCC_PHY_SERDES_ANEG,
> >>> +			      reg_val);
> >>> +
> >>> +	mutex_unlock(&phydev->lock);
> >>
> >> What is the reason for the locking here?
> >>
> >> phy_modify_paged() itself is safe due to the MDIO bus lock, so you
> >> shouldn't need locking around it.
> >>
> > 
> > True.
> > 
> > My initial thought was to have serialized access at PHY level,
> > as we have multiple ports to work with.
> > But I guess MDIO bus lock could do the job as well.
> > 
> > Will fix it in v2 if required.
> 
> Could you please let me know if you plan to post the v2 patch?
> 
> The autonegotiation feature is also required for VSC8514, and has to be invoked
> in vsc8514_config_init(). Let me know if you need my help for this.
> 

Maybe this is what you're looking for.
https://www.spinics.net/lists/netdev/msg768517.html

Cheers,
Raag

> Regards,
> Siddharth