netdev - Re: Bug#645589: linux-image-3.0.0-2-amd64: sky2 rx errors on 3.0, 2.6.32 works

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Date:	Wed, 19 Oct 2011 05:09:25 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	645589@...s.debian.org, Antti Salmela <asalmela@....fi>,
	netdev <netdev@...r.kernel.org>
Subject: Re: Bug#645589: linux-image-3.0.0-2-amd64: sky2 rx errors on 3.0,
 2.6.32 works

On Tue, 2011-10-18 at 11:13 -0700, Stephen Hemminger wrote:
> On Tue, 18 Oct 2011 04:43:06 +0100
> Ben Hutchings <ben@...adent.org.uk> wrote:
> 
> > On Mon, 2011-10-17 at 10:40 +0300, Antti Salmela wrote:
> > > Package: linux-2.6
> > > Version: 3.0.0-5
> > > Severity: normal
> > > 
> > > 
> > > sky2 loses packets on 3.0 (-3 and -5) and 3.1-rc7, 2.6.32-38 and
> > > setting interface to promiscuous works.
> > > 
> > > [   60.118244] sky2 0000:02:00.0: eth0: rx error, status 0xb92100 length 185
> > > [   62.664370] sky2 0000:02:00.0: eth0: rx error, status 0x602100 length 96
> > > [   63.370051] sky2 0000:02:00.0: eth0: rx error, status 0x422100 length 66
> > > [   63.714672] sky2 0000:02:00.0: eth0: rx error, status 0x722100 length 114
> > > [   64.513458] device eth0 entered promiscuous mode
> > 
> > It looks like this is a bug in accounting of VLAN tags, though I don't
> > see what difference promiscuous mode should make.
> > 
> > The log messages show that status has the VLAN flag (bit 13) set and the
> > length field (bits 16:28) equals the length passed into sky2_receive(),
> > but that function expects the length field to be greater by VLAN_HLEN.
> > 
> > This device is:
> > 
> > [...]
> > > 02:00.0 Ethernet controller [0200]: Marvell Technology Group Ltd. 88E8053 PCI-E Gigabit Ethernet Controller [11ab:4362] (rev 19)
> > > 	Subsystem: ASUSTeK Computer Inc. Marvell 88E8053 Gigabit Ethernet controller PCIe (Asus) [1043:8142]
> > > 	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
> > > 	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
> > > 	Latency: 0, Cache Line Size: 16 bytes
> > > 	Interrupt: pin A routed to IRQ 43
> > > 	Region 0: Memory at cdefc000 (64-bit, non-prefetchable) [size=16K]
> > > 	Region 2: I/O ports at c800 [size=256]
> > > 	Expansion ROM at cdec0000 [disabled] [size=128K]
> > > 	Capabilities: <access denied>
> > > 	Kernel driver in use: sky2
> > [...]
> 
> The accounting is supposed to be:
>    MAC = total length of packet (including vlan)
>    DMA = bytes dma'd to buffer (does not include vlan)
> Looks like the code is incorrect for the case where hardware
> VLAN stripping is disabled.

But if that's true, I'd expect to see these errors in 2.6.32 (where VLAN
tag extraction is disabled until a VLAN group is created) and not in 3.0
(where it is enabled by default).  Instead it's 3.0 that is broken.

I also don't see why changing promiscuous mode would make a difference.

> What happens is that status bit
> still has the VLAN flag, but DMA engine leaves the VLAN tag
> in the DMA buffer so the check fails.
> 
> Proper accounting would involve more state machine mechanics
> about whether VLAN tag has already been seen in current receive
> status ring.

Shouldn't you should restart the relevant queue when changing VLAN tag
extraction/insertion?

> For now probably best to do something like:
> 
> --- net-next.orig/drivers/net/ethernet/marvell/sky2.c	2011-10-18 11:09:04.108683763 -0700
> +++ net-next/drivers/net/ethernet/marvell/sky2.c	2011-10-18 11:09:53.661264323 -0700
> @@ -2543,7 +2543,8 @@ static struct sk_buff *sky2_receive(stru
>  	struct sk_buff *skb = NULL;
>  	u16 count = (status & GMR_FS_LEN) >> 16;
>  
> -	if (status & GMR_FS_VLAN)
> +	if ((dev->features & NETIF_F_HW_VLAN_RX) &&
> +	    (status & GMR_FS_VLAN))
>  		count -= VLAN_HLEN;	/* Account for vlan tag */

It looks like this is needed to restore the workaround for broken status
flags on the FE+.  But I doubt it will fix this problem.

Ben.

>  	netif_printk(sky2, rx_status, KERN_DEBUG, dev,
> 
> 
> 
> 
> 

-- 
Ben Hutchings
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