From: Keith Busch <keith.busch@xxxxxxxxx>
Firmware typically configures the PCIe fabric with a consistent Max Payload
Size setting based on the devices present at boot. A hot-added device
typically has the power-on default MPS setting (128 bytes), which may not
match the fabric.
When adding a new device via pci_device_add(), set its Max Payload Size to
match the upstream bridge (unless PCIe bus tuning is disabled). Note that
pcie_bus_configure_settings() may further change MPS based on the tuning
policy.
This makes it more likely that a hot-added device will work in a system
with optimized MPS configuration.
If we hot-add a device that only supports 128-byte MPS, it still likely
won't work because we don't reconfigure the rest of the fabric. Booting
with "pci=pcie_bus_peer2peer" is a workaround for this because it sets MPS
to 128 for everything.
Signed-off-by: Keith Busch <keith.busch@xxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
---
drivers/pci/probe.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index eb32395..f73dd7a 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1278,7 +1278,7 @@ int pci_setup_device(struct pci_dev *dev)
static void pci_configure_mps(struct pci_dev *dev)
{
struct pci_dev *bridge = pci_upstream_bridge(dev);
- int mps, p_mps;
+ int mps, p_mps, rc;
if (!pci_is_pcie(dev) || !bridge || !pci_is_pcie(bridge))
return;
@@ -1294,6 +1294,16 @@ static void pci_configure_mps(struct pci_dev *dev)
mps, pci_name(bridge), p_mps);
return;
}
+
+ rc = pcie_set_mps(dev, p_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",
+ p_mps);
+ return;
+ }
+
+ dev_info(&dev->dev, "Max Payload Size set to %d (was %d, max %d)\n",
+ p_mps, mps, 128 << dev->pcie_mpss);
}
static struct hpp_type0 pci_default_type0 = {
--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
