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

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Date:	Thu, 10 Dec 2009 11:57:40 -0800
From:	Roland Dreier <rdreier@...co.com>
To:	"Waskiewicz Jr\, Peter P" <peter.p.waskiewicz.jr@...el.com>
Cc:	"Rose\, Gregory V" <gregory.v.rose@...el.com>,
	"chavey\@google.com" <chavey@...gle.com>,
	"Kirsher\, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"netdev\@vger.kernel.org" <netdev@...r.kernel.org>,
	"gospo\@redhat.com" <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.

 - R.
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