96 lines
2.6 KiB
Plaintext
96 lines
2.6 KiB
Plaintext
FPGA Regions
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Alan Tull 2017
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CONTENTS
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- Introduction
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- The FPGA region API
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- Usage example
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Introduction
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============
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This document is meant to be an brief overview of the FPGA region API usage. A
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more conceptual look at regions can be found in [1].
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For the purposes of this API document, let's just say that a region associates
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an FPGA Manager and a bridge (or bridges) with a reprogrammable region of an
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FPGA or the whole FPGA. The API provides a way to register a region and to
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program a region.
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Currently the only layer above fpga-region.c in the kernel is the Device Tree
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support (of-fpga-region.c) described in [1]. The DT support layer uses regions
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to program the FPGA and then DT to handle enumeration. The common region code
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is intended to be used by other schemes that have other ways of accomplishing
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enumeration after programming.
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An fpga-region can be set up to know the following things:
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* which FPGA manager to use to do the programming
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* which bridges to disable before programming and enable afterwards.
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Additional info needed to program the FPGA image is passed in the struct
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fpga_image_info [2] including:
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* pointers to the image as either a scatter-gather buffer, a contiguous
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buffer, or the name of firmware file
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* flags indicating specifics such as whether the image if for partial
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reconfiguration.
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===================
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The FPGA region API
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===================
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To register or unregister a region:
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-----------------------------------
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int fpga_region_register(struct device *dev,
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struct fpga_region *region);
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int fpga_region_unregister(struct fpga_region *region);
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An example of usage can be seen in the probe function of [3]
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To program an FPGA:
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-------------------
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int fpga_region_program_fpga(struct fpga_region *region);
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This function operates on info passed in the fpga_image_info
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(region->info).
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This function will attempt to:
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* lock the region's mutex
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* lock the region's FPGA manager
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* build a list of FPGA bridges if a method has been specified to do so
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* disable the bridges
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* program the FPGA
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* re-enable the bridges
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* release the locks
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=============
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Usage example
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=============
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First, allocate the info struct:
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info = fpga_image_info_alloc(dev);
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if (!info)
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return -ENOMEM;
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Set flags as needed, i.e.
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info->flags |= FPGA_MGR_PARTIAL_RECONFIG;
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Point to your FPGA image, such as:
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info->sgt = &sgt;
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Add info to region and do the programming:
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region->info = info;
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ret = fpga_region_program_fpga(region);
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Then enumerate whatever hardware has appeared in the FPGA.
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--
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[1] ../devicetree/bindings/fpga/fpga-region.txt
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[2] ./fpga-mgr.txt
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[3] ../../drivers/fpga/of-fpga-region.c
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