RE: [PATCH] bnx2: turn off the network statck during initialization

On Thu, 2012-08-16 at 19:15 +0000, Jiang Wang wrote: 

Hi Michael,

I just checked the code for netif_carrier_off(), and it will return if
the dev is not initialized (registered) as follows:

void netif_carrier_off(struct net_device *dev)
{
        if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
                if (dev->reg_state == NETREG_UNINITIALIZED)
                        return;
                linkwatch_fire_event(dev);
        }
}

So linkwatch_fire_event should not fire in this case, right? Thanks
for the quick response.

Yes, you're right.  Your patch should not cause any problem then.

But I still don't understand what problem you're trying to solve.  The
link status from ethtool is determined by bnx2_get_link() and it should
always return link down before bnx2_open() is called.  Can you please
elborate?  Thanks.

Regards,

Jiang

-------------------------------------
Jiang Wang
Member of Technical Staff
Riverbed Technology
Tel: (408) 522-5109
Email: Jiang.Wang@riverbed.com
www.riverbed.com


-----Original Message-----
From: Michael Chan [mailto:mchan@broadcom.com] 
Sent: Thursday, August 16, 2012 11:57 AM
To: Jiang Wang
Cc: netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Chaitanya Lala; Francis St. Amant; Jiang Wang
Subject: Re: [PATCH] bnx2: turn off the network statck during initialization

On Thu, 2012-08-16 at 11:21 -0700, Jiang Wang wrote: 

quoted

The initialization state of bnx2 driver is wrong. It does not turn of 
the Linux network stack using netif_carrier_off. This may lead to 
inconsistent report from ethtool as the link is up but speed is 
unknown when the cable is not plugged in.

E.g.
        Speed: Unknown! (0)<--------------------------------------
        Duplex: Half       <--------------------------------------
        MDI: Unknown! (0)
        Port: Twisted Pair
        PHYAD: 1
        Transceiver: internal
        Auto-negotiation: on
        Supports Wake-on: g
        Wake-on: d
        Link detected: yes <---------------------------------------

This patches fixed the problem by turning off the network stack during 
initialization.

Signed-off-by: Jiang Wang <redacted>
---
 drivers/net/ethernet/broadcom/bnx2.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnx2.c 

b/drivers/net/ethernet/broadcom/bnx2.c
index ac7b744..ce4548d 100644

--- a/drivers/net/ethernet/broadcom/bnx2.c
+++ b/drivers/net/ethernet/broadcom/bnx2.c

@@ -8463,6 +8463,10 @@ bnx2_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	dev->features |= dev->hw_features;
 	dev->priv_flags |= IFF_UNICAST_FLT;
 
+	/* tell the stack to leave us alone until bnx2_open() is called */
+	netif_carrier_off(dev);

We have tried this before and this didn't work.  netif_carrier_off() calls linkwatch_fire_event() to schedule the event.  If
register_netdev() fails for whatever reason, the netdev will be freed but the link_watch event may still be scheduled.

Calling netif_carrier_off() after register_netdev() returns successfully also may not work as it will race with bnx2_open() which enables IRQ.
An linkup IRQ can happen at time and we may end up with the wrong carrier state because of the race condition.

quoted

+	netif_stop_queue(dev);
+
 	if ((rc = register_netdev(dev))) {
 		dev_err(&pdev->dev, "Cannot register net device\n");
 		goto error;