[PATCH net] net: phy: fix save wrong speed and duplex problem if autoneg is on

From: Guangbin Huang <redacted>

If phy uses generic driver and autoneg is on, enter command
"ethtool -s eth0 speed 50" will not change phy speed actually, but
command "ethtool eth0" shows speed is 50Mb/s because phydev->speed
has been set to 50 and no update later.

And duplex setting has same problem too.

However, if autoneg is on, phy only changes speed and duplex according to
phydev->advertising, but not phydev->speed and phydev->duplex. So in this
case, phydev->speed and phydev->duplex don't need to be set in function
phy_ethtool_ksettings_set() if autoneg is on.

Signed-off-by: Guangbin Huang <redacted>
Signed-off-by: Huazhong Tan <redacted>
---
 drivers/net/phy/phy.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 1be07e4..fc2e7cb 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c

@@ -276,14 +276,16 @@ int phy_ethtool_ksettings_set(struct phy_device *phydev,
 
 	phydev->autoneg = autoneg;
 
-	phydev->speed = speed;
+	if (autoneg == AUTONEG_DISABLE) {
+		phydev->speed = speed;
+		phydev->duplex = duplex;
+	}
 
 	linkmode_copy(phydev->advertising, advertising);
 
 	linkmode_mod_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
 			 phydev->advertising, autoneg == AUTONEG_ENABLE);
 
-	phydev->duplex = duplex;
 	phydev->master_slave_set = cmd->base.master_slave_cfg;
 	phydev->mdix_ctrl = cmd->base.eth_tp_mdix_ctrl;
 

-- 
2.7.4

On Fri, 26 Feb 2021 15:44:42 +0800 Huazhong Tan wrote:

From: Guangbin Huang <redacted>

If phy uses generic driver and autoneg is on, enter command
"ethtool -s eth0 speed 50" will not change phy speed actually, but
command "ethtool eth0" shows speed is 50Mb/s because phydev->speed
has been set to 50 and no update later.

And duplex setting has same problem too.

However, if autoneg is on, phy only changes speed and duplex according to
phydev->advertising, but not phydev->speed and phydev->duplex. So in this
case, phydev->speed and phydev->duplex don't need to be set in function
phy_ethtool_ksettings_set() if autoneg is on.

Can we get a Fixes tag for this one? How far back does this behavior
date?

On Fri, Feb 26, 2021 at 03:44:42PM +0800, Huazhong Tan wrote:

From: Guangbin Huang <redacted>

If phy uses generic driver and autoneg is on, enter command
"ethtool -s eth0 speed 50" will not change phy speed actually, but
command "ethtool eth0" shows speed is 50Mb/s because phydev->speed
has been set to 50 and no update later.

And duplex setting has same problem too.

However, if autoneg is on, phy only changes speed and duplex according to
phydev->advertising, but not phydev->speed and phydev->duplex. So in this
case, phydev->speed and phydev->duplex don't need to be set in function
phy_ethtool_ksettings_set() if autoneg is on.

Signed-off-by: Guangbin Huang <redacted>
Signed-off-by: Huazhong Tan <redacted>

I'm not sure, but i think this happens after

commit 51e2a3846eab18711f4eb59cd0a4c33054e2980a
Author: Trent Piepho [off-list ref]
Date:   Wed Sep 24 10:55:46 2008 +0000

    PHY: Avoid unnecessary aneg restarts
    
    The PHY's aneg is configured and restarted whenever the link is brought up,
    e.g. when DHCP is started after the kernel has booted.  This can take the
    link down for several seconds while auto-negotiation is redone.
    
    If the advertised features haven't changed, then it shouldn't be necessary
    to bring down the link and start auto-negotiation over again.
    
    genphy_config_advert() is enhanced to return 0 when the advertised features
    haven't been changed and >0 when they have been.
    
    genphy_config_aneg() then uses this information to not call
    genphy_restart_aneg() if there has been no change.

Before then, i think autoneg was unconditionally restarted, and so the
speed would get overwritten when autoneg completed. After this patch,
since autoneg is not being changed when only speed is set, autoneg is
not triggered.

	Andrew

On 2021/2/27 7:56, Jakub Kicinski wrote:

On Fri, 26 Feb 2021 15:44:42 +0800 Huazhong Tan wrote:

quoted

From: Guangbin Huang <redacted>

If phy uses generic driver and autoneg is on, enter command
"ethtool -s eth0 speed 50" will not change phy speed actually, but
command "ethtool eth0" shows speed is 50Mb/s because phydev->speed
has been set to 50 and no update later.

And duplex setting has same problem too.

However, if autoneg is on, phy only changes speed and duplex according to
phydev->advertising, but not phydev->speed and phydev->duplex. So in this
case, phydev->speed and phydev->duplex don't need to be set in function
phy_ethtool_ksettings_set() if autoneg is on.

Can we get a Fixes tag for this one? How far back does this behavior
date?

will add a fixes tag in V2, thanks.

.

On 2021/2/27 8:53, Andrew Lunn wrote:

On Fri, Feb 26, 2021 at 03:44:42PM +0800, Huazhong Tan wrote:

quoted

From: Guangbin Huang <redacted>

If phy uses generic driver and autoneg is on, enter command
"ethtool -s eth0 speed 50" will not change phy speed actually, but
command "ethtool eth0" shows speed is 50Mb/s because phydev->speed
has been set to 50 and no update later.

And duplex setting has same problem too.

However, if autoneg is on, phy only changes speed and duplex according to
phydev->advertising, but not phydev->speed and phydev->duplex. So in this
case, phydev->speed and phydev->duplex don't need to be set in function
phy_ethtool_ksettings_set() if autoneg is on.

Signed-off-by: Guangbin Huang <redacted>
Signed-off-by: Huazhong Tan <redacted>

I'm not sure, but i think this happens after

commit 51e2a3846eab18711f4eb59cd0a4c33054e2980a
Author: Trent Piepho [off-list ref]
Date:   Wed Sep 24 10:55:46 2008 +0000

     PHY: Avoid unnecessary aneg restarts
     
     The PHY's aneg is configured and restarted whenever the link is brought up,
     e.g. when DHCP is started after the kernel has booted.  This can take the
     link down for several seconds while auto-negotiation is redone.
     
     If the advertised features haven't changed, then it shouldn't be necessary
     to bring down the link and start auto-negotiation over again.
     
     genphy_config_advert() is enhanced to return 0 when the advertised features
     haven't been changed and >0 when they have been.
     
     genphy_config_aneg() then uses this information to not call
     genphy_restart_aneg() if there has been no change.

Before then, i think autoneg was unconditionally restarted, and so the
speed would get overwritten when autoneg completed. After this patch,
since autoneg is not being changed when only speed is set, autoneg is
not triggered.

	Andrew

Thanks.

.