2 * Device tree helpers for DMA request / controller
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>
19 #include <linux/of_dma.h>
21 static LIST_HEAD(of_dma_list);
22 static DEFINE_SPINLOCK(of_dma_lock);
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)
37 spin_lock(&of_dma_lock);
39 list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
40 if ((ofdma->of_node == dma_spec->np) &&
41 (ofdma->of_dma_nbcells == dma_spec->args_count)) {
43 spin_unlock(&of_dma_lock);
47 spin_unlock(&of_dma_lock);
49 pr_debug("%s: can't find DMA controller %s\n", __func__,
50 dma_spec->np->full_name);
56 * of_dma_put_controller - Decrement use count for a registered DMA controller
57 * @of_dma: pointer to DMA controller data
59 * Decrements the use_count variable in the DMA data structure. This function
60 * should be called only when a valid pointer is returned from
61 * of_dma_get_controller() and no further accesses to data referenced by that
64 static void of_dma_put_controller(struct of_dma *ofdma)
66 spin_lock(&of_dma_lock);
68 spin_unlock(&of_dma_lock);
72 * of_dma_controller_register - Register a DMA controller to DT DMA helpers
73 * @np: device node of DMA controller
74 * @of_dma_xlate: translation function which converts a phandle
75 * arguments list into a dma_chan structure
76 * @data pointer to controller specific data to be used by
77 * translation function
79 * Returns 0 on success or appropriate errno value on error.
81 * Allocated memory should be freed with appropriate of_dma_controller_free()
84 int of_dma_controller_register(struct device_node *np,
85 struct dma_chan *(*of_dma_xlate)
86 (struct of_phandle_args *, struct of_dma *),
93 if (!np || !of_dma_xlate) {
94 pr_err("%s: not enough information provided\n", __func__);
98 ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
102 prop = of_get_property(np, "#dma-cells", NULL);
104 nbcells = be32_to_cpup(prop);
106 if (!prop || !nbcells) {
107 pr_err("%s: #dma-cells property is missing or invalid\n",
114 ofdma->of_dma_nbcells = nbcells;
115 ofdma->of_dma_xlate = of_dma_xlate;
116 ofdma->of_dma_data = data;
117 ofdma->use_count = 0;
119 /* Now queue of_dma controller structure in list */
120 spin_lock(&of_dma_lock);
121 list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
122 spin_unlock(&of_dma_lock);
126 EXPORT_SYMBOL_GPL(of_dma_controller_register);
129 * of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
130 * @np: device node of DMA controller
132 * Memory allocated by of_dma_controller_register() is freed here.
134 int of_dma_controller_free(struct device_node *np)
136 struct of_dma *ofdma;
138 spin_lock(&of_dma_lock);
140 if (list_empty(&of_dma_list)) {
141 spin_unlock(&of_dma_lock);
145 list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
146 if (ofdma->of_node == np) {
147 if (ofdma->use_count) {
148 spin_unlock(&of_dma_lock);
152 list_del(&ofdma->of_dma_controllers);
153 spin_unlock(&of_dma_lock);
158 spin_unlock(&of_dma_lock);
161 EXPORT_SYMBOL_GPL(of_dma_controller_free);
164 * of_dma_match_channel - Check if a DMA specifier matches name
165 * @np: device node to look for DMA channels
166 * @name: channel name to be matched
167 * @index: index of DMA specifier in list of DMA specifiers
168 * @dma_spec: pointer to DMA specifier as found in the device tree
170 * Check if the DMA specifier pointed to by the index in a list of DMA
171 * specifiers, matches the name provided. Returns 0 if the name matches and
172 * a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
174 static int of_dma_match_channel(struct device_node *np, const char *name,
175 int index, struct of_phandle_args *dma_spec)
179 if (of_property_read_string_index(np, "dma-names", index, &s))
185 if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
193 * of_dma_request_slave_channel - Get the DMA slave channel
194 * @np: device node to get DMA request from
195 * @name: name of desired channel
197 * Returns pointer to appropriate dma channel on success or NULL on error.
199 struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
202 struct of_phandle_args dma_spec;
203 struct of_dma *ofdma;
204 struct dma_chan *chan;
208 pr_err("%s: not enough information provided\n", __func__);
212 count = of_property_count_strings(np, "dma-names");
214 pr_err("%s: dma-names property missing or empty\n", __func__);
218 for (i = 0; i < count; i++) {
219 if (of_dma_match_channel(np, name, i, &dma_spec))
222 ofdma = of_dma_get_controller(&dma_spec);
227 chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
229 of_dma_put_controller(ofdma);
231 of_node_put(dma_spec.np);
241 * of_dma_simple_xlate - Simple DMA engine translation function
242 * @dma_spec: pointer to DMA specifier as found in the device tree
243 * @of_dma: pointer to DMA controller data
245 * A simple translation function for devices that use a 32-bit value for the
246 * filter_param when calling the DMA engine dma_request_channel() function.
247 * Note that this translation function requires that #dma-cells is equal to 1
248 * and the argument of the dma specifier is the 32-bit filter_param. Returns
249 * pointer to appropriate dma channel on success or NULL on error.
251 struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
252 struct of_dma *ofdma)
254 int count = dma_spec->args_count;
255 struct of_dma_filter_info *info = ofdma->of_dma_data;
257 if (!info || !info->filter_fn)
263 return dma_request_channel(info->dma_cap, info->filter_fn,
266 EXPORT_SYMBOL_GPL(of_dma_simple_xlate);