[PATCH 4.4 082/101] PCI: Program MPS for RCiEP devices

Greg Kroah-Hartman
2020-06-19T16:50:28Z

From: Ashok Raj <ashok.raj@intel.com>

commit aa0ce96d72dd2e1b0dfd0fb868f82876e7790878 upstream.

Root Complex Integrated Endpoints (RCiEPs) do not have an upstream bridge,
so pci_configure_mps() previously ignored them, which may result in reduced
performance.

Instead, program the Max_Payload_Size of RCiEPs to the maximum supported
value (unless it is limited for the PCIE_BUS_PEER2PEER case). This also
affects the subsequent programming of Max_Read_Request_Size because Linux
programs MRRS based on the MPS value.

Fixes: 9dae3a97297f ("PCI: Move MPS configuration check to pci_configure_device()")
Link: https://lore.kernel.org/r/1585343775-4019-1-git-send-email-ashok.raj@intel.com
Tested-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/pci/probe.c | 22 +++++++++++++++++++++-
1 file changed, 21 insertions(+), 1 deletion(-)

--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1335,13 +1335,33 @@ static void pci_configure_mps(struct pci
struct pci_dev *bridge = pci_upstream_bridge(dev);
int mps, 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;

+ /*
+ * For Root Complex Integrated Endpoints, program the maximum
+ * supported value unless limited by the PCIE_BUS_PEER2PEER case.
+ */
+ 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) {
+ dev_warn(&dev->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);