virt-dma.c
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/*
* Virtual DMA channel support for DMAengine
*
* Copyright (C) 2012 Russell King
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/device.h>
#include <linux/dmaengine.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include "virt-dma.h"
static struct virt_dma_desc *to_virt_desc(struct dma_async_tx_descriptor *tx)
{
return container_of(tx, struct virt_dma_desc, tx);
}
dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *tx)
{
struct virt_dma_chan *vc = to_virt_chan(tx->chan);
struct virt_dma_desc *vd = to_virt_desc(tx);
unsigned long flags;
dma_cookie_t cookie;
spin_lock_irqsave(&vc->lock, flags);
cookie = dma_cookie_assign(tx);
list_move_tail(&vd->node, &vc->desc_submitted);
spin_unlock_irqrestore(&vc->lock, flags);
dev_dbg(vc->chan.device->dev, "vchan %p: txd %p[%x]: submitted\n",
vc, vd, cookie);
return cookie;
}
EXPORT_SYMBOL_GPL(vchan_tx_submit);
/**
* vchan_tx_desc_free - free a reusable descriptor
* @tx: the transfer
*
* This function frees a previously allocated reusable descriptor. The only
* other way is to clear the DMA_CTRL_REUSE flag and submit one last time the
* transfer.
*
* Returns 0 upon success
*/
int vchan_tx_desc_free(struct dma_async_tx_descriptor *tx)
{
struct virt_dma_chan *vc = to_virt_chan(tx->chan);
struct virt_dma_desc *vd = to_virt_desc(tx);
unsigned long flags;
spin_lock_irqsave(&vc->lock, flags);
list_del(&vd->node);
spin_unlock_irqrestore(&vc->lock, flags);
dev_dbg(vc->chan.device->dev, "vchan %p: txd %p[%x]: freeing\n",
vc, vd, vd->tx.cookie);
vc->desc_free(vd);
return 0;
}
EXPORT_SYMBOL_GPL(vchan_tx_desc_free);
struct virt_dma_desc *vchan_find_desc(struct virt_dma_chan *vc,
dma_cookie_t cookie)
{
struct virt_dma_desc *vd;
list_for_each_entry(vd, &vc->desc_issued, node)
if (vd->tx.cookie == cookie)
return vd;
return NULL;
}
EXPORT_SYMBOL_GPL(vchan_find_desc);
/*
* This tasklet handles the completion of a DMA descriptor by
* calling its callback and freeing it.
*/
static void vchan_complete(unsigned long arg)
{
struct virt_dma_chan *vc = (struct virt_dma_chan *)arg;
struct virt_dma_desc *vd, *_vd;
struct dmaengine_desc_callback cb;
LIST_HEAD(head);
spin_lock_irq(&vc->lock);
list_splice_tail_init(&vc->desc_completed, &head);
vd = vc->cyclic;
if (vd) {
vc->cyclic = NULL;
dmaengine_desc_get_callback(&vd->tx, &cb);
} else {
memset(&cb, 0, sizeof(cb));
}
spin_unlock_irq(&vc->lock);
dmaengine_desc_callback_invoke(&cb, NULL);
list_for_each_entry_safe(vd, _vd, &head, node) {
dmaengine_desc_get_callback(&vd->tx, &cb);
list_del(&vd->node);
dmaengine_desc_callback_invoke(&cb, NULL);
if (dmaengine_desc_test_reuse(&vd->tx))
list_add(&vd->node, &vc->desc_allocated);
else
vc->desc_free(vd);
}
}
void vchan_dma_desc_free_list(struct virt_dma_chan *vc, struct list_head *head)
{
struct virt_dma_desc *vd, *_vd;
list_for_each_entry_safe(vd, _vd, head, node) {
if (dmaengine_desc_test_reuse(&vd->tx)) {
list_move_tail(&vd->node, &vc->desc_allocated);
} else {
dev_dbg(vc->chan.device->dev, "txd %p: freeing\n", vd);
list_del(&vd->node);
vc->desc_free(vd);
}
}
}
EXPORT_SYMBOL_GPL(vchan_dma_desc_free_list);
void vchan_init(struct virt_dma_chan *vc, struct dma_device *dmadev)
{
dma_cookie_init(&vc->chan);
spin_lock_init(&vc->lock);
INIT_LIST_HEAD(&vc->desc_allocated);
INIT_LIST_HEAD(&vc->desc_submitted);
INIT_LIST_HEAD(&vc->desc_issued);
INIT_LIST_HEAD(&vc->desc_completed);
tasklet_init(&vc->task, vchan_complete, (unsigned long)vc);
vc->chan.device = dmadev;
list_add_tail(&vc->chan.device_node, &dmadev->channels);
}
EXPORT_SYMBOL_GPL(vchan_init);
MODULE_AUTHOR("Russell King");
MODULE_LICENSE("GPL");