Hello Vinod,
On 14/05/17 15:16, Vinod Koul wrote:
>> As dmaengine.h suggests, device_terminate_all() "Aborts all transfers on a
>> channel". Seems that no other driver tried to busy-wait and actually drain
>> the data. Moreover, this happens with IRQs disabled, therefore induces huge
>> latency:
> Perhaps you should move current code to device_synchronize callback to allow
> people to do so, if desired.
you are right, otherwise device_free_chan_resources() can be called on running
channel... Will do!
>> 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.
>>
>> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
>> Cc: stable@xxxxxxxxxxxxxxx
>> ---
>> drivers/dma/ep93xx_dma.c | 13 ++-----------
>> 1 file changed, 2 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c
>> index a3d946d2a8e1..e78d1fbf2179 100644
>> --- a/drivers/dma/ep93xx_dma.c
>> +++ b/drivers/dma/ep93xx_dma.c
>> @@ -345,19 +345,10 @@ static inline u32 m2p_channel_state(struct ep93xx_dma_chan *edmac)
>>
>> static void m2p_hw_shutdown(struct ep93xx_dma_chan *edmac)
>> {
>> - u32 control;
>> -
>> - control = readl(edmac->regs + M2P_CONTROL);
>> - control &= ~(M2P_CONTROL_STALLINT | M2P_CONTROL_NFBINT);
>> - m2p_set_control(edmac, control);
>> -
>> - while (m2p_channel_state(edmac) >= M2P_STATE_ON)
>> - cpu_relax();
>> -
>> 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");
>> }
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