netdev - RE: [RFC PATCH 05/12] ixgbe: Add SR-IOV features to main module

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Date:	Thu, 10 Dec 2009 12:02:38 -0800
From:	"Rose, Gregory V" <gregory.v.rose@...el.com>
To:	Roland Dreier <rdreier@...co.com>,
	"Waskiewicz Jr, Peter P" <peter.p.waskiewicz.jr@...el.com>
CC:	"chavey@...gle.com" <chavey@...gle.com>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"gospo@...hat.com" <gospo@...hat.com>
Subject: RE: [RFC PATCH 05/12] ixgbe: Add SR-IOV features to main module

>-----Original Message-----
>From: Roland Dreier [mailto:rdreier@...co.com]
>Sent: Thursday, December 10, 2009 11:58 AM
>To: Waskiewicz Jr, Peter P
>Cc: Rose, Gregory V; chavey@...gle.com; Kirsher, Jeffrey T;
>netdev@...r.kernel.org; gospo@...hat.com
>Subject: Re: [RFC PATCH 05/12] ixgbe: Add SR-IOV features to main module
>
>
> > > >+#ifdef CONFIG_PCI_IOV
> > > >+       /* disable iov and allow time for transactions to clear */
> > > >+       pci_disable_sriov(adapter->pdev);
> > > >+#endif
> > > >+       msleep(500);
> > > >
> > > >what is the sleep used for ?
> > > [Rose, Gregory V]
> > >
> > > It's mostly a safety valve to give plenty of time for all bus
>transactions to complete or time out.
> >
> > I think Chavey is pointing out that if CONFIG_PCI_IOV is not enabled,
> > you'd be sleeping for 500 msecs for no reason.  You should probably
>stick
> > the msleep(500) inside the ifdef.
>
>pci_disable_sriov() calls sriov_disable(), which already does
>ssleep(1).  Do you really need another 500 msec of sleep after that 1000
>msecs?  My impression of the PCI spec was that the 1 second wait is
>supposed to be sufficient.
[Rose, Gregory V] 

I think you're correct.  I'll just pull the msleep(500) and do some local functional testing to make sure it doesn't cause any problems.  If not then I'll remove it permanently.

- Greg

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