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| author | Matthew Gerlach <matthew.gerlach@linux.intel.com> | 2021-01-07 05:37:08 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-01-07 15:21:27 +0100 |
| commit | fa41d10589be124404492b5181a818a509d8cb1c (patch) | |
| tree | 3e3aeffcc744212668012280eacf2bb19071f626 /Documentation | |
| parent | fpga: dfl: refactor cci_enumerate_feature_devs() (diff) | |
| download | linux-fa41d10589be124404492b5181a818a509d8cb1c.tar.xz linux-fa41d10589be124404492b5181a818a509d8cb1c.zip | |
fpga: dfl-pci: locate DFLs by PCIe vendor specific capability
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>
Link: https://lore.kernel.org/r/20210107043714.991646-3-mdf@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/fpga/dfl.rst | 27 |
1 files changed, 27 insertions, 0 deletions
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 =============== |