ASoC: SOF: ipc4-pcm: Correct the delay calculation

This patch improves the delay calculation by relying on the
LLP (Linear Link Position) on the DAI side and the
LDP (Linear Data Pointer) on the host side. The LDP provides the same DMA
position as LPIB, but with a linear count instead of a position in the
ALSA ring buffer. The LDP values are provided in bytes and must be
converted to frames. The difference in units means that the host counter
will wrap earlier than the LLP. We need to wrap the LLP at the same
boundary as the host counter.

The ASoC framework relies on separate pointer and delay callback.
Measurement errors can be reduced by processing all the counter values in
the pointer callback. The delay value is stored, and will be reported to
higher levels in the delay callback.

For playback, the firmware provides a stream_start offset to handle
mixing/pause usages, where the DAI might have started earlier than the
PCM device. The delay calculation must be special-cased when the link
counter has not reached the start offset value, i.e. no valid audio has
left the DSP.

Cc: stable@vger.kernel.org # 6.8
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://msgid.link/r/20240321130814.4412-16-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

0 files changed, 0 insertions, 0 deletions