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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
commit | 2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch) | |
tree | 848558de17fb3008cdf4d861b01ac7781903ce39 /Documentation/driver-api/fpga | |
parent | Initial commit. (diff) | |
download | linux-upstream.tar.xz linux-upstream.zip |
Adding upstream version 6.1.76.upstream/6.1.76upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | Documentation/driver-api/fpga/fpga-bridge.rst | 22 | ||||
-rw-r--r-- | Documentation/driver-api/fpga/fpga-mgr.rst | 162 | ||||
-rw-r--r-- | Documentation/driver-api/fpga/fpga-programming.rst | 107 | ||||
-rw-r--r-- | Documentation/driver-api/fpga/fpga-region.rst | 109 | ||||
-rw-r--r-- | Documentation/driver-api/fpga/index.rst | 15 | ||||
-rw-r--r-- | Documentation/driver-api/fpga/intro.rst | 54 |
6 files changed, 469 insertions, 0 deletions
diff --git a/Documentation/driver-api/fpga/fpga-bridge.rst b/Documentation/driver-api/fpga/fpga-bridge.rst new file mode 100644 index 000000000..604208534 --- /dev/null +++ b/Documentation/driver-api/fpga/fpga-bridge.rst @@ -0,0 +1,22 @@ +FPGA Bridge +=========== + +API to implement a new FPGA bridge +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +* struct fpga_bridge - The FPGA Bridge structure +* struct fpga_bridge_ops - Low level Bridge driver ops +* fpga_bridge_register() - Create and register a bridge +* fpga_bridge_unregister() - Unregister a bridge + +.. kernel-doc:: include/linux/fpga/fpga-bridge.h + :functions: fpga_bridge + +.. kernel-doc:: include/linux/fpga/fpga-bridge.h + :functions: fpga_bridge_ops + +.. kernel-doc:: drivers/fpga/fpga-bridge.c + :functions: fpga_bridge_register + +.. kernel-doc:: drivers/fpga/fpga-bridge.c + :functions: fpga_bridge_unregister diff --git a/Documentation/driver-api/fpga/fpga-mgr.rst b/Documentation/driver-api/fpga/fpga-mgr.rst new file mode 100644 index 000000000..49c0a9512 --- /dev/null +++ b/Documentation/driver-api/fpga/fpga-mgr.rst @@ -0,0 +1,162 @@ +FPGA Manager +============ + +Overview +-------- + +The FPGA manager core exports a set of functions for programming an FPGA with +an image. The API is manufacturer agnostic. All manufacturer specifics are +hidden away in a low level driver which registers a set of ops with the core. +The FPGA image data itself is very manufacturer specific, but for our purposes +it's just binary data. The FPGA manager core won't parse it. + +The FPGA image to be programmed can be in a scatter gather list, a single +contiguous buffer, or a firmware file. Because allocating contiguous kernel +memory for the buffer should be avoided, users are encouraged to use a scatter +gather list instead if possible. + +The particulars for programming the image are presented in a structure (struct +fpga_image_info). This struct contains parameters such as pointers to the +FPGA image as well as image-specific particulars such as whether the image was +built for full or partial reconfiguration. + +How to support a new FPGA device +-------------------------------- + +To add another FPGA manager, write a driver that implements a set of ops. The +probe function calls fpga_mgr_register() or fpga_mgr_register_full(), such as:: + + static const struct fpga_manager_ops socfpga_fpga_ops = { + .write_init = socfpga_fpga_ops_configure_init, + .write = socfpga_fpga_ops_configure_write, + .write_complete = socfpga_fpga_ops_configure_complete, + .state = socfpga_fpga_ops_state, + }; + + static int socfpga_fpga_probe(struct platform_device *pdev) + { + struct device *dev = &pdev->dev; + struct socfpga_fpga_priv *priv; + struct fpga_manager *mgr; + int ret; + + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + /* + * do ioremaps, get interrupts, etc. and save + * them in priv + */ + + mgr = fpga_mgr_register(dev, "Altera SOCFPGA FPGA Manager", + &socfpga_fpga_ops, priv); + if (IS_ERR(mgr)) + return PTR_ERR(mgr); + + platform_set_drvdata(pdev, mgr); + + return 0; + } + + static int socfpga_fpga_remove(struct platform_device *pdev) + { + struct fpga_manager *mgr = platform_get_drvdata(pdev); + + fpga_mgr_unregister(mgr); + + return 