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

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Date:	Wed, 9 Dec 2009 17:44:17 -0800 (Pacific Standard Time)
From:	"Waskiewicz Jr, Peter P" <peter.p.waskiewicz.jr@...el.com>
To:	"Rose, Gregory V" <gregory.v.rose@...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>,
	"Waskiewicz Jr, Peter P" <peter.p.waskiewicz.jr@...el.com>
Subject: RE: [RFC PATCH 05/12] ixgbe: Add SR-IOV features to main module

On Wed, 9 Dec 2009, Rose, Gregory V wrote:

> >-----Original Message-----
> >From: chavey@...gle.com [mailto:chavey@...gle.com]
> >Sent: Wednesday, December 09, 2009 5:15 PM
> >To: Kirsher, Jeffrey T
> >Cc: netdev@...r.kernel.org; gospo@...hat.com; Rose, Gregory V;
> >Waskiewicz Jr, Peter P
> >Subject: Re: [RFC PATCH 05/12] ixgbe: Add SR-IOV features to main module
> >
> >From: Greg Rose <gregory.v.rose@...el.com>
> >
> >Adds SR-IOV features supported by the 82599 controller to the main
> >driver
> >module.  If the CONFIG_PCI_IOV kernel option is selected then the SR-IOV
> >features are enabled.  Use the max_vfs module option to allocate up to
> >63
> >virtual functions per physical port.
> >
> >---
> >
> >+static inline void ixgbe_disable_sriov(struct ixgbe_adapter *adapter)
> >+{
> >+       struct ixgbe_hw *hw = &adapter->hw;
> >+       u32 gcr;
> >+       u32 gpie;
> >+       u32 vmdctl;
> >+
> >+#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.

-PJ

> 
> >if this is to wait for pci_disable then add it
> >in the #ifdef above.
> >i s there a registerthat can be checked to ensure that
> >the device is in the expected state ? (similar to line 311 of
> >the orginal patch)
> [Rose, Gregory V] 
> 
> Not reliably.
> 
> >
> >
> >@@ -2269,6 +2376,20 @@ static void ixgbe_configure_rx(struct
> >ixgbe_adapter *adapter)
> >       }
> >       IXGBE_WRITE_REG(hw, IXGBE_MRQC, mrqc);
> >
> >+       if (adapter->num_vfs) {
> >+               u32 reg;
> >+
> >+               /* Map PF MAC address in RAR Entry 0 to first pool
> >+                * following VFs */
> >+               hw->mac.ops.set_vmdq(hw, 0, adapter->num_vfs);
> >+
> >+               /* Set up VF register offsets for selected VT Mode, i.e.
> >+                * 64 VFs for SR-IOV */
> >+               reg = IXGBE_READ_REG(hw, IXGBE_GCR_EXT);
> >+               reg |= 0x80000003;
> >
> >what is the significance of the 0x80000003 ?
> 
> [Rose, Gregory V] 
> 
> Oh, a magic number.  We'll fix that.
> 
> In this case it's to set up the correct PCIe configuration on the device.
> 
> - Greg
> 
> 
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