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>
165 lines
4.3 KiB
C
165 lines
4.3 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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#ifndef VIRT_DMA_H
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#define VIRT_DMA_H
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#include <linux/dmaengine.h>
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#include <linux/interrupt.h>
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#include "dmaengine.h"
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struct virt_dma_desc {
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struct dma_async_tx_descriptor tx;
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/* protected by vc.lock */
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struct list_head node;
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};
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struct virt_dma_chan {
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struct dma_chan chan;
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struct tasklet_struct task;
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void (*desc_free)(struct virt_dma_desc *);
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spinlock_t lock;
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/* protected by vc.lock */
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struct list_head desc_allocated;
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struct list_head desc_submitted;
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struct list_head desc_issued;
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struct list_head desc_completed;
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struct virt_dma_desc *cyclic;
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};
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static inline struct virt_dma_chan *to_virt_chan(struct dma_chan *chan)
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{
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return container_of(chan, struct virt_dma_chan, chan);
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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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void vchan_init(struct virt_dma_chan *vc, struct dma_device *dmadev);
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struct virt_dma_desc *vchan_find_desc(struct virt_dma_chan *, dma_cookie_t);
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/**
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* vchan_tx_prep - prepare a descriptor
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* vc: virtual channel allocating this descriptor
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* vd: virtual descriptor to prepare
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* tx_flags: flags argument passed in to prepare function
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*/
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static inline struct dma_async_tx_descriptor *vchan_tx_prep(struct virt_dma_chan *vc,
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struct virt_dma_desc *vd, unsigned long tx_flags)
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{
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extern dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *);
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unsigned long flags;
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dma_async_tx_descriptor_init(&vd->tx, &vc->chan);
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vd->tx.flags = tx_flags;
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vd->tx.tx_submit = vchan_tx_submit;
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spin_lock_irqsave(&vc->lock, flags);
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list_add_tail(&vd->node, &vc->desc_allocated);
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spin_unlock_irqrestore(&vc->lock, flags);
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return &vd->tx;
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}
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/**
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* vchan_issue_pending - move submitted descriptors to issued list
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* vc: virtual channel to update
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*
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* vc.lock must be held by caller
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*/
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static inline bool vchan_issue_pending(struct virt_dma_chan *vc)
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{
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list_splice_tail_init(&vc->desc_submitted, &vc->desc_issued);
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return !list_empty(&vc->desc_issued);
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}
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/**
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* vchan_cookie_complete - report completion of a descriptor
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* vd: virtual descriptor to update
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*
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* vc.lock must be held by caller
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*/
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static inline void vchan_cookie_complete(struct virt_dma_desc *vd)
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{
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struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
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dma_cookie_t cookie;
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cookie = vd->tx.cookie;
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dma_cookie_complete(&vd->tx);
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dev_vdbg(vc->chan.device->dev, "txd %p[%x]: marked complete\n",
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vd, cookie);
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list_add_tail(&vd->node, &vc->desc_completed);
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tasklet_schedule(&vc->task);
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}
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/**
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* vchan_cyclic_callback - report the completion of a period
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* vd: virtual descriptor
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*/
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static inline void vchan_cyclic_callback(struct virt_dma_desc *vd)
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{
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struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
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vc->cyclic = vd;
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tasklet_schedule(&vc->task);
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}
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/**
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* vchan_next_desc - peek at the next descriptor to be processed
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* vc: virtual channel to obtain descriptor from
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*
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* vc.lock must be held by caller
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*/
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static inline struct virt_dma_desc *vchan_next_desc(struct virt_dma_chan *vc)
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{
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if (list_empty(&vc->desc_issued))
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return NULL;
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return list_first_entry(&vc->desc_issued, struct virt_dma_desc, node);
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}
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/**
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* vchan_get_all_descriptors - obtain all allocated, submitted and issued
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* descriptors
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* vc: virtual channel to get descriptors from
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* head: list of descriptors found
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*
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* vc.lock must be held by caller
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*
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* Removes all submitted and issued descriptors from internal lists, and
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* provides a list of all descriptors found
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*/
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static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc,
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struct list_head *head)
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{
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list_splice_tail_init(&vc->desc_allocated, head);
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list_splice_tail_init(&vc->desc_submitted, head);
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list_splice_tail_init(&vc->desc_issued, head);
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list_splice_tail_init(&vc->desc_completed, head);
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}
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static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
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{
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struct virt_dma_desc *vd;
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unsigned long flags;
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LIST_HEAD(head);
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spin_lock_irqsave(&vc->lock, flags);
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vchan_get_all_descriptors(vc, &head);
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list_for_each_entry(vd, &head, node)
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async_tx_clear_ack(&vd->tx);
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spin_unlock_irqrestore(&vc->lock, flags);
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vchan_dma_desc_free_list(vc, &head);
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}
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#endif
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