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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-06 01:02:30 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-06 01:02:30 +0000 |
commit | 76cb841cb886eef6b3bee341a2266c76578724ad (patch) | |
tree | f5892e5ba6cc11949952a6ce4ecbe6d516d6ce58 /Documentation/fmc/FMC-and-SDB.txt | |
parent | Initial commit. (diff) | |
download | linux-upstream/4.19.249.tar.xz linux-upstream/4.19.249.zip |
Adding upstream version 4.19.249.upstream/4.19.249upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/fmc/FMC-and-SDB.txt')
-rw-r--r-- | Documentation/fmc/FMC-and-SDB.txt | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/Documentation/fmc/FMC-and-SDB.txt b/Documentation/fmc/FMC-and-SDB.txt new file mode 100644 index 000000000..fa14e0b24 --- /dev/null +++ b/Documentation/fmc/FMC-and-SDB.txt @@ -0,0 +1,88 @@ + +FMC (FPGA Mezzanine Card) is the standard we use for our I/O devices, +in the context of White Rabbit and related hardware. + +In our I/O environments we need to write drivers for each mezzanine +card, and such drivers must work regardless of the carrier being used. +To achieve this, we abstract the FMC interface. + +We have a carrier for PCI-E called SPEC and one for VME called SVEC, +but more are planned. Also, we support stand-alone devices (usually +plugged on a SPEC card), controlled through Etherbone, developed by GSI. + +Code and documentation for the FMC bus was born as part of the spec-sw +project, but now it lives in its own project. Other projects, i.e. +software support for the various carriers, should include this as a +submodule. + +The most up to date version of code and documentation is always +available from the repository you can clone from: + + git://ohwr.org/fmc-projects/fmc-bus.git (read-only) + git@ohwr.org:fmc-projects/fmc-bus.git (read-write for developers) + +Selected versions of the documentation, as well as complete tar +archives for selected revisions are placed to the Files section of the +project: `http://www.ohwr.org/projects/fmc-bus/files' + + +What is FMC +*********** + +FMC, as said, stands for "FPGA Mezzanine Card". It is a standard +developed by the VME consortium called VITA (VMEbus International Trade +Association and ratified by ANSI, the American National Standard +Institute. The official documentation is called "ANSI-VITA 57.1". + +The FMC card is an almost square PCB, around 70x75 millimeters, that is +called mezzanine in this document. It usually lives plugged into +another PCB for power supply and control; such bigger circuit board is +called carrier from now on, and a single carrier may host more than one +mezzanine. + +In the typical application the mezzanine is mostly analog while the +carrier is mostly digital, and hosts an FPGA that must be configured to +match the specific mezzanine and the desired application. Thus, you may +need to load different FPGA images to drive different instances of the +same mezzanine. + +FMC, as such, is not a bus in the usual meaning of the term, because +most carriers have only one connector, and carriers with several +connectors have completely separate electrical connections to them. +This package, however, implements a bus as a software abstraction. + + +What is SDB +*********** + +SDB (Self Describing Bus) is a set of data structures that we use for +enumerating the internal structure of an FPGA image. We also use it as +a filesystem inside the FMC EEPROM. + +SDB is not mandatory for use of this FMC kernel bus, but if you have SDB +this package can make good use of it. SDB itself is developed in the +fpga-config-space OHWR project. The link to the repository is +`git://ohwr.org/hdl-core-lib/fpga-config-space.git' and what is used in +this project lives in the sdbfs subdirectory in there. + +SDB support for FMC is described in *note FMC Identification:: and +*note SDB Support:: + + +SDB Support +*********** + +The fmc.ko bus driver exports a few functions to help drivers taking +advantage of the SDB information that may be present in your own FPGA +memory image. + +The module exports the following functions, in the special header +<linux/fmc-sdb.h>. The linux/ prefix in the name is there because we +plan to submit it upstream in the future, and don't want to force +changes on our drivers if that happens. + + int fmc_scan_sdb_tree(struct fmc_device *fmc, unsigned long address); + void fmc_show_sdb_tree(struct fmc_device *fmc); + signed long fmc_find_sdb_device(struct sdb_array *tree, uint64_t vendor, + uint32_t device, unsigned long *sz); + int fmc_free_sdb_tree(struct fmc_device *fmc); |