diff options
| author | Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> | 2025-06-10 14:48:02 +0300 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2025-08-11 15:00:51 -0500 |
| commit | a22250fe933dbd1da9a9683506ae3f489ccc579d (patch) | |
| tree | b4fcf93f34778883925cff06901250812602b1a3 | |
| parent | c763fae8c4231e426033f62c21be60db4b6659a9 (diff) | |
PCI: Add Extended Tag + MRRS quirk for Xeon 6
When bifurcated to x2, Xeon 6 Root Port performance is sensitive to the
configuration of Extended Tags, Max Read Request Size (MRRS), and 10-Bit
Tag Requester (note: there is currently no 10-Bit Tag support in the
kernel). While those can be configured to the recommended values by FW,
kernel may decide to overwrite the initial values.
Add a quirk that disallows enabling Extended Tags and setting MRRS
larger than 128B for devices under Xeon 6 Root Ports if the Root Port
is bifurcated to x2. Use the host bridge's enable_device hook to
overwrite MRRS if it's set to >128B for the device to be enabled.
The earlier attempts to implement this quirk polluted PCI core code with
the checks necessary to support this quirk. Using the enable_device hook
keeps the quirk well-contained, away from the PCI core code.
Suggested-by: Lukas Wunner <lukas@wunner.de>
Link: https://cdrdv2.intel.com/v1/dl/getContent/837176
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
[bhelgaas: 2x -> x2, rename quirk]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Link: https://patch.msgid.link/20250610114802.7460-1-ilpo.jarvinen@linux.intel.com
| -rw-r--r-- | arch/x86/pci/fixup.c | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/arch/x86/pci/fixup.c b/arch/x86/pci/fixup.c index e7e71490bd25..25076a5acd96 100644 --- a/arch/x86/pci/fixup.c +++ b/arch/x86/pci/fixup.c @@ -295,6 +295,46 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_MCH_PC, pcie_ro DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_MCH_PC1, pcie_rootport_aspm_quirk); /* + * PCIe devices underneath Xeon 6 PCIe Root Port bifurcated to x2 have lower + * performance with Extended Tags and MRRS > 128B. Work around the performance + * problems by disabling Extended Tags and limiting MRRS to 128B. + * + * https://cdrdv2.intel.com/v1/dl/getContent/837176 + */ +static int limit_mrrs_to_128(struct pci_host_bridge *b, struct pci_dev *pdev) +{ + int readrq = pcie_get_readrq(pdev); + + if (readrq > 128) + pcie_set_readrq(pdev, 128); + + return 0; +} + +static void pci_xeon_x2_bifurc_quirk(struct pci_dev *pdev) +{ + struct pci_host_bridge *bridge = pci_find_host_bridge(pdev->bus); + u32 linkcap; + + pcie_capability_read_dword(pdev, PCI_EXP_LNKCAP, &linkcap); + if (FIELD_GET(PCI_EXP_LNKCAP_MLW, linkcap) != 0x2) + return; + + bridge->no_ext_tags = 1; + bridge->enable_device = limit_mrrs_to_128; + pci_info(pdev, "Disabling Extended Tags and limiting MRRS to 128B (performance reasons due to x2 PCIe link)\n"); +} + +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x0db0, pci_xeon_x2_bifurc_quirk); +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x0db1, pci_xeon_x2_bifurc_quirk); +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x0db2, pci_xeon_x2_bifurc_quirk); +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x0db3, pci_xeon_x2_bifurc_quirk); +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x0db6, pci_xeon_x2_bifurc_quirk); +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x0db7, pci_xeon_x2_bifurc_quirk); +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x0db8, pci_xeon_x2_bifurc_quirk); +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x0db9, pci_xeon_x2_bifurc_quirk); + +/* * Fixup to mark boot BIOS video selected by BIOS before it changes * * From information provided by "Jon Smirl" <jonsmirl@gmail.com> |