103 lines
2.9 KiB
ReStructuredText
103 lines
2.9 KiB
ReStructuredText
FPGA Region
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===========
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Overview
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--------
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This document is meant to be a brief overview of the FPGA region API usage. A
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more conceptual look at regions can be found in the Device Tree binding
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document [#f1]_.
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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 [#f1]_. 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 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 is for partial
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reconfiguration.
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How to program an FPGA using a region
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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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:c:func:`fpga_region_program_fpga()` operates on info passed in the
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fpga_image_info (region->info). 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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Then you will want to enumerate whatever hardware has appeared in the FPGA.
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How to add a new FPGA region
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----------------------------
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An example of usage can be seen in the probe function of [#f2]_.
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.. [#f1] ../devicetree/bindings/fpga/fpga-region.txt
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.. [#f2] ../../drivers/fpga/of-fpga-region.c
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API to program an FPGA
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----------------------
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.. kernel-doc:: drivers/fpga/fpga-region.c
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:functions: fpga_region_program_fpga
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API to add a new FPGA region
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----------------------------
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.. kernel-doc:: include/linux/fpga/fpga-region.h
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:functions: fpga_region
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.. kernel-doc:: drivers/fpga/fpga-region.c
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:functions: fpga_region_create
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.. kernel-doc:: drivers/fpga/fpga-region.c
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:functions: fpga_region_free
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.. kernel-doc:: drivers/fpga/fpga-region.c
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:functions: fpga_region_register
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.. kernel-doc:: drivers/fpga/fpga-region.c
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:functions: fpga_region_unregister
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