[PATCH v2 1/3] PCI/DPC: Request DPC only if also requesting AER

Bjorn Helgaas
2024-02-22T22:15:36Z

From: Bjorn Helgaas <bhelgaas@google.com>

When booting with "pci=noaer", we don't request control of AER, but we
previously *did* request control of DPC, as in the dmesg log attached at
the bugzilla below:

Command line: ... pci=noaer
acpi PNP0A08:00: _OSC: OS supports [ExtendedConfig ASPM ClockPM Segments MSI EDR HPX-Type3]
acpi PNP0A08:00: _OSC: OS now controls [PCIeHotplug SHPCHotplug PME PCIeCapability LTR DPC]

That's illegal per PCI Firmware Spec, r3.3, sec 4.5.1, table 4-5, which
says:

If the operating system sets this bit [OSC_PCI_EXPRESS_DPC_CONTROL], it
must also set bit 7 of the Support field (indicating support for Error
Disconnect Recover notifications) and bits 3 and 4 of the Control field
(requesting control of PCI Express Advanced Error Reporting and the PCI
Express Capability Structure).

Request DPC control only if we have also requested AER control.

Fixes: ac1c8e35a326 ("PCI/DPC: Add Error Disconnect Recover (EDR) support")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218491#c12
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: <stable@vger.kernel.org> # v5.7+
Cc: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: Matthew W Carlis <mattc@purestorage.com>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Lukas Wunner <lukas@wunner.de>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>
---
drivers/acpi/pci_root.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 58b89b8d950e..efc292b6214e 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -518,17 +518,19 @@ static u32 calculate_control(void)
if (IS_ENABLED(CONFIG_HOTPLUG_PCI_SHPC))
control |= OSC_PCI_SHPC_NATIVE_HP_CONTROL;

- if (pci_aer_available())
+ if (pci_aer_available()) {
control |= OSC_PCI_EXPRESS_AER_CONTROL;

- /*
- * Per the Downstream Port Containment Related Enhancements ECN to
- * the PCI Firmware Spec, r3.2, sec 4.5.1, table 4-5,
- * OSC_PCI_EXPRESS_DPC_CONTROL indicates the OS supports both DPC
- * and EDR.
- */
- if (IS_ENABLED(CONFIG_PCIE_DPC) && IS_ENABLED(CONFIG_PCIE_EDR))
- control |= OSC_PCI_EXPRESS_DPC_CONTROL;
+ /*
+ * Per PCI Firmware Spec, r3.3, sec 4.5.1, table 4-5, the
+ * OS can request DPC control only if it has advertised
+ * OSC_PCI_EDR_SUPPORT and requested both
+ * OSC_PCI_EXPRESS_CAPABILITY_CONTROL and
+ * OSC_PCI_EXPRESS_AER_CONTROL.
+ */
+ if (IS_ENABLED(CONFIG_PCIE_DPC))
+ control |= OSC_PCI_EXPRESS_DPC_CONTROL;
+ }

return control;
}
--
2.34.1