Re: [PATCH v2 2/2] fpga: dfl: look for vendor specific capability

Moritz Fischer
2020-11-22T01:19:19Z

Hi Matthew,

On Wed, Nov 18, 2020 at 11:01:51AM -0800, matthew.gerlach@linux.intel.com wrote:
> From: Matthew Gerlach <matthew.gerlach@linux.intel.com>
>
> 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>
> ---
> v2: Update documentation for clarity.
> Clean up macro names.
> Use GENMASK.
> Removed spurious blank lines.
> Changed some calls from dev_info to dev_dbg.
> Specifically check for VSEC not found, -ENODEV.
> Ensure correct pci vendor id.
> Remove check for page alignment.
> Rename find_dfl_in_cfg to find_dfls_by_vsec.
> Initialize target memory of pci_read_config_dword to invalid values before use.
> ---
> Documentation/fpga/dfl.rst | 13 ++++++
> drivers/fpga/dfl-pci.c | 87 +++++++++++++++++++++++++++++++++++++-
> 2 files changed, 98 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst
> index 0404fe6ffc74..37016ff35a90 100644
> --- a/Documentation/fpga/dfl.rst
> +++ b/Documentation/fpga/dfl.rst
> @@ -501,6 +501,19 @@ 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 Device
> +===========================

Maybe start with: "There are two ways of locating the DFLs"
> +The start of the first DFL is assumed to be 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 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.
It's nice to have details, thanks! Nit: This could be a table maybe?
>
> Open discussion
> ===============
> diff --git a/drivers/fpga/dfl-pci.c b/drivers/fpga/dfl-pci.c
> index b27fae045536..3a6807e3e10c 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 8
> +#define PCI_VNDR_DFLS_RES 0x0c
> +
> +#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 */
> };
> @@ -119,8 +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 bar, offset, vndr_hdr, dfl_cnt, dfl_res;
> + int dfl_res_off, i, voff = 0;
> + resource_size_t start, len;
> +
> + if (pcidev->vendor != PCI_VENDOR_ID_INTEL)
> + return -ENODEV;
> +
> + 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);
Are there concerns around those failing?
> +
> + 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_VSEC_ID_INTEL_DFLS)
> + break;
> + }
> +
> + if (!voff) {
> + dev_dbg(&pcidev->dev, "%s no VSEC found\n", __func__);
> + return -ENODEV;
> + }
> +
> + dfl_cnt = 0;
> + pci_read_config_dword(pcidev, voff + PCI_VNDR_DFLS_CNT, &dfl_cnt);
I guess this could fall on it's face if you'd read back ~0 ... maybe
I'm being too paranoid :)
> + dev_dbg(&pcidev->dev, "dfl_cnt %d\n", dfl_cnt);
> + for (i = 0; i < dfl_cnt; i++) {
> + dfl_res_off = voff + PCI_VNDR_DFLS_RES +
> + (i * sizeof(dfl_res));
> + dfl_res = GENMASK(31, 0);
> + 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_VNDR_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_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__, bar, offset);
> +
> + len -= offset;
> +
> + start = pci_resource_start(pcidev, bar) + offset;
> +
> + dfl_fpga_enum_info_add_dfl(info, start, len);
> + }
> +
> + return 0;
> +}
> +
> static int find_dfls_by_default(struct pci_dev *pcidev,
> - struct dfl_fpga_enum_info *info)
> + struct dfl_fpga_enum_info *info)
> {
> resource_size_t start, len;
> int port_num, bar, i;
> @@ -220,7 +300,10 @@ 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;
>
> --
> 2.25.2
>

Thanks,
Moritz