0; + } + +Alternatively, the probe function could call one of the resource managed +register functions, devm_fpga_mgr_register() or devm_fpga_mgr_register_full(). +When these functions are used, the parameter syntax is the same, but the call +to fpga_mgr_unregister() should be removed. In the above example, the +socfpga_fpga_remove() function would not be required. + +The ops will implement whatever device specific register writes are needed to +do the programming sequence for this particular FPGA. These ops return 0 for +success or negative error codes otherwise. + +The programming sequence is:: + 1. .parse_header (optional, may be called once or multiple times) + 2. .write_init + 3. .write or .write_sg (may be called once or multiple times) + 4. .write_complete + +The .parse_header function will set header_size and data_size to +struct fpga_image_info. Before parse_header call, header_size is initialized +with initial_header_size. If flag skip_header of fpga_manager_ops is true, +.write function will get image buffer starting at header_size offset from the +beginning. If data_size is set, .write function will get data_size bytes of +the image buffer, otherwise .write will get data up to the end of image buffer. +This will not affect .write_sg, .write_sg will still get whole image in +sg_table form. If FPGA image is already mapped as a single contiguous buffer, +whole buffer will be passed into .parse_header. If image is in scatter-gather +form, core code will buffer up at least .initial_header_size before the first +call of .parse_header, if it is not enough, .parse_header should set desired +size into info->header_size and return -EAGAIN, then it will be called again +with greater part of image buffer on the input. + +The .write_init function will prepare the FPGA to receive the image data. The +buffer passed into .write_init will be at least info->header_size bytes long; +if the whole bitstream is not immediately available then the core code will +buffer up at least this much before starting. + +The .write function writes a buffer to the FPGA. The buffer may be contain the +whole FPGA image or may be a smaller chunk of an FPGA image. In the latter +case, this function is called multiple times for successive chunks. This interface +is suitable for drivers which use PIO. + +The .write_sg version behaves the same as .write except the input is a sg_table +scatter list. This interface is suitable for drivers which use DMA. + +The .write_complete function is called after all the image has been written +to put the FPGA into operating mode. + +The ops include a .state function which will determine the state the FPGA is in +and return a code of type enum fpga_mgr_states. It doesn't result in a change +in state. + +API for implementing a new FPGA Manager driver +---------------------------------------------- + +* ``fpga_mgr_states`` - Values for :c:expr:`fpga_manager->state`. +* struct fpga_manager - the FPGA manager struct +* struct fpga_manager_ops - Low level FPGA manager driver ops +* struct fpga_manager_info - Parameter structure for fpga_mgr_register_full() +* fpga_mgr_register_full() - Create and register an FPGA manager using the + fpga_mgr_info structure to provide the full flexibility of options +* fpga_mgr_register() - Create and register an FPGA manager using standard + arguments +* devm_fpga_mgr_register_full() - Resource managed version of + fpga_mgr_register_full() +* devm_fpga_mgr_register() - Resource managed version of fpga_mgr_register() +* fpga_mgr_unregister() - Unregister an FPGA manager + +.. kernel-doc:: include/linux/fpga/fpga-mgr.h + :functions: fpga_mgr_states + +.. kernel-doc:: include/linux/fpga/fpga-mgr.h + :functions: fpga_manager + +.. kernel-doc:: include/linux/fpga/fpga-mgr.h + :functions: fpga_manager_ops + +.. kernel-doc:: include/linux/fpga/fpga-mgr.h + :functions: fpga_manager_info + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: fpga_mgr_register_full + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: fpga_mgr_register + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: devm_fpga_mgr_register_full + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: