linux/drivers/dma/of-dma.c
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   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                    (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 */
  61int 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}
 102EXPORT_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 */
 110void 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}
 125EXPORT_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 */
 138static 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 */
 163struct 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 */
 216struct 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}
 231EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
 232
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