Audio: Modify audio_stream_avail_frames_aligned() to align for source

This change fixes an issue that is caused by the logic in the
function that calculates the aligned frames counts separately
for source and sink and then returns the smaller number of them.
The fixed logic checks the maximum number of frames that could
be processed from source to sink and adjusts the the number down
with source align constraints.

It prevents an issue where a downstream module in pipeline modifies
align constraint for it's source that is previous module's sink. A
more relaxed constraint could then break source align criteria if
the number of frames to process is limited by sink.

The proposed logic for align follows only source align criteria to
avoid conflicting constraints.

Signed-off-by: Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>

Author: singalsu

src/include/sof/audio/audio_stream.h

@@ -590,28 +590,6 @@ audio_stream_avail_frames(const struct audio_stream *source,
 	return MIN(src_frames, sink_frames);
 }
 
-/**
- * Computes maximum number of frames aligned that can be copied from
- * source buffer to sink buffer, verifying number of available source
- * frames vs. free space available in sink.
- * @param source Buffer of source.
- * @param sink Buffer of sink.
- * @return Number of frames.
- */
-static inline uint32_t
-audio_stream_avail_frames_aligned(const struct audio_stream *source,
-				  const struct audio_stream *sink)
-{
-	uint32_t src_frames = (audio_stream_get_avail_bytes(source) >>
-			source->runtime_stream_params.align_shift_idx) *
-					source->runtime_stream_params.align_frame_cnt;
-	uint32_t sink_frames = (audio_stream_get_free_bytes(sink) >>
-			sink->runtime_stream_params.align_shift_idx) *
-					sink->runtime_stream_params.align_frame_cnt;
-
-	return MIN(src_frames, sink_frames);
-}
-
 /**
  * Rounds down a frame count to meet the alignment constraint of the stream.
  * @param stream Audio stream with alignment requirements set.
@@ -658,6 +636,25 @@ static inline uint32_t audio_stream_align_frames_round_nearest(const struct audi
 	return ROUND_DOWN(frames + (align >> 1), align);
 }
 
+/**
+ * Computes maximum number of frames aligned with source align criteria
+ * that can be copied from source buffer to sink buffer, verifying number
+ * of available source frames vs. free space available in sink.
+ * @param source Buffer of source.
+ * @param sink Buffer of sink.
+ * @return Number of frames.
+ */
+static inline uint32_t
+audio_stream_avail_frames_aligned(const struct audio_stream *source,
+				  const struct audio_stream *sink)
+{
+	uint32_t src_frames = audio_stream_get_avail_frames(source);
+	uint32_t sink_frames = audio_stream_get_free_frames(sink);
+	uint32_t n = MIN(src_frames, sink_frames);
+
+	return audio_stream_align_frames_round_down(source, n);
+}
+
 /**
  * Updates the buffer state after writing to the buffer.
  * @param buffer Buffer to update.