1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Device tree helpers for DMA request / controller
4 *
5 * Based on of_gpio.c
6 *
7 * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
8 */
9
10 #include <linux/device.h>
11 #include <linux/err.h>
12 #include <linux/module.h>
13 #include <linux/mutex.h>
14 #include <linux/slab.h>
15 #include <linux/of.h>
16 #include <linux/of_dma.h>
17
18 static LIST_HEAD(of_dma_list);
19 static DEFINE_MUTEX(of_dma_lock);
20
21 /**
22 * of_dma_find_controller - Get a DMA controller in DT DMA helpers list
23 * @dma_spec: pointer to DMA specifier as found in the device tree
24 *
25 * Finds a DMA controller with matching device node and number for dma cells
26 * in a list of registered DMA controllers. If a match is found a valid pointer
27 * to the DMA data stored is retuned. A NULL pointer is returned if no match is
28 * found.
29 */
of_dma_find_controller(struct of_phandle_args * dma_spec)30 static struct of_dma *of_dma_find_controller(struct of_phandle_args *dma_spec)
31 {
32 struct of_dma *ofdma;
33
34 list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
35 if (ofdma->of_node == dma_spec->np)
36 return ofdma;
37
38 pr_debug("%s: can't find DMA controller %pOF\n", __func__,
39 dma_spec->np);
40
41 return NULL;
42 }
43
44 /**
45 * of_dma_router_xlate - translation function for router devices
46 * @dma_spec: pointer to DMA specifier as found in the device tree
47 * @of_dma: pointer to DMA controller data (router information)
48 *
49 * The function creates new dma_spec to be passed to the router driver's
50 * of_dma_route_allocate() function to prepare a dma_spec which will be used
51 * to request channel from the real DMA controller.
52 */
of_dma_router_xlate(struct of_phandle_args * dma_spec,struct of_dma * ofdma)53 static struct dma_chan *of_dma_router_xlate(struct of_phandle_args *dma_spec,
54 struct of_dma *ofdma)
55 {
56 struct dma_chan *chan;
57 struct of_dma *ofdma_target;
58 struct of_phandle_args dma_spec_target;
59 void *route_data;
60
61 /* translate the request for the real DMA controller */
62 memcpy(&dma_spec_target, dma_spec, sizeof(dma_spec_target));
63 route_data = ofdma->of_dma_route_allocate(&dma_spec_target, ofdma);
64 if (IS_ERR(route_data))
65 return NULL;
66
67 ofdma_target = of_dma_find_controller(&dma_spec_target);
68 if (!ofdma_target) {
69 ofdma->dma_router->route_free(ofdma->dma_router->dev,
70 route_data);
71 chan = ERR_PTR(-EPROBE_DEFER);
72 goto err;
73 }
74
75 chan = ofdma_target->of_dma_xlate(&dma_spec_target, ofdma_target);
76 if (IS_ERR_OR_NULL(chan)) {
77 ofdma->dma_router->route_free(ofdma->dma_router->dev,
78 route_data);
79 } else {
80 chan->router = ofdma->dma_router;
81 chan->route_data = route_data;
82 }
83
84 err:
85 /*
86 * Need to put the node back since the ofdma->of_dma_route_allocate
87 * has taken it for generating the new, translated dma_spec
88 */
89 of_node_put(dma_spec_target.np);
90 return chan;
91 }
92
93 /**
94 * of_dma_controller_register - Register a DMA controller to DT DMA helpers
95 * @np: device node of DMA controller
96 * @of_dma_xlate: translation function which converts a phandle
97 * arguments list into a dma_chan structure
98 * @data pointer to controller specific data to be used by
99 * translation function
100 *
101 * Returns 0 on success or appropriate errno value on error.
102 *
103 * Allocated memory should be freed with appropriate of_dma_controller_free()
104 * call.
