RE: [BUG] net: phy: genphy_loopback: add link speed configuration

[Ismail, Mohammad Athari]

> -----Original Message-----
> From: Andrew Lunn <andrew@xxxxxxx>
> Sent: Tuesday, December 14, 2021 5:39 PM
> To: Ismail, Mohammad Athari <mohammad.athari.ismail@xxxxxxxxx>
> Cc: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; Voon, Weifeng <weifeng.voon@xxxxxxxxx>;
> Wong, Vee Khee <vee.khee.wong@xxxxxxxxx>
> Subject: Re: [BUG] net: phy: genphy_loopback: add link speed configuration
> 
> On Tue, Dec 14, 2021 at 07:00:37AM +0000, Ismail, Mohammad Athari wrote:
> > Hi Oleksij,
> >
> > "net: phy: genphy_loopback: add link speed configuration" patch causes
> Marvell 88E1510 PHY not able to perform PHY loopback using ethtool
> command (ethtool -t eth0 offline). Below is the error message:
> >
> > "Marvell 88E1510 stmmac-3:01: genphy_loopback failed: -110"
> 
> -110 is ETIMEDOUT. So that points to the phy_read_poll_timeout().
> 
> Ah, that points to the fact the Marvell PHYs are odd. You need to perform a
> software reset after changing some registers to actually execute the change.
> 
> As a quick test, please could you try:
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 74d8e1dc125f..b45f3ffc7c7f 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -2625,6 +2625,10 @@ int genphy_loopback(struct phy_device *phydev,
> bool enable)
> 
>                 phy_modify(phydev, MII_BMCR, ~0, ctl);
> 
> +               ret = genphy_soft_reset(phydev);
> +               if (ret < 0)
> +                       return ret;
> +
>                 ret = phy_read_poll_timeout(phydev, MII_BMSR, val,
>                                             val & BMSR_LSTATUS,
>                                     5000, 500000, true);
> 
> If this fixes it for you, the actual fix will be more complex, Marvell cannot use
> genphy_loopback, it will need its own implementation.

Thanks for the suggestion. The proposed solution also doesn't work. Still get -110 error.

-Athari-

> 
>        Andrew