linux/drivers/dma/virt-dma.c
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   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
  17static 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
  22dma_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}
  40EXPORT_SYMBOL_GPL(vchan_tx_submit);
  41
  42struct 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}
  53EXPORT_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 */
  59static 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
  94void 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}
 104EXPORT_SYMBOL_GPL(vchan_dma_desc_free_list);
 105
 106void 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}
 120EXPORT_SYMBOL_GPL(vchan_init);
 121
 122MODULE_AUTHOR("Russell King");
 123MODULE_LICENSE("GPL");
 124
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