1/*
2 * Device tree helpers for DMA request / controller
3 *
4 * Based on of_gpio.c
5 *
6 * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
7 *
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.
11 */
12
13#include <linux/device.h>
14#include <linux/err.h>
15#include <linux/module.h>
16#include <linux/mutex.h>
17#include <linux/slab.h>
18#include <linux/of.h>
19#include <linux/of_dma.h>
20
21static LIST_HEAD(of_dma_list);
22static DEFINE_MUTEX(of_dma_lock);
23
24/**
25 * of_dma_find_controller - Get a DMA controller in DT DMA helpers list
26 * @dma_spec:	pointer to DMA specifier as found in the device tree
27 *
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 a valid pointer
30 * to the DMA data stored is retuned. A NULL pointer is returned if no match is
31 * found.
32 */
33static struct of_dma *of_dma_find_controller(struct of_phandle_args *dma_spec)
34{
35	struct of_dma *ofdma;
36
37	list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
38		if (ofdma->of_node == dma_spec->np)
39			return ofdma;
40
41	pr_debug("%s: can't find DMA controller %s\n", __func__,
42		 dma_spec->np->full_name);
43
44	return NULL;
45}
46
47/**
48 * of_dma_controller_register - Register a DMA controller to DT DMA helpers
49 * @np:			device node of DMA controller
50 * @of_dma_xlate:	translation function which converts a phandle
51 *			arguments list into a dma_chan structure
52 * @data		pointer to controller specific data to be used by
53 *			translation function
54 *
55 * Returns 0 on success or appropriate errno value on error.
56 *
57 * Allocated memory should be freed with appropriate of_dma_controller_free()
58 * call.
59 */
60int of_dma_controller_register(struct device_node *np,
61				struct dma_chan *(*of_dma_xlate)
62				(struct of_phandle_args *, struct of_dma *),
63				void *data)
64{
65	struct of_dma	*ofdma;
66
67	if (!np || !of_dma_xlate) {
68		pr_err("%s: not enough information provided\n", __func__);
69		return -EINVAL;
70	}
71
72	ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
73	if (!ofdma)
74		return -ENOMEM;
75
76	ofdma->of_node = np;
77	ofdma->of_dma_xlate = of_dma_xlate;
78	ofdma->of_dma_data = data;
79
80	/* Now queue of_dma controller structure in list */
81	mutex_lock(&of_dma_lock);
82	list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
83	mutex_unlock(&of_dma_lock);
84
85	return 0;
86}
87EXPORT_SYMBOL_GPL(of_dma_controller_register);
88
89/**
90 * of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
91 * @np:		device node of DMA controller
92 *
93 * Memory allocated by of_dma_controller_register() is freed here.
94 */
95void of_dma_controller_free(struct device_node *np)
96{
97	struct of_dma *ofdma;
98
99	mutex_lock(&of_dma_lock);
100
101	list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
102		if (ofdma->of_node == np) {
103			list_del(&ofdma->of_dma_controllers);
104			kfree(ofdma);
105			break;
106		}
107
108	mutex_unlock(&of_dma_lock);
109}
110EXPORT_SYMBOL_GPL(of_dma_controller_free);
111
112/**
113 * of_dma_match_channel - Check if a DMA specifier matches name
114 * @np:		device node to look for DMA channels
115 * @name:	channel name to be matched
116 * @index:	index of DMA specifier in list of DMA specifiers
117 * @dma_spec:	pointer to DMA specifier as found in the device tree
118 *
119 * Check if the DMA specifier pointed to by the index in a list of DMA
120 * specifiers, matches the name provided. Returns 0 if the name matches and
121 * a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
122 */
123static int of_dma_match_channel(struct device_node *np, const char *name,
124				int index, struct of_phandle_args *dma_spec)
125{
126	const char *s;
127
128	if (of_property_read_string_index(np, "dma-names", index, &s))
129		return -ENODEV;
130
131	if (strcmp(name, s))
132		return -ENODEV;
133
134	if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
135				       dma_spec))
136		return -ENODEV;
137
138	return 0;
139}
140
141/**
142 * of_dma_request_slave_channel - Get the DMA slave channel
143 * @np:		device node to get DMA request from
144 * @name:	name of desired channel
145 *
146 * Returns pointer to appropriate DMA channel on success or an error pointer.
