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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#include "dmaengine.h"
19
20static LIST_HEAD(of_dma_list);
21static DEFINE_MUTEX(of_dma_lock);
22
23/**
24 * of_dma_find_controller - Get a DMA controller in DT DMA helpers list
25 * @dma_spec: pointer to DMA specifier as found in the device tree
26 *
27 * Finds a DMA controller with matching device node and number for dma cells
28 * in a list of registered DMA controllers. If a match is found a valid pointer
29 * to the DMA data stored is retuned. A NULL pointer is returned if no match is
30 * found.
31 */
32static struct of_dma *of_dma_find_controller(struct of_phandle_args *dma_spec)
33{
34 struct of_dma *ofdma;
35
36 list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
37 if (ofdma->of_node == dma_spec->np)
38 return ofdma;
39
40 pr_debug("%s: can't find DMA controller %pOF\n", __func__,
41 dma_spec->np);
42
43 return NULL;
44}
45
46/**
47 * of_dma_router_xlate - translation function for router devices
48 * @dma_spec: pointer to DMA specifier as found in the device tree
49 * @ofdma: pointer to DMA controller data (router information)
50 *
51 * The function creates new dma_spec to be passed to the router driver's
52 * of_dma_route_allocate() function to prepare a dma_spec which will be used
53 * to request channel from the real DMA controller.
54 */
55static struct dma_chan *of_dma_router_xlate(struct of_phandle_args *dma_spec,
56 struct of_dma *ofdma)
57{
58 struct dma_chan *chan;
59 struct of_dma *ofdma_target;
60 struct of_phandle_args dma_spec_target;
61 void *route_data;
62
63 /* translate the request for the real DMA controller */
64 memcpy(&dma_spec_target, dma_spec, sizeof(dma_spec_target));
65 route_data = ofdma->of_dma_route_allocate(&dma_spec_target, ofdma);
66 if (IS_ERR(route_data))
67 return NULL;
68
69 ofdma_target = of_dma_find_controller(&dma_spec_target);
70 if (!ofdma_target) {
71 ofdma->dma_router->route_free(ofdma->dma_router->dev,
72 route_data);
73 chan = ERR_PTR(-EPROBE_DEFER);
74 goto err;
75 }
76
77 chan = ofdma_target->of_dma_xlate(&dma_spec_target, ofdma_target);
78 if (IS_ERR_OR_NULL(chan)) {
79 ofdma->dma_router->route_free(ofdma->dma_router->dev,
80 route_data);
81 } else {
82 int ret = 0;
83
84 chan->router = ofdma->dma_router;
85 chan->route_data = route_data;
86
87 if (chan->device->device_router_config)
88 ret = chan->device->device_router_config(chan);
89
90 if (ret) {
91 dma_release_channel(chan);
92 chan = ERR_PTR(ret);
93 }
94 }
95
96err:
97 /*
98 * Need to put the node back since the ofdma->of_dma_route_allocate
99 * has taken it for generating the new, translated dma_spec
100 */
101 of_node_put(dma_spec_target.np);
102 return chan;
103}
104
105/**
106 * of_dma_controller_register - Register a DMA controller to DT DMA helpers
107 * @np: device node of DMA controller
108 * @of_dma_xlate: translation function which converts a phandle
109 * arguments list into a dma_chan structure
110 * @data: pointer to controller specific data to be used by
111 * translation function
112 *
113 * Returns 0 on success or appropriate errno value on error.
114 *
115 * Allocated memory should be freed with appropriate of_dma_controller_free()
116 * call.
117 */
118int of_dma_controller_register(struct device_node *np,
119 struct dma_chan *(*of_dma_xlate)
120 (struct of_phandle_args *, struct of_dma *),
121 void *data)
122{
123 struct of_dma *ofdma;
124
125 if (!np || !of_dma_xlate) {
126 pr_err("%s: not enough information provided\n", __func__);
127 return -EINVAL;
128 }
129
130 ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
131 if (!ofdma)
132 return -ENOMEM;
133
134 ofdma->of_node = np;
135 ofdma->of_dma_xlate = of_dma_xlate;
136 ofdma->of_dma_data = data;
137
138 /* Now queue of_dma controller structure in list */
139 mutex_lock(&of_dma_lock);
140 list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
141 mutex_unlock(&of_dma_lock);
142
143 return 0;
144}
145EXPORT_SYMBOL_GPL(of_dma_controller_register);
146
147/**
148 * of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
149 * @np: device node of DMA controller
150 *
151 * Memory allocated by of_dma_controller_register() is freed here.
