Re: [PATCH] net: phy: Fix phy_modify() semantic difference fallout

[Niklas Cassel <niklas.cassel@axis.com>]

On 09/01/18 12:11, Geert Uytterhoeven wrote:
> In case of success, the return values of (__)phy_write() and
> (__)phy_modify() are not compatible: (__)phy_write() returns 0, while
> (__)phy_modify() returns the old PHY register value.
> 
> Apparently this change was catered for in drivers/net/phy/marvell.c, but
> not in other source files.
> 
> Hence genphy_restart_aneg() now returns 4416 instead zero, which is
> considered an error:
> 
>     ravb e6800000.ethernet eth0: failed to connect PHY
>     IP-Config: Failed to open eth0
>     IP-Config: No network devices available
> 
> Fix this by converting positive values to zero in all callers of
> phy_modify().
> 
> Fixes: fea23fb591cce995 ("net: phy: convert read-modify-write to phy_modify()")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> Alternatively, __phy_modify() could be changed to follow __phy_write()
> semantics?
> ---
>  drivers/net/phy/at803x.c     |  4 +++-
>  drivers/net/phy/phy_device.c | 29 +++++++++++++++++++++--------
>  2 files changed, 24 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/net/phy/at803x.c b/drivers/net/phy/at803x.c
> index 411cf1072bae5796..6b6b9cef517f1bc3 100644
> --- a/drivers/net/phy/at803x.c
> +++ b/drivers/net/phy/at803x.c
> @@ -230,7 +230,9 @@ static int at803x_suspend(struct phy_device *phydev)
>  
>  static int at803x_resume(struct phy_device *phydev)
>  {
> -	return phy_modify(phydev, MII_BMCR, BMCR_PDOWN | BMCR_ISOLATE, 0);
> +	int ret = phy_modify(phydev, MII_BMCR, BMCR_PDOWN | BMCR_ISOLATE, 0);
> +
> +	return ret < 0 ? ret : 0;
>  }
>  
>  static int at803x_probe(struct phy_device *phydev)
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 6bd11a070ec8147b..a132e845e4aec3d5 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -1369,6 +1369,7 @@ static int genphy_config_eee_advert(struct phy_device *phydev)
>  int genphy_setup_forced(struct phy_device *phydev)
>  {
>  	u16 ctl = 0;
> +	int ret;
>  
>  	phydev->pause = 0;
>  	phydev->asym_pause = 0;
> @@ -1381,8 +1382,12 @@ int genphy_setup_forced(struct phy_device *phydev)
>  	if (DUPLEX_FULL == phydev->duplex)
>  		ctl |= BMCR_FULLDPLX;
>  
> -	return phy_modify(phydev, MII_BMCR,
> -			  BMCR_LOOPBACK | BMCR_ISOLATE | BMCR_PDOWN, ctl);
> +	ret = phy_modify(phydev, MII_BMCR,
> +			 BMCR_LOOPBACK | BMCR_ISOLATE | BMCR_PDOWN, ctl);
> +	if (ret < 0)
> +		return ret;
> +
> +	return 0;
>  }
>  EXPORT_SYMBOL(genphy_setup_forced);
>  
> @@ -1393,8 +1398,10 @@ EXPORT_SYMBOL(genphy_setup_forced);
>  int genphy_restart_aneg(struct phy_device *phydev)
>  {
>  	/* Don't isolate the PHY if we're negotiating */
> -	return phy_modify(phydev, MII_BMCR, BMCR_ISOLATE,
> -			  BMCR_ANENABLE | BMCR_ANRESTART);
> +	int ret = phy_modify(phydev, MII_BMCR, BMCR_ISOLATE,
> +			     BMCR_ANENABLE | BMCR_ANRESTART);
> +
> +	return ret < 0 ? ret : 0;
>  }
>  EXPORT_SYMBOL(genphy_restart_aneg);
>  
> @@ -1660,20 +1667,26 @@ EXPORT_SYMBOL(genphy_config_init);
>  
>  int genphy_suspend(struct phy_device *phydev)
>  {
> -	return phy_modify(phydev, MII_BMCR, 0, BMCR_PDOWN);
> +	int ret = phy_modify(phydev, MII_BMCR, 0, BMCR_PDOWN);
> +
> +	return ret < 0 ? ret : 0;
>  }
>  EXPORT_SYMBOL(genphy_suspend);
>  
>  int genphy_resume(struct phy_device *phydev)
>  {
> -	return phy_modify(phydev, MII_BMCR, BMCR_PDOWN, 0);
> +	int ret = phy_modify(phydev, MII_BMCR, BMCR_PDOWN, 0);
> +
> +	return ret < 0 ? ret : 0;
>  }
>  EXPORT_SYMBOL(genphy_resume);
>  
>  int genphy_loopback(struct phy_device *phydev, bool enable)
>  {
> -	return phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK,
> -			  enable ? BMCR_LOOPBACK : 0);
> +	int ret = phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK,
> +			     enable ? BMCR_LOOPBACK : 0);
> +
> +	return ret < 0 ? ret : 0;
>  }
>  EXPORT_SYMBOL(genphy_loopback);
>  
> 

This patch solves the following problem on ARTPEC-6:

[    2.562607] dwc-eth-dwmac f8010000.ethernet eth0: device MAC address 00:aa:bb:cc:13:36
[    2.670029] dwc-eth-dwmac f8010000.ethernet eth0: Could not attach to PHY
[    2.676826] dwc-eth-dwmac f8010000.ethernet eth0: stmmac_open: Cannot attach to PHY (error: -19)

When using linux-next: next-20180109

next-20180109 contains:
fea23fb591cc ("net: phy: convert read-modify-write to phy_modify()")
and
f102852f980e ("net: phy: fix wrong masks to phy_modify()")

Tested-by: Niklas Cassel <niklas.cassel@axis.com>