USB: keyspan: pull in one indent level
[linux-2.6/btrfs-unstable.git] / drivers / dma / of-dma.c
blob69d04d28b1efbe78cb871b22af17bb851071e606
1 /*
2 * Device tree helpers for DMA request / controller
4 * Based on of_gpio.c
6 * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
13 #include <linux/device.h>
14 #include <linux/err.h>
15 #include <linux/module.h>
16 #include <linux/rculist.h>
17 #include <linux/slab.h>
18 #include <linux/of.h>
19 #include <linux/of_dma.h>
21 static LIST_HEAD(of_dma_list);
22 static DEFINE_SPINLOCK(of_dma_lock);
24 /**
25 * of_dma_get_controller - Get a DMA controller in DT DMA helpers list
26 * @dma_spec: pointer to DMA specifier as found in the device tree
28 * Finds a DMA controller with matching device node and number for dma cells
29 * in a list of registered DMA controllers. If a match is found the use_count
30 * variable is increased and a valid pointer to the DMA data stored is retuned.
31 * A NULL pointer is returned if no match is found.
33 static struct of_dma *of_dma_get_controller(struct of_phandle_args *dma_spec)
35 struct of_dma *ofdma;
37 spin_lock(&of_dma_lock);
39 if (list_empty(&of_dma_list)) {
40 spin_unlock(&of_dma_lock);
41 return NULL;
44 list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
45 if ((ofdma->of_node == dma_spec->np) &&
46 (ofdma->of_dma_nbcells == dma_spec->args_count)) {
47 ofdma->use_count++;
48 spin_unlock(&of_dma_lock);
49 return ofdma;
52 spin_unlock(&of_dma_lock);
54 pr_debug("%s: can't find DMA controller %s\n", __func__,
55 dma_spec->np->full_name);
57 return NULL;
60 /**
61 * of_dma_put_controller - Decrement use count for a registered DMA controller
62 * @of_dma: pointer to DMA controller data
64 * Decrements the use_count variable in the DMA data structure. This function
65 * should be called only when a valid pointer is returned from
66 * of_dma_get_controller() and no further accesses to data referenced by that
67 * pointer are needed.
69 static void of_dma_put_controller(struct of_dma *ofdma)
71 spin_lock(&of_dma_lock);
72 ofdma->use_count--;
73 spin_unlock(&of_dma_lock);
76 /**
77 * of_dma_controller_register - Register a DMA controller to DT DMA helpers
78 * @np: device node of DMA controller
79 * @of_dma_xlate: translation function which converts a phandle
80 * arguments list into a dma_chan structure
81 * @data pointer to controller specific data to be used by
82 * translation function
84 * Returns 0 on success or appropriate errno value on error.
86 * Allocated memory should be freed with appropriate of_dma_controller_free()
87 * call.
89 int of_dma_controller_register(struct device_node *np,
90 struct dma_chan *(*of_dma_xlate)
91 (struct of_phandle_args *, struct of_dma *),
92 void *data)
94 struct of_dma *ofdma;
95 int nbcells;
97 if (!np || !of_dma_xlate) {
98 pr_err("%s: not enough information provided\n", __func__);
99 return -EINVAL;
102 ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
103 if (!ofdma)
104 return -ENOMEM;
106 nbcells = be32_to_cpup(of_get_property(np, "#dma-cells", NULL));
107 if (!nbcells) {
108 pr_err("%s: #dma-cells property is missing or invalid\n",
109 __func__);
110 kfree(ofdma);
111 return -EINVAL;
114 ofdma->of_node = np;
115 ofdma->of_dma_nbcells = nbcells;
116 ofdma->of_dma_xlate = of_dma_xlate;
117 ofdma->of_dma_data = data;
118 ofdma->use_count = 0;
120 /* Now queue of_dma controller structure in list */
121 spin_lock(&of_dma_lock);
122 list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
123 spin_unlock(&of_dma_lock);
125 return 0;
127 EXPORT_SYMBOL_GPL(of_dma_controller_register);
130 * of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
131 * @np: device node of DMA controller
133 * Memory allocated by of_dma_controller_register() is freed here.
135 int of_dma_controller_free(struct device_node *np)
137 struct of_dma *ofdma;
139 spin_lock(&of_dma_lock);
141 if (list_empty(&of_dma_list)) {
142 spin_unlock(&of_dma_lock);
143 return -ENODEV;
146 list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
147 if (ofdma->of_node == np) {
148 if (ofdma->use_count) {
149 spin_unlock(&of_dma_lock);
150 return -EBUSY;
153 list_del(&ofdma->of_dma_controllers);
154 spin_unlock(&of_dma_lock);
155 kfree(ofdma);
156 return 0;
159 spin_unlock(&of_dma_lock);
160 return -ENODEV;
162 EXPORT_SYMBOL_GPL(of_dma_controller_free);
165 * of_dma_match_channel - Check if a DMA specifier matches name
166 * @np: device node to look for DMA channels
167 * @name: channel name to be matched
168 * @index: index of DMA specifier in list of DMA specifiers
169 * @dma_spec: pointer to DMA specifier as found in the device tree
171 * Check if the DMA specifier pointed to by the index in a list of DMA
172 * specifiers, matches the name provided. Returns 0 if the name matches and
173 * a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
175 static int of_dma_match_channel(struct device_node *np, char *name, int index,
176 struct of_phandle_args *dma_spec)
178 const char *s;
180 if (of_property_read_string_index(np, "dma-names", index, &s))
181 return -ENODEV;
183 if (strcmp(name, s))
184 return -ENODEV;
186 if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
187 dma_spec))
188 return -ENODEV;
190 return 0;
194 * of_dma_request_slave_channel - Get the DMA slave channel
195 * @np: device node to get DMA request from
196 * @name: name of desired channel
198 * Returns pointer to appropriate dma channel on success or NULL on error.
200 struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
201 char *name)
203 struct of_phandle_args dma_spec;
204 struct of_dma *ofdma;
205 struct dma_chan *chan;
206 int count, i;
208 if (!np || !name) {
209 pr_err("%s: not enough information provided\n", __func__);
210 return NULL;
213 count = of_property_count_strings(np, "dma-names");
214 if (count < 0) {
215 pr_err("%s: dma-names property missing or empty\n", __func__);
216 return NULL;
219 for (i = 0; i < count; i++) {
220 if (of_dma_match_channel(np, name, i, &dma_spec))
221 continue;
223 ofdma = of_dma_get_controller(&dma_spec);
225 if (!ofdma)
226 continue;
228 chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
230 of_dma_put_controller(ofdma);
232 of_node_put(dma_spec.np);
234 if (chan)
235 return chan;
238 return NULL;
242 * of_dma_simple_xlate - Simple DMA engine translation function
243 * @dma_spec: pointer to DMA specifier as found in the device tree
244 * @of_dma: pointer to DMA controller data
246 * A simple translation function for devices that use a 32-bit value for the
247 * filter_param when calling the DMA engine dma_request_channel() function.
248 * Note that this translation function requires that #dma-cells is equal to 1
249 * and the argument of the dma specifier is the 32-bit filter_param. Returns
250 * pointer to appropriate dma channel on success or NULL on error.
252 struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
253 struct of_dma *ofdma)
255 int count = dma_spec->args_count;
256 struct of_dma_filter_info *info = ofdma->of_dma_data;
258 if (!info || !info->filter_fn)
259 return NULL;
261 if (count != 1)
262 return NULL;
264 return dma_request_channel(info->dma_cap, info->filter_fn,
265 &dma_spec->args[0]);
267 EXPORT_SYMBOL_GPL(of_dma_simple_xlate);