152 */
153void of_dma_controller_free(struct device_node *np)
154{
155 struct of_dma *ofdma;
156
157 mutex_lock(&of_dma_lock);
158
159 list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
160 if (ofdma->of_node == np) {
161 list_del(&ofdma->of_dma_controllers);
162 kfree(ofdma);
163 break;
164 }
165
166 mutex_unlock(&of_dma_lock);
167}
168EXPORT_SYMBOL_GPL(of_dma_controller_free);
169
170/**
171 * of_dma_router_register - Register a DMA router to DT DMA helpers as a
172 * controller
173 * @np: device node of DMA router
174 * @of_dma_route_allocate: setup function for the router which need to
175 * modify the dma_spec for the DMA controller to
176 * use and to set up the requested route.
177 * @dma_router: pointer to dma_router structure to be used when
178 * the route need to be free up.
179 *
180 * Returns 0 on success or appropriate errno value on error.
181 *
182 * Allocated memory should be freed with appropriate of_dma_controller_free()
183 * call.
184 */
185int of_dma_router_register(struct device_node *np,
186 void *(*of_dma_route_allocate)
187 (struct of_phandle_args *, struct of_dma *),
188 struct dma_router *dma_router)
189{
190 struct of_dma *ofdma;
191
192 if (!np || !of_dma_route_allocate || !dma_router) {
193 pr_err("%s: not enough information provided\n", __func__);
194 return -EINVAL;
195 }
196
197 ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
198 if (!ofdma)
199 return -ENOMEM;
200
201 ofdma->of_node = np;
202 ofdma->of_dma_xlate = of_dma_router_xlate;
203 ofdma->of_dma_route_allocate = of_dma_route_allocate;
204 ofdma->dma_router = dma_router;
205
206 /* Now queue of_dma controller structure in list */
207 mutex_lock(&of_dma_lock);
208 list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
209 mutex_unlock(&of_dma_lock);
210
211 return 0;
212}
213EXPORT_SYMBOL_GPL(of_dma_router_register);
214
215/**
216 * of_dma_match_channel - Check if a DMA specifier matches name
217 * @np: device node to look for DMA channels
218 * @name: channel name to be matched
219 * @index: index of DMA specifier in list of DMA specifiers
220 * @dma_spec: pointer to DMA specifier as found in the device tree
221 *
222 * Check if the DMA specifier pointed to by the index in a list of DMA
223 * specifiers, matches the name provided. Returns 0 if the name matches and
224 * a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
225 */
226static int of_dma_match_channel(struct device_node *np, const char *name,
227 int index, struct of_phandle_args *dma_spec)
228{
229 const char *s;
230
231 if (of_property_read_string_index(np, "dma-names", index, &s))
232 return -ENODEV;
233
234 if (strcmp(name, s))
235 return -ENODEV;
236
237 if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
238 dma_spec))
239 return -ENODEV;
240
241 return 0;
242}
243
244/**
245 * of_dma_request_slave_channel - Get the DMA slave channel
246 * @np: device node to get DMA request from
247 * @name: name of desired channel
248 *
249 * Returns pointer to appropriate DMA channel on success or an error pointer.
