linux/drivers/dma/virt-dma.h
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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#ifndef VIRT_DMA_H
  11#define VIRT_DMA_H
  12
  13#include <linux/dmaengine.h>
  14#include <linux/interrupt.h>
  15
  16#include "dmaengine.h"
  17
  18struct virt_dma_desc {
  19        struct dma_async_tx_descriptor tx;
  20        /* protected by vc.lock */
  21        struct list_head node;
  22};
  23
  24struct virt_dma_chan {
  25        struct dma_chan chan;
  26        struct tasklet_struct task;
  27        void (*desc_free)(struct virt_dma_desc *);
  28
  29        spinlock_t lock;
  30
  31        /* protected by vc.lock */
  32        struct list_head desc_submitted;
  33        struct list_head desc_issued;
  34        struct list_head desc_completed;
  35
  36        struct virt_dma_desc *cyclic;
  37};
  38
  39static inline struct virt_dma_chan *to_virt_chan(struct dma_chan *chan)
  40{
  41        return container_of(chan, struct virt_dma_chan, chan);
  42}
  43
  44void vchan_dma_desc_free_list(struct virt_dma_chan *vc, struct list_head *head);
  45void vchan_init(struct virt_dma_chan *vc, struct dma_device *dmadev);
  46struct virt_dma_desc *vchan_find_desc(struct virt_dma_chan *, dma_cookie_t);
  47
  48/**
  49 * vchan_tx_prep - prepare a descriptor
  50 * vc: virtual channel allocating this descriptor
  51 * vd: virtual descriptor to prepare
  52 * tx_flags: flags argument passed in to prepare function
  53 */
  54static inline struct dma_async_tx_descriptor *vchan_tx_prep(struct virt_dma_chan *vc,
  55        struct virt_dma_desc *vd, unsigned long tx_flags)
  56{
  57        extern dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *);
  58
  59        dma_async_tx_descriptor_init(&vd->tx, &vc->chan);
  60        vd->tx.flags = tx_flags;
  61        vd->tx.tx_submit = vchan_tx_submit;
  62
  63        return &vd->tx;
  64}
  65
  66/**
  67 * vchan_issue_pending - move submitted descriptors to issued list
  68 * vc: virtual channel to update
  69 *
  70 * vc.lock must be held by caller
  71 */
  72static inline bool vchan_issue_pending(struct virt_dma_chan *vc)
  73{
  74        list_splice_tail_init(&vc->desc_submitted, &vc->desc_issued);
  75        return !list_empty(&vc->desc_issued);
  76}
  77
  78/**
  79 * vchan_cookie_complete - report completion of a descriptor
  80 * vd: virtual descriptor to update
  81 *
  82 * vc.lock must be held by caller
  83 */
  84static inline void vchan_cookie_complete(struct virt_dma_desc *vd)
  85{
  86        struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
  87
  88        dma_cookie_complete(&vd->tx);
  89        dev_vdbg(vc->chan.device->dev, "txd %p[%x]: marked complete\n",
  90                vd, vd->tx.cookie);
  91        list_add_tail(&vd->node, &vc->desc_completed);
  92
  93        tasklet_schedule(&vc->task);
  94}
  95
  96/**
  97 * vchan_cyclic_callback - report the completion of a period
  98 * vd: virtual descriptor
  99 */
 100static inline void vchan_cyclic_callback(struct virt_dma_desc *vd)
 101{
 102        struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
 103
 104        vc->cyclic = vd;
 105        tasklet_schedule(&vc->task);
 106}
 107
 108/**
 109 * vchan_next_desc - peek at the next descriptor to be processed
 110 * vc: virtual channel to obtain descriptor from
 111 *
 112 * vc.lock must be held by caller
 113 */
 114static inline struct virt_dma_desc *vchan_next_desc(struct virt_dma_chan *vc)
 115{
 116        if (list_empty(&vc->desc_issued))
 117                return NULL;
 118
 119        return list_first_entry(&vc->desc_issued, struct virt_dma_desc, node);
 120}
 121
 122/**
 123 * vchan_get_all_descriptors - obtain all submitted and issued descriptors
 124 * vc: virtual channel to get descriptors from
 125 * head: list of descriptors found
 126 *
 127 * vc.lock must be held by caller
 128 *
 129 * Removes all submitted and issued descriptors from internal lists, and
 130 * provides a list of all descriptors found
 131 */
 132static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc,
 133        struct list_head *head)
 134{
 135        list_splice_tail_init(&vc->desc_submitted, head);
 136        list_splice_tail_init(&vc->desc_issued, head);
 137        list_splice_tail_init(&vc->desc_completed, head);
 138}
 139
 140static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
 141{
 142        unsigned long flags;
 143        LIST_HEAD(head);
 144
 145        spin_lock_irqsave(&vc->lock, flags);
 146        vchan_get_all_descriptors(vc, &head);
 147        spin_unlock_irqrestore(&vc->lock, flags);
 148
 149        vchan_dma_desc_free_list(vc, &head);
 150}
 151
 152#endif
 153
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