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Documentation / fmc / FMC-and-SDB.txt




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Based on kernel version 3.13. Page generated on 2014-01-20 22:03 EST.

1	
2	FMC (FPGA Mezzanine Card) is the standard we use for our I/O devices,
3	in the context of White Rabbit and related hardware.
4	
5	In our I/O environments we need to write drivers for each mezzanine
6	card, and such drivers must work regardless of the carrier being used.
7	To achieve this, we abstract the FMC interface.
8	
9	We have a carrier for PCI-E called SPEC and one for VME called SVEC,
10	but more are planned.  Also, we support stand-alone devices (usually
11	plugged on a SPEC card), controlled through Etherbone, developed by GSI.
12	
13	Code and documentation for the FMC bus was born as part of the spec-sw
14	project, but now it lives in its own project. Other projects, i.e.
15	software support for the various carriers, should include this as a
16	submodule.
17	
18	The most up to date version of code and documentation is always
19	available from the repository you can clone from:
20	
21	        git://ohwr.org/fmc-projects/fmc-bus.git (read-only)
22	        git@ohwr.org:fmc-projects/fmc-bus.git (read-write for developers)
23	
24	Selected versions of the documentation, as well as complete tar
25	archives for selected revisions are placed to the Files section of the
26	project: `http://www.ohwr.org/projects/fmc-bus/files'
27	
28	
29	What is FMC
30	***********
31	
32	FMC, as said, stands for "FPGA Mezzanine Card". It is a standard
33	developed by the VME consortium called VITA (VMEbus International Trade
34	Association and ratified by ANSI, the American National Standard
35	Institute.  The official documentation is called "ANSI-VITA 57.1".
36	
37	The FMC card is an almost square PCB, around 70x75 millimeters, that is
38	called mezzanine in this document.  It usually lives plugged into
39	another PCB for power supply and control; such bigger circuit board is
40	called carrier from now on, and a single carrier may host more than one
41	mezzanine.
42	
43	In the typical application the mezzanine is mostly analog while the
44	carrier is mostly digital, and hosts an FPGA that must be configured to
45	match the specific mezzanine and the desired application. Thus, you may
46	need to load different FPGA images to drive different instances of the
47	same mezzanine.
48	
49	FMC, as such, is not a bus in the usual meaning of the term, because
50	most carriers have only one connector, and carriers with several
51	connectors have completely separate electrical connections to them.
52	This package, however, implements a bus as a software abstraction.
53	
54	
55	What is SDB
56	***********
57	
58	SDB (Self Describing Bus) is a set of data structures that we use for
59	enumerating the internal structure of an FPGA image. We also use it as
60	a filesystem inside the FMC EEPROM.
61	
62	SDB is not mandatory for use of this FMC kernel bus, but if you have SDB
63	this package can make good use of it.  SDB itself is developed in the
64	fpga-config-space OHWR project. The link to the repository is
65	`git://ohwr.org/hdl-core-lib/fpga-config-space.git' and what is used in
66	this project lives in the sdbfs subdirectory in there.
67	
68	SDB support for FMC is described in *note FMC Identification:: and
69	*note SDB Support::
70	
71	
72	SDB Support
73	***********
74	
75	The fmc.ko bus driver exports a few functions to help drivers taking
76	advantage of the SDB information that may be present in your own FPGA
77	memory image.
78	
79	The module exports the following functions, in the special header
80	<linux/fmc-sdb.h>. The linux/ prefix in the name is there because we
81	plan to submit it upstream in the future, and don't want to force
82	changes on our drivers if that happens.
83	
84	         int fmc_scan_sdb_tree(struct fmc_device *fmc, unsigned long address);
85	         void fmc_show_sdb_tree(struct fmc_device *fmc);
86	         signed long fmc_find_sdb_device(struct sdb_array *tree, uint64_t vendor,
87	                                         uint32_t device, unsigned long *sz);
88	         int fmc_free_sdb_tree(struct fmc_device *fmc);
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