250 */
251struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
252 const char *name)
253{
254 struct of_phandle_args dma_spec;
255 struct of_dma *ofdma;
256 struct dma_chan *chan;
257 int count, i, start;
258 int ret_no_channel = -ENODEV;
259 static atomic_t last_index;
260
261 if (!np || !name) {
262 pr_err("%s: not enough information provided\n", __func__);
263 return ERR_PTR(-ENODEV);
264 }
265
266 /* Silently fail if there is not even the "dmas" property */
267 if (!of_property_present(np, "dmas"))
268 return ERR_PTR(-ENODEV);
269
270 count = of_property_count_strings(np, "dma-names");
271 if (count < 0) {
272 pr_err("%s: dma-names property of node '%pOF' missing or empty\n",
273 __func__, np);
274 return ERR_PTR(-ENODEV);
275 }
276
277 /*
278 * approximate an average distribution across multiple
279 * entries with the same name
280 */
281 start = atomic_inc_return(&last_index);
282 for (i = 0; i < count; i++) {
283 if (of_dma_match_channel(np, name,
284 (i + start) % count,
285 &dma_spec))
286 continue;
287
288 mutex_lock(&of_dma_lock);
289 ofdma = of_dma_find_controller(&dma_spec);
290
291 if (ofdma) {
292 chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
293 } else {
294 ret_no_channel = -EPROBE_DEFER;
295 chan = NULL;
296 }
297
298 mutex_unlock(&of_dma_lock);
299
300 of_node_put(dma_spec.np);
301
302 if (chan)
303 return chan;
304 }
305
306 return ERR_PTR(ret_no_channel);
307}
308EXPORT_SYMBOL_GPL(of_dma_request_slave_channel);
309
310/**
311 * of_dma_simple_xlate - Simple DMA engine translation function
312 * @dma_spec: pointer to DMA specifier as found in the device tree
313 * @ofdma: pointer to DMA controller data
314 *
315 * A simple translation function for devices that use a 32-bit value for the
316 * filter_param when calling the DMA engine dma_request_channel() function.
317 * Note that this translation function requires that #dma-cells is equal to 1
318 * and the argument of the dma specifier is the 32-bit filter_param. Returns
319 * pointer to appropriate dma channel on success or NULL on error.
320 */
321struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
322 struct of_dma *ofdma)
323{
324 int count = dma_spec->args_count;
325 struct of_dma_filter_info *info = ofdma->of_dma_data;
326
327 if (!info || !info->filter_fn)
328 return NULL;
329
330 if (count != 1)
331 return NULL;
332
333 return __dma_request_channel(&info->dma_cap, info->filter_fn,
334 &dma_spec->args[0], dma_spec->np);
335}
336EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
337
338/**
339 * of_dma_xlate_by_chan_id - Translate dt property to DMA channel by channel id
340 * @dma_spec: pointer to DMA specifier as found in the device tree
341 * @ofdma: pointer to DMA controller data
342 *
343 * This function can be used as the of xlate callback for DMA driver which wants
344 * to match the channel based on the channel id. When using this xlate function
345 * the #dma-cells propety of the DMA controller dt node needs to be set to 1.
346 * The data parameter of of_dma_controller_register must be a pointer to the
347 * dma_device struct the function should match upon.
348 *
349 * Returns pointer to appropriate dma channel on success or NULL on error.
350 */
351struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
352 struct of_dma *ofdma)
353{
354 struct dma_device *dev = ofdma->of_dma_data;
355 struct dma_chan *chan, *candidate = NULL;
356
357 if (!dev || dma_spec->args_count != 1)
358 return NULL;
359
360 list_for_each_entry(chan, &dev->channels, device_node)
361 if (chan->chan_id == dma_spec->args[0]) {
362 candidate = chan;
363 break;
364 }
365
366 if (!candidate)
367 return NULL;
368
369 return dma_get_slave_channel(candidate);
370}
371EXPORT_SYMBOL_GPL(of_dma_xlate_by_chan_id);
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
18static LIST_HEAD(of_dma_list);
19static 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 */
30static 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 */
53static 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 return NULL;
70
71 chan = ofdma_target->of_dma_xlate(&dma_spec_target, ofdma_target);
72 if (chan) {
73 chan->router = ofdma->dma_router;
74 chan->route_data = route_data;
75 } else {
76 ofdma->dma_router->route_free(ofdma->dma_router->dev,
77 route_data);
78 }
79
80 /*
81 * Need to put the node back since the ofdma->of_dma_route_allocate
82 * has taken it for generating the new, translated dma_spec
83 */
84 of_node_put(dma_spec_target.np);
85 return chan;
86}
87
88/**
89 * of_dma_controller_register - Register a DMA controller to DT DMA helpers
90 * @np: device node of DMA controller
91 * @of_dma_xlate: translation function which converts a phandle
92 * arguments list into a dma_chan structure
93 * @data pointer to controller specific data to be used by
94 * translation function
95 *
96 * Returns 0 on success or appropriate errno value on error.
