Documentation/fpga/debugfs.txt

FPGA Manager DebugFS interface for FPGA reprogramming.

Alan Tull 2016

Each FPGA gets its own directory such as <debugfs>/fpga_manager/fpga0 and
three files:

 - [RW] flags:          flags as defined in fpga-mgr.h.  For example:

   $ echo 1 > /sys/kernel/debug/fpga_manager/fpga0/flags

 - [RW] config_complete_timeout_us:	time out in microseconds to wait for
					FPGA to go to operating state after
					region has been programmed.

   $ echo 4 > /sys/kernel/debug/fpga_manager/fpga0/config_complete_timeout_us

 - [RW] firmware_name:  Name of an FPGA image firmware file.  Writing initiates
                        a complete FPGA programming cycle.  Note that the image
                        file must be in a directory on the firmware search path
                        such as /lib/firmware.

   $ echo image.rbf > /sys/kernel/debug/fpga_manager/fpga0/firmware_name

 - [WO] image:          Raw FPGA image data.  Writing the FPGA image data will
                        initiate a complete FPGA programming cycle.  Data must
                        be written in one chunk, for example:

   $ dd bs=10M if=./image.rbf of=/sys/kernel/debug/fpga_manager/fpga0/image
    (where image.rbf < 10M)

To program the FPGA, write the flags (if needed), then use either the
firmware_name or image file to program.

This interface does not handle bridges or loading/unloading of soft IP device
drivers.  This makes it really easy to mess things up by doing things like
reprogramming the hardware out from under a driver or reprogramming while a
bridge is enabled, causing gunk to go out on a cpu bus.  It should go without
saying that this interface is for debug only.  Not intended for production use.