Patch "dmaengine: ep93xx: Don't drain the transfers in terminate_all()" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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@vger.kernel.org> know about it.


>From 98f9de366fccee7572c646af226b2d4b4841e3b5 Mon Sep 17 00:00:00 2001
From: Alexander Sverdlin <alexander.sverdlin@gmail.com>
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@gmail.com>

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@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 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@gmail.com 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