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_allocated;
 33	struct list_head desc_submitted;
 34	struct list_head desc_issued;
 35	struct list_head desc_completed;
 36
 37	struct virt_dma_desc *cyclic;
 38};
 39
 40static inline struct virt_dma_chan *to_virt_chan(struct dma_chan *chan)
 41{
 42	return container_of(chan, struct virt_dma_chan, chan);
 43}
 44
 45void vchan_dma_desc_free_list(struct virt_dma_chan *vc, struct list_head *head);
 46void vchan_init(struct virt_dma_chan *vc, struct dma_device *dmadev);
 47struct virt_dma_desc *vchan_find_desc(struct virt_dma_chan *, dma_cookie_t);
 48
 49/**
 50 * vchan_tx_prep - prepare a descriptor
 51 * @vc: virtual channel allocating this descriptor
 52 * @vd: virtual descriptor to prepare
 53 * @tx_flags: flags argument passed in to prepare function
 54 */
 55static inline struct dma_async_tx_descriptor *vchan_tx_prep(struct virt_dma_chan *vc,
 56	struct virt_dma_desc *vd, unsigned long tx_flags)
 57{
 58	extern dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *);
 59	extern int vchan_tx_desc_free(struct dma_async_tx_descriptor *);
 60	unsigned long flags;
 61
 62	dma_async_tx_descriptor_init(&vd->tx, &vc->chan);
 63	vd->tx.flags = tx_flags;
 64	vd->tx.tx_submit = vchan_tx_submit;
 65	vd->tx.desc_free = vchan_tx_desc_free;
 66
 67	spin_lock_irqsave(&vc->lock, flags);
 68	list_add_tail(&vd->node, &vc->desc_allocated);
 69	spin_unlock_irqrestore(&vc->lock, flags);
 70
 71	return &vd->tx;
 72}
 73
 74/**
 75 * vchan_issue_pending - move submitted descriptors to issued list
 76 * @vc: virtual channel to update
 77 *
 78 * vc.lock must be held by caller
 79 */
 80static inline bool vchan_issue_pending(struct virt_dma_chan *vc)
 81{
 82	list_splice_tail_init(&vc->desc_submitted, &vc->desc_issued);
 83	return !list_empty(&vc->desc_issued);
 84}
 85
 86/**
 87 * vchan_cookie_complete - report completion of a descriptor
 88 * @vd: virtual descriptor to update
 89 *
 90 * vc.lock must be held by caller
 91 */
 92static inline void vchan_cookie_complete(struct virt_dma_desc *vd)
 93{
 94	struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
 95	dma_cookie_t cookie;
 96
 97	cookie = vd->tx.cookie;
 98	dma_cookie_complete(&vd->tx);
 99	dev_vdbg(vc->chan.device->dev, "txd %p[%x]: marked complete\n",
100		 vd, cookie);
101	list_add_tail(&vd->node, &vc->desc_completed);
102
103	tasklet_schedule(&vc->task);
104}
105
106/**
107 * vchan_cyclic_callback - report the completion of a period
108 * @vd: virtual descriptor
109 */
110static inline void vchan_cyclic_callback(struct virt_dma_desc *vd)
111{
112	struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
113
114	vc->cyclic = vd;
115	tasklet_schedule(&vc->task);
116}
117
118/**
119 * vchan_next_desc - peek at the next descriptor to be processed
120 * @vc: virtual channel to obtain descriptor from
121 *
122 * vc.lock must be held by caller
123 */
124static inline struct virt_dma_desc *vchan_next_desc(struct virt_dma_chan *vc)
125{
126	if (list_empty(&vc->desc_issued))
127		return NULL;
128
129	return list_first_entry(&vc->desc_issued, struct virt_dma_desc, node);
130}
131
132/**
133 * vchan_get_all_descriptors - obtain all submitted and issued descriptors
134 * @vc: virtual channel to get descriptors from
135 * @head: list of descriptors found
136 *
137 * vc.lock must be held by caller
138 *
139 * Removes all submitted and issued descriptors from internal lists, and
140 * provides a list of all descriptors found
141 */
142static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc,
143	struct list_head *head)
144{
145	list_splice_tail_init(&vc->desc_allocated, head);
146	list_splice_tail_init(&vc->desc_submitted, head);
147	list_splice_tail_init(&vc->desc_issued, head);
148	list_splice_tail_init(&vc->desc_completed, head);
149}
150
151static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
152{
153	struct virt_dma_desc *vd;
154	unsigned long flags;
155	LIST_HEAD(head);
156
157	spin_lock_irqsave(&vc->lock, flags);
158	vchan_get_all_descriptors(vc, &head);
159	list_for_each_entry(vd, &head, node)
160		dmaengine_desc_clear_reuse(&vd->tx);
161	spin_unlock_irqrestore(&vc->lock, flags);
162
163	vchan_dma_desc_free_list(vc, &head);
164}
165
166/**
167 * vchan_synchronize() - synchronize callback execution to the current context
168 * @vc: virtual channel to synchronize
169 *
170 * Makes sure that all scheduled or active callbacks have finished running. For
171 * proper operation the caller has to ensure that no new callbacks are scheduled
172 * after the invocation of this function started.
173 */
174static inline void vchan_synchronize(struct virt_dma_chan *vc)
175{
176	tasklet_kill(&vc->task);
177}
178
179#endif