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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>
51 lines
1.8 KiB
C
51 lines
1.8 KiB
C
/*
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* Copyright (C) 2012, Analog Devices Inc.
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* Author: Lars-Peter Clausen <lars@metafoo.de>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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*/
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#ifndef __SOUND_DMAENGINE_PCM_H__
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#define __SOUND_DMAENGINE_PCM_H__
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#include <sound/pcm.h>
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#include <linux/dmaengine.h>
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/**
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* snd_pcm_substream_to_dma_direction - Get dma_transfer_direction for a PCM
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* substream
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* @substream: PCM substream
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*/
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static inline enum dma_transfer_direction
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snd_pcm_substream_to_dma_direction(const struct snd_pcm_substream *substream)
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{
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if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
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return DMA_MEM_TO_DEV;
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else
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return DMA_DEV_TO_MEM;
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}
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void snd_dmaengine_pcm_set_data(struct snd_pcm_substream *substream, void *data);
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void *snd_dmaengine_pcm_get_data(struct snd_pcm_substream *substream);
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int snd_hwparams_to_dma_slave_config(const struct snd_pcm_substream *substream,
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const struct snd_pcm_hw_params *params, struct dma_slave_config *slave_config);
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int snd_dmaengine_pcm_trigger(struct snd_pcm_substream *substream, int cmd);
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snd_pcm_uframes_t snd_dmaengine_pcm_pointer(struct snd_pcm_substream *substream);
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snd_pcm_uframes_t snd_dmaengine_pcm_pointer_no_residue(struct snd_pcm_substream *substream);
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int snd_dmaengine_pcm_open(struct snd_pcm_substream *substream,
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dma_filter_fn filter_fn, void *filter_data);
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int snd_dmaengine_pcm_close(struct snd_pcm_substream *substream);
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struct dma_chan *snd_dmaengine_pcm_get_chan(struct snd_pcm_substream *substream);
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#endif
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