tree d7cb76e7018f03f0490bcd7c6d6b258da5c27c4e
parent 9883ab229d61b884323f9186b1bd4a41373a491b
author Lars-Peter Clausen <lars@metafoo.de> 1339438302 +0200
committer Mark Brown <broonie@opensource.wolfsonmicro.com> 1340203145 +0100

ASoC: dmaengine-pcm: Add support for querying stream position from DMA driver

Currently the sound dmaengine pcm helper functions implement the pcm_pointer
callback by trying to count the number of elapsed periods. This is done by
advancing the stream position in the dmaengine callback by one period.
Unfortunately there is no guarantee that the callback will be called for each
elapsed period. It may be possible that under high system load it is only called
once for multiple elapsed periods. This patch addresses the issue by
implementing support for querying the current stream position directly from the
dmaengine driver. Since not all dmaengine drivers support reporting the stream
position yet the old period counting implementation is kept for now.

Furthermore the new mechanism allows to report the stream position with a
sub-period granularity, given that the dmaengine driver supports this.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>