Issue is in the mr_alsa_audio_pcm_playback_copy_internal() function of audio_driver.c that transfers the PCM samples from the ALSA buffer to the Ravenna buffer using the get_user() function.
In case of memory access mode the ALSA buffer can be directly accessed by the kernel and the samples must be copied.
mr_alsa_audio_pcm_playback_copy_internal() has been modified to handle the transfer of the ALSA buffer from user space (used with read/write access mode) and from kernel space (used by memory access mode).
The issue is common to all the platform but impacting ARM only.
Additional changes:
- changed type for dma_playback_offset and dma_capture_offset variables to uint32_t instead of atomic_t since the pointer callback mr_alsa_audio_pcm_pointer() is now atomic
- added variables to the mr_alsa_audio_chip scructure to decrease the number of calls to snd_pcm_lib_xxx() functions. These get assigned in the prepare callback mr_alsa_audio_pcm_prepare()
- changed mr_alsa_audio_get_playback_buffer_size_in_frames() to return configured size of Ravenna playback buffer (same as mr_alsa_audio_get_capture_buffer_size_in_frames())
- some rework of the existing patches
This fixes issue #20
PCM samples are transferred by the PCM interrupt routine from the memory of the ALSA playback device to the RAVENNA buffer and from the RAVENNA buffer to the memory of the ALSA capture device.
This patch will enabled the use of the ALSA plugins and it has been testes with the ALSA Dmix plugin.
This patch applies to issues #7 and #15.
