[PATCH 2/8] fpga: dfl-pci: locate DFLs by PCIe vendor specific capability

Moritz Fischer
2021-01-07T04:39:40Z

From: Matthew Gerlach <matthew.gerlach@linux.intel.com>

A PCIe vendor specific extended capability is introduced by Intel to
specify the start of a number of DFLs.

Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Signed-off-by: Moritz Fischer <mdf@kernel.org>
---
Documentation/fpga/dfl.rst | 27 ++++++++++++
drivers/fpga/dfl-pci.c | 87 +++++++++++++++++++++++++++++++++++++-
2 files changed, 113 insertions(+), 1 deletion(-)

diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst
index 0404fe6ffc74..ea8cefc18bdb 100644
--- a/Documentation/fpga/dfl.rst
+++ b/Documentation/fpga/dfl.rst
@@ -501,6 +501,33 @@ 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 a PCI Device
+===========================
+The original method for finding a DFL on a PCI device assumed the start of the
+first DFL to offset 0 of bar 0. If the first node of the DFL is an FME,
+then further DFLs in the port(s) are specified in FME header registers.
+Alternatively, a PCIe vendor specific capability structure can be used to
+specify the location of all the DFLs on the device, providing flexibility
+for the type of starting node in the DFL. Intel has reserved the
+VSEC ID of 0x43 for this purpose. The vendor specific
+data begins with a 4 byte vendor specific register for the number of DFLs followed 4 byte
+Offset/BIR vendor specific registers for each DFL. Bits 2:0 of Offset/BIR register
+indicates the BAR, and bits 31:3 form the 8 byte aligned offset where bits 2:0 are
+zero.
+
+ +----------------------------+
+ |31 Number of DFLS 0|
+ +----------------------------+
+ |31 Offset 3|2 BIR 0|
+ +----------------------------+
+ . . .
+ +----------------------------+
+ |31 Offset 3|2 BIR 0|
+ +----------------------------+
+
+Being able to specify more than one DFL per BAR has been considered, but it
+was determined the use case did not provide value. Specifying a single DFL
+per BAR simplifies the implementation and allows for extra error checking.

Open discussion
===============
diff --git a/drivers/fpga/dfl-pci.c b/drivers/fpga/dfl-pci.c
index 5100695e27cd..04e47e266f26 100644
--- a/drivers/fpga/dfl-pci.c
+++ b/drivers/fpga/dfl-pci.c
@@ -27,6 +27,14 @@
#define DRV_VERSION "0.8"
#define DRV_NAME "dfl-pci"

+#define PCI_VSEC_ID_INTEL_DFLS 0x43
+
+#define PCI_VNDR_DFLS_CNT 0x8
+#define PCI_VNDR_DFLS_RES 0xc
+
+#define PCI_VNDR_DFLS_RES_BAR_MASK GENMASK(2, 0)
+#define PCI_VNDR_DFLS_RES_OFF_MASK GENMASK(31, 3)
+
struct cci_drvdata {
struct dfl_fpga_cdev *cdev; /* container device */
};
@@ -119,6 +127,80 @@ static int *cci_pci_create_irq_table(struct pci_dev *pcidev, unsigned int nvec)
return table;
}

+static int find_dfls_by_vsec(struct pci_dev *pcidev, struct dfl_fpga_enum_info *info)
+{
+ u32 bir, offset, vndr_hdr, dfl_cnt, dfl_res;
+ int dfl_res_off, i, bars, voff = 0;
+ resource_size_t start, len;
+
+ while ((voff = pci_find_next_ext_capability(pcidev, voff, PCI_EXT_CAP_ID_VNDR))) {
+ vndr_hdr = 0;
+ pci_read_config_dword(pcidev, voff + PCI_VNDR_HEADER, &vndr_hdr);
+
+ if (PCI_VNDR_HEADER_ID(vndr_hdr) == PCI_VSEC_ID_INTEL_DFLS &&
+ pcidev->vendor == PCI_VENDOR_ID_INTEL)
+ break;
+ }
+
+ if (!voff) {
+ dev_dbg(&pcidev->dev, "%s no DFL VSEC found\n", __func__);
+ return -ENODEV;
+ }
+
+ dfl_cnt = 0;
+ pci_read_config_dword(pcidev, voff + PCI_VNDR_DFLS_CNT, &dfl_cnt);
+ if (dfl_cnt > PCI_STD_NUM_BARS) {
+ dev_err(&pcidev->dev, "%s too many DFLs %d > %d\n",
+ __func__, dfl_cnt, PCI_STD_NUM_BARS);
+ return -EINVAL;
+ }
+
+ dfl_res_off = voff + PCI_VNDR_DFLS_RES;
+ if (dfl_res_off + (dfl_cnt * sizeof(u32)) > PCI_CFG_SPACE_EXP_SIZE) {
+ dev_err(&pcidev->dev, "%s DFL VSEC too big for PCIe config space\n",
+ __func__);
+ return -EINVAL;
+ }
+
+ for (i = 0, bars = 0; i < dfl_cnt; i++, dfl_res_off += sizeof(u32)) {
+ dfl_res = GENMASK(31, 0);
+ pci_read_config_dword(pcidev, dfl_res_off, &dfl_res);
+
+ bir = dfl_res & PCI_VNDR_DFLS_RES_BAR_MASK;
+ if (bir >= PCI_STD_NUM_BARS) {
+ dev_err(&pcidev->dev, "%s bad bir number %d\n",
+ __func__, bir);
+ return -EINVAL;
+ }
+
+ if (bars & BIT(bir)) {
+ dev_err(&pcidev->dev, "%s DFL for BAR %d already specified\n",
+ __func__, bir);
+ return -EINVAL;
+ }
+
+ bars |= BIT(bir);
+
+ len = pci_resource_len(pcidev, bir);
+ offset = dfl_res & PCI_VNDR_DFLS_RES_OFF_MASK;
+ if (offset >= len) {
+ dev_err(&pcidev->dev, "%s bad offset %u >= %pa\n",
+ __func__, offset, &len);
+ return -EINVAL;
+ }
+
+ dev_dbg(&pcidev->dev, "%s BAR %d offset 0x%x\n", __func__, bir, offset);
+
+ len -= offset;
+
+ start = pci_resource_start(pcidev, bir) + offset;
+
+ dfl_fpga_enum_info_add_dfl(info, start, len);
+ }
+
+ return 0;
+}
+
/* default method of finding dfls starting at offset 0 of bar 0 */
static int find_dfls_by_default(struct pci_dev *pcidev,
struct dfl_fpga_enum_info *info)
@@ -220,7 +302,10 @@ static int cci_enumerate_feature_devs(struct pci_dev *pcidev)
goto irq_free_exit;
}

- ret = find_dfls_by_default(pcidev, info);
+ ret = find_dfls_by_vsec(pcidev, info);
+ if (ret == -ENODEV)
+ ret = find_dfls_by_default(pcidev, info);
+
if (ret)
goto irq_free_exit;

--
2.30.0