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_move_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 /**
  43  * vchan_tx_desc_free - free a reusable descriptor
  44  * @tx: the transfer
  45  *
  46  * This function frees a previously allocated reusable descriptor. The only
  47  * other way is to clear the DMA_CTRL_REUSE flag and submit one last time the
  48  * transfer.
  49  *
  50  * Returns 0 upon success
  51  */
  52 int vchan_tx_desc_free(struct dma_async_tx_descriptor *tx)
  53 {
  54         struct virt_dma_chan *vc = to_virt_chan(tx->chan);
  55         struct virt_dma_desc *vd = to_virt_desc(tx);
  56         unsigned long flags;
  57
  58         spin_lock_irqsave(&vc->lock, flags);
  59         list_del(&vd->node);
  60         spin_unlock_irqrestore(&vc->lock, flags);
  61
  62         dev_dbg(vc->chan.device->dev, "vchan %p: txd %p[%x]: freeing\n",
  63                 vc, vd, vd->tx.cookie);
  64         vc->desc_free(vd);
  65         return 0;
  66 }
  67 EXPORT_SYMBOL_GPL(vchan_tx_desc_free);
  68
  69 struct virt_dma_desc *vchan_find_desc(struct virt_dma_chan *vc,
  70         dma_cookie_t cookie)
  71 {
  72         struct virt_dma_desc *vd;
  73
  74         list_for_each_entry(vd, &vc->desc_issued, node)
  75                 if (vd->tx.cookie == cookie)
  76                         return vd;
  77
  78         return NULL;
  79 }
  80 EXPORT_SYMBOL_GPL(vchan_find_desc);
  81
  82 /*
  83  * This tasklet handles the completion of a DMA descriptor by
  84  * calling its callback and freeing it.
  85  */
  86 static void vchan_complete(unsigned long arg)
  87 {
  88         struct virt_dma_chan *vc = (struct virt_dma_chan *)arg;
  89         struct virt_dma_desc *vd;
  90         struct dmaengine_desc_callback cb;
  91         LIST_HEAD(head);
  92
  93         spin_lock_irq(&vc->lock);
  94         list_splice_tail_init(&vc->desc_completed, &head);
  95         vd = vc->cyclic;
  96         if (vd) {
  97                 vc->cyclic = NULL;
  98                 dmaengine_desc_get_callback(&vd->tx, &cb);
  99         } else {
 100                 memset(&cb, 0, sizeof(cb));
 101         }
 102         spin_unlock_irq(&vc->lock);
 103
 104         dmaengine_desc_callback_invoke(&cb, NULL);
 105
 106         while (!list_empty(&head)) {
 107                 vd = list_first_entry(&head, struct virt_dma_desc, node);
 108                 dmaengine_desc_get_callback(&vd->tx, &cb);
 109
 110                 list_del(&vd->node);
 111                 if (dmaengine_desc_test_reuse(&vd->tx))
 112                         list_add(&vd->node, &vc->desc_allocated);
 113                 else
 114                         vc->desc_free(vd);
 115
 116                 dmaengine_desc_callback_invoke(&cb, NULL);
 117         }
 118 }
 119
 120 void vchan_dma_desc_free_list(struct virt_dma_chan *vc, struct list_head *head)
 121 {
 122         while (!list_empty(head)) {
 123                 struct virt_dma_desc *vd = list_first_entry(head,
 124                         struct virt_dma_desc, node);
 125                 if (dmaengine_desc_test_reuse(&vd->tx)) {
 126                         list_move_tail(&vd->node, &vc->desc_allocated);
 127                 } else {
 128                         dev_dbg(vc->chan.device->dev, "txd %p: freeing\n", vd);
 129                         list_del(&vd->node);
 130                         vc->desc_free(vd);
 131                 }
 132         }
 133 }
 134 EXPORT_SYMBOL_GPL(vchan_dma_desc_free_list);
 135
 136 void vchan_init(struct virt_dma_chan *vc, struct dma_device *dmadev)
 137 {
 138         dma_cookie_init(&vc->chan);
 139
 140         spin_lock_init(&vc->lock);
 141         INIT_LIST_HEAD(&vc->desc_allocated);
 142         INIT_LIST_HEAD(&vc->desc_submitted);
 143         INIT_LIST_HEAD(&vc->desc_issued);
 144         INIT_LIST_HEAD(&vc->desc_completed);
 145
 146         tasklet_init(&vc->task, vchan_complete, (unsigned long)vc);
 147
 148         vc->chan.device = dmadev;
 149         list_add_tail(&vc->chan.device_node, &dmadev->channels);
 150 }
 151 EXPORT_SYMBOL_GPL(vchan_init);
 152
 153 MODULE_AUTHOR("Russell King");
 154 MODULE_LICENSE("GPL");