89 строки
3.7 KiB
Plaintext
89 строки
3.7 KiB
Plaintext
|
|
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);
|