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 %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  */
  60 int 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 }
  87 EXPORT_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  */
  95 void 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 }
 110 EXPORT_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  */
 123 static 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 an error pointer.
 147  */
 148 struct 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         int                     ret_no_channel = -ENODEV;
 156
 157         if (!np || !name) {
 158                 pr_err("%s: not enough information provided\n", __func__);
 159                 return ERR_PTR(-ENODEV);
 160         }
 161
 162         count = of_property_count_strings(np, "dma-names");
 163         if (count < 0) {
 164                 pr_err("%s: dma-names property of node '%s' missing or empty\n",
 165                         __func__, np->full_name);
 166                 return ERR_PTR(-ENODEV);
 167         }
 168
 169         for (i = 0; i < count; i++) {
 170                 if (of_dma_match_channel(np, name, i, &dma_spec))
 171                         continue;
 172
 173                 mutex_lock(&of_dma_lock);
 174                 ofdma = of_dma_find_controller(&dma_spec);
 175
 176                 if (ofdma) {
 177                         chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
 178                 } else {
 179                         ret_no_channel = -EPROBE_DEFER;
 180                         chan = NULL;
 181                 }
 182
 183                 mutex_unlock(&of_dma_lock);
 184
 185                 of_node_put(dma_spec.np);
 186
 187                 if (chan)
 188                         return chan;
 189         }
 190
 191         return ERR_PTR(ret_no_channel);
 192 }
 193
 194 /**
 195  * of_dma_simple_xlate - Simple DMA engine translation function
 196  * @dma_spec:   pointer to DMA specifier as found in the device tree
 197  * @of_dma:     pointer to DMA controller data
 198  *
 199  * A simple translation function for devices that use a 32-bit value for the
 200  * filter_param when calling the DMA engine dma_request_channel() function.
 201  * Note that this translation function requires that #dma-cells is equal to 1
 202  * and the argument of the dma specifier is the 32-bit filter_param. Returns
 203  * pointer to appropriate dma channel on success or NULL on error.
 204  */
 205 struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
 206                                                 struct of_dma *ofdma)
 207 {
 208         int count = dma_spec->args_count;
 209         struct of_dma_filter_info *info = ofdma->of_dma_data;
 210
 211         if (!info || !info->filter_fn)
 212                 return NULL;
 213
 214         if (count != 1)
 215                 return NULL;
 216
 217         return dma_request_channel(info->dma_cap, info->filter_fn,
 218                         &dma_spec->args[0]);
 219 }
 220 EXPORT_SYMBOL_GPL(of_dma_simple_xlate);