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b9855f03d5
This patch attempts to enhance the case of a transfer submitted multiple
times, and where the cost of creating the descriptors chain is not
negligible.
This happens with big video buffers (several megabytes, ie. several
thousands of linked descriptors in one scatter-gather list). In these
cases, a video driver would want to do :
- tx = dmaengine_prep_slave_sg()
- dma_engine_submit(tx);
- dma_async_issue_pending()
- wait for video completion
- read video data (or not, skipping a frame is also possible)
- dma_engine_submit(tx)
=> here, the descriptors chain recalculation will take time
=> the dma coherent allocation over and over might create holes in
the dma pool, which is counter-productive.
- dma_async_issue_pending()
- etc ...
In order to cope with this case, virt-dma is modified to prevent freeing
the descriptors upon completion if DMA_CTRL_ACK flag is set in the
transfer.
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
131 lines
3.1 KiB
C
131 lines
3.1 KiB
C
/*
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* Virtual DMA channel support for DMAengine
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*
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* Copyright (C) 2012 Russell King
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/device.h>
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#include <linux/dmaengine.h>
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#include <linux/module.h>
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#include <linux/spinlock.h>
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#include "virt-dma.h"
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static struct virt_dma_desc *to_virt_desc(struct dma_async_tx_descriptor *tx)
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{
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return container_of(tx, struct virt_dma_desc, tx);
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}
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dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *tx)
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{
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struct virt_dma_chan *vc = to_virt_chan(tx->chan);
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struct virt_dma_desc *vd = to_virt_desc(tx);
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unsigned long flags;
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dma_cookie_t cookie;
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spin_lock_irqsave(&vc->lock, flags);
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cookie = dma_cookie_assign(tx);
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list_move_tail(&vd->node, &vc->desc_submitted);
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spin_unlock_irqrestore(&vc->lock, flags);
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dev_dbg(vc->chan.device->dev, "vchan %p: txd %p[%x]: submitted\n",
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vc, vd, cookie);
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return cookie;
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}
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EXPORT_SYMBOL_GPL(vchan_tx_submit);
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struct virt_dma_desc *vchan_find_desc(struct virt_dma_chan *vc,
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dma_cookie_t cookie)
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{
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struct virt_dma_desc *vd;
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list_for_each_entry(vd, &vc->desc_issued, node)
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if (vd->tx.cookie == cookie)
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return vd;
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return NULL;
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}
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EXPORT_SYMBOL_GPL(vchan_find_desc);
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/*
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* This tasklet handles the completion of a DMA descriptor by
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* calling its callback and freeing it.
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*/
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static void vchan_complete(unsigned long arg)
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{
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struct virt_dma_chan *vc = (struct virt_dma_chan *)arg;
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struct virt_dma_desc *vd;
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dma_async_tx_callback cb = NULL;
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void *cb_data = NULL;
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LIST_HEAD(head);
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spin_lock_irq(&vc->lock);
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list_splice_tail_init(&vc->desc_completed, &head);
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vd = vc->cyclic;
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if (vd) {
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vc->cyclic = NULL;
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cb = vd->tx.callback;
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cb_data = vd->tx.callback_param;
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}
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spin_unlock_irq(&vc->lock);
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if (cb)
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cb(cb_data);
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while (!list_empty(&head)) {
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vd = list_first_entry(&head, struct virt_dma_desc, node);
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cb = vd->tx.callback;
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cb_data = vd->tx.callback_param;
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list_del(&vd->node);
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if (async_tx_test_ack(&vd->tx))
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list_add(&vd->node, &vc->desc_allocated);
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else
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vc->desc_free(vd);
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if (cb)
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cb(cb_data);
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}
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}
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void vchan_dma_desc_free_list(struct virt_dma_chan *vc, struct list_head *head)
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{
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while (!list_empty(head)) {
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struct virt_dma_desc *vd = list_first_entry(head,
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struct virt_dma_desc, node);
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if (async_tx_test_ack(&vd->tx)) {
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list_move_tail(&vd->node, &vc->desc_allocated);
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} else {
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dev_dbg(vc->chan.device->dev, "txd %p: freeing\n", vd);
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list_del(&vd->node);
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vc->desc_free(vd);
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}
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}
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}
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EXPORT_SYMBOL_GPL(vchan_dma_desc_free_list);
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void vchan_init(struct virt_dma_chan *vc, struct dma_device *dmadev)
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{
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dma_cookie_init(&vc->chan);
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spin_lock_init(&vc->lock);
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INIT_LIST_HEAD(&vc->desc_allocated);
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INIT_LIST_HEAD(&vc->desc_submitted);
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INIT_LIST_HEAD(&vc->desc_issued);
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INIT_LIST_HEAD(&vc->desc_completed);
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tasklet_init(&vc->task, vchan_complete, (unsigned long)vc);
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vc->chan.device = dmadev;
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list_add_tail(&vc->chan.device_node, &dmadev->channels);
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}
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EXPORT_SYMBOL_GPL(vchan_init);
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MODULE_AUTHOR("Russell King");
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MODULE_LICENSE("GPL");
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