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	dma_cookie_t cookie;
 88
 89	cookie = vd->tx.cookie;
 90	dma_cookie_complete(&vd->tx);
 91	dev_vdbg(vc->chan.device->dev, "txd %p[%x]: marked complete\n",
 92		 vd, cookie);
 93	list_add_tail(&vd->node, &vc->desc_completed);
 94
 95	tasklet_schedule(&vc->task);
 96}
 97
 98/**
 99 * vchan_cyclic_callback - report the completion of a period
100 * vd: virtual descriptor
101 */
102static inline void vchan_cyclic_callback(struct virt_dma_desc *vd)
103{
104	struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
105
106	vc->cyclic = vd;
107	tasklet_schedule(&vc->task);
108}
109
110/**
111 * vchan_next_desc - peek at the next descriptor to be processed
112 * vc: virtual channel to obtain descriptor from
113 *
114 * vc.lock must be held by caller
115 */
116static inline struct virt_dma_desc *vchan_next_desc(struct virt_dma_chan *vc)
117{
118	if (list_empty(&vc->desc_issued))
119		return NULL;
120
121	return list_first_entry(&vc->desc_issued, struct virt_dma_desc, node);
122}
123
124/**
125 * vchan_get_all_descriptors - obtain all submitted and issued descriptors
126 * vc: virtual channel to get descriptors from
127 * head: list of descriptors found
128 *
129 * vc.lock must be held by caller
130 *
131 * Removes all submitted and issued descriptors from internal lists, and
132 * provides a list of all descriptors found
133 */
134static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc,
135	struct list_head *head)
136{
137	list_splice_tail_init(&vc->desc_submitted, head);
138	list_splice_tail_init(&vc->desc_issued, head);
139	list_splice_tail_init(&vc->desc_completed, head);
140}
141
142static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
143{
144	unsigned long flags;
145	LIST_HEAD(head);
146
147	spin_lock_irqsave(&vc->lock, flags);
148	vchan_get_all_descriptors(vc, &head);
149	spin_unlock_irqrestore(&vc->lock, flags);
150
151	vchan_dma_desc_free_list(vc, &head);
152}
153
154#endif