linux/drivers/dma/of-dma.c
<<
>>
Prefs
   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                        return ofdma;
  40
  41        pr_debug("%s: can't find DMA controller %s\n", __func__,
  42                 dma_spec->np->full_name);
  43
  44        return NULL;
  45}
  46
  47/**
  48 * of_dma_controller_register - Register a DMA controller to DT DMA helpers
  49 * @np:                 device node of DMA controller
  50 * @of_dma_xlate:       translation function which converts a phandle
  51 *                      arguments list into a dma_chan structure
  52 * @data                pointer to controller specific data to be used by
  53 *                      translation function
  54 *
  55 * Returns 0 on success or appropriate errno value on error.
  56 *
  57 * Allocated memory should be freed with appropriate of_dma_controller_free()
  58 * call.
  59 */
  60int of_dma_controller_register(struct device_node *np,
  61                                struct dma_chan *(*of_dma_xlate)
  62                                (struct of_phandle_args *, struct of_dma *),
  63                                void *data)
  64{
  65        struct of_dma   *ofdma;
  66
  67        if (!np || !of_dma_xlate) {
  68                pr_err("%s: not enough information provided\n", __func__);
  69                return -EINVAL;
  70        }
  71
  72        ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
  73        if (!ofdma)
  74                return -ENOMEM;
  75
  76        ofdma->of_node = np;
  77        ofdma->of_dma_xlate = of_dma_xlate;
  78        ofdma->of_dma_data = data;
  79
  80        /* Now queue of_dma controller structure in list */
  81        mutex_lock(&of_dma_lock);
  82        list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
  83        mutex_unlock(&of_dma_lock);
  84
  85        return 0;
  86}
  87EXPORT_SYMBOL_GPL(of_dma_controller_register);
  88
  89/**
  90 * of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
  91 * @np:         device node of DMA controller
  92 *
  93 * Memory allocated by of_dma_controller_register() is freed here.
  94 */
  95void of_dma_controller_free(struct device_node *np)
  96{
  97        struct of_dma *ofdma;
  98
  99        mutex_lock(&of_dma_lock);
 100
 101        list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
 102                if (ofdma->of_node == np) {
 103                        list_del(&ofdma->of_dma_controllers);
 104                        kfree(ofdma);
 105                        break;
 106                }
 107
 108        mutex_unlock(&of_dma_lock);
 109}
 110EXPORT_SYMBOL_GPL(of_dma_controller_free);
 111
 112/**
 113 * of_dma_match_channel - Check if a DMA specifier matches name
 114 * @np:         device node to look for DMA channels
 115 * @name:       channel name to be matched
 116 * @index:      index of DMA specifier in list of DMA specifiers
 117 * @dma_spec:   pointer to DMA specifier as found in the device tree
 118 *
 119 * Check if the DMA specifier pointed to by the index in a list of DMA
 120 * specifiers, matches the name provided. Returns 0 if the name matches and
 121 * a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
 122 */
 123static int of_dma_match_channel(struct device_node *np, const char *name,
 124                                int index, struct of_phandle_args *dma_spec)
 125{
 126        const char *s;
 127
 128        if (of_property_read_string_index(np, "dma-names", index, &s))
 129                return -ENODEV;
 130
 131        if (strcmp(name, s))
 132                return -ENODEV;
 133
 134        if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
 135                                       dma_spec))
 136                return -ENODEV;
 137
 138        return 0;
 139}
 140
 141/**
 142 * of_dma_request_slave_channel - Get the DMA slave channel
 143 * @np:         device node to get DMA request from
 144 * @name:       name of desired channel
 145 *
 146 * Returns pointer to appropriate dma channel on success or NULL on error.
 147 */
 148struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
 149                                              const char *name)
 150{
 151        struct of_phandle_args  dma_spec;
 152        struct of_dma           *ofdma;
 153        struct dma_chan         *chan;
 154        int                     count, i;
 155
 156        if (!np || !name) {
 157                pr_err("%s: not enough information provided\n", __func__);
 158                return NULL;
 159        }
 160
 161        count = of_property_count_strings(np, "dma-names");
 162        if (count < 0) {
 163                pr_err("%s: dma-names property missing or empty\n", __func__);
 164                return NULL;
 165        }
 166
 167        for (i = 0; i < count; i++) {
 168                if (of_dma_match_channel(np, name, i, &dma_spec))
 169                        continue;
 170
 171                mutex_lock(&of_dma_lock);
 172                ofdma = of_dma_find_controller(&dma_spec);
 173
 174                if (ofdma)
 175                        chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
 176                else
 177                        chan = NULL;
 178
 179                mutex_unlock(&of_dma_lock);
 180
 181                of_node_put(dma_spec.np);
 182
 183                if (chan)
 184                        return chan;
 185        }
 186
 187        return NULL;
 188}
 189
 190/**
 191 * of_dma_simple_xlate - Simple DMA engine translation function
 192 * @dma_spec:   pointer to DMA specifier as found in the device tree
 193 * @of_dma:     pointer to DMA controller data
 194 *
 195 * A simple translation function for devices that use a 32-bit value for the
 196 * filter_param when calling the DMA engine dma_request_channel() function.
 197 * Note that this translation function requires that #dma-cells is equal to 1
 198 * and the argument of the dma specifier is the 32-bit filter_param. Returns
 199 * pointer to appropriate dma channel on success or NULL on error.
 200 */
 201struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
 202                                                struct of_dma *ofdma)
 203{
 204        int count = dma_spec->args_count;
 205        struct of_dma_filter_info *info = ofdma->of_dma_data;
 206
 207        if (!info || !info->filter_fn)
 208                return NULL;
 209
 210        if (count != 1)
 211                return NULL;
 212
 213        return dma_request_channel(info->dma_cap, info->filter_fn,
 214                        &dma_spec->args[0]);
 215}
 216EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
 217
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.