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From: Bjorn Helgaas <helgaas@kernel.org>
To: linux-pci@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
	Bjorn Helgaas <bhelgaas@google.com>,
	stable@vger.kernel.org,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>,
	Matthew W Carlis <mattc@purestorage.com>,
	Keith Busch <kbusch@kernel.org>,
	Lukas Wunner <lukas@wunner.de>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Jesse Brandeburg <jesse.brandeburg@intel.com>
Subject: [PATCH] PCI/DPC: Request DPC only if also requesting AER
Date: Tue, 20 Feb 2024 17:55:20 -0600
Message-Id: <20240220235520.1514548-1-helgaas@kernel.org>
Precedence: bulk
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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..1c16965427b3 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) && IS_ENABLED(CONFIG_PCIE_EDR))
+			control |= OSC_PCI_EXPRESS_DPC_CONTROL;
+	}
 
 	return control;
 }
-- 
2.34.1