devm_fpga_mgr_register + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: fpga_mgr_unregister diff --git a/Documentation/driver-api/fpga/fpga-programming.rst b/Documentation/driver-api/fpga/fpga-programming.rst new file mode 100644 index 000000000..fb4da4240 --- /dev/null +++ b/Documentation/driver-api/fpga/fpga-programming.rst @@ -0,0 +1,107 @@ +In-kernel API for FPGA Programming +================================== + +Overview +-------- + +The in-kernel API for FPGA programming is a combination of APIs from +FPGA manager, bridge, and regions. The actual function used to +trigger FPGA programming is fpga_region_program_fpga(). + +fpga_region_program_fpga() uses functionality supplied by +the FPGA manager and bridges. It will: + + * lock the region's mutex + * lock the mutex of the region's FPGA manager + * build a list of FPGA bridges if a method has been specified to do so + * disable the bridges + * program the FPGA using info passed in :c:expr:`fpga_region->info`. + * re-enable the bridges + * release the locks + +The struct fpga_image_info specifies what FPGA image to program. It is +allocated/freed by fpga_image_info_alloc() and freed with +fpga_image_info_free() + +How to program an FPGA using a region +------------------------------------- + +When the FPGA region driver probed, it was given a pointer to an FPGA manager +driver so it knows which manager to use. The region also either has a list of +bridges to control during programming or it has a pointer to a function that +will generate that list. Here's some sample code of what to do next:: + + #include <linux/fpga/fpga-mgr.h> + #include <linux/fpga/fpga-region.h> + + struct fpga_image_info *info; + int ret; + + /* + * First, alloc the struct with information about the FPGA image to + * program. + */ + info = fpga_image_info_alloc(dev); + if (!info) + return -ENOMEM; + + /* Set flags as needed, such as: */ + info->flags = FPGA_MGR_PARTIAL_RECONFIG; + + /* + * Indicate where the FPGA image is. This is pseudo-code; you're + * going to use one of these three. + */ + if (image is in a scatter gather table) { + + info->sgt = [your scatter gather table] + + } else if (image is in a buffer) { + + info->buf = [your image buffer] + info->count = [image buffer size] + + } else if (image is in a firmware file) { + + info->firmware_name = devm_kstrdup(dev, firmware_name, + GFP_KERNEL); + + } + + /* Add info to region and do the programming */ + region->info = info; + ret = fpga_region_program_fpga(region); + + /* Deallocate the image info if you're done with it */ + region->info = NULL; + fpga_image_info_free(info); + + if (ret) + return ret; + + /* Now enumerate whatever hardware has appeared in the FPGA. */ + +API for programming an FPGA +--------------------------- + +* fpga_region_program_fpga() - Program an FPGA +* fpga_image_info() - Specifies what FPGA image to program +* fpga_image_info_alloc() - Allocate an FPGA image info struct +* fpga_image_info_free() - Free an FPGA image info struct + +.. kernel-doc:: drivers/fpga/fpga-region.c + :functions: fpga_region_program_fpga + +FPGA Manager flags + +.. kernel-doc:: include/linux/fpga/fpga-mgr.h + :doc: FPGA Manager flags + +.. kernel-doc:: include/linux/fpga/fpga-mgr.h + :functions: fpga_image_info + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: fpga_image_info_alloc + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: fpga_image_info_free diff --git a/Documentation/driver-api/fpga/fpga-region.rst b/Documentation/driver-api/fpga/fpga-region.rst new file mode 100644 index 000000000..dc55d60a0 --- /dev/null +++ b/Documentation/driver-api/fpga/fpga-region.rst @@ -0,0 +1,109 @@ +FPGA Region +=========== + +Overview +-------- + +This document is meant to be a brief overview of the FPGA region API usage. A +more conceptual look at regions can be found in the Device Tree binding +document [#f1]_. + +For the purposes of this API document, let's just say that a region associates +an FPGA Manager and a bridge (or bridges) with a reprogrammable region of an +FPGA or the whole FPGA. The API provides a way to register a region and to +program a region. + +Currently the only layer