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/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         list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
 122
 123         return 0;
 124 }
 125 EXPORT_SYMBOL_GPL(of_dma_controller_register);
 126
 127 /**
 128  * of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
 129  * @np:         device node of DMA controller
 130  *
 131  * Memory allocated by of_dma_controller_register() is freed here.
 132  */
 133 int of_dma_controller_free(struct device_node *np)
 134 {
 135         struct of_dma *ofdma;
 136
 137         spin_lock(&of_dma_lock);
 138
 139         if (list_empty(&of_dma_list)) {
 140                 spin_unlock(&of_dma_lock);
 141                 return -ENODEV;
 142         }
 143
 144         list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
 145                 if (ofdma->of_node == np) {
 146                         if (ofdma->use_count) {
 147                                 spin_unlock(&of_dma_lock);
 148                                 return -EBUSY;
 149                         }
 150
 151                         list_del(&ofdma->of_dma_controllers);
 152                         spin_unlock(&of_dma_lock);
 153                         kfree(ofdma);
 154                         return 0;
 155                 }
 156
 157         spin_unlock(&of_dma_lock);
 158         return -ENODEV;
 159 }
 160 EXPORT_SYMBOL_GPL(of_dma_controller_free);
 161
 162 /**
 163  * of_dma_match_channel - Check if a DMA specifier matches name
 164  * @np:         device node to look for DMA channels
 165  * @name:       channel name to be matched
 166  * @index:      index of DMA specifier in list of DMA specifiers
 167  * @dma_spec:   pointer to DMA specifier as found in the device tree
 168  *
 169  * Check if the DMA specifier pointed to by the index in a list of DMA
 170  * specifiers, matches the name provided. Returns 0 if the name matches and
 171  * a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
 172  */
 173 static int of_dma_match_channel(struct device_node *np, char *name, int index,
 174                                 struct of_phandle_args *dma_spec)
 175 {
 176         const char *s;
 177
 178         if (of_property_read_string_index(np, "dma-names", index, &s))
 179                 return -ENODEV;
 180
 181         if (strcmp(name, s))
 182                 return -ENODEV;
 183
 184         if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
 185                                        dma_spec))
 186                 return -ENODEV;
 187
 188         return 0;
 189 }
 190
 191 /**
 192  * of_dma_request_slave_channel - Get the DMA slave channel
 193  * @np:         device node to get DMA request from
 194  * @name:       name of desired channel
 195  *
 196  * Returns pointer to appropriate dma channel on success or NULL on error.
 197  */
 198 struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
 199                                               char *name)
 200 {
 201         struct of_phandle_args  dma_spec;
 202         struct of_dma           *ofdma;
 203         struct dma_chan         *chan;
 204         int                     count, i;
 205
 206         if (!np || !name) {
 207                 pr_err("%s: not enough information provided\n", __func__);
 208                 return NULL;
 209         }
 210
 211         count = of_property_count_strings(np, "dma-names");
 212         if (count < 0) {
 213                 pr_err("%s: dma-names property missing or empty\n", __func__);
 214                 return NULL;
 215         }
 216
 217         for (i = 0; i < count; i++) {
 218                 if (of_dma_match_channel(np, name, i, &dma_spec))
 219                         continue;
 220
 221                 ofdma = of_dma_get_controller(&dma_spec);
 222
 223                 if (!ofdma)
 224                         continue;
 225
 226                 chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
 227
 228                 of_dma_put_controller(ofdma);
 229
 230                 of_node_put(dma_spec.np);
 231
 232                 if (chan)
 233                         return chan;
 234         }
 235
 236         return NULL;
 237 }
 238
 239 /**
 240  * of_dma_simple_xlate - Simple DMA engine translation function
 241  * @dma_spec:   pointer to DMA specifier as found in the device tree
 242  * @of_dma:     pointer to DMA controller data
 243  *
 244  * A simple translation function for devices that use a 32-bit value for the
 245  * filter_param when calling the DMA engine dma_request_channel() function.
 246  * Note that this translation function requires that #dma-cells is equal to 1
 247  * and the argument of the dma specifier is the 32-bit filter_param. Returns
 248  * pointer to appropriate dma channel on success or NULL on error.
 249  */
 250 struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
 251                                                 struct of_dma *ofdma)
 252 {
 253         int count = dma_spec->args_count;
 254         struct of_dma_filter_info *info = ofdma->of_dma_data;
 255
 256         if (!info || !info->filter_fn)
 257                 return NULL;
 258
 259         if (count != 1)
 260                 return NULL;
 261
 262         return dma_request_channel(info->dma_cap, info->filter_fn,
 263                         &dma_spec->args[0]);
 264 }
 265 EXPORT_SYMBOL_GPL(of_dma_simple_xlate);