kernel/drivers/dma/virt-dma.c

   1 /*
   2  * Virtual DMA channel support for DMAengine
   3  *
   4  * Copyright (C) 2012 Russell King
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10 #include <linux/device.h>
  11 #include <linux/dmaengine.h>
  12 #include <linux/module.h>
  13 #include <linux/spinlock.h>
  14
  15 #include "virt-dma.h"
  16
  17 static struct virt_dma_desc *to_virt_desc(struct dma_async_tx_descriptor *tx)
  18 {
  19         return container_of(tx, struct virt_dma_desc, tx);
  20 }
  21
  22 dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *tx)
  23 {
  24         struct virt_dma_chan *vc = to_virt_chan(tx->chan);
  25         struct virt_dma_desc *vd = to_virt_desc(tx);
  26         unsigned long flags;
  27         dma_cookie_t cookie;
  28
  29         spin_lock_irqsave(&vc->lock, flags);
  30         cookie = dma_cookie_assign(tx);
  31
  32         list_add_tail(&vd->node, &vc->desc_submitted);
  33         spin_unlock_irqrestore(&vc->lock, flags);
  34
  35         dev_dbg(vc->chan.device->dev, "vchan %p: txd %p[%x]: submitted\n",
  36                 vc, vd, cookie);
  37
  38         return cookie;
  39 }
  40 EXPORT_SYMBOL_GPL(vchan_tx_submit);
  41
  42 struct virt_dma_desc *vchan_find_desc(struct virt_dma_chan *vc,
  43         dma_cookie_t cookie)
  44 {
  45         struct virt_dma_desc *vd;
  46
  47         list_for_each_entry(vd, &vc->desc_issued, node)
  48                 if (vd->tx.cookie == cookie)
  49                         return vd;
  50
  51         return NULL;
  52 }
  53 EXPORT_SYMBOL_GPL(vchan_find_desc);
  54
  55 /*
  56  * This tasklet handles the completion of a DMA descriptor by
  57  * calling its callback and freeing it.
  58  */
  59 static void vchan_complete(unsigned long arg)
  60 {
  61         struct virt_dma_chan *vc = (struct virt_dma_chan *)arg;
  62         struct virt_dma_desc *vd;
  63         dma_async_tx_callback cb = NULL;
  64         void *cb_data = NULL;
  65         LIST_HEAD(head);
  66
  67         spin_lock_irq(&vc->lock);
  68         list_splice_tail_init(&vc->desc_completed, &head);
  69         vd = vc->cyclic;
  70         if (vd) {
  71                 vc->cyclic = NULL;
  72                 cb = vd->tx.callback;
  73                 cb_data = vd->tx.callback_param;
  74         }
  75         spin_unlock_irq(&vc->lock);
  76
  77         if (cb)
  78                 cb(cb_data);
  79
  80         while (!list_empty(&head)) {
  81                 vd = list_first_entry(&head, struct virt_dma_desc, node);
  82                 cb = vd->tx.callback;
  83                 cb_data = vd->tx.callback_param;
  84
  85                 list_del(&vd->node);
  86
  87                 vc->desc_free(vd);
  88
  89                 if (cb)
  90                         cb(cb_data);
  91         }
  92 }
  93
  94 void vchan_dma_desc_free_list(struct virt_dma_chan *vc, struct list_head *head)
  95 {
  96         while (!list_empty(head)) {
  97                 struct virt_dma_desc *vd = list_first_entry(head,
  98                         struct virt_dma_desc, node);
  99                 list_del(&vd->node);
 100                 dev_dbg(vc->chan.device->dev, "txd %p: freeing\n", vd);
 101                 vc->desc_free(vd);
 102         }
 103 }
 104 EXPORT_SYMBOL_GPL(vchan_dma_desc_free_list);
 105
 106 void vchan_init(struct virt_dma_chan *vc, struct dma_device *dmadev)
 107 {
 108         dma_cookie_init(&vc->chan);
 109
 110         spin_lock_init(&vc->lock);
 111         INIT_LIST_HEAD(&vc->desc_submitted);
 112         INIT_LIST_HEAD(&vc->desc_issued);
 113         INIT_LIST_HEAD(&vc->desc_completed);
 114
 115         tasklet_init(&vc->task, vchan_complete, (unsigned long)vc);
 116
 117         vc->chan.device = dmadev;
 118         list_add_tail(&vc->chan.device_node, &dmadev->channels);
 119 }
 120 EXPORT_SYMBOL_GPL(vchan_init);
 121
 122 MODULE_AUTHOR("Russell King");
 123 MODULE_LICENSE("GPL");