above fpga-region.c in the kernel is the Device Tree +support (of-fpga-region.c) described in [#f1]_. The DT support layer uses regions +to program the FPGA and then DT to handle enumeration. The common region code +is intended to be used by other schemes that have other ways of accomplishing +enumeration after programming. + +An fpga-region can be set up to know the following things: + + * which FPGA manager to use to do the programming + + * which bridges to disable before programming and enable afterwards. + +Additional info needed to program the FPGA image is passed in the struct +fpga_image_info including: + + * pointers to the image as either a scatter-gather buffer, a contiguous + buffer, or the name of firmware file + + * flags indicating specifics such as whether the image is for partial + reconfiguration. + +How to add a new FPGA region +---------------------------- + +An example of usage can be seen in the probe function of [#f2]_. + +.. [#f1] ../devicetree/bindings/fpga/fpga-region.txt +.. [#f2] ../../drivers/fpga/of-fpga-region.c + +API to add a new FPGA region +---------------------------- + +* struct fpga_region - The FPGA region struct +* struct fpga_region_info - Parameter structure for fpga_region_register_full() +* fpga_region_register_full() - Create and register an FPGA region using the + fpga_region_info structure to provide the full flexibility of options +* fpga_region_register() - Create and register an FPGA region using standard + arguments +* fpga_region_unregister() - Unregister an FPGA region + +The FPGA region's probe function will need to get a reference to the FPGA +Manager it will be using to do the programming. This usually would happen +during the region's probe function. + +* fpga_mgr_get() - Get a reference to an FPGA manager, raise ref count +* of_fpga_mgr_get() - Get a reference to an FPGA manager, raise ref count, + given a device node. +* fpga_mgr_put() - Put an FPGA manager + +The FPGA region will need to specify which bridges to control while programming +the FPGA. The region driver can build a list of bridges during probe time +(:c:expr:`fpga_region->bridge_list`) or it can have a function that creates +the list of bridges to program just before programming +(:c:expr:`fpga_region->get_bridges`). The FPGA bridge framework supplies the +following APIs to handle building or tearing down that list. + +* fpga_bridge_get_to_list() - Get a ref of an FPGA bridge, add it to a + list +* of_fpga_bridge_get_to_list() - Get a ref of an FPGA bridge, add it to a + list, given a device node +* fpga_bridges_put() - Given a list of bridges, put them + +.. kernel-doc:: include/linux/fpga/fpga-region.h + :functions: fpga_region + +.. kernel-doc:: include/linux/fpga/fpga-region.h + :functions: fpga_region_info + +.. kernel-doc:: drivers/fpga/fpga-region.c + :functions: fpga_region_register_full + +.. kernel-doc:: drivers/fpga/fpga-region.c + :functions: fpga_region_register + +.. kernel-doc:: drivers/fpga/fpga-region.c + :functions: fpga_region_unregister + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: fpga_mgr_get + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: of_fpga_mgr_get + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: fpga_mgr_put + +.. kernel-doc:: drivers/fpga/fpga-bridge.c + :functions: fpga_bridge_get_to_list + +.. kernel-doc:: drivers/fpga/fpga-bridge.c + :functions: of_fpga_bridge_get_to_list + +.. kernel-doc:: drivers/fpga/fpga-bridge.c + :functions: fpga_bridges_put diff --git a/Documentation/driver-api/fpga/index.rst b/Documentation/driver-api/fpga/index.rst new file mode 100644 index 000000000..31a4773bd --- /dev/null +++ b/Documentation/driver-api/fpga/index.rst @@ -0,0 +1,15 @@ +============== +FPGA Subsystem +============== + +:Author: Alan Tull + +.. toctree:: + :maxdepth: 2 + + intro + fpga-mgr + fpga-bridge + fpga-region + fpga-programming + diff --git a/Documentation/driver-api/fpga/intro.rst b/Documentation/driver-api/fpga/intro.rst new file mode 100644 index 000000000..f54c7dabc --- /dev/null +++ b/Documentation/driver-api/fpga/intro.rst @@ -0,0 +1,54 @@ +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. |