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SubjectRe: [PATCH v4 3/5] net: macb: fix macb_get/set_wol() when moving to phylink
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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@microchip.com wrote:
>> From: Nicolas Ferre <nicolas.ferre@microchip.com>
>>
>> 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@microchip.com>
>> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
>> Cc: Claudiu Beznea <claudiu.beznea@microchip.com>
>> Cc: Harini Katakam <harini.katakam@xilinx.com>
>> Cc: Antoine Tenart <antoine.tenart@bootlin.com>
>> ---
>> 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

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