PCI/DOE: Support discovery version 2

PCIe r6.1, sec 6.30.1.1 defines a "DOE Discovery Version" field in
the DOE Discovery Request Data Object Contents (3rd DW) as:

15:8 DOE Discovery Version – must be 02h if the Capability Version in
the Data Object Exchange Extended Capability is 02h or greater.

Add support for the version on devices with the DOE v2 capability.

Link: https://lore.kernel.org/r/20240307022006.3657433-1-aik@amd.com
Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

Author: aik

drivers/pci/doe.c

@@ -383,11 +383,13 @@ static void pci_doe_task_complete(struct pci_doe_task *task)
 	complete(task->private);
 }
 
-static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
+static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 capver, u8 *index, u16 *vid,
 			     u8 *protocol)
 {
 	u32 request_pl = FIELD_PREP(PCI_DOE_DATA_OBJECT_DISC_REQ_3_INDEX,
-				    *index);
+				    *index) |
+			 FIELD_PREP(PCI_DOE_DATA_OBJECT_DISC_REQ_3_VER,
+				    (capver >= 2) ? 2 : 0);
 	__le32 request_pl_le = cpu_to_le32(request_pl);
 	__le32 response_pl_le;
 	u32 response_pl;
@@ -421,13 +423,17 @@ static int pci_doe_cache_protocols(struct pci_doe_mb *doe_mb)
 {
 	u8 index = 0;
 	u8 xa_idx = 0;
+	u32 hdr = 0;
+
+	pci_read_config_dword(doe_mb->pdev, doe_mb->cap_offset, &hdr);
 
 	do {
 		int rc;
 		u16 vid;
 		u8 prot;
 
-		rc = pci_doe_discovery(doe_mb, &index, &vid, &prot);
+		rc = pci_doe_discovery(doe_mb, PCI_EXT_CAP_VER(hdr), &index,
+				       &vid, &prot);
 		if (rc)
 			return rc;
 

include/uapi/linux/pci_regs.h

@@ -1144,6 +1144,7 @@
 #define PCI_DOE_DATA_OBJECT_HEADER_2_LENGTH		0x0003ffff
 
 #define PCI_DOE_DATA_OBJECT_DISC_REQ_3_INDEX		0x000000ff
+#define PCI_DOE_DATA_OBJECT_DISC_REQ_3_VER		0x0000ff00
 #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_VID		0x0000ffff
 #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL		0x00ff0000
 #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_NEXT_INDEX	0xff000000