xref: /openbmc/linux/drivers/dma/of-dma.c (revision f5c27da4)
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  
20  static LIST_HEAD(of_dma_list);
21  static 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   */
32  static 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   */
55  static 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  
96  err:
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   */
118  int 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  }
145  EXPORT_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   */
153  void 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  }
168  EXPORT_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   */
185  int 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  }
213  EXPORT_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   */
226  static 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   */
251  struct 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_find_property(np, "dmas", NULL))
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  }
308  EXPORT_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   */
321  struct 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  }
336  EXPORT_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   */
351  struct 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  }
371  EXPORT_SYMBOL_GPL(of_dma_xlate_by_chan_id);
372