drivers/dma/of-dma.c

   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
  21 static LIST_HEAD(of_dma_list);
  22 static 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  */
  33 static 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 %pOF\n", __func__,
  42                  dma_spec->np);
  43
  44         return NULL;
  45 }
  46
  47 /**
  48  * of_dma_router_xlate - translation function for router devices
  49  * @dma_spec:   pointer to DMA specifier as found in the device tree
  50  * @of_dma:     pointer to DMA controller data (router information)
  51  *
  52  * The function creates new dma_spec to be passed to the router driver's
  53  * of_dma_route_allocate() function to prepare a dma_spec which will be used
  54  * to request channel from the real DMA controller.
  55  */
  56 static struct dma_chan *of_dma_router_xlate(struct of_phandle_args *dma_spec,
  57                                             struct of_dma *ofdma)
  58 {
  59         struct dma_chan         *chan;
  60         struct of_dma           *ofdma_target;
  61         struct of_phandle_args  dma_spec_target;
  62         void                    *route_data;
  63
  64         /* translate the request for the real DMA controller */
  65         memcpy(&dma_spec_target, dma_spec, sizeof(dma_spec_target));
  66         route_data = ofdma->of_dma_route_allocate(&dma_spec_target, ofdma);
  67         if (IS_ERR(route_data))
  68                 return NULL;
  69
  70         ofdma_target = of_dma_find_controller(&dma_spec_target);
  71         if (!ofdma_target)
  72                 return NULL;
  73
  74         chan = ofdma_target->of_dma_xlate(&dma_spec_target, ofdma_target);
  75         if (chan) {
  76                 chan->router = ofdma->dma_router;
  77                 chan->route_data = route_data;
  78         } else {
  79                 ofdma->dma_router->route_free(ofdma->dma_router->dev,
  80                                               route_data);
  81         }
  82
  83         /*
  84          * Need to put the node back since the ofdma->of_dma_route_allocate
  85          * has taken it for generating the new, translated dma_spec
  86          */
  87         of_node_put(dma_spec_target.np);
  88         return chan;
  89 }
  90
  91 /**
  92  * of_dma_controller_register - Register a DMA controller to DT DMA helpers
  93  * @np:                 device node of DMA controller
  94  * @of_dma_xlate:       translation function which converts a phandle
  95  *                      arguments list into a dma_chan structure
  96  * @data                pointer to controller specific data to be used by
  97  *                      translation function
  98  *
  99  * Returns 0 on success or appropriate errno value on error.
 100  *
 101  * Allocated memory should be freed with appropriate of_dma_controller_free()
 102  * call.
 103  */
 104 int of_dma_controller_register(struct device_node *np,
 105                                 struct dma_chan *(*of_dma_xlate)
 106                                 (struct of_phandle_args *, struct of_dma *),
 107                                 void *data)
 108 {
 109         struct of_dma   *ofdma;
 110
 111         if (!np || !of_dma_xlate) {
 112                 pr_err("%s: not enough information provided\n", __func__);
 113                 return -EINVAL;
 114         }
 115
 116         ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
 117         if (!ofdma)
 118                 return -ENOMEM;
 119
 120         ofdma->of_node = np;
 121         ofdma->of_dma_xlate = of_dma_xlate;
 122         ofdma->of_dma_data = data;
 123
 124         /* Now queue of_dma controller structure in list */
 125         mutex_lock(&of_dma_lock);
 126         list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
 127         mutex_unlock(&of_dma_lock);
 128
 129         return 0;
 130 }
 131 EXPORT_SYMBOL_GPL(of_dma_controller_register);
 132
 133 /**
 134  * of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
 135  * @np:         device node of DMA controller
 136  *
 137  * Memory allocated by of_dma_controller_register() is freed here.
