1FPGA Manager Core
  2
  3Alan Tull 2015
  4
  5Overview
  6========
  7
  8The FPGA manager core exports a set of functions for programming an FPGA with
  9an image.  The API is manufacturer agnostic.  All manufacturer specifics are
 10hidden away in a low level driver which registers a set of ops with the core.
 11The FPGA image data itself is very manufacturer specific, but for our purposes
 12it's just binary data.  The FPGA manager core won't parse it.
 13
 14The FPGA image to be programmed can be in a scatter gather list, a single
 15contiguous buffer, or a firmware file.  Because allocating contiguous kernel
 16memory for the buffer should be avoided, users are encouraged to use a scatter
 17gather list instead if possible.
 18
 19The particulars for programming the image are presented in a structure (struct
 20fpga_image_info).  This struct contains parameters such as pointers to the
 21FPGA image as well as image-specific particulars such as whether the image was
 22built for full or partial reconfiguration.
 23
 24API Functions:
 25==============
 26
 27To program the FPGA:
 28--------------------
 29
 30	int fpga_mgr_load(struct fpga_manager *mgr,
 31			  struct fpga_image_info *info);
 32
 33Load the FPGA from an image which is indicated in the info.  If successful,
 34the FPGA ends up in operating mode.  Return 0 on success or a negative error
 35code.
 36
 37To allocate or free a struct fpga_image_info:
 38---------------------------------------------
 39
 40	struct fpga_image_info *fpga_image_info_alloc(struct device *dev);
 41
 42	void fpga_image_info_free(struct fpga_image_info *info);
 43
 44To get/put a reference to a FPGA manager:
 45-----------------------------------------
 46
 47	struct fpga_manager *of_fpga_mgr_get(struct device_node *node);
 48	struct fpga_manager *fpga_mgr_get(struct device *dev);
 49	void fpga_mgr_put(struct fpga_manager *mgr);
 50
 51Given a DT node or device, get a reference to a FPGA manager.  This pointer
 52can be saved until you are ready to program the FPGA.  fpga_mgr_put releases
 53the reference.
 54
 55
 56To get exclusive control of a FPGA manager:
 57-------------------------------------------
 58
 59	int fpga_mgr_lock(struct fpga_manager *mgr);
 60	void fpga_mgr_unlock(struct fpga_manager *mgr);
 61
 62The user should call fpga_mgr_lock and verify that it returns 0 before
 63attempting to program the FPGA.  Likewise, the user should call
 64fpga_mgr_unlock when done programming the FPGA.
 65
 66
 67To register or unregister the low level FPGA-specific driver:
 68-------------------------------------------------------------
 69
 70	int fpga_mgr_register(struct device *dev, const char *name,
 71			      const struct fpga_manager_ops *mops,
 72			      void *priv);
 73
 74	void fpga_mgr_unregister(struct device *dev);
 75
 76Use of these two functions is described below in "How To Support a new FPGA
 77device."
 78
 79
 80How to write an image buffer to a supported FPGA
 81================================================
 82#include <linux/fpga/fpga-mgr.h>
 83
 84struct fpga_manager *mgr;
 85struct fpga_image_info *info;
 86int ret;
 87
 88/*
 89 * Get a reference to FPGA manager.  The manager is not locked, so you can
 90 * hold onto this reference without it preventing programming.
 91 *
 92 * This example uses the device node of the manager.  Alternatively, use
 93 * fpga_mgr_get(dev) instead if you have the device.
 94 */
 95mgr = of_fpga_mgr_get(mgr_node);
 96
 97/* struct with information about the FPGA image to program. */
 98info = fpga_image_info_alloc(dev);
 99
100/* flags indicates whether to do full or partial reconfiguration */
101info->flags = FPGA_MGR_PARTIAL_RECONFIG;
102
103/*
104 * At this point, indicate where the image is. This is pseudo-code; you're
105 * going to use one of these three.
106 */
107if (image is in a scatter gather table) {
108
109	info->sgt = [your scatter gather table]
110
111} else if (image is in a buffer) {
112
113	info->buf = [your image buffer]
114	info->count = [image buffer size]
115
116} else if (image is in a firmware file) {
117
118	info->firmware_name = devm_kstrdup(dev, firmware_name, GFP_KERNEL);
119
120}
121
122/* Get exclusive control of FPGA manager */
123ret = fpga_mgr_lock(mgr);
124
125/* Load the buffer to the FPGA */
126ret = fpga_mgr_buf_load(mgr, &info, buf, count);
127
128/* Release the FPGA manager */
129fpga_mgr_unlock(mgr);
130fpga_mgr_put(mgr);
131
132/* Deallocate the image info if you're done with it */
133fpga_image_info_free(info);
134
135How to support a new FPGA device
136================================
137To add another FPGA manager, write a driver that implements a set of ops.  The
138probe function calls fpga_mgr_register(), such as:
139
140static const struct fpga_manager_ops socfpga_fpga_ops = {
141       .write_init = socfpga_fpga_ops_configure_init,
142       .write = socfpga_fpga_ops_configure_write,
143       .write_complete = socfpga_fpga_ops_configure_complete,
144       .state = socfpga_fpga_ops_state,
145};
146
147static int socfpga_fpga_probe(struct platform_device *pdev)
148{
149	struct device *dev = &pdev->dev;
150	struct socfpga_fpga_priv *priv;
151	int ret;
152
153	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
154	if (!priv)
155		return -ENOMEM;
156
157	/* ... do ioremaps, get interrupts, etc. and save
158	   them in priv... */
159
160	return fpga_mgr_register(dev, "Altera SOCFPGA FPGA Manager",
161				 &socfpga_fpga_ops, priv);
162}
163
164static int socfpga_fpga_remove(struct platform_device *pdev)
165{
166	fpga_mgr_unregister(&pdev->dev);
167
168	return 0;
169}
170
171
172The ops will implement whatever device specific register writes are needed to
173do the programming sequence for this particular FPGA.  These ops return 0 for
174success or negative error codes otherwise.
175
176The programming sequence is:
177 1. .write_init
178 2. .write or .write_sg (may be called once or multiple times)
179 3. .write_complete
180
181The .write_init function will prepare the FPGA to receive the image data.  The
182buffer passed into .write_init will be atmost .initial_header_size bytes long,
183if the whole bitstream is not immediately available then the core code will
184buffer up at least this much before starting.
185
186The .write function writes a buffer to the FPGA. The buffer may be contain the
187whole FPGA image or may be a smaller chunk of an FPGA image.  In the latter
188case, this function is called multiple times for successive chunks. This interface
189is suitable for drivers which use PIO.
190
191The .write_sg version behaves the same as .write except the input is a sg_table
192scatter list. This interface is suitable for drivers which use DMA.
193
194The .write_complete function is called after all the image has been written
195to put the FPGA into operating mode.
196
197The ops include a .state function which will read the hardware FPGA manager and
198return a code of type enum fpga_mgr_states.  It doesn't result in a change in
199hardware state.