fpga: dfl: look for vendor specific capability

A DFL may not begin at offset 0 of BAR 0.  A PCIe vendor
specific capability can be used to specify the start of a
number of DFLs.

Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>

Documentation/fpga/dfl.rst

@@ -501,6 +501,16 @@ Developer only needs to provide a sub feature driver with matched feature id.
 FME Partial Reconfiguration Sub Feature driver (see drivers/fpga/dfl-fme-pr.c)
 could be a reference.
 
+Location of DFLs on PCI bus
+===========================
+The start of the DFL is assumed to be offset 0 of bar 0.
+Alternatively, a vendor specific capability structure can be used to
+specify the location of one or more DFLs.  Intel has reserved the
+vendor specific id of 0x43 for this purpose.  The vendor specific
+data begins with a 4 byte count of the number of DFLs followed 4 byte
+Offset/BIR fields for each DFL. Bits 2:0 of Offset/BIR field indicates
+the BAR, and bits 31:3 form the 8 byte aligned offset where bits 2:0 are
+zero.
 
 Open discussion
 ===============

drivers/fpga/dfl-pci.c

@@ -27,6 +27,13 @@
 #define DRV_VERSION	"0.8"
 #define DRV_NAME	"dfl-pci"
 
+#define PCI_VNDR_ID_DFLS 0x43
+
+#define PCI_VNDR_DFLS_CNT_OFFSET 8
+#define PCI_VNDR_DFLS_RES_OFFSET 0x0c
+
+#define PCI_VND_DFLS_RES_BAR_MASK 0x7
+
 struct cci_drvdata {
 	struct dfl_fpga_cdev *cdev;	/* container device */
 };
@@ -119,6 +126,82 @@ static int *cci_pci_create_irq_table(struct pci_dev *pcidev, unsigned int nvec)
 	return table;
 }
 
+static int find_dfl_in_cfg(struct pci_dev *pcidev,
+			   struct dfl_fpga_enum_info *info)
+{
+	u32 bar, offset, vndr_hdr, dfl_cnt, dfl_res;
+	int dfl_res_off, i, voff = 0;
+	resource_size_t start, len;
+
+	while ((voff = pci_find_next_ext_capability(pcidev, voff, PCI_EXT_CAP_ID_VNDR))) {
+
+		pci_read_config_dword(pcidev, voff + PCI_VNDR_HEADER, &vndr_hdr);
+
+		dev_dbg(&pcidev->dev,
+			"vendor-specific capability id 0x%x, rev 0x%x len 0x%x\n",
+			PCI_VNDR_HEADER_ID(vndr_hdr),
+			PCI_VNDR_HEADER_REV(vndr_hdr),
+			PCI_VNDR_HEADER_LEN(vndr_hdr));
+
+		if (PCI_VNDR_HEADER_ID(vndr_hdr) == PCI_VNDR_ID_DFLS)
+			break;
+	}
+
+	if (!voff) {
+		dev_dbg(&pcidev->dev, "%s no VSEC found\n", __func__);
+		return -ENODEV;
+	}
+
+	pci_read_config_dword(pcidev, voff + PCI_VNDR_DFLS_CNT_OFFSET, &dfl_cnt);
+	dev_info(&pcidev->dev, "dfl_cnt %d\n", dfl_cnt);
+	for (i = 0; i < dfl_cnt; i++) {
+		dfl_res_off = voff + PCI_VNDR_DFLS_RES_OFFSET +
+				      (i * sizeof(dfl_res));
+		pci_read_config_dword(pcidev, dfl_res_off, &dfl_res);
+
+		dev_dbg(&pcidev->dev, "dfl_res 0x%x\n", dfl_res);
+
+		bar = dfl_res & PCI_VND_DFLS_RES_BAR_MASK;
+
+		if (bar >= PCI_STD_NUM_BARS) {
+			dev_err(&pcidev->dev, "%s bad bar number %d\n",
+				__func__, bar);
+			return -EINVAL;
+		}
+
+		len = pci_resource_len(pcidev, bar);
+
+		if (len == 0) {
+			dev_err(&pcidev->dev, "%s unmapped bar number %d\n",
+				__func__, bar);
+			return -EINVAL;
+		}
+
+		offset = dfl_res & ~PCI_VND_DFLS_RES_BAR_MASK;
+
+		if (offset >= len) {
+			dev_err(&pcidev->dev, "%s bad offset %u >= %llu\n",
+				__func__, offset, len);
+			return -EINVAL;
+		}
+
+		dev_info(&pcidev->dev, "%s BAR %d offset 0x%x\n", __func__, bar, offset);
+
+		start = pci_resource_start(pcidev, bar) + offset;
+		len -= offset;
+
+		if (!PAGE_ALIGNED(start)) {
+			dev_err(&pcidev->dev, "%s unaliged start 0x%llx\n",
+				__func__, start);
+			return -EINVAL;
+		}
+
+		dfl_fpga_enum_info_add_dfl(info, start, len);
+	}
+
+	return 0;
+}
+
 static int find_dfl_in_bar0(struct pci_dev *pcidev,
 			    struct dfl_fpga_enum_info *info)
 {
@@ -221,7 +304,10 @@ static int cci_enumerate_feature_devs(struct pci_dev *pcidev)
 			goto irq_free_exit;
 	}
 
-	ret = find_dfl_in_bar0(pcidev, info);
+	ret = find_dfl_in_cfg(pcidev, info);
+
+	if (ret)
+		ret = find_dfl_in_bar0(pcidev, info);
 
 	if (ret)
 		goto irq_free_exit;