105 */
of_dma_controller_register(struct device_node * np,struct dma_chan * (* of_dma_xlate)(struct of_phandle_args *,struct of_dma *),void * data)106 int of_dma_controller_register(struct device_node *np,
107 struct dma_chan *(*of_dma_xlate)
108 (struct of_phandle_args *, struct of_dma *),
109 void *data)
110 {
111 struct of_dma *ofdma;
112
113 if (!np || !of_dma_xlate) {
114 pr_err("%s: not enough information provided\n", __func__);
115 return -EINVAL;
116 }
117
118 ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
119 if (!ofdma)
120 return -ENOMEM;
121
122 ofdma->of_node = np;
123 ofdma->of_dma_xlate = of_dma_xlate;
124 ofdma->of_dma_data = data;
125
126 /* Now queue of_dma controller structure in list */
127 mutex_lock(&of_dma_lock);
128 list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
129 mutex_unlock(&of_dma_lock);
130
131 return 0;
132 }
133 EXPORT_SYMBOL_GPL(of_dma_controller_register);
134
135 /**
136 * of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
137 * @np: device node of DMA controller
138 *
139 * Memory allocated by of_dma_controller_register() is freed here.
140 */
of_dma_controller_free(struct device_node * np)141 void of_dma_controller_free(struct device_node *np)
142 {
143 struct of_dma *ofdma;
144
145 mutex_lock(&of_dma_lock);
146
147 list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
148 if (ofdma->of_node == np) {
149 list_del(&ofdma->of_dma_controllers);
150 kfree(ofdma);
151 break;
152 }
153
154 mutex_unlock(&of_dma_lock);
155 }
156 EXPORT_SYMBOL_GPL(of_dma_controller_free);
157
158 /**
159 * of_dma_router_register - Register a DMA router to DT DMA helpers as a
160 * controller
161 * @np: device node of DMA router
162 * @of_dma_route_allocate: setup function for the router which need to
163 * modify the dma_spec for the DMA controller to
164 * use and to set up the requested route.
165 * @dma_router: pointer to dma_router structure to be used when
166 * the route need to be free up.
167 *
168 * Returns 0 on success or appropriate errno value on error.
169 *
170 * Allocated memory should be freed with appropriate of_dma_controller_free()
171 * call.
172 */
of_dma_router_register(struct device_node * np,void * (* of_dma_route_allocate)(struct of_phandle_args *,struct of_dma *),struct dma_router * dma_router)173 int of_dma_router_register(struct device_node *np,
174 void *(*of_dma_route_allocate)
175 (struct of_phandle_args *, struct of_dma *),
176 struct dma_router *dma_router)
177 {
178 struct of_dma *ofdma;
179
180 if (!np || !of_dma_route_allocate || !dma_router) {
181 pr_err("%s: not enough information provided\n", __func__);
182 return -EINVAL;
183 }
184
185 ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
186 if (!ofdma)
187 return -ENOMEM;
188
189 ofdma->of_node = np;
190 ofdma->of_dma_xlate = of_dma_router_xlate;
191 ofdma->of_dma_route_allocate = of_dma_route_allocate;
192 ofdma->dma_router = dma_router;
193
194 /* Now queue of_dma controller structure in list */
195 mutex_lock(&of_dma_lock);
196 list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
197 mutex_unlock(&of_dma_lock);
198
199 return 0;
200 }
201 EXPORT_SYMBOL_GPL(of_dma_router_register);
202
203 /**
204 * of_dma_match_channel - Check if a DMA specifier matches name
205 * @np: device node to look for DMA channels
206 * @name: channel name to be matched
207 * @index: index of DMA specifier in list of DMA specifiers
208 * @dma_spec: pointer to DMA specifier as found in the device tree
209 *
210 * Check if the DMA specifier pointed to by the index in a list of DMA
211 * specifiers, matches the name provided. Returns 0 if the name matches and
212 * a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
213 */
of_dma_match_channel(struct device_node * np,const char * name,int index,struct of_phandle_args * dma_spec)214 static int of_dma_match_channel(struct device_node *np, const char *name,
215 int index, struct of_phandle_args *dma_spec)
216 {
217 const char *s;
218
219 if (of_property_read_string_index(np, "dma-names", index, &s))
220 return -ENODEV;
221
222 if (strcmp(name, s))
223 return -ENODEV;
224
225 if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
226 dma_spec))
227 return -ENODEV;
228
229 return 0;
230 }
231
232 /**
233 * of_dma_request_slave_channel - Get the DMA slave channel
234 * @np: device node to get DMA request from
235 * @name: name of desired channel
236 *
237 * Returns pointer to appropriate DMA channel on success or an error pointer.
