1FPGA Manager
2============
3
4Overview
5--------
6
7The FPGA manager core exports a set of functions for programming an FPGA with
8an image.  The API is manufacturer agnostic.  All manufacturer specifics are
9hidden away in a low level driver which registers a set of ops with the core.
10The FPGA image data itself is very manufacturer specific, but for our purposes
11it's just binary data.  The FPGA manager core won't parse it.
12
13The FPGA image to be programmed can be in a scatter gather list, a single
14contiguous buffer, or a firmware file.  Because allocating contiguous kernel
15memory for the buffer should be avoided, users are encouraged to use a scatter
16gather list instead if possible.
17
18The particulars for programming the image are presented in a structure (struct
19fpga_image_info).  This struct contains parameters such as pointers to the
20FPGA image as well as image-specific particulars such as whether the image was
21built for full or partial reconfiguration.
22
23How to support a new FPGA device
24--------------------------------
25
26To add another FPGA manager, write a driver that implements a set of ops.  The
27probe function calls ``fpga_mgr_register()`` or ``fpga_mgr_register_full()``,
28such as::
29
30	static const struct fpga_manager_ops socfpga_fpga_ops = {
31		.write_init = socfpga_fpga_ops_configure_init,
32		.write = socfpga_fpga_ops_configure_write,
33		.write_complete = socfpga_fpga_ops_configure_complete,
34		.state = socfpga_fpga_ops_state,
35	};
36
37	static int socfpga_fpga_probe(struct platform_device *pdev)
38	{
39		struct device *dev = &pdev->dev;
40		struct socfpga_fpga_priv *priv;
41		struct fpga_manager *mgr;
42		int ret;
43
44		priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
45		if (!priv)
46			return -ENOMEM;
47
48		/*
49		 * do ioremaps, get interrupts, etc. and save
50		 * them in priv
51		 */
52
53		mgr = fpga_mgr_register(dev, "Altera SOCFPGA FPGA Manager",
54					&socfpga_fpga_ops, priv);
55		if (IS_ERR(mgr))
56			return PTR_ERR(mgr);
57
58		platform_set_drvdata(pdev, mgr);
59
60		return 0;
61	}
62
63	static int socfpga_fpga_remove(struct platform_device *pdev)
64	{
65		struct fpga_manager *mgr = platform_get_drvdata(pdev);
66
67		fpga_mgr_unregister(mgr);
68
69		return 0;
70	}
71
72Alternatively, the probe function could call one of the resource managed
73register functions, ``devm_fpga_mgr_register()`` or
74``devm_fpga_mgr_register_full()``.  When these functions are used, the
75parameter syntax is the same, but the call to ``fpga_mgr_unregister()`` should be
76removed. In the above example, the ``socfpga_fpga_remove()`` function would not be
77required.
78
79The ops will implement whatever device specific register writes are needed to
80do the programming sequence for this particular FPGA.  These ops return 0 for
81success or negative error codes otherwise.
82
83The programming sequence is::
84 1. .parse_header (optional, may be called once or multiple times)
85 2. .write_init
86 3. .write or .write_sg (may be called once or multiple times)
87 4. .write_complete
88
89The .parse_header function will set header_size and data_size to
90struct fpga_image_info. Before parse_header call, header_size is initialized
91with initial_header_size. If flag skip_header of fpga_manager_ops is true,
92.write function will get image buffer starting at header_size offset from the
93beginning. If data_size is set, .write function will get data_size bytes of
94the image buffer, otherwise .write will get data up to the end of image buffer.
95This will not affect .write_sg, .write_sg will still get whole image in
96sg_table form. If FPGA image is already mapped as a single contiguous buffer,
97whole buffer will be passed into .parse_header. If image is in scatter-gather
98form, core code will buffer up at least .initial_header_size before the first
99call of .parse_header, if it is not enough, .parse_header should set desired
100size into info->header_size and return -EAGAIN, then it will be called again
101with greater part of image buffer on the input.
102
103The .write_init function will prepare the FPGA to receive the image data. The
104buffer passed into .write_init will be at least info->header_size bytes long;
105if the whole bitstream is not immediately available then the core code will
106buffer up at least this much before starting.
107
108The .write function writes a buffer to the FPGA. The buffer may be contain the
109whole FPGA image or may be a smaller chunk of an FPGA image.  In the latter
110case, this function is called multiple times for successive chunks. This interface
111is suitable for drivers which use PIO.
112
113The .write_sg version behaves the same as .write except the input is a sg_table
114scatter list. This interface is suitable for drivers which use DMA.
115
116The .write_complete function is called after all the image has been written
117to put the FPGA into operating mode.
118
119The ops include a .state function which will determine the state the FPGA is in
120and return a code of type enum fpga_mgr_states.  It doesn't result in a change
121in state.
122
123API for implementing a new FPGA Manager driver
124----------------------------------------------
125
126* ``fpga_mgr_states`` -  Values for :c:expr:`fpga_manager->state`.
127* struct fpga_manager -  the FPGA manager struct
128* struct fpga_manager_ops -  Low level FPGA manager driver ops
129* struct fpga_manager_info -  Parameter structure for fpga_mgr_register_full()
130* __fpga_mgr_register_full() -  Create and register an FPGA manager using the
131  fpga_mgr_info structure to provide the full flexibility of options
132* __fpga_mgr_register() -  Create and register an FPGA manager using standard
133  arguments
134* __devm_fpga_mgr_register_full() -  Resource managed version of
135  __fpga_mgr_register_full()
136* __devm_fpga_mgr_register() -  Resource managed version of __fpga_mgr_register()
137* fpga_mgr_unregister() -  Unregister an FPGA manager
138
139Helper macros ``fpga_mgr_register_full()``, ``fpga_mgr_register()``,
140``devm_fpga_mgr_register_full()``, and ``devm_fpga_mgr_register()`` are available
141to ease the registration.
142
143.. kernel-doc:: include/linux/fpga/fpga-mgr.h
144   :functions: fpga_mgr_states
145
146.. kernel-doc:: include/linux/fpga/fpga-mgr.h
147   :functions: fpga_manager
148
149.. kernel-doc:: include/linux/fpga/fpga-mgr.h
150   :functions: fpga_manager_ops
151
152.. kernel-doc:: include/linux/fpga/fpga-mgr.h
153   :functions: fpga_manager_info
154
155.. kernel-doc:: drivers/fpga/fpga-mgr.c
156   :functions: __fpga_mgr_register_full
157
158.. kernel-doc:: drivers/fpga/fpga-mgr.c
159   :functions: __fpga_mgr_register
160
161.. kernel-doc:: drivers/fpga/fpga-mgr.c
162   :functions: __devm_fpga_mgr_register_full
163
164.. kernel-doc:: drivers/fpga/fpga-mgr.c
165   :functions: __devm_fpga_mgr_register
166
167.. kernel-doc:: drivers/fpga/fpga-mgr.c
168   :functions: fpga_mgr_unregister
169