97 *
98 * Allocated memory should be freed with appropriate of_dma_controller_free()
99 * call.
100 */
101int of_dma_controller_register(struct device_node *np,
102 struct dma_chan *(*of_dma_xlate)
103 (struct of_phandle_args *, struct of_dma *),
104 void *data)
105{
106 struct of_dma *ofdma;
107
108 if (!np || !of_dma_xlate) {
109 pr_err("%s: not enough information provided\n", __func__);
110 return -EINVAL;
111 }
112
113 ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
114 if (!ofdma)
115 return -ENOMEM;
116
117 ofdma->of_node = np;
118 ofdma->of_dma_xlate = of_dma_xlate;
119 ofdma->of_dma_data = data;
120
121 /* Now queue of_dma controller structure in list */
122 mutex_lock(&of_dma_lock);
123 list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
124 mutex_unlock(&of_dma_lock);
125
126 return 0;
127}
128EXPORT_SYMBOL_GPL(of_dma_controller_register);
129
130/**
131 * of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
132 * @np: device node of DMA controller
133 *
134 * Memory allocated by of_dma_controller_register() is freed here.
135 */
136void of_dma_controller_free(struct device_node *np)
137{
138 struct of_dma *ofdma;
139
140 mutex_lock(&of_dma_lock);
141
142 list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
143 if (ofdma->of_node == np) {
144 list_del(&ofdma->of_dma_controllers);
145 kfree(ofdma);
146 break;
147 }
148
149 mutex_unlock(&of_dma_lock);
150}
151EXPORT_SYMBOL_GPL(of_dma_controller_free);
152
153/**
154 * of_dma_router_register - Register a DMA router to DT DMA helpers as a
155 * controller
156 * @np: device node of DMA router
157 * @of_dma_route_allocate: setup function for the router which need to
158 * modify the dma_spec for the DMA controller to
159 * use and to set up the requested route.
160 * @dma_router: pointer to dma_router structure to be used when
161 * the route need to be free up.
162 *
163 * Returns 0 on success or appropriate errno value on error.
164 *
165 * Allocated memory should be freed with appropriate of_dma_controller_free()
166 * call.
167 */
168int of_dma_router_register(struct device_node *np,
169 void *(*of_dma_route_allocate)
170 (struct of_phandle_args *, struct of_dma *),
171 struct dma_router *dma_router)
172{
173 struct of_dma *ofdma;
174
175 if (!np || !of_dma_route_allocate || !dma_router) {
176 pr_err("%s: not enough information provided\n", __func__);
177 return -EINVAL;
178 }
179
180 ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
181 if (!ofdma)
182 return -ENOMEM;
183
184 ofdma->of_node = np;
185 ofdma->of_dma_xlate = of_dma_router_xlate;
186 ofdma->of_dma_route_allocate = of_dma_route_allocate;
187 ofdma->dma_router = dma_router;
188
189 /* Now queue of_dma controller structure in list */
190 mutex_lock(&of_dma_lock);
191 list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
192 mutex_unlock(&of_dma_lock);
193
194 return 0;
195}
196EXPORT_SYMBOL_GPL(of_dma_router_register);
197
198/**
199 * of_dma_match_channel - Check if a DMA specifier matches name
200 * @np: device node to look for DMA channels
201 * @name: channel name to be matched
202 * @index: index of DMA specifier in list of DMA specifiers
203 * @dma_spec: pointer to DMA specifier as found in the device tree
204 *
205 * Check if the DMA specifier pointed to by the index in a list of DMA
206 * specifiers, matches the name provided. Returns 0 if the name matches and
207 * a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
208 */
209static int of_dma_match_channel(struct device_node *np, const char *name,
210 int index, struct of_phandle_args *dma_spec)
211{
212 const char *s;
213
214 if (of_property_read_string_index(np, "dma-names", index, &s))
215 return -ENODEV;
216
217 if (strcmp(name, s))
218 return -ENODEV;
219
220 if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
221 dma_spec))
222 return -ENODEV;
223
224 return 0;
225}
226
227/**
228 * of_dma_request_slave_channel - Get the DMA slave channel
229 * @np: device node to get DMA request from
230 * @name: name of desired channel
231 *
232 * Returns pointer to appropriate DMA channel on success or an error pointer.
