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                     (ofdma->of_dma_nbcells == dma_spec->args_count))
  40                         return ofdma;
  41
  42         pr_debug("%s: can't find DMA controller %s\n", __func__,
  43                  dma_spec->np->full_name);
  44
  45         return NULL;
  46 }
  47
  48 /**
  49  * of_dma_controller_register - Register a DMA controller to DT DMA helpers
  50  * @np:                 device node of DMA controller
  51  * @of_dma_xlate:       translation function which converts a phandle
  52  *                      arguments list into a dma_chan structure
  53  * @data                pointer to controller specific data to be used by
  54  *                      translation function
  55  *
  56  * Returns 0 on success or appropriate errno value on error.
  57  *
  58  * Allocated memory should be freed with appropriate of_dma_controller_free()
  59  * call.
  60  */
  61 int of_dma_controller_register(struct device_node *np,
  62                                 struct dma_chan *(*of_dma_xlate)
  63                                 (struct of_phandle_args *, struct of_dma *),
  64                                 void *data)
  65 {
  66         struct of_dma   *ofdma;
  67         int             nbcells;
  68         const __be32    *prop;
  69
  70         if (!np || !of_dma_xlate) {
  71                 pr_err("%s: not enough information provided\n", __func__);
  72                 return -EINVAL;
  73         }
  74
  75         ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
  76         if (!ofdma)
  77                 return -ENOMEM;
  78
  79         prop = of_get_property(np, "#dma-cells", NULL);
  80         if (prop)
  81                 nbcells = be32_to_cpup(prop);
  82
  83         if (!prop || !nbcells) {
  84                 pr_err("%s: #dma-cells property is missing or invalid\n",
  85                        __func__);
  86                 kfree(ofdma);
  87                 return -EINVAL;
  88         }
  89
  90         ofdma->of_node = np;
  91         ofdma->of_dma_nbcells = nbcells;
  92         ofdma->of_dma_xlate = of_dma_xlate;
  93         ofdma->of_dma_data = data;
  94
  95         /* Now queue of_dma controller structure in list */
  96         mutex_lock(&of_dma_lock);
  97         list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
  98         mutex_unlock(&of_dma_lock);
  99
 100         return 0;
 101 }
 102 EXPORT_SYMBOL_GPL(of_dma_controller_register);
 103
 104 /**
 105  * of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
 106  * @np:         device node of DMA controller
 107  *
 108  * Memory allocated by of_dma_controller_register() is freed here.
 109  */
 110 void of_dma_controller_free(struct device_node *np)
 111 {
 112         struct of_dma *ofdma;
 113
 114         mutex_lock(&of_dma_lock);
 115
 116         list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
 117                 if (ofdma->of_node == np) {
 118                         list_del(&ofdma->of_dma_controllers);
 119                         kfree(ofdma);
 120                         break;
 121                 }
 122
 123         mutex_unlock(&of_dma_lock);
 124 }
 125 EXPORT_SYMBOL_GPL(of_dma_controller_free);
 126
 127 /**
 128  * of_dma_match_channel - Check if a DMA specifier matches name
 129  * @np:         device node to look for DMA channels
 130  * @name:       channel name to be matched
 131  * @index:      index of DMA specifier in list of DMA specifiers
 132  * @dma_spec:   pointer to DMA specifier as found in the device tree
 133  *
 134  * Check if the DMA specifier pointed to by the index in a list of DMA
 135  * specifiers, matches the name provided. Returns 0 if the name matches and
 136  * a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
 137  */
 138 static int of_dma_match_channel(struct device_node *np, const char *name,
 139                                 int index, struct of_phandle_args *dma_spec)
 140 {
 141         const char *s;
 142
 143         if (of_property_read_string_index(np, "dma-names", index, &s))
 144                 return -ENODEV;
 145
 146         if (strcmp(name, s))
 147                 return -ENODEV;
 148
 149         if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
 150                                        dma_spec))
 151                 return -ENODEV;
 152
 153         return 0;
 154 }
 155
 156 /**
 157  * of_dma_request_slave_channel - Get the DMA slave channel
 158  * @np:         device node to get DMA request from
 159  * @name:       name of desired channel
 160  *
 161  * Returns pointer to appropriate dma channel on success or NULL on error.
 162  */
 163 struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
 164                                               const char *name)
 165 {
 166         struct of_phandle_args  dma_spec;
 167         struct of_dma           *ofdma;
 168         struct dma_chan         *chan;
 169         int                     count, i;
 170
 171         if (!np || !name) {
 172                 pr_err("%s: not enough information provided\n", __func__);
 173                 return NULL;
 174         }
 175
 176         count = of_property_count_strings(np, "dma-names");
 177         if (count < 0) {
 178                 pr_err("%s: dma-names property missing or empty\n", __func__);
 179                 return NULL;
 180         }
 181
 182         for (i = 0; i < count; i++) {
 183                 if (of_dma_match_channel(np, name, i, &dma_spec))
 184                         continue;
 185
 186                 mutex_lock(&of_dma_lock);
 187                 ofdma = of_dma_find_controller(&dma_spec);
 188
 189                 if (ofdma)
 190                         chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
 191                 else
 192                         chan = NULL;
 193
 194                 mutex_unlock(&of_dma_lock);
 195
 196                 of_node_put(dma_spec.np);
 197
 198                 if (chan)
 199                         return chan;
 200         }
 201
 202         return NULL;
 203 }
 204
 205 /**
 206  * of_dma_simple_xlate - Simple DMA engine translation function
 207  * @dma_spec:   pointer to DMA specifier as found in the device tree
 208  * @of_dma:     pointer to DMA controller data
 209  *
 210  * A simple translation function for devices that use a 32-bit value for the
 211  * filter_param when calling the DMA engine dma_request_channel() function.
 212  * Note that this translation function requires that #dma-cells is equal to 1
 213  * and the argument of the dma specifier is the 32-bit filter_param. Returns
 214  * pointer to appropriate dma channel on success or NULL on error.
 215  */
 216 struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
 217                                                 struct of_dma *ofdma)
 218 {
 219         int count = dma_spec->args_count;
 220         struct of_dma_filter_info *info = ofdma->of_dma_data;
 221
 222         if (!info || !info->filter_fn)
 223                 return NULL;
 224
 225         if (count != 1)
 226                 return NULL;
 227
 228         return dma_request_channel(info->dma_cap, info->filter_fn,
 229                         &dma_spec->args[0]);
 230 }
 231 EXPORT_SYMBOL_GPL(of_dma_simple_xlate);