RE: [PATCH] PCI: Align MPS to upstream bridge for SAFE and PERFORMANCE mode

["Z.Q. Hou" <zhiqiang.hou@nxp.com>]

Hi Bjorn and Lorenzo,

Any comments on this change?

-----Original Message-----
From: Z.Q. Hou <zhiqiang.hou@nxp.com> 
Sent: 2022年6月10日 23:02
To: linux-pci@vger.kernel.org; bhelgaas@google.com
Cc: Z.Q. Hou <zhiqiang.hou@nxp.com>
Subject: [PATCH] PCI: Align MPS to upstream bridge for SAFE and PERFORMANCE mode

From: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>

The commit 27d868b5e6cf ("PCI: Set MPS to match upstream bridge") made the device's MPS matches upstream bridge for PCIE_BUS_DEFAULT mode, so that it's more likely that a hot-added device will work in a system with an optimized MPS configuration.

Obviously, the Linux itself optimizes the MPS settings in the PCIE_BUS_SAFE and PCIE_BUS_PERFORMANCE mode, so let's do this also for these modes.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
---
 drivers/pci/probe.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 17a969942d37..2c5a1aefd9cb 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2034,7 +2034,9 @@ static void pci_configure_mps(struct pci_dev *dev)
 	 * Fancier MPS configuration is done later by
 	 * pcie_bus_configure_settings()
 	 */
-	if (pcie_bus_config != PCIE_BUS_DEFAULT)
+	if (pcie_bus_config != PCIE_BUS_DEFAULT &&
+	    pcie_bus_config != PCIE_BUS_SAFE &&
+	    pcie_bus_config != PCIE_BUS_PERFORMANCE)
 		return;
 
 	mpss = 128 << dev->pcie_mpss;
@@ -2047,7 +2049,7 @@ static void pci_configure_mps(struct pci_dev *dev)
 
 	rc = pcie_set_mps(dev, p_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",
+		pci_warn(dev, "can't set Max Payload Size to %d; if necessary, use 
+\"pci=pcie_bus_peer2peer\" and report a bug\n",
 			 p_mps);
 		return;
 	}
--
2.17.1

Thanks,
Zhiqiang