233 */
234struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
235 const char *name)
236{
237 struct of_phandle_args dma_spec;
238 struct of_dma *ofdma;
239 struct dma_chan *chan;
240 int count, i, start;
241 int ret_no_channel = -ENODEV;
242 static atomic_t last_index;
243
244 if (!np || !name) {
245 pr_err("%s: not enough information provided\n", __func__);
246 return ERR_PTR(-ENODEV);
247 }
248
249 /* Silently fail if there is not even the "dmas" property */
250 if (!of_find_property(np, "dmas", NULL))
251 return ERR_PTR(-ENODEV);
252
253 count = of_property_count_strings(np, "dma-names");
254 if (count < 0) {
255 pr_err("%s: dma-names property of node '%pOF' missing or empty\n",
256 __func__, np);
257 return ERR_PTR(-ENODEV);
258 }
259
260 /*
261 * approximate an average distribution across multiple
262 * entries with the same name
263 */
264 start = atomic_inc_return(&last_index);
265 for (i = 0; i < count; i++) {
266 if (of_dma_match_channel(np, name,
267 (i + start) % count,
268 &dma_spec))
269 continue;
270
271 mutex_lock(&of_dma_lock);
272 ofdma = of_dma_find_controller(&dma_spec);
273
274 if (ofdma) {
275 chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
276 } else {
277 ret_no_channel = -EPROBE_DEFER;
278 chan = NULL;
279 }
280
281 mutex_unlock(&of_dma_lock);
282
283 of_node_put(dma_spec.np);
284
285 if (chan)
286 return chan;
287 }
288
289 return ERR_PTR(ret_no_channel);
290}
291EXPORT_SYMBOL_GPL(of_dma_request_slave_channel);
292
293/**
294 * of_dma_simple_xlate - Simple DMA engine translation function
295 * @dma_spec: pointer to DMA specifier as found in the device tree
296 * @of_dma: pointer to DMA controller data
297 *
298 * A simple translation function for devices that use a 32-bit value for the
299 * filter_param when calling the DMA engine dma_request_channel() function.
300 * Note that this translation function requires that #dma-cells is equal to 1
301 * and the argument of the dma specifier is the 32-bit filter_param. Returns
302 * pointer to appropriate dma channel on success or NULL on error.
303 */
304struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
305 struct of_dma *ofdma)
306{
307 int count = dma_spec->args_count;
308 struct of_dma_filter_info *info = ofdma->of_dma_data;
309
310 if (!info || !info->filter_fn)
311 return NULL;
312
313 if (count != 1)
314 return NULL;
315
316 return __dma_request_channel(&info->dma_cap, info->filter_fn,
317 &dma_spec->args[0], dma_spec->np);
318}
319EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
320
321/**
322 * of_dma_xlate_by_chan_id - Translate dt property to DMA channel by channel id
323 * @dma_spec: pointer to DMA specifier as found in the device tree
324 * @of_dma: pointer to DMA controller data
325 *
326 * This function can be used as the of xlate callback for DMA driver which wants
327 * to match the channel based on the channel id. When using this xlate function
328 * the #dma-cells propety of the DMA controller dt node needs to be set to 1.
329 * The data parameter of of_dma_controller_register must be a pointer to the
330 * dma_device struct the function should match upon.
331 *
332 * Returns pointer to appropriate dma channel on success or NULL on error.
333 */
334struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
335 struct of_dma *ofdma)
336{
337 struct dma_device *dev = ofdma->of_dma_data;
338 struct dma_chan *chan, *candidate = NULL;
339
340 if (!dev || dma_spec->args_count != 1)
341 return NULL;
342
343 list_for_each_entry(chan, &dev->channels, device_node)
344 if (chan->chan_id == dma_spec->args[0]) {
345 candidate = chan;
346 break;
347 }
348
349 if (!candidate)
350 return NULL;
351
352 return dma_get_slave_channel(candidate);
353}
354EXPORT_SYMBOL_GPL(of_dma_xlate_by_chan_id);