[Sound-open-firmware] [PATCH V3] dma-trace: Fix reschedule bug to avoid dma buffer overflow

[Xiuli Pan]

From: Pan Xiuli <xiuli.pan at linux.intel.com>

We have wrong logic in reschedule, we always reschedule the trace_work
once the buffer is half full and new trace coming. We will delay the old
schedule before the old scheduled trace_work is finally run.
Thus the trace_work will like the carrot in front of the DSP as the donkey,
the DSP will never run the trace_work that scheduled in the furture
while we are in busy state and lots of trace are coming continuously.

Signed-off-by: Pan Xiuli <xiuli.pan at linux.intel.com>
Reviewed-by: Zhigang Wu <zhigang.wu at linux.intel.com>
Reviewed-by: Yan Wang <yan.wang at linux.intel.com>
Tested-by: Zhigang Wu <zhigang.wu at linux.intel.com>

---
V2: reuse copy in progress as Yan suggest.
V3: Fix a typo in refine

Test with:
Mininow max rt5651 and GP-MRB nocodec and CNL nocodec
SOF 1.1-stable: 210989dffeea811de2370fccb7cf5d53106b1e6e
SOF-Tool 1.1-stable: 49c1b450e635ac0c893d67ff0ddfd34e03a85b46
https://github.com/plbossart/sound/tree/topic/sof-v4.14:
8d8c1bb32537800726b14d00d13f324b7f536386
---
 src/lib/dma-trace.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/lib/dma-trace.c b/src/lib/dma-trace.c
index 1ff2bd4..10e6102 100644
--- a/src/lib/dma-trace.c
+++ b/src/lib/dma-trace.c
@@ -115,7 +115,7 @@ out:
 		buffer->avail -= size;
 	}
 
-	/* DMA trace copying is done */
+	/* DMA trace copying is done, allow reschedule */
 	d->copy_in_progress = 0;
 
 	spin_unlock_irq(&d->lock, flags);
@@ -335,9 +335,15 @@ void dtrace_event(const char *e, uint32_t length)
 	spin_unlock_irq(&trace_data->lock, flags);
 
 	/* schedule copy now if buffer > 50% full */
-	if (trace_data->enabled && buffer->avail >= (DMA_TRACE_LOCAL_SIZE / 2))
+	if (trace_data->enabled &&
+	    buffer->avail >= (DMA_TRACE_LOCAL_SIZE / 2)) {
 		work_reschedule_default(&trace_data->dmat_work,
 		DMA_TRACE_RESCHEDULE_TIME);
+		/* reschedule should not be intrrupted */
+		/* just like we are in copy progress */
+		trace_data->copy_in_progress = 1;
+	}
+
 }
 
 void dtrace_event_atomic(const char *e, uint32_t length)
-- 
2.7.4