 138  */
 139 void of_dma_controller_free(struct device_node *np)
 140 {
 141         struct of_dma *ofdma;
 142
 143         mutex_lock(&of_dma_lock);
 144
 145         list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
 146                 if (ofdma->of_node == np) {
 147                         list_del(&ofdma->of_dma_controllers);
 148                         kfree(ofdma);
 149                         break;
 150                 }
 151
 152         mutex_unlock(&of_dma_lock);
 153 }
 154 EXPORT_SYMBOL_GPL(of_dma_controller_free);
 155
 156 /**
 157  * of_dma_router_register - Register a DMA router to DT DMA helpers as a
 158  *                          controller
 159  * @np:                         device node of DMA router
 160  * @of_dma_route_allocate:      setup function for the router which need to
 161  *                              modify the dma_spec for the DMA controller to
 162  *                              use and to set up the requested route.
 163  * @dma_router:                 pointer to dma_router structure to be used when
 164  *                              the route need to be free up.
 165  *
 166  * Returns 0 on success or appropriate errno value on error.
 167  *
 168  * Allocated memory should be freed with appropriate of_dma_controller_free()
 169  * call.
 170  */
 171 int of_dma_router_register(struct device_node *np,
 172                            void *(*of_dma_route_allocate)
 173                            (struct of_phandle_args *, struct of_dma *),
 174                            struct dma_router *dma_router)
 175 {
 176         struct of_dma   *ofdma;
 177
 178         if (!np || !of_dma_route_allocate || !dma_router) {
 179                 pr_err("%s: not enough information provided\n", __func__);
 180                 return -EINVAL;
 181         }
 182
 183         ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
 184         if (!ofdma)
 185                 return -ENOMEM;
 186
 187         ofdma->of_node = np;
 188         ofdma->of_dma_xlate = of_dma_router_xlate;
 189         ofdma->of_dma_route_allocate = of_dma_route_allocate;
 190         ofdma->dma_router = dma_router;
 191
 192         /* Now queue of_dma controller structure in list */
 193         mutex_lock(&of_dma_lock);
 194         list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
 195         mutex_unlock(&of_dma_lock);
 196
 197         return 0;
 198 }
 199 EXPORT_SYMBOL_GPL(of_dma_router_register);
 200
 201 /**
 202  * of_dma_match_channel - Check if a DMA specifier matches name
 203  * @np:         device node to look for DMA channels
 204  * @name:       channel name to be matched
 205  * @index:      index of DMA specifier in list of DMA specifiers
 206  * @dma_spec:   pointer to DMA specifier as found in the device tree
 207  *
 208  * Check if the DMA specifier pointed to by the index in a list of DMA
 209  * specifiers, matches the name provided. Returns 0 if the name matches and
 210  * a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
 211  */
 212 static int of_dma_match_channel(struct device_node *np, const char *name,
 213                                 int index, struct of_phandle_args *dma_spec)
 214 {
 215         const char *s;
 216
 217         if (of_property_read_string_index(np, "dma-names", index, &s))
 218                 return -ENODEV;
 219
 220         if (strcmp(name, s))
 221                 return -ENODEV;
 222
 223         if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
 224                                        dma_spec))
 225                 return -ENODEV;
 226
 227         return 0;
 228 }
 229
 230 /**
 231  * of_dma_request_slave_channel - Get the DMA slave channel
 232  * @np:         device node to get DMA request from
 233  * @name:       name of desired channel
 234  *
 235  * Returns pointer to appropriate DMA channel on success or an error pointer.
