Each PCIe device can issue up to 32 transactions at a time by default.
Each transaction is tracked by a tag number on the bus. 32 outstanding
transactions is not enough for some performance critical applications
especially when a lot of small sized frames are transmitted.
Extended tags support increases this number to 256. Devices not
supporting extended tags tie-off this field to 0. According to ECN, it
is safe to enable this feature for all PCIe endpoints.
Signed-off-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx>
---
drivers/pci/probe.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 93f280d..2424f38 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1505,12 +1505,19 @@ static void program_hpp_type2(struct pci_dev *dev, struct hpp_type2 *hpp)
*/
}
+static int pci_configure_extended_tags(struct pci_dev *dev)
+{
+ return pcie_capability_set_word(dev, PCI_EXP_DEVCTL,
+ PCI_EXP_DEVCTL_EXT_TAG);
+}
+
static void pci_configure_device(struct pci_dev *dev)
{
struct hotplug_params hpp;
int ret;
pci_configure_mps(dev);
+ pci_configure_extended_tags(dev);
memset(&hpp, 0, sizeof(hpp));
ret = pci_get_hp_params(dev, &hpp);
--
1.9.1
--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