238 */
of_dma_request_slave_channel(struct device_node * np,const char * name)239 struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
240 const char *name)
241 {
242 struct of_phandle_args dma_spec;
243 struct of_dma *ofdma;
244 struct dma_chan *chan;
245 int count, i, start;
246 int ret_no_channel = -ENODEV;
247 static atomic_t last_index;
248
249 if (!np || !name) {
250 pr_err("%s: not enough information provided\n", __func__);
251 return ERR_PTR(-ENODEV);
252 }
253
254 /* Silently fail if there is not even the "dmas" property */
255 if (!of_find_property(np, "dmas", NULL))
256 return ERR_PTR(-ENODEV);
257
258 count = of_property_count_strings(np, "dma-names");
259 if (count < 0) {
260 pr_err("%s: dma-names property of node '%pOF' missing or empty\n",
261 __func__, np);
262 return ERR_PTR(-ENODEV);
263 }
264
265 /*
266 * approximate an average distribution across multiple
267 * entries with the same name
268 */
269 start = atomic_inc_return(&last_index);
270 for (i = 0; i < count; i++) {
271 if (of_dma_match_channel(np, name,
272 (i + start) % count,
273 &dma_spec))
274 continue;
275
276 mutex_lock(&of_dma_lock);
277 ofdma = of_dma_find_controller(&dma_spec);
278
279 if (ofdma) {
280 chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
281 } else {
282 ret_no_channel = -EPROBE_DEFER;
283 chan = NULL;
284 }
285
286 mutex_unlock(&of_dma_lock);
287
288 of_node_put(dma_spec.np);
289
290 if (chan)
291 return chan;
292 }
293
294 return ERR_PTR(ret_no_channel);
295 }
296 EXPORT_SYMBOL_GPL(of_dma_request_slave_channel);
297
298 /**
299 * of_dma_simple_xlate - Simple DMA engine translation function
300 * @dma_spec: pointer to DMA specifier as found in the device tree
301 * @of_dma: pointer to DMA controller data
302 *
303 * A simple translation function for devices that use a 32-bit value for the
304 * filter_param when calling the DMA engine dma_request_channel() function.
305 * Note that this translation function requires that #dma-cells is equal to 1
306 * and the argument of the dma specifier is the 32-bit filter_param. Returns
307 * pointer to appropriate dma channel on success or NULL on error.
308 */
of_dma_simple_xlate(struct of_phandle_args * dma_spec,struct of_dma * ofdma)309 struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
310 struct of_dma *ofdma)
311 {
312 int count = dma_spec->args_count;
313 struct of_dma_filter_info *info = ofdma->of_dma_data;
314
315 if (!info || !info->filter_fn)
316 return NULL;
317
318 if (count != 1)
319 return NULL;
320
321 return __dma_request_channel(&info->dma_cap, info->filter_fn,
322 &dma_spec->args[0], dma_spec->np);
323 }
324 EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
325
326 /**
327 * of_dma_xlate_by_chan_id - Translate dt property to DMA channel by channel id
328 * @dma_spec: pointer to DMA specifier as found in the device tree
329 * @of_dma: pointer to DMA controller data
330 *
331 * This function can be used as the of xlate callback for DMA driver which wants
332 * to match the channel based on the channel id. When using this xlate function
333 * the #dma-cells propety of the DMA controller dt node needs to be set to 1.
334 * The data parameter of of_dma_controller_register must be a pointer to the
335 * dma_device struct the function should match upon.
336 *
337 * Returns pointer to appropriate dma channel on success or NULL on error.
338 */
of_dma_xlate_by_chan_id(struct of_phandle_args * dma_spec,struct of_dma * ofdma)339 struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
340 struct of_dma *ofdma)
341 {
342 struct dma_device *dev = ofdma->of_dma_data;
343 struct dma_chan *chan, *candidate = NULL;
344
345 if (!dev || dma_spec->args_count != 1)
346 return NULL;
347
348 list_for_each_entry(chan, &dev->channels, device_node)
349 if (chan->chan_id == dma_spec->args[0]) {
350 candidate = chan;
351 break;
352 }
353
354 if (!candidate)
355 return NULL;
356
357 return dma_get_slave_channel(candidate);
358 }
359 EXPORT_SYMBOL_GPL(of_dma_xlate_by_chan_id);
360