 236  */
 237 struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
 238                                               const char *name)
 239 {
 240         struct of_phandle_args  dma_spec;
 241         struct of_dma           *ofdma;
 242         struct dma_chan         *chan;
 243         int                     count, i, start;
 244         int                     ret_no_channel = -ENODEV;
 245         static atomic_t         last_index;
 246
 247         if (!np || !name) {
 248                 pr_err("%s: not enough information provided\n", __func__);
 249                 return ERR_PTR(-ENODEV);
 250         }
 251
 252         /* Silently fail if there is not even the "dmas" property */
 253         if (!of_find_property(np, "dmas", NULL))
 254                 return ERR_PTR(-ENODEV);
 255
 256         count = of_property_count_strings(np, "dma-names");
 257         if (count < 0) {
 258                 pr_err("%s: dma-names property of node '%pOF' missing or empty\n",
 259                         __func__, np);
 260                 return ERR_PTR(-ENODEV);
 261         }
 262
 263         /*
 264          * approximate an average distribution across multiple
 265          * entries with the same name
 266          */
 267         start = atomic_inc_return(&last_index);
 268         for (i = 0; i < count; i++) {
 269                 if (of_dma_match_channel(np, name,
 270                                          (i + start) % count,
 271                                          &dma_spec))
 272                         continue;
 273
 274                 mutex_lock(&of_dma_lock);
 275                 ofdma = of_dma_find_controller(&dma_spec);
 276
 277                 if (ofdma) {
 278                         chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
 279                 } else {
 280                         ret_no_channel = -EPROBE_DEFER;
 281                         chan = NULL;
 282                 }
 283
 284                 mutex_unlock(&of_dma_lock);
 285
 286                 of_node_put(dma_spec.np);
 287
 288                 if (chan)
 289                         return chan;
 290         }
 291
 292         return ERR_PTR(ret_no_channel);
 293 }
 294 EXPORT_SYMBOL_GPL(of_dma_request_slave_channel);
 295
 296 /**
 297  * of_dma_simple_xlate - Simple DMA engine translation function
 298  * @dma_spec:   pointer to DMA specifier as found in the device tree
 299  * @of_dma:     pointer to DMA controller data
 300  *
 301  * A simple translation function for devices that use a 32-bit value for the
 302  * filter_param when calling the DMA engine dma_request_channel() function.
 303  * Note that this translation function requires that #dma-cells is equal to 1
 304  * and the argument of the dma specifier is the 32-bit filter_param. Returns
 305  * pointer to appropriate dma channel on success or NULL on error.
 306  */
 307 struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
 308                                                 struct of_dma *ofdma)
 309 {
 310         int count = dma_spec->args_count;
 311         struct of_dma_filter_info *info = ofdma->of_dma_data;
 312
 313         if (!info || !info->filter_fn)
 314                 return NULL;
 315
 316         if (count != 1)
 317                 return NULL;
 318
 319         return dma_request_channel(info->dma_cap, info->filter_fn,
 320                         &dma_spec->args[0]);
 321 }
 322 EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
 323
 324 /**
 325  * of_dma_xlate_by_chan_id - Translate dt property to DMA channel by channel id
 326  * @dma_spec:   pointer to DMA specifier as found in the device tree
 327  * @of_dma:     pointer to DMA controller data
 328  *
 329  * This function can be used as the of xlate callback for DMA driver which wants
 330  * to match the channel based on the channel id. When using this xlate function
 331  * the #dma-cells propety of the DMA controller dt node needs to be set to 1.
 332  * The data parameter of of_dma_controller_register must be a pointer to the
 333  * dma_device struct the function should match upon.
 334  *
 335  * Returns pointer to appropriate dma channel on success or NULL on error.
 336  */
 337 struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
 338                                          struct of_dma *ofdma)
 339 {
 340         struct dma_device *dev = ofdma->of_dma_data;
 341         struct dma_chan *chan, *candidate = NULL;
 342
 343         if (!dev || dma_spec->args_count != 1)
 344                 return NULL;
 345
 346         list_for_each_entry(chan, &dev->channels, device_node)
 347                 if (chan->chan_id == dma_spec->args[0]) {
 348                         candidate = chan;
 349                         break;
 350                 }
 351
 352         if (!candidate)
 353                 return NULL;
 354
 355         return dma_get_slave_channel(candidate);
 356 }
 357 EXPORT_SYMBOL_GPL(of_dma_xlate_by_chan_id);