DP: implementation of Get Last Feeding time for a buffers

This commit introduces calculating of LFT for a module
following description from zephyr_dp_scheduler.c

The implementation is ready for DP to DP deadline
calculations, however, the rest of the code is not.
Therefore the DP to DP part has been deactivated with proper
comment

Signed-off-by: Marcin Szkudlinski <marcin.szkudlinski@intel.com>

Author: marcinszkudlinski

src/audio/buffers/audio_buffer.c

@@ -10,6 +10,10 @@
 #include <rtos/panic.h>
 #include <rtos/alloc.h>
 #include <ipc/stream.h>
+#include <sof/audio/module_adapter/module/generic.h>
+#include <module/ipc4/base-config.h>
+#include <sof/audio/component.h>
+#include <module/module/base.h>
 #include <sof/audio/audio_buffer.h>
 #include <sof/audio/sink_api.h>
 #include <sof/audio/source_api.h>
@@ -182,12 +186,36 @@ int audio_buffer_source_set_alignment_constants(struct sof_source *source,
 	return 0;
 }
 
-/**
- * this is stub, always return Last Feeding Time - 0, meaning "NOW"
- */
 uint32_t audio_buffer_sink_get_lft(struct sof_sink *sink)
 {
-	return 0;
+	struct sof_audio_buffer *buffer = sof_audio_buffer_from_sink(sink);
+	/* get number of ms in the buffer */
+	size_t bytes_per_sec = sink_get_frame_bytes(&buffer->_sink_api) *
+			       sink_get_rate(&buffer->_sink_api);
+	size_t bytes_per_ms = bytes_per_sec / 1000;
+
+	/* round up for frequencies like 44100 */
+	if (bytes_per_ms * 1000 != bytes_per_sec)
+		bytes_per_ms++;
+	uint32_t us_in_buffer =
+			1000 * source_get_data_available(&buffer->_source_api) / bytes_per_ms;
+
+	return us_in_buffer;
+
+	/*
+	 * TODO, Currently there's no DP to DP connection
+	 * >>> the code below is never accessible and won't work because of cache incoherence <<<
+	 *
+	 * to make DP to DP connection possible:
+	 *
+	 * 1) module data must be ALWAYS located in non cached memory alias, allowing
+	 *    cross core access to params like period (needed below) and calling
+	 *    module_get_deadline for the next module, regardless of cores the modules are
+	 *    running on
+	 * 2) comp_buffer must be removed from all pipeline code, replaced with a generic abstract
+	 *    class audio_buffer - allowing using comp_buffer and ring_buffer without current
+	 *    "hybrid buffer" solution
+	 */
 }
 
 void audio_buffer_init(struct sof_audio_buffer *buffer, uint32_t buffer_type, bool is_shared,