netdev - Re: [Bugme-new] [Bug 30092] New: smsc911x.c drops long packets with VLAN tags

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Date:	Wed, 02 Mar 2011 15:07:21 +0100
From:	weinholt@...net.se (Göran Weinholt)
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	netdev@...r.kernel.org, bugzilla-daemon@...zilla.kernel.org,
	bugme-daemon@...zilla.kernel.org,
	Steve Glendinning <steve.glendinning@...c.com>
Subject: Re: [Bugme-new] [Bug 30092] New: smsc911x.c drops long packets with VLAN tags

Andrew Morton <akpm@...ux-foundation.org> writes:

> (switched to email.  Please respond via emailed reply-to-all, not via the
> bugzilla web interface).
>
> On Mon, 28 Feb 2011 15:57:14 GMT
> bugzilla-daemon@...zilla.kernel.org wrote:
>
>> https://bugzilla.kernel.org/show_bug.cgi?id=30092
>> 
> Thanks.  Become famous, get more girls: send us a patch as per
> Documentation/SubmittingPatches :)

There's a register called VLAN1 that wasn't being configured. Setting it
to 0x8100 fixes the problem I reported. There's also a VLAN2 register,
possibly meant for stacked VLANs, but the description in the datasheet
doesn't make sense to me, and I can't test stacked VLANs, so I'm not
going to change it.

Subject: [PATCH] net/smsc911x.c: Set the VLAN1 register to fix VLAN MTU problem
From: Göran Weinholt <weinholt@...net.se>

The smsc911x driver would drop frames longer than 1518 bytes, which is a
problem for networks with VLAN tagging. The VLAN1 tag register is used
to increase the legal frame size to 1522 when a VLAN tag is identified.

Signed-off-by: Göran Weinholt <weinholt@...net.se>
---
diff -uprN linux-2.6.36.4-vanilla/drivers/net/smsc911x.c linux-2.6.36.4/drivers/net/smsc911x.c
--- linux-2.6.36.4-vanilla/drivers/net/smsc911x.c	2011-02-18 00:14:38.000000000 +0100
+++ linux-2.6.36.4/drivers/net/smsc911x.c	2011-03-02 14:29:11.884382251 +0100
@@ -1178,6 +1178,11 @@ static int smsc911x_open(struct net_devi
 	smsc911x_reg_write(pdata, HW_CFG, 0x00050000);
 	smsc911x_reg_write(pdata, AFC_CFG, 0x006E3740);
 
+	/* Increase the legal frame size of VLAN tagged frames to 1522 bytes */
+	spin_lock_irq(&pdata->mac_lock);
+	smsc911x_mac_write(pdata, VLAN1, ETH_P_8021Q);
+	spin_unlock_irq(&pdata->mac_lock);
+
 	/* Make sure EEPROM has finished loading before setting GPIO_CFG */
 	timeout = 50;
 	while ((smsc911x_reg_read(pdata, E2P_CMD) & E2P_CMD_EPC_BUSY_) &&



-- 
Göran Weinholt
Network Administrator
Chalmers Studentbostäder (AS48514)
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