[Xen-devel] [PATCH] Re-enable LTR/OBFF when device is owned by pciback

["Hao, Xudong" <xudong.hao@xxxxxxxxx>]

When PCIE device which has LTR/OBFF capabilities is owned by pciback, LTR/OBFF 
feature may be disabled. This patch re-enable LTR and OBFF, so that guest with 
device assigned can be benefitted.

Signed-off-by: Xudong Hao <xudong.hao@xxxxxxxxx>

diff --git a/drivers/xen/xen-pciback/pci_stub.c 
b/drivers/xen/xen-pciback/pci_stub.c
index 19834d1..82aac5b 100644
--- a/drivers/xen/xen-pciback/pci_stub.c
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -334,6 +334,14 @@ static int __devinit pcistub_init_device(struct pci_dev 
*dev)
        dev_dbg(&dev->dev, "reset device\n");
        xen_pcibk_reset_device(dev);
 
+       /* set default value */
+       unsigned long type = PCI_EXP_OBFF_SIGNAL_ALWAYS;
+       int snoop_lat_ns = 1024, nosnoop_lat_ns = 1024; /* 1024ns is max value 
*/
+
+       /* Enable LTR and OBFF before do device assignment */
+       /* LTR(Latency tolerance reporting) allows devices to send messages to 
the
+        * root complex indicating their latency tolerance for snooped & 
unsnooped
+        * memory transactions. 
+        */
+       pci_enable_ltr(dev);
+       pci_set_ltr(dev, snoop_lat_ns, nosnoop_lat_ns);
+
+       /* OBFF (optimized buffer flush/fill), where supported, can help improve
+        * energy efficiency by giving devices information about when 
interrupts and
+        * other activity will have a reduced power impact.
+        */
+       pci_enable_obff(dev, type);
+
        dev->dev_flags |= PCI_DEV_FLAGS_ASSIGNED;
        return 0;


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