147 */
148struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
149					      const char *name)
150{
151	struct of_phandle_args	dma_spec;
152	struct of_dma		*ofdma;
153	struct dma_chan		*chan;
154	int			count, i;
155	int			ret_no_channel = -ENODEV;
156
157	if (!np || !name) {
158		pr_err("%s: not enough information provided\n", __func__);
159		return ERR_PTR(-ENODEV);
160	}
161
162	/* Silently fail if there is not even the "dmas" property */
163	if (!of_find_property(np, "dmas", NULL))
164		return ERR_PTR(-ENODEV);
165
166	count = of_property_count_strings(np, "dma-names");
167	if (count < 0) {
168		pr_err("%s: dma-names property of node '%s' missing or empty\n",
169			__func__, np->full_name);
170		return ERR_PTR(-ENODEV);
171	}
172
173	for (i = 0; i < count; i++) {
174		if (of_dma_match_channel(np, name, i, &dma_spec))
175			continue;
176
177		mutex_lock(&of_dma_lock);
178		ofdma = of_dma_find_controller(&dma_spec);
179
180		if (ofdma) {
181			chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
182		} else {
183			ret_no_channel = -EPROBE_DEFER;
184			chan = NULL;
185		}
186
187		mutex_unlock(&of_dma_lock);
188
189		of_node_put(dma_spec.np);
190
191		if (chan)
192			return chan;
193	}
194
195	return ERR_PTR(ret_no_channel);
196}
197EXPORT_SYMBOL_GPL(of_dma_request_slave_channel);
198
199/**
200 * of_dma_simple_xlate - Simple DMA engine translation function
201 * @dma_spec:	pointer to DMA specifier as found in the device tree
202 * @of_dma:	pointer to DMA controller data
203 *
204 * A simple translation function for devices that use a 32-bit value for the
205 * filter_param when calling the DMA engine dma_request_channel() function.
206 * Note that this translation function requires that #dma-cells is equal to 1
207 * and the argument of the dma specifier is the 32-bit filter_param. Returns
208 * pointer to appropriate dma channel on success or NULL on error.
209 */
210struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
211						struct of_dma *ofdma)
212{
213	int count = dma_spec->args_count;
214	struct of_dma_filter_info *info = ofdma->of_dma_data;
215
216	if (!info || !info->filter_fn)
217		return NULL;
218
219	if (count != 1)
220		return NULL;
221
222	return dma_request_channel(info->dma_cap, info->filter_fn,
223			&dma_spec->args[0]);
224}
225EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
226
227/**
228 * of_dma_xlate_by_chan_id - Translate dt property to DMA channel by channel id
229 * @dma_spec:	pointer to DMA specifier as found in the device tree
230 * @of_dma:	pointer to DMA controller data
231 *
232 * This function can be used as the of xlate callback for DMA driver which wants
233 * to match the channel based on the channel id. When using this xlate function
234 * the #dma-cells propety of the DMA controller dt node needs to be set to 1.
235 * The data parameter of of_dma_controller_register must be a pointer to the
236 * dma_device struct the function should match upon.
237 *
238 * Returns pointer to appropriate dma channel on success or NULL on error.
239 */
240struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
241					 struct of_dma *ofdma)
242{
243	struct dma_device *dev = ofdma->of_dma_data;
244	struct dma_chan *chan, *candidate = NULL;
245
246	if (!dev || dma_spec->args_count != 1)
247		return NULL;
248
249	list_for_each_entry(chan, &dev->channels, device_node)
250		if (chan->chan_id == dma_spec->args[0]) {
251			candidate = chan;
252			break;
253		}
254
255	if (!candidate)
256		return NULL;
257
258	return dma_get_slave_channel(candidate);
259}
260EXPORT_SYMBOL_GPL(of_dma_xlate_by_chan_id);
261