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/rculist.h> 17 #include <linux/slab.h> 18 #include <linux/of.h> 19 #include <linux/of_dma.h> 20 21 static LIST_HEAD(of_dma_list); 22 static DEFINE_SPINLOCK(of_dma_lock); 23 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 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 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. 32 */ 33 static struct of_dma *of_dma_get_controller(struct of_phandle_args *dma_spec) 34 { 35 struct of_dma *ofdma; 36 37 spin_lock(&of_dma_lock); 38 39 if (list_empty(&of_dma_list)) { 40 spin_unlock(&of_dma_lock); 41 return NULL; 42 } 43 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; 50 } 51 52 spin_unlock(&of_dma_lock); 53 54 pr_debug("%s: can't find DMA controller %s\n", __func__, 55 dma_spec->np->full_name); 56 57 return NULL; 58 } 59 60 /** 61 * of_dma_put_controller - Decrement use count for a registered DMA controller 62 * @of_dma: pointer to DMA controller data 63 * 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. 68 */ 69 static void of_dma_put_controller(struct of_dma *ofdma) 70 { 71 spin_lock(&of_dma_lock); 72 ofdma->use_count--; 73 spin_unlock(&of_dma_lock); 74 } 75 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 83 * 84 * Returns 0 on success or appropriate errno value on error. 85 * 86 * Allocated memory should be freed with appropriate of_dma_controller_free() 87 * call. 88 */ 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) 93 { 94 struct of_dma *ofdma; 95 int nbcells; 96 97 if (!np || !of_dma_xlate) { 98 pr_err("%s: not enough information provided\n", __func__); 99 return -EINVAL; 100 } 101 102 ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL); 103 if (!ofdma) 104 return -ENOMEM; 105 106 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; 112 } 113 114 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; 119 120 /* 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); 124 125 return 0; 126 } 127 EXPORT_SYMBOL_GPL(of_dma_controller_register); 128 129 /** 130 * of_dma_controller_free - Remove a DMA controller from DT DMA helpers list 131 * @np: device node of DMA controller 132 * 133 * Memory allocated by of_dma_controller_register() is freed here. 134 */ 135 int of_dma_controller_free(struct device_node *np) 136 { 137 struct of_dma *ofdma; 138 139 spin_lock(&of_dma_lock); 140 141 if (list_empty(&of_dma_list)) { 142 spin_unlock(&of_dma_lock); 143 return -ENODEV; 144 } 145 146 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; 151 } 152 153 list_del(&ofdma->of_dma_controllers); 154 spin_unlock(&of_dma_lock); 155 kfree(ofdma); 156 return 0; 157 } 158 159 spin_unlock(&of_dma_lock); 160 return -ENODEV; 161 } 162 EXPORT_SYMBOL_GPL(of_dma_controller_free); 163 164 /** 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 170 * 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. 174 */ 175 static int of_dma_match_channel(struct device_node *np, char *name, int index, 176 struct of_phandle_args *dma_spec) 177 { 178 const char *s; 179 180 if (of_property_read_string_index(np, "dma-names", index, &s)) 181 return -ENODEV; 182 183 if (strcmp(name, s)) 184 return -ENODEV; 185 186 if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index, 187 dma_spec)) 188 return -ENODEV; 189 190 return 0; 191 } 192 193 /** 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 197 * 198 * Returns pointer to appropriate dma channel on success or NULL on error. 199 */ 200 struct dma_chan *of_dma_request_slave_channel(struct device_node *np, 201 char *name) 202 { 203 struct of_phandle_args dma_spec; 204 struct of_dma *ofdma; 205 struct dma_chan *chan; 206 int count, i; 207 208 if (!np || !name) { 209 pr_err("%s: not enough information provided\n", __func__); 210 return NULL; 211 } 212 213 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; 217 } 218 219 for (i = 0; i < count; i++) { 220 if (of_dma_match_channel(np, name, i, &dma_spec)) 221 continue; 222 223 ofdma = of_dma_get_controller(&dma_spec); 224 225 if (!ofdma) 226 continue; 227 228 chan = ofdma->of_dma_xlate(&dma_spec, ofdma); 229 230 of_dma_put_controller(ofdma); 231 232 of_node_put(dma_spec.np); 233 234 if (chan) 235 return chan; 236 } 237 238 return NULL; 239 } 240 241 /** 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 245 * 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. 251 */ 252 struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec, 253 struct of_dma *ofdma) 254 { 255 int count = dma_spec->args_count; 256 struct of_dma_filter_info *info = ofdma->of_dma_data; 257 258 if (!info || !info->filter_fn) 259 return NULL; 260 261 if (count != 1) 262 return NULL; 263 264 return dma_request_channel(info->dma_cap, info->filter_fn, 265 &dma_spec->args[0]); 266 } 267 EXPORT_SYMBOL_GPL(of_dma_simple_xlate); 268