linux-kernel - RE: [PATCH net-next v2] net: phy: marvell: add sleep time after enabling the loopback bit

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Date:   Fri, 11 Nov 2022 03:40:25 +0000
From:   "Jamaluddin, Aminuddin" <aminuddin.jamaluddin@...el.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "Ismail, Mohammad Athari" <mohammad.athari.ismail@...el.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "Tan, Tee Min" <tee.min.tan@...el.com>,
        "Zulkifli, Muhammad Husaini" <muhammad.husaini.zulkifli@...el.com>,
        "Looi, Hong Aun" <hong.aun.looi@...el.com>
Subject: RE: [PATCH net-next v2] net: phy: marvell: add sleep time after
 enabling the loopback bit

> -----Original Message-----
> From: Florian Fainelli <f.fainelli@...il.com>
> Sent: Thursday, 10 November, 2022 11:54 AM
> To: Jamaluddin, Aminuddin <aminuddin.jamaluddin@...el.com>; Andrew
> Lunn <andrew@...n.ch>; Heiner Kallweit <hkallweit1@...il.com>; Russell
> King <linux@...linux.org.uk>; David S . Miller <davem@...emloft.net>; Eric
> Dumazet <edumazet@...gle.com>; Jakub Kicinski <kuba@...nel.org>;
> Paolo Abeni <pabeni@...hat.com>; Ismail, Mohammad Athari
> <mohammad.athari.ismail@...el.com>
> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org;
> stable@...r.kernel.org; Tan, Tee Min <tee.min.tan@...el.com>; Zulkifli,
> Muhammad Husaini <muhammad.husaini.zulkifli@...el.com>; Looi, Hong
> Aun <hong.aun.looi@...el.com>
> Subject: Re: [PATCH net-next v2] net: phy: marvell: add sleep time after
> enabling the loopback bit
> 
> 
> 
> On 11/7/2022 11:40 PM, Aminuddin Jamaluddin wrote:
> > Sleep time is added to ensure the phy to be ready after loopback bit
> > was set. This to prevent the phy loopback test from failing.
> >
> > ---
> > V1:
> >
> https://patchwork.kernel.org/project/netdevbpf/patch/20220825082238.11
> > 056-1-aminuddin.jamaluddin@...el.com/
> > ---
> >
> > Fixes: 020a45aff119 ("net: phy: marvell: add Marvell specific PHY
> > loopback")
> > Cc: <stable@...r.kernel.org> # 5.15.x
> > Signed-off-by: Muhammad Husaini Zulkifli
> > <muhammad.husaini.zulkifli@...el.com>
> > Signed-off-by: Aminuddin Jamaluddin <aminuddin.jamaluddin@...el.com>
> > ---
> >   drivers/net/phy/marvell.c | 16 +++++++++-------
> >   1 file changed, 9 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/net/phy/marvell.c b/drivers/net/phy/marvell.c
> > index a3e810705ce2..860610ba4d00 100644
> > --- a/drivers/net/phy/marvell.c
> > +++ b/drivers/net/phy/marvell.c
> > @@ -2015,14 +2015,16 @@ static int m88e1510_loopback(struct
> phy_device *phydev, bool enable)
> >   		if (err < 0)
> >   			return err;
> >
> > -		/* FIXME: Based on trial and error test, it seem 1G need to
> have
> > -		 * delay between soft reset and loopback enablement.
> > -		 */
> > -		if (phydev->speed == SPEED_1000)
> > -			msleep(1000);
> > +		err = phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK,
> > +				 BMCR_LOOPBACK);
> >
> > -		return phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK,
> > -				  BMCR_LOOPBACK);
> > +		if (!err) {
> > +			/* It takes some time for PHY device to switch
> > +			 * into/out-of loopback mode.
> > +			 */
> > +			msleep(1000);
> 
> Is not there a better indication than waiting a full second to ensure the PHY
> exited loopback?

Previously we implemented the link status check that waiting phy to be ready
before the loopback bit being set in V1. But we removed it due to simpler
behaviour as that can be achieve with this. And previous discussion with Marvell
stated the delay timing was needed after loopback bit is set. 

> --

Amin