From: Alan Tull <atull@xxxxxxxxxxxxxxxxxxxxx> Add a document spelling out usage of the simple fpga bus. Signed-off-by: Alan Tull <atull@xxxxxxxxxxxxxxxxxxxxx> --- .../staging/fpga/Documentation/simple-fpga-bus.txt | 48 ++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 drivers/staging/fpga/Documentation/simple-fpga-bus.txt diff --git a/drivers/staging/fpga/Documentation/simple-fpga-bus.txt b/drivers/staging/fpga/Documentation/simple-fpga-bus.txt new file mode 100644 index 0000000..9df519f --- /dev/null +++ b/drivers/staging/fpga/Documentation/simple-fpga-bus.txt @@ -0,0 +1,48 @@ + Simple FPGA Bus + + Alan Tull 2015 + + Overview + -------- +The simple FPGA bus adds device tree overlay support for FPGA's. Loading a +DT overlay will result in the FGPA getting an image loaded, its bridges will +be released, and the DT populated for nodes below the simple-fpga-bus. This +results in drivers getting probed for the hardware that just got added. This +is intended to support the FPGA usage where the FPGA has hardware that +requires drivers. Removing the overlay will result in the drivers getting +removed and the bridges being disabled. + + + Requirements + ------------ + 1. An FPGA image that has a hardware block or blocks that use drivers that are + supported in the kernel. + 2. A device tree overlay. + 3. A FPGA manager driver supporting writing the FPGA. + 4. FPGA bridge resets supported as reset controllers. + +The DT overlay includes bindings (documented in bindings/simple-fpga-bus.txt) +that specify: + * Which fpga manager to use + * Which image file to load + * Flags indicating whether this this image is for full reconfiguration or + partial. + * a list of resets that should be released. These enable the FPGA bridges. + * child nodes specifying the devices that will be added with appropriate + compatible strings, etc. + +Since this code uses the firmware interface to get the image and DT overlay, +they currently have to be files on the filesystem. It doesn't have to be that +way forever as DT bindings could be added to point to other sources for the +image. + + + Sequence + -------- + 1. Load the DT overlay. One convenient way to do that is to use Pantelis' + handy configfs interface (more below). + 2. The simple FPGA bus gets probed and will do the following: + a. call the fpga manager core to program the FPGA + b. release the FPGA bridges + c. call of_platform_populate resulting in device drivers getting probed. + -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
