PCI/EDR: Align EDR_PORT_DPC_ENABLE_DSM with PCI Firmware r3.3

The "Downstream Port Containment related Enhancements" ECN of Jan 28, 2019
(document 12888 below), defined the EDR_PORT_DPC_ENABLE_DSM function with
Revision ID 5 with Arg3 being an integer.  But when the ECN was integrated
into PCI Firmware r3.3, sec 4.6.12, it was defined as Revision ID 6 with
Arg3 being a package containing an integer.

The implementation in acpi_enable_dpc() supplies a package as Arg3 (arg4 in
the code), but it previously specified Revision ID 5.  Align this with PCI
Firmware r3.3 by using Revision ID 6.

If firmware implemented per the ECN, its Revision 5 function would receive
a package as Arg3 when it expects an integer, so acpi_enable_dpc() would
likely fail.  If such firmware exists and lacks a Revision 6 function that
expects a package, we may have to add support for Revision 5.

Link: https://lore.kernel.org/r/20240501022543.1626025-1-sathyanarayanan.kuppuswamy@linux.intel.com
Link: https://members.pcisig.com/wg/PCI-SIG/document/12888
Fixes: ac1c8e3 ("PCI/DPC: Add Error Disconnect Recover (EDR) support")
Signed-off-by: Kuppuswamy Sathyanarayanan <[email protected]>
[bhelgaas: split into two patches, update commit log]
Signed-off-by: Bjorn Helgaas <[email protected]>
Tested-by: Satish Thatchanamurthy <[email protected]> # one platform

Author: Kuppuswamy Sathyanarayanan

drivers/pci/pcie/edr.c

@@ -32,10 +32,10 @@ static int acpi_enable_dpc(struct pci_dev *pdev)
 	int status = 0;
 
 	/*
-	 * Behavior when calling unsupported _DSM functions is undefined,
-	 * so check whether EDR_PORT_DPC_ENABLE_DSM is supported.
+	 * Per PCI Firmware r3.3, sec 4.6.12, EDR_PORT_DPC_ENABLE_DSM is
+	 * optional. Return success if it's not implemented.
 	 */
-	if (!acpi_check_dsm(adev->handle, &pci_acpi_dsm_guid, 5,
+	if (!acpi_check_dsm(adev->handle, &pci_acpi_dsm_guid, 6,
 			    1ULL << EDR_PORT_DPC_ENABLE_DSM))
 		return 0;
 
@@ -46,12 +46,7 @@ static int acpi_enable_dpc(struct pci_dev *pdev)
 	argv4.package.count = 1;
 	argv4.package.elements = &req;
 
-	/*
-	 * Per Downstream Port Containment Related Enhancements ECN to PCI
-	 * Firmware Specification r3.2, sec 4.6.12, EDR_PORT_DPC_ENABLE_DSM is
-	 * optional.  Return success if it's not implemented.
-	 */
-	obj = acpi_evaluate_dsm(adev->handle, &pci_acpi_dsm_guid, 5,
+	obj = acpi_evaluate_dsm(adev->handle, &pci_acpi_dsm_guid, 6,
 				EDR_PORT_DPC_ENABLE_DSM, &argv4);
 	if (!obj)
 		return 0;