Re: [PATCH v4 3/5] net: macb: fix macb_get/set_wol() when moving to phylink

[Nicolas Ferre]

Russell,

Thanks for the feedback.

On 13/05/2020 at 15:05, Russell King - ARM Linux admin wrote:
> On Wed, May 06, 2020 at 01:37:39PM +0200, nicolas.ferre@xxxxxxxxxxxxx wrote:
> > From: Nicolas Ferre <nicolas.ferre@xxxxxxxxxxxxx>
> >
> > Keep previous function goals and integrate phylink actions to them.
> >
> > phylink_ethtool_get_wol() is not enough to figure out if Ethernet driver
> > supports Wake-on-Lan.
> > Initialization of "supported" and "wolopts" members is done in phylink
> > function, no need to keep them in calling function.
> >
> > phylink_ethtool_set_wol() return value is not enough to determine
> > if WoL is enabled for the calling Ethernet driver. Call it first
> > but don't rely on its return value as most of simple PHY drivers
> > don't implement a set_wol() function.
> >
> > Fixes: 7897b071ac3b ("net: macb: convert to phylink")
> > Signed-off-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxxxxxx>
> > Reviewed-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
> > Cc: Claudiu Beznea <claudiu.beznea@xxxxxxxxxxxxx>
> > Cc: Harini Katakam <harini.katakam@xxxxxxxxxx>
> > Cc: Antoine Tenart <antoine.tenart@xxxxxxxxxxx>
> > ---
> >   drivers/net/ethernet/cadence/macb_main.c | 18 ++++++++++--------
> >   1 file changed, 10 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> > index 53e81ab048ae..24c044dc7fa0 100644
> > --- a/drivers/net/ethernet/cadence/macb_main.c
> > +++ b/drivers/net/ethernet/cadence/macb_main.c
> > @@ -2817,21 +2817,23 @@ static void macb_get_wol(struct net_device *netdev, struct ethtool_wolinfo *wol)
> >   {
> >        struct macb *bp = netdev_priv(netdev);
> >
> > -     wol->supported = 0;
> > -     wol->wolopts = 0;
> > -
> > -     if (bp->wol & MACB_WOL_HAS_MAGIC_PACKET)
> > +     if (bp->wol & MACB_WOL_HAS_MAGIC_PACKET) {
> >                phylink_ethtool_get_wol(bp->phylink, wol);
> > +             wol->supported |= WAKE_MAGIC;
> > +
> > +             if (bp->wol & MACB_WOL_ENABLED)
> > +                     wol->wolopts |= WAKE_MAGIC;
> > +     }
> >   }
> >
> >   static int macb_set_wol(struct net_device *netdev, struct ethtool_wolinfo *wol)
> >   {
> >        struct macb *bp = netdev_priv(netdev);
> > -     int ret;
> >
> > -     ret = phylink_ethtool_set_wol(bp->phylink, wol);
> > -     if (!ret)
> > -             return 0;
> > +     /* Pass the order to phylink layer.
> > +      * Don't test return value as set_wol() is often not supported.
> > +      */
> > +     phylink_ethtool_set_wol(bp->phylink, wol);
>
> If this returns an error, does that mean WOL works or does it not?

In my use case (simple phy: "Micrel KSZ8081"), if I have the error 
"-EOPNOTSUPP", it simply means that this phy driver doesn't have the 
set_wol() function. But on the MAC side, I can perfectly wake-up on WoL 
event as the phy acts as a pass-through.

> Note that if set_wol() is not supported, this will return -EOPNOTSUPP.
> What about other errors?

True, I don't manage them. But for now this patch is a fix that only 
reverts to previous behavior. In other terms, it only fixes the regression.

But can I make the difference, and how, between?
1/ the phy doesn't support WoL and could prevent the WoL to happen on 
the MAC
2/ the phy doesn't implement (yet) the set_wol() function, if MAC can 
manage, it's fine


> If you want to just ignore the case where it's not supported, then
> this looks like a sledge hammer to crack a nut.

Do you suggest that I just don't call phylink_ethtool_set_wol() at all?

But what if the underlying phy does support WoL?

Best regards,
--
Nicolas Ferre