This is a note to let you know that I've just added the patch titled
dmaengine: ep93xx: Don't drain the transfers in terminate_all()
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dmaengine-ep93xx-don-t-drain-the-transfers-in-terminate_all.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 98f9de366fccee7572c646af226b2d4b4841e3b5 Mon Sep 17 00:00:00 2001
From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
Date: Mon, 22 May 2017 16:05:23 +0200
Subject: dmaengine: ep93xx: Don't drain the transfers in terminate_all()
From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
commit 98f9de366fccee7572c646af226b2d4b4841e3b5 upstream.
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 : <stack trace>
=> 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 <alexander.sverdlin@xxxxxxxxx>
Signed-off-by: Vinod Koul <vinod.koul@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/dma/ep93xx_dma.c | 37 +++++++++++++++++++++++++++++++++----
1 file changed, 33 insertions(+), 4 deletions(-)
--- 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 *);
@@ -335,21 +336,27 @@ static inline u32 m2p_channel_state(stru
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)
@@ -1165,6 +1172,26 @@ 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
*
@@ -1327,6 +1354,7 @@ static int __init ep93xx_dma_probe(struc
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;
@@ -1344,6 +1372,7 @@ static int __init ep93xx_dma_probe(struc
} 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;
Patches currently in stable-queue which might be from alexander.sverdlin@xxxxxxxxx are
queue-4.4/dmaengine-ep93xx-always-start-from-base0.patch
queue-4.4/dmaengine-ep93xx-don-t-drain-the-transfers-in-terminate_all.patch