Root Complex Integrated devices (RCiEP) do not have a Root Port before the
device. pci_configure_mps() should simply stick the max value for MaxPayload
size in Device Control, and for MaxReadReq. Unless pcie=pcie_bus-peer2peer
is used in kernel commandline PCIE_BUS_PEER2PEER.
When MPS is configured lower, it could result in reduced performance.
Fixes: 9dae3a97297f ("PCI: Move MPS configuration check to pci_configure_device()")
Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx>
Tested-by: Dave Jiang <dave.jiang@xxxxxxxxx>
To: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
To: linux-pci@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
---
drivers/pci/probe.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index eeff8a07..a738b1c 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1895,13 +1895,34 @@ static void pci_configure_mps(struct pci_dev *dev)
struct pci_dev *bridge = pci_upstream_bridge(dev);
int mps, mpss, p_mps, rc;
- if (!pci_is_pcie(dev) || !bridge || !pci_is_pcie(bridge))
+ if (!pci_is_pcie(dev))
return;
/* MPS and MRRS fields are of type 'RsvdP' for VFs, short-circuit out */
if (dev->is_virtfn)
return;
+ /*
+ * If this is a Root Complex Integrated Endpoint
+ * Simply program the max value from DEVCAP. No additional
+ * Lookup is necessary
+ */
+ if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END) {
+ if (pcie_bus_config == PCIE_BUS_PEER2PEER)
+ mps = 128;
+ else
+ mps = 128 << dev->pcie_mpss;
+ rc = pcie_set_mps(dev, mps);
+ if (rc) {
+ pci_warn(dev, "can't set Max Payload Size to %d; if necessary, use \"pci=pcie_bus_safe\" and report a bug\n",
+ mps);
+ return;
+ }
+ }
+
+ if (!bridge || !pci_is_pcie(bridge))
+ return;
+
mps = pcie_get_mps(dev);
p_mps = pcie_get_mps(bridge);
--
2.7.4
