[PATCH] PCI: enable extended tags support for PCIe endpoints

From: Sinan Kaya
Date: Sat Sep 24 2016 - 22:10:58 EST

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,
static void pci_configure_device(struct pci_dev *dev)
struct hotplug_params hpp;
int ret;

+ pci_configure_extended_tags(dev);

memset(&hpp, 0, sizeof(hpp));
ret = pci_get_hp_params(dev, &hpp);