netdev - Re: [PATCH net-next 1/5] sky2: force receive checksum when using RSS on some hardware (v2)

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Message-ID: <20110708083240.09e8cce8@nehalam.ftrdhcpuser.net>
Date:	Fri, 8 Jul 2011 08:32:40 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Michał Mirosław <mirqus@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/5] sky2: force receive checksum when using
 RSS on some hardware (v2)

On Fri, 8 Jul 2011 10:45:33 +0200
Michał Mirosław <mirqus@...il.com> wrote:

> 2011/7/8 Stephen Hemminger <shemminger@...tta.com>:
> > Found when reviewing the vendor driver. Apparently some chip versions
> > require receive checksumming to be enabled in order for RSS to work.
> >
> > Also, if fix_features has to change some settings; put in message
> > in log in similar manner to netdev_fix_features.
> >
> > Signed-off-by: Stephen Hemminger <shemminger@...tta.com>
> >
> > ---
> > v2 - enforce the requirement in fix_features rather than set features
> >
> > --- a/drivers/net/sky2.c        2011-07-07 13:56:03.575420273 -0700
> > +++ b/drivers/net/sky2.c        2011-07-07 14:03:17.775403938 -0700
> [...]
> > @@ -4176,8 +4180,18 @@ static u32 sky2_fix_features(struct net_
> >        /* In order to do Jumbo packets on these chips, need to turn off the
> >         * transmit store/forward. Therefore checksum offload won't work.
> >         */
> > -       if (dev->mtu > ETH_DATA_LEN && hw->chip_id == CHIP_ID_YUKON_EC_U)
> > +       if (dev->mtu > ETH_DATA_LEN && hw->chip_id == CHIP_ID_YUKON_EC_U) {
> > +               netdev_warn(dev, "checksum offload not possible with jumbo frames\n");
> >                features &= ~(NETIF_F_TSO|NETIF_F_SG|NETIF_F_ALL_CSUM);
> > +       }
> > +
> > +       /* Some hardware requires receive checksum for RSS to work. */
> > +       if ( (features & NETIF_F_RXHASH) &&
> > +            !(features & NETIF_F_RXCSUM) &&
> > +            (sky2->hw->flags & SKY2_HW_RSS_CHKSUM)) {
> > +               netdev_warn(dev, "receive hashing forces receive checksum\n");
> > +               features |= NETIF_F_RXCSUM;
> > +       }
> >
> >        return features;
> >  }
> 
> I suggest using netdev_dbg() instead of netdev_warn() so it won't spam
> dmesg on every features update.

I was just copying existing policy in netdev_fix_features.
netdev_dbg() is useless because most user turn off debug messages.
Maybe notice or info is more appropriate level here.

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