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 if (list_empty(&of_dma_list
)) {
40 spin_unlock(&of_dma_lock
);
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
)) {
48 spin_unlock(&of_dma_lock
);
52 spin_unlock(&of_dma_lock
);
54 pr_debug("%s: can't find DMA controller %s\n", __func__
,
55 dma_spec
->np
->full_name
);
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
69 static void of_dma_put_controller(struct of_dma
*ofdma
)
71 spin_lock(&of_dma_lock
);
73 spin_unlock(&of_dma_lock
);
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()
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
*),
97 if (!np
|| !of_dma_xlate
) {
98 pr_err("%s: not enough information provided\n", __func__
);
102 ofdma
= kzalloc(sizeof(*ofdma
), GFP_KERNEL
);
106 nbcells
= be32_to_cpup(of_get_property(np
, "#dma-cells", NULL
));
108 pr_err("%s: #dma-cells property is missing or invalid\n",
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
);
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
);
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
);
153 list_del(&ofdma
->of_dma_controllers
);
154 spin_unlock(&of_dma_lock
);
159 spin_unlock(&of_dma_lock
);
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
)
180 if (of_property_read_string_index(np
, "dma-names", index
, &s
))
186 if (of_parse_phandle_with_args(np
, "dmas", "#dma-cells", index
,
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
,
203 struct of_phandle_args dma_spec
;
204 struct of_dma
*ofdma
;
205 struct dma_chan
*chan
;
209 pr_err("%s: not enough information provided\n", __func__
);
213 count
= of_property_count_strings(np
, "dma-names");
215 pr_err("%s: dma-names property missing or empty\n", __func__
);
219 for (i
= 0; i
< count
; i
++) {
220 if (of_dma_match_channel(np
, name
, i
, &dma_spec
))
223 ofdma
= of_dma_get_controller(&dma_spec
);
228 chan
= ofdma
->of_dma_xlate(&dma_spec
, ofdma
);
230 of_dma_put_controller(ofdma
);
232 of_node_put(dma_spec
.np
);
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
)
264 return dma_request_channel(info
->dma_cap
, info
->filter_fn
,
267 EXPORT_SYMBOL_GPL(of_dma_simple_xlate
);