On Fri, Mar 27, 2020 at 02:16:15PM -0700, Ashok Raj wrote:

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@intel.com Tested-by: Dave Jiang dave.jiang@intel.com To: Bjorn Helgaas bhelgaas@google.com To: linux-pci@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org Cc: Ashok Raj ashok.raj@intel.com

Applied to pci/enumeration for v5.8, thanks!

---

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