55 lines
2.0 KiB
ReStructuredText
55 lines
2.0 KiB
ReStructuredText
|
Introduction
|
||
|
|
============
|
||
|
|
|
||
|
|
The FPGA subsystem supports reprogramming FPGAs dynamically under
|
||
|
|
Linux. Some of the core intentions of the FPGA subsystems are:
|
||
|
|
|
||
|
|
* The FPGA subsystem is vendor agnostic.
|
||
|
|
|
||
|
|
* The FPGA subsystem separates upper layers (userspace interfaces and
|
||
|
|
enumeration) from lower layers that know how to program a specific
|
||
|
|
FPGA.
|
||
|
|
|
||
|
|
* Code should not be shared between upper and lower layers. This
|
||
|
|
should go without saying. If that seems necessary, there's probably
|
||
|
|
framework functionality that can be added that will benefit
|
||
|
|
other users. Write the linux-fpga mailing list and maintainers and
|
||
|
|
seek out a solution that expands the framework for broad reuse.
|
||
|
|
|
||
|
|
* Generally, when adding code, think of the future. Plan for reuse.
|
||
|
|
|
||
|
|
The framework in the kernel is divided into:
|
||
|
|
|
||
|
|
FPGA Manager
|
||
|
|
------------
|
||
|
|
|
||
|
|
If you are adding a new FPGA or a new method of programming an FPGA,
|
||
|
|
this is the subsystem for you. Low level FPGA manager drivers contain
|
||
|
|
the knowledge of how to program a specific device. This subsystem
|
||
|
|
includes the framework in fpga-mgr.c and the low level drivers that
|
||
|
|
are registered with it.
|
||
|
|
|
||
|
|
FPGA Bridge
|
||
|
|
-----------
|
||
|
|
|
||
|
|
FPGA Bridges prevent spurious signals from going out of an FPGA or a
|
||
|
|
region of an FPGA during programming. They are disabled before
|
||
|
|
programming begins and re-enabled afterwards. An FPGA bridge may be
|
||
|
|
actual hard hardware that gates a bus to a CPU or a soft ("freeze")
|
||
|
|
bridge in FPGA fabric that surrounds a partial reconfiguration region
|
||
|
|
of an FPGA. This subsystem includes fpga-bridge.c and the low level
|
||
|
|
drivers that are registered with it.
|
||
|
|
|
||
|
|
FPGA Region
|
||
|
|
-----------
|
||
|
|
|
||
|
|
If you are adding a new interface to the FPGA framework, add it on top
|
||
|
|
of an FPGA region.
|
||
|
|
|
||
|
|
The FPGA Region framework (fpga-region.c) associates managers and
|
||
|
|
bridges as reconfigurable regions. A region may refer to the whole
|
||
|
|
FPGA in full reconfiguration or to a partial reconfiguration region.
|
||
|
|
|
||
|
|
The Device Tree FPGA Region support (of-fpga-region.c) handles
|
||
|
|
reprogramming FPGAs when device tree overlays are applied.
|