From 98f9de366fccee7572c646af226b2d4b4841e3b5 Mon Sep 17 00:00:00 2001 From: Alexander Sverdlin Date: Mon, 22 May 2017 16:05:23 +0200 Subject: [PATCH] dmaengine: ep93xx: Don't drain the transfers in terminate_all() Draining the transfers in terminate_all callback happens with IRQs disabled, therefore induces huge latency: irqsoff latency trace v1.1.5 on 4.11.0 -------------------------------------------------------------------- latency: 39770 us, #57/57, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0) ----------------- | task: process-129 (uid:0 nice:0 policy:2 rt_prio:50) ----------------- => started at: _snd_pcm_stream_lock_irqsave => ended at: snd_pcm_stream_unlock_irqrestore _------=> CPU# / _-----=> irqs-off | / _----=> need-resched || / _---=> hardirq/softirq ||| / _--=> preempt-depth |||| / delay cmd pid ||||| time | caller \ / ||||| \ | / process-129 0d.s. 3us : _snd_pcm_stream_lock_irqsave process-129 0d.s1 9us : snd_pcm_stream_lock <-_snd_pcm_stream_lock_irqsave process-129 0d.s1 15us : preempt_count_add <-snd_pcm_stream_lock process-129 0d.s2 22us : preempt_count_add <-snd_pcm_stream_lock process-129 0d.s3 32us : snd_pcm_update_hw_ptr0 <-snd_pcm_period_elapsed process-129 0d.s3 41us : soc_pcm_pointer <-snd_pcm_update_hw_ptr0 process-129 0d.s3 50us : dmaengine_pcm_pointer <-soc_pcm_pointer process-129 0d.s3 58us+: snd_dmaengine_pcm_pointer_no_residue <-dmaengine_pcm_pointer process-129 0d.s3 96us : update_audio_tstamp <-snd_pcm_update_hw_ptr0 process-129 0d.s3 103us : snd_pcm_update_state <-snd_pcm_update_hw_ptr0 process-129 0d.s3 112us : xrun <-snd_pcm_update_state process-129 0d.s3 119us : snd_pcm_stop <-xrun process-129 0d.s3 126us : snd_pcm_action <-snd_pcm_stop process-129 0d.s3 134us : snd_pcm_action_single <-snd_pcm_action process-129 0d.s3 141us : snd_pcm_pre_stop <-snd_pcm_action_single process-129 0d.s3 150us : snd_pcm_do_stop <-snd_pcm_action_single process-129 0d.s3 157us : soc_pcm_trigger <-snd_pcm_do_stop process-129 0d.s3 166us : snd_dmaengine_pcm_trigger <-soc_pcm_trigger process-129 0d.s3 175us : ep93xx_dma_terminate_all <-snd_dmaengine_pcm_trigger process-129 0d.s3 182us : preempt_count_add <-ep93xx_dma_terminate_all process-129 0d.s4 189us*: m2p_hw_shutdown <-ep93xx_dma_terminate_all process-129 0d.s4 39472us : m2p_hw_setup <-ep93xx_dma_terminate_all ... rest skipped... process-129 0d.s. 40080us : => ep93xx_dma_tasklet => tasklet_action => __do_softirq => irq_exit => __handle_domain_irq => vic_handle_irq => __irq_usr => 0xb66c6668 Just abort the transfers and warn if the HW state is not what we expect. Move draining into device_synchronize callback. Signed-off-by: Alexander Sverdlin Cc: stable@vger.kernel.org Signed-off-by: Vinod Koul --- drivers/dma/ep93xx_dma.c | 37 +++++++++++++++++++++++++++++++++---- 1 file changed, 33 insertions(+), 4 deletions(-) diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c index deb009c..ec24059 100644 --- a/drivers/dma/ep93xx_dma.c +++ b/drivers/dma/ep93xx_dma.c @@ -201,6 +201,7 @@ struct ep93xx_dma_engine { struct dma_device dma_dev; bool m2m; int (*hw_setup)(struct ep93xx_dma_chan *); + void (*hw_synchronize)(struct ep93xx_dma_chan *); void (*hw_shutdown)(struct ep93xx_dma_chan *); void (*hw_submit)(struct ep93xx_dma_chan *); int (*hw_interrupt)(struct ep93xx_dma_chan *); @@ -333,21 +334,27 @@ static inline u32 m2p_channel_state(struct ep93xx_dma_chan *edmac) return (readl(edmac->regs + M2P_STATUS) >> 4) & 0x3; } -static void m2p_hw_shutdown(struct ep93xx_dma_chan *edmac) +static void m2p_hw_synchronize(struct ep93xx_dma_chan *edmac) { + unsigned long flags; u32 control; + spin_lock_irqsave(&edmac->lock, flags); control = readl(edmac->regs + M2P_CONTROL); control &= ~(M2P_CONTROL_STALLINT | M2P_CONTROL_NFBINT); m2p_set_control(edmac, control); + spin_unlock_irqrestore(&edmac->lock, flags); while (m2p_channel_state(edmac) >= M2P_STATE_ON) - cpu_relax(); + schedule(); +} +static void m2p_hw_shutdown(struct ep93xx_dma_chan *edmac) +{ m2p_set_control(edmac, 0); - while (m2p_channel_state(edmac) == M2P_STATE_STALL) - cpu_relax(); + while (m2p_channel_state(edmac) != M2P_STATE_IDLE) + dev_warn(chan2dev(edmac), "M2P: Not yet IDLE\n"); } static void m2p_fill_desc(struct ep93xx_dma_chan *edmac) @@ -1163,6 +1170,26 @@ fail: } /** + * ep93xx_dma_synchronize - Synchronizes the termination of transfers to the + * current context. + * @chan: channel + * + * Synchronizes the DMA channel termination to the current context. When this + * function returns it is guaranteed that all transfers for previously issued + * descriptors have stopped and and it is safe to free the memory associated + * with them. Furthermore it is guaranteed that all complete callback functions + * for a previously submitted descriptor have finished running and it is safe to + * free resources accessed from within the complete callbacks. + */ +static void ep93xx_dma_synchronize(struct dma_chan *chan) +{ + struct ep93xx_dma_chan *edmac = to_ep93xx_dma_chan(chan); + + if (edmac->edma->hw_synchronize) + edmac->edma->hw_synchronize(edmac); +} + +/** * ep93xx_dma_terminate_all - terminate all transactions * @chan: channel * @@ -1325,6 +1352,7 @@ static int __init ep93xx_dma_probe(struct platform_device *pdev) dma_dev->device_prep_slave_sg = ep93xx_dma_prep_slave_sg; dma_dev->device_prep_dma_cyclic = ep93xx_dma_prep_dma_cyclic; dma_dev->device_config = ep93xx_dma_slave_config; + dma_dev->device_synchronize = ep93xx_dma_synchronize; dma_dev->device_terminate_all = ep93xx_dma_terminate_all; dma_dev->device_issue_pending = ep93xx_dma_issue_pending; dma_dev->device_tx_status = ep93xx_dma_tx_status; @@ -1342,6 +1370,7 @@ static int __init ep93xx_dma_probe(struct platform_device *pdev) } else { dma_cap_set(DMA_PRIVATE, dma_dev->cap_mask); + edma->hw_synchronize = m2p_hw_synchronize; edma->hw_setup = m2p_hw_setup; edma->hw_shutdown = m2p_hw_shutdown; edma->hw_submit = m2p_hw_submit; -- 2.7.4