Re: [PATCH net-next] net: phy: fix autoneg mismatch case in genphy_read_status

[Simon Horman <horms@xxxxxxxxxxxx>]

On Tue, Apr 02, 2019 at 08:43:30PM +0200, Heiner Kallweit wrote:
> The original patch didn't consider the case that autoneg process
> finishes successfully but both link partners have no mode in common.
> In this case there's no link, nevertheless we may be interested in
> what the link partner advertised.
> 
> Like phydev->link we set phydev->autoneg_complete in
> genphy_update_link() and use the stored value in genphy_read_status().
> This way we don't have to read register BMSR again.
> 
> Fixes: b6163f194c69 ("net: phy: improve genphy_read_status")
> Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>

Hi,

I have observed a regression with this patch as present as
4950c2ba49cc ("net: phy: fix autoneg mismatch case in genphy_read_status")
in net-next.

The platform is the Renesas R-Car E3 (r8a77990) based Ebisu-4D board.


Without this patch (commit before 4950c2ba49cc) the link is negotiated
as follows:

[    3.257699] libphy: ravb_mii: probed
[    3.266498] ravb e6800000.ethernet eth0: Base address at 0xe6800000, 2e:09:0a:03:85:38, IRQ 104.
[    3.537082] Micrel KSZ9031 Gigabit PHY e6800000.ethernet-ffffffff:00: attached PHY driver [Micrel KSZ9031 Gigabit PHY] (mii_bus:phy_addr=e6800000.ethernet-ffffffff:00, irq=165)
[    9.667161] ravb e6800000.ethernet eth0: Link is Up - 1Gbps/Full - flow control off

# ethtool --version
ethtool version 3.16
# ethtool eth0
Settings for eth0:
        Supported ports: [ TP MII ]
        Supported link modes:   100baseT/Full 
                                1000baseT/Full 
        Supported pause frame use: No
        Supports auto-negotiation: Yes
        Advertised link modes:  100baseT/Full 
                                1000baseT/Full 
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Link partner advertised link modes:  10baseT/Half 10baseT/Full 
                                             100baseT/Half 100baseT/Full 
                                             1000baseT/Full 
        Link partner advertised pause frame use: No
        Link partner advertised auto-negotiation: Yes
        Speed: 1000Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 0
        Transceiver: external
        Auto-negotiation: on
        Supports Wake-on: g
        Wake-on: d
        Current message level: 0x000000cc (204)
                               link timer rx_err tx_err
        Link detected: yes


With this patch the link is negotiated as follows, note the "Unknown":

[    3.268609] libphy: ravb_mii: probed
[    3.277402] ravb e6800000.ethernet eth0: Base address at 0xe6800000, 2e:09:0a:03:85:38, IRQ 104.
[    3.565057] Micrel KSZ9031 Gigabit PHY e6800000.ethernet-ffffffff:00: attached PHY driver [Micrel KSZ9031 Gigabit PHY] (mii_bus:phy_addr=e6800000.ethernet-ffffffff:00, irq=165)
[    9.804423] ravb e6800000.ethernet eth0: Link is Up - Unknown/Unknown - flow control off

And ethtool reports:

# ethtool eth0
Settings for eth0:
        Supported ports: [ TP MII ]
        Supported link modes:   100baseT/Full 
                                1000baseT/Full 
        Supported pause frame use: No
        Supports auto-negotiation: Yes
        Advertised link modes:  100baseT/Full 
                                1000baseT/Full 
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Speed: Unknown!
        Duplex: Unknown! (255)
        Port: MII
        PHYAD: 0
        Transceiver: external
        Auto-negotiation: on
        Supports Wake-on: g
        Wake-on: d
        Current message level: 0x000000cc (204)
                               link timer rx_err tx_err
        Link detected: yes



I noticed this when preparing a patch limit the maximum speed the device to
100Mbit/s as follows:

--- a/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts
+++ b/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts
@@ -272,6 +272,7 @@
                interrupt-parent = <&gpio2>;
                interrupts = <21 IRQ_TYPE_LEVEL_LOW>;
                reset-gpios = <&gpio1 20 GPIO_ACTIVE_LOW>;
+               max-speed = <100>;
        };
 };
 
While the 100Mbit/s limit applied on top of the commit before 4950c2ba49cc
things work as expected:

[    3.258347] libphy: ravb_mii: probed
[    3.266739] ravb e6800000.ethernet eth0: Base address at 0xe6800000, 2e:09:0a:03:85:38, IRQ 104.
[    3.553642] Micrel KSZ9031 Gigabit PHY e6800000.ethernet-ffffffff:00: attached PHY driver [Micrel KSZ9031 Gigabit PHY] (mii_bus:phy_addr=e6800000.ethernet-ffffffff:00, irq=165)
[    5.585027] ravb e6800000.ethernet eth0: Link is Up - 100Mbps/Full - flow control off

# ethtool eth0
Settings for eth0:
        Supported ports: [ TP MII ]
        Supported link modes:   100baseT/Full 
        Supported pause frame use: No
        Supports auto-negotiation: Yes
        Advertised link modes:  100baseT/Full 
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Link partner advertised link modes:  10baseT/Half 10baseT/Full 
                                             100baseT/Half 100baseT/Full 
        Link partner advertised pause frame use: No
        Link partner advertised auto-negotiation: Yes
        Speed: 100Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 0
        Transceiver: external
        Auto-negotiation: on
        Supports Wake-on: g
        Wake-on: d
        Current message level: 0x000000cc (204)
                               link timer rx_err tx_err
        Link detected: yes


However, with the 100Mbit/s limit applied on top of 4950c2ba49cc the boot hangs
while (or just after?) negotiating the link:

[    3.541549] Micrel KSZ9031 Gigabit PHY e6800000.ethernet-ffffffff:00: attached PHY driver [Micrel KSZ9031 Gigabit PHY] (mii_bus:phy_addr=e6800000.ethernet-ffffffff:00, irq=165)
[    5.536389] ravb e6800000.ethernet eth0: Link is Up - Unknown/Unknown - flow control off