From 13bb26ae8850ede9cfb5ba20e646fe08e23aca97 Mon Sep 17 00:00:00 2001 From: Robert Jarzmik Date: Tue, 13 Oct 2015 21:54:28 +0200 Subject: dmaengine: virt-dma: don't always free descriptor upon completion 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_REUSE flag is set in the transfer. This patch is a respin of the former DMA_CTRL_ACK approach, which was reverted due to a regression in audio drivers. Signed-off-by: Robert Jarzmik Signed-off-by: Vinod Koul --- drivers/dma/virt-dma.c | 46 ++++++++++++++++++++++++++++++++++++++++------ drivers/dma/virt-dma.h | 12 ++++++++++++ 2 files changed, 52 insertions(+), 6 deletions(-) (limited to 'drivers/dma') diff --git a/drivers/dma/virt-dma.c b/drivers/dma/virt-dma.c index 6f80432a3f0a..a35c211857dd 100644 --- a/drivers/dma/virt-dma.c +++ b/drivers/dma/virt-dma.c @@ -29,7 +29,7 @@ dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *tx) spin_lock_irqsave(&vc->lock, flags); cookie = dma_cookie_assign(tx); - list_add_tail(&vd->node, &vc->desc_submitted); + 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", @@ -39,6 +39,33 @@ dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *tx) } 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) { @@ -83,8 +110,10 @@ static void vchan_complete(unsigned long arg) cb_data = vd->tx.callback_param; list_del(&vd->node); - - vc->desc_free(vd); + if (dmaengine_desc_test_reuse(&vd->tx)) + list_add(&vd->node, &vc->desc_allocated); + else + vc->desc_free(vd); if (cb) cb(cb_data); @@ -96,9 +125,13 @@ void vchan_dma_desc_free_list(struct virt_dma_chan *vc, struct list_head *head) while (!list_empty(head)) { struct virt_dma_desc *vd = list_first_entry(head, struct virt_dma_desc, node); - list_del(&vd->node); - dev_dbg(vc->chan.device->dev, "txd %p: freeing\n", vd); - vc->desc_free(vd); + 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); @@ -108,6 +141,7 @@ 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); diff --git a/drivers/dma/virt-dma.h b/drivers/dma/virt-dma.h index 2fa47745a41f..bff8c39dd716 100644 --- a/drivers/dma/virt-dma.h +++ b/drivers/dma/virt-dma.h @@ -29,6 +29,7 @@ struct virt_dma_chan { spinlock_t lock; /* protected by vc.lock */ + struct list_head desc_allocated; struct list_head desc_submitted; struct list_head desc_issued; struct list_head desc_completed; @@ -55,10 +56,17 @@ static inline struct dma_async_tx_descriptor *vchan_tx_prep(struct virt_dma_chan struct virt_dma_desc *vd, unsigned long tx_flags) { extern dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *); + extern int vchan_tx_desc_free(struct dma_async_tx_descriptor *); + unsigned long flags; dma_async_tx_descriptor_init(&vd->tx, &vc->chan); vd->tx.flags = tx_flags; vd->tx.tx_submit = vchan_tx_submit; + vd->tx.desc_free = vchan_tx_desc_free; + + spin_lock_irqsave(&vc->lock, flags); + list_add_tail(&vd->node, &vc->desc_allocated); + spin_unlock_irqrestore(&vc->lock, flags); return &vd->tx; } @@ -134,6 +142,7 @@ static inline struct virt_dma_desc *vchan_next_desc(struct virt_dma_chan *vc) static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc, struct list_head *head) { + list_splice_tail_init(&vc->desc_allocated, head); list_splice_tail_init(&vc->desc_submitted, head); list_splice_tail_init(&vc->desc_issued, head); list_splice_tail_init(&vc->desc_completed, head); @@ -141,11 +150,14 @@ static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc, static inline void vchan_free_chan_resources(struct virt_dma_chan *vc) { + struct virt_dma_desc *vd; unsigned long flags; LIST_HEAD(head); spin_lock_irqsave(&vc->lock, flags); vchan_get_all_descriptors(vc, &head); + list_for_each_entry(vd, &head, node) + dmaengine_desc_clear_reuse(&vd->tx); spin_unlock_irqrestore(&vc->lock, flags); vchan_dma_desc_free_list(vc, &head); -- cgit v1.2.3 From 9eeacd3a2f17438d9d286ff2f78c4709a4148be7 Mon Sep 17 00:00:00 2001 From: Robert Jarzmik Date: Tue, 13 Oct 2015 21:54:29 +0200 Subject: dmaengine: enable DMA_CTRL_REUSE In the current state, the capability of transfer reuse can neither be set by a slave dmaengine driver, nor used by a client driver, because the capability is not available to dma_get_slave_caps(). Fix this by adding a way to declare the capability. Fixes: 272420214d26 ("dmaengine: Add DMA_CTRL_REUSE") Signed-off-by: Robert Jarzmik Signed-off-by: Vinod Koul --- drivers/dma/dmaengine.c | 1 + include/linux/dmaengine.h | 2 ++ 2 files changed, 3 insertions(+) (limited to 'drivers/dma') diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index 3ecec1445adf..4aced6689734 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -493,6 +493,7 @@ int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps) caps->dst_addr_widths = device->dst_addr_widths; caps->directions = device->directions; caps->residue_granularity = device->residue_granularity; + caps->descriptor_reuse = device->descriptor_reuse; /* * Some devices implement only pause (e.g. to get residuum) but no diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index c47c68e535e8..6f94b5cbd97c 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -659,6 +659,7 @@ enum dmaengine_alignment { * struct with auxiliary transfer status information, otherwise the call * will just return a simple status code * @device_issue_pending: push pending transactions to hardware + * @descriptor_reuse: a submitted transfer can be resubmitted after completion */ struct dma_device { @@ -681,6 +682,7 @@ struct dma_device { u32 src_addr_widths; u32 dst_addr_widths; u32 directions; + bool descriptor_reuse; enum dma_residue_granularity residue_granularity; int (*device_alloc_chan_resources)(struct dma_chan *chan); -- cgit v1.2.3 From d3651b8e5cdf8773a7d74839e53454e4a0d48ffe Mon Sep 17 00:00:00 2001 From: Robert Jarzmik Date: Tue, 13 Oct 2015 21:54:30 +0200 Subject: dmaengine: pxa_dma: declare transfer are reusable As this driver provides a mechanism to reuse transfers, declare it in its probe function. Signed-off-by: Robert Jarzmik Signed-off-by: Vinod Koul --- drivers/dma/pxa_dma.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/dma') diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c index fc4156afa070..f2a0310ae771 100644 --- a/drivers/dma/pxa_dma.c +++ b/drivers/dma/pxa_dma.c @@ -1414,6 +1414,7 @@ static int pxad_probe(struct platform_device *op) pdev->slave.dst_addr_widths = widths; pdev->slave.directions = BIT(DMA_MEM_TO_DEV) | BIT(DMA_DEV_TO_MEM); pdev->slave.residue_granularity = DMA_RESIDUE_GRANULARITY_DESCRIPTOR; + pdev->slave.descriptor_reuse = true; pdev->slave.dev = &op->dev; ret = pxad_init_dmadev(op, pdev, dma_channels); -- cgit v1.2.3