RE: [PATCH net v3] net: phy: marvell: add Marvell specific PHY loopback

[Ismail, Mohammad Athari]

> -----Original Message-----
> From: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> Sent: Saturday, January 15, 2022 4:34 AM
> To: Ismail, Mohammad Athari <mohammad.athari.ismail@xxxxxxxxx>;
> Andrew Lunn <andrew@xxxxxxx>; David S . Miller <davem@xxxxxxxxxxxxx>;
> Jakub Kicinski <kuba@xxxxxxxxxx>; Oleksij Rempel <linux@rempel-
> privat.de>; Russell King <linux@xxxxxxxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> stable@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH net v3] net: phy: marvell: add Marvell specific PHY
> loopback
> 
> On 13.01.2022 10:56, Mohammad Athari Bin Ismail wrote:
> > Existing genphy_loopback() is not applicable for Marvell PHY. Besides
> > configuring bit-6 and bit-13 in Page 0 Register 0 (Copper Control
> > Register), it is also required to configure same bits  in Page 2
> > Register 21 (MAC Specific Control Register 2) according to speed of
> > the loopback is operating.
> >
> > Tested working on Marvell88E1510 PHY for all speeds (1000/100/10Mbps).
> >
> > FIXME: Based on trial and error test, it seem 1G need to have delay
> > between soft reset and loopback enablement.
> >
> > Fixes: 014068dcb5b1 ("net: phy: genphy_loopback: add link speed
> > configuration")
> > Cc: <stable@xxxxxxxxxxxxxxx> # 5.15.x
> > Signed-off-by: Mohammad Athari Bin Ismail
> > <mohammad.athari.ismail@xxxxxxxxx>
> > ---
> > v3 changelog:
> > - Use phy_write() to configure speed for BMCR.
> > - Add error handling.
> > All commented by Russell King <linux@xxxxxxxxxxxxxxx>
> >
> > v2 changelog:
> > - For loopback enabled, add bit-6 and bit-13 configuration in both Page
> >   0 Register 0 and Page 2 Register 21. Commented by Heiner Kallweit
> > <hkallweit1@xxxxxxxxx>.
> > - For loopback disabled, follow genphy_loopback() implementation
> > ---
> >  drivers/net/phy/marvell.c | 56
> > ++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 55 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/phy/marvell.c b/drivers/net/phy/marvell.c
> > index 4fcfca4e1702..5c371c2de9a0 100644
> > --- a/drivers/net/phy/marvell.c
> > +++ b/drivers/net/phy/marvell.c
> > @@ -189,6 +189,8 @@
> >  #define MII_88E1510_GEN_CTRL_REG_1_MODE_RGMII_SGMII	0x4
> >  #define MII_88E1510_GEN_CTRL_REG_1_RESET	0x8000	/* Soft reset
> */
> >
> > +#define MII_88E1510_MSCR_2		0x15
> > +
> >  #define MII_VCT5_TX_RX_MDI0_COUPLING	0x10
> >  #define MII_VCT5_TX_RX_MDI1_COUPLING	0x11
> >  #define MII_VCT5_TX_RX_MDI2_COUPLING	0x12
> > @@ -1932,6 +1934,58 @@ static void marvell_get_stats(struct phy_device
> *phydev,
> >  		data[i] = marvell_get_stat(phydev, i);  }
> >
> > +static int marvell_loopback(struct phy_device *phydev, bool enable)
> 
> Marvell PHY's use different bits for the loopback speed, e.g.:
> 
> 88E1510 bits 13, 6
> 88E1545 bits 2..0

Thank you for the info.

> 
> Your function is usable with certain Marvell PHY's only, therefore the
> function name is misleading. At a first glance I see two options:
> 
> 1. Leave the function name and add a version-specific section that returns
>    an error for (not yet) supported versions.
> 2. Name it m88e1510_loopback()

I'll go for option 2. Thank you for the suggestion.

-Athari-

> 
> > +{
> > +	int err;
> > +
> > +	if (enable) {
> > +		u16 bmcr_ctl = 0, mscr2_ctl = 0;
> > +
> > +		if (phydev->speed == SPEED_1000)
> > +			bmcr_ctl = BMCR_SPEED1000;
> > +		else if (phydev->speed == SPEED_100)
> > +			bmcr_ctl = BMCR_SPEED100;
> > +
> > +		if (phydev->duplex == DUPLEX_FULL)
> > +			bmcr_ctl |= BMCR_FULLDPLX;
> > +
> > +		err = phy_write(phydev, MII_BMCR, bmcr_ctl);
> > +		if (err < 0)
> > +			return err;
> > +
> > +		if (phydev->speed == SPEED_1000)
> > +			mscr2_ctl = BMCR_SPEED1000;
> > +		else if (phydev->speed == SPEED_100)
> > +			mscr2_ctl = BMCR_SPEED100;
> > +
> > +		err = phy_modify_paged(phydev,
> MII_MARVELL_MSCR_PAGE,
> > +				       MII_88E1510_MSCR_2, BMCR_SPEED1000
> |
> > +				       BMCR_SPEED100, mscr2_ctl);
> > +		if (err < 0)
> > +			return err;
> > +
> > +		/* Need soft reset to have speed configuration takes effect
> */
> > +		err = genphy_soft_reset(phydev);
> > +		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);
> > +
> > +		return phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK,
> > +				  BMCR_LOOPBACK);
> > +	} else {
> > +		err = phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK, 0);
> > +		if (err < 0)
> > +			return err;
> > +
> > +		return phy_config_aneg(phydev);
> > +	}
> > +}
> > +
> >  static int marvell_vct5_wait_complete(struct phy_device *phydev)  {
> >  	int i;
> > @@ -3078,7 +3132,7 @@ static struct phy_driver marvell_drivers[] = {
> >  		.get_sset_count = marvell_get_sset_count,
> >  		.get_strings = marvell_get_strings,
> >  		.get_stats = marvell_get_stats,
> > -		.set_loopback = genphy_loopback,
> > +		.set_loopback = marvell_loopback,
> >  		.get_tunable = m88e1011_get_tunable,
> >  		.set_tunable = m88e1011_set_tunable,
> >  		.cable_test_start = marvell_vct7_cable_test_start,