1 // SPDX-License-Identifier: GPL-2.0-only
3 * Device tree helpers for DMA request / controller
7 * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
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>
16 #include <linux/of_dma.h>
18 static LIST_HEAD(of_dma_list);
19 static DEFINE_MUTEX(of_dma_lock);
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
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
30 static struct of_dma *of_dma_find_controller(struct of_phandle_args *dma_spec)
34 list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
35 if (ofdma->of_node == dma_spec->np)
38 pr_debug("%s: can't find DMA controller %pOF\n", __func__,
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)
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.
53 static struct dma_chan *of_dma_router_xlate(struct of_phandle_args *dma_spec,
56 struct dma_chan *chan;
57 struct of_dma *ofdma_target;
58 struct of_phandle_args dma_spec_target;
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))
67 ofdma_target = of_dma_find_controller(&dma_spec_target);
69 ofdma->dma_router->route_free(ofdma->dma_router->dev,
71 chan = ERR_PTR(-EPROBE_DEFER);
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,
80 chan->router = ofdma->dma_router;
81 chan->route_data = route_data;
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
89 of_node_put(dma_spec_target.np);
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
101 * Returns 0 on success or appropriate errno value on error.
103 * Allocated memory should be freed with appropriate of_dma_controller_free()
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 *),
111 struct of_dma *ofdma;
113 if (!np || !of_dma_xlate) {
114 pr_err("%s: not enough information provided\n", __func__);
118 ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
123 ofdma->of_dma_xlate = of_dma_xlate;
124 ofdma->of_dma_data = data;
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);
133 EXPORT_SYMBOL_GPL(of_dma_controller_register);
136 * of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
137 * @np: device node of DMA controller
139 * Memory allocated by of_dma_controller_register() is freed here.
141 void of_dma_controller_free(struct device_node *np)
143 struct of_dma *ofdma;
145 mutex_lock(&of_dma_lock);
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);
154 mutex_unlock(&of_dma_lock);
156 EXPORT_SYMBOL_GPL(of_dma_controller_free);
159 * of_dma_router_register - Register a DMA router to DT DMA helpers as a
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.
168 * Returns 0 on success or appropriate errno value on error.
170 * Allocated memory should be freed with appropriate of_dma_controller_free()
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)
178 struct of_dma *ofdma;
180 if (!np || !of_dma_route_allocate || !dma_router) {
181 pr_err("%s: not enough information provided\n", __func__);
185 ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
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;
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);
201 EXPORT_SYMBOL_GPL(of_dma_router_register);
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
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.
214 static int of_dma_match_channel(struct device_node *np, const char *name,
215 int index, struct of_phandle_args *dma_spec)
219 if (of_property_read_string_index(np, "dma-names", index, &s))
225 if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
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
237 * Returns pointer to appropriate DMA channel on success or an error pointer.
239 struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
242 struct of_phandle_args dma_spec;
243 struct of_dma *ofdma;
244 struct dma_chan *chan;
246 int ret_no_channel = -ENODEV;
247 static atomic_t last_index;
250 pr_err("%s: not enough information provided\n", __func__);
251 return ERR_PTR(-ENODEV);
254 /* Silently fail if there is not even the "dmas" property */
255 if (!of_find_property(np, "dmas", NULL))
256 return ERR_PTR(-ENODEV);
258 count = of_property_count_strings(np, "dma-names");
260 pr_err("%s: dma-names property of node '%pOF' missing or empty\n",
262 return ERR_PTR(-ENODEV);
266 * approximate an average distribution across multiple
267 * entries with the same name
269 start = atomic_inc_return(&last_index);
270 for (i = 0; i < count; i++) {
271 if (of_dma_match_channel(np, name,
276 mutex_lock(&of_dma_lock);
277 ofdma = of_dma_find_controller(&dma_spec);
280 chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
282 ret_no_channel = -EPROBE_DEFER;
286 mutex_unlock(&of_dma_lock);
288 of_node_put(dma_spec.np);
294 return ERR_PTR(ret_no_channel);
296 EXPORT_SYMBOL_GPL(of_dma_request_slave_channel);
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
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.
309 struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
310 struct of_dma *ofdma)
312 int count = dma_spec->args_count;
313 struct of_dma_filter_info *info = ofdma->of_dma_data;
315 if (!info || !info->filter_fn)
321 return __dma_request_channel(&info->dma_cap, info->filter_fn,
322 &dma_spec->args[0], dma_spec->np);
324 EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
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
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.
337 * Returns pointer to appropriate dma channel on success or NULL on error.
339 struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
340 struct of_dma *ofdma)
342 struct dma_device *dev = ofdma->of_dma_data;
343 struct dma_chan *chan, *candidate = NULL;
345 if (!dev || dma_spec->args_count != 1)
348 list_for_each_entry(chan, &dev->channels, device_node)
349 if (chan->chan_id == dma_spec->args[0]) {
357 return dma_get_slave_channel(candidate);
359 EXPORT_SYMBOL_GPL(of_dma_xlate_by_chan_id);