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From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
To: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Thatchanamurthy Satish <Satish.Thatchanamurt@Dell.com>
Subject: [PATCH v1] PCI/EDR: Align EDR implementation with PCI firmware r3.3 spec
Date: Wed,  1 May 2024 02:25:43 +0000
Message-Id: <20240501022543.1626025-1-sathyanarayanan.kuppuswamy@linux.intel.com>
Precedence: bulk
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During the Error Disconnect Recover (EDR) spec transition from r3.2 ECN
to PCI firmware spec r3.3, improvements were made to definitions of
EDR_PORT_DPC_ENABLE_DSM (0x0C) and EDR_PORT_LOCATE_DSM(0x0D) _DSMs.

Specifically,

* EDR_PORT_DPC_ENABLE_DSM _DSM version changed from 5 to 6, and
  arg4 is now a package type instead of an integer in version 5.
* EDR_PORT_LOCATE_DSM _DSM uses BIT(31) to return the status of the
  operation.

Ensure _DSM implementation aligns with PCI firmware r3.3 spec
recommendation. More details about the EDR_PORT_DPC_ENABLE_DSM and
EDR_PORT_LOCATE_DSM _DSMs can be found in PCI firmware specification,
r3.3, sec 4.6.12 and sec 4.6.13.

While at it, fix a typo in EDR_PORT_LOCATE_DSM comments.

Fixes: ac1c8e35a326 ("PCI/DPC: Add Error Disconnect Recover (EDR) support")
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---
 drivers/pci/pcie/edr.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/pcie/edr.c b/drivers/pci/pcie/edr.c
index 5f4914d313a1..fea098e22e3e 100644
--- a/drivers/pci/pcie/edr.c
+++ b/drivers/pci/pcie/edr.c
@@ -35,7 +35,7 @@ static int acpi_enable_dpc(struct pci_dev *pdev)
 	 * Behavior when calling unsupported _DSM functions is undefined,
 	 * so check whether EDR_PORT_DPC_ENABLE_DSM is supported.
 	 */
-	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;
 
@@ -47,11 +47,11 @@ static int acpi_enable_dpc(struct pci_dev *pdev)
 	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.
+	 * Per PCI Firmware Specification r3.3, 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;
@@ -86,7 +86,7 @@ static struct pci_dev *acpi_dpc_port_get(struct pci_dev *pdev)
 
 	/*
 	 * Behavior when calling unsupported _DSM functions is undefined,
-	 * so check whether EDR_PORT_DPC_ENABLE_DSM is supported.
+	 * so check whether EDR_PORT_LOCATE_DSM is supported.
 	 */
 	if (!acpi_check_dsm(adev->handle, &pci_acpi_dsm_guid, 5,
 			    1ULL << EDR_PORT_LOCATE_DSM))
@@ -103,6 +103,17 @@ static struct pci_dev *acpi_dpc_port_get(struct pci_dev *pdev)
 		return NULL;
 	}
 
+	/*
+	 * Per PCI Firmware Specification r3.3, sec 4.6.13, bit 31 represents
+	 * the success/failure of the operation. If bit 31 is set, the operation
+	 * is failed.
+	 */
+	if (obj->integer.value & BIT(31)) {
+		ACPI_FREE(obj);
+		pci_err(pdev, "Locate Port _DSM failed\n");
+		return NULL;
+	}
+
 	/*
 	 * Firmware returns DPC port BDF details in following format:
 	 *	15:8 = bus
-- 
2.25.1