Re: [PATCH net-next 4/4] net: dsa: Do not clobber PHY link outside of state machine

From: Andrew Lunn
Date: Mon Feb 06 2017 - 19:11:50 EST


On Mon, Feb 06, 2017 at 03:55:23PM -0800, Florian Fainelli wrote:
> Calling phy_read_status() means that we may call into
> genphy_read_status() which in turn will use genphy_update_link() which
> can make changes to phydev->link outside of the state machine's state
> transitions. This is an invalid behavior that is now caught as of
> 811a919135b9 ("phy state machine: failsafe leave invalid RUNNING state")
>
> Reported-by: Zefir Kurtisi <zefir.kurtisi@xxxxxxxxxxx>
> Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
> ---
> net/dsa/slave.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> index 09fc3e9462c1..4b6fb6b14de4 100644
> --- a/net/dsa/slave.c
> +++ b/net/dsa/slave.c
> @@ -651,14 +651,10 @@ dsa_slave_get_link_ksettings(struct net_device *dev,
> struct ethtool_link_ksettings *cmd)
> {
> struct dsa_slave_priv *p = netdev_priv(dev);
> - int err;
> + int err = -EOPNOTSUPP;
>
> - err = -EOPNOTSUPP;
> - if (p->phy != NULL) {
> - err = phy_read_status(p->phy);
> - if (err == 0)
> - err = phy_ethtool_ksettings_get(p->phy, cmd);
> - }
> + if (p->phy != NULL)
> + err = phy_ethtool_ksettings_get(p->phy, cmd);

Hi Florian

So what we are effectively doing is returning the state from the last
poll/interrupt. The poll information could be up to 1 second out of
date, but those PHYs using interrupts should give more fresh
information.

Seems reasonable.

Reviewed-by: Andrew Lunn <andrew@xxxxxxx>

Andrew