netdev - Re: [PATCH] net: sky2: convert to hw

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Message-ID: <20110411075829.7b9bf1e5@nehalam>
Date:	Mon, 11 Apr 2011 07:58:29 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] net: sky2: convert to hw_features

On Mon, 11 Apr 2011 02:51:00 +0200
Michał Mirosław <mirq-linux@...e.qmqm.pl> wrote:

> On Sun, Apr 10, 2011 at 11:53:02AM -0700, Stephen Hemminger wrote:
> > On Sun, 10 Apr 2011 15:13:21 +0200 (CEST)
> > Michał Mirosław <mirq-linux@...e.qmqm.pl> wrote:
> > > Caveats:
> > >  - driver modifies vlan_features on HW VLAN TX changes
> > >  - broken RX checksum will be reenabled on features change
> > To be more precise. This is acceptable if and only if all cases
> > where features are disabled in response to MTU and chip versions
> > are exactly the same. We don't want to let some user stumble upon
> > cases where hardware features don't work in their configuration.
> 
> I was referring to the unlikely case detected by sky2_rx_checksum().
> Before this conversion, user could reenable the feature using ethtool.
> The change is that now, in this case, it's reenabled also when other
> features are changed (i.e. whenever netdev_update_features() gets called).
> 
> Best Regards,
> Michał Mirosław

Ok.

It does expose a pre-existing issue. If this logic trips (and I have
gotten reports of it happening), then the GRO will not get disabled.
Probably need to mask of GRO as well, since GRO depends on RXCSUM.

--- a/drivers/net/sky2.c	2011-04-11 07:56:50.569361209 -0700
+++ b/drivers/net/sky2.c	2011-04-11 07:57:34.502312648 -0700
@@ -2538,7 +2538,7 @@ static void sky2_rx_checksum(struct sky2
 		 * It will be reenabled on next ndo_set_features, but if it's
 		 * really broken, will get disabled again
 		 */
-		sky2->netdev->features &= ~NETIF_F_RXCSUM;
+		sky2->netdev->features &= ~(NETIF_F_RXCSUM | NETIF_F_GRO);
 		sky2_write32(sky2->hw, Q_ADDR(rxqaddr[sky2->port], Q_CSR),
 			     BMU_DIS_RX_CHKSUM);
 	}
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