ASoC: dmaengine-pcm: Rename and deprecate snd_dmaengine_pcm_pointer

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 renames the current implementation
and documents its shortcomings and that it should not be used anymore in new
drivers.

The next patch will introduce a new snd_dmaengine_pcm_pointer which will be
implemented based on querying the current stream position from the dma device.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by Vinod Koul <vinod.koul@linux.intel.com>
Acked-by: Dong Aisheng <dong.aisheng@linaro.org
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

include/sound/dmaengine_pcm.h

@@ -38,7 +38,7 @@ void *snd_dmaengine_pcm_get_data(struct snd_pcm_substream *substream);
 int snd_hwparams_to_dma_slave_config(const struct snd_pcm_substream *substream,
 	const struct snd_pcm_hw_params *params, struct dma_slave_config *slave_config);
 int snd_dmaengine_pcm_trigger(struct snd_pcm_substream *substream, int cmd);
-snd_pcm_uframes_t snd_dmaengine_pcm_pointer(struct snd_pcm_substream *substream);
+snd_pcm_uframes_t snd_dmaengine_pcm_pointer_no_residue(struct snd_pcm_substream *substream);
 
 int snd_dmaengine_pcm_open(struct snd_pcm_substream *substream,
 	dma_filter_fn filter_fn, void *filter_data);

sound/soc/ep93xx/ep93xx-pcm.c

@@ -136,7 +136,7 @@ static struct snd_pcm_ops ep93xx_pcm_ops = {
 	.hw_params	= ep93xx_pcm_hw_params,
 	.hw_free	= ep93xx_pcm_hw_free,
 	.trigger	= snd_dmaengine_pcm_trigger,
-	.pointer	= snd_dmaengine_pcm_pointer,
+	.pointer	= snd_dmaengine_pcm_pointer_no_residue,
 	.mmap		= ep93xx_pcm_mmap,
 };
 

sound/soc/fsl/imx-pcm-dma.c

@@ -141,7 +141,7 @@ static struct snd_pcm_ops imx_pcm_ops = {
 	.ioctl		= snd_pcm_lib_ioctl,
 	.hw_params	= snd_imx_pcm_hw_params,
 	.trigger	= snd_dmaengine_pcm_trigger,
-	.pointer	= snd_dmaengine_pcm_pointer,
+	.pointer	= snd_dmaengine_pcm_pointer_no_residue,
 	.mmap		= snd_imx_pcm_mmap,
 };
 

sound/soc/mxs/mxs-pcm.c

@@ -141,7 +141,7 @@ static struct snd_pcm_ops mxs_pcm_ops = {
 	.ioctl		= snd_pcm_lib_ioctl,
 	.hw_params	= snd_mxs_pcm_hw_params,
 	.trigger	= snd_dmaengine_pcm_trigger,
-	.pointer	= snd_dmaengine_pcm_pointer,
+	.pointer	= snd_dmaengine_pcm_pointer_no_residue,
 	.mmap		= snd_mxs_pcm_mmap,
 };
 

sound/soc/soc-dmaengine-pcm.c

@@ -200,18 +200,18 @@ int snd_dmaengine_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
 EXPORT_SYMBOL_GPL(snd_dmaengine_pcm_trigger);
 
 /**
- * snd_dmaengine_pcm_pointer - dmaengine based PCM pointer implementation
+ * snd_dmaengine_pcm_pointer_no_residue - dmaengine based PCM pointer implementation
  * @substream: PCM substream
  *
- * This function can be used as the PCM pointer callback for dmaengine based PCM
- * driver implementations.
+ * This function is deprecated and should not be used by new drivers, as its
+ * results may be unreliable.
  */
-snd_pcm_uframes_t snd_dmaengine_pcm_pointer(struct snd_pcm_substream *substream)
+snd_pcm_uframes_t snd_dmaengine_pcm_pointer_no_residue(struct snd_pcm_substream *substream)
 {
 	struct dmaengine_pcm_runtime_data *prtd = substream_to_prtd(substream);
 	return bytes_to_frames(substream->runtime, prtd->pos);
 }
-EXPORT_SYMBOL_GPL(snd_dmaengine_pcm_pointer);
+EXPORT_SYMBOL_GPL(snd_dmaengine_pcm_pointer_no_residue);
 
 static int dmaengine_pcm_request_channel(struct dmaengine_pcm_runtime_data *prtd,
 	dma_filter_fn filter_fn, void *filter_data)

sound/soc/ux500/ux500_pcm.c

@@ -261,7 +261,7 @@ static struct snd_pcm_ops ux500_pcm_ops = {
 	.hw_params	= ux500_pcm_hw_params,
 	.hw_free	= ux500_pcm_hw_free,
 	.trigger	= snd_dmaengine_pcm_trigger,
-	.pointer	= snd_dmaengine_pcm_pointer,
+	.pointer	= snd_dmaengine_pcm_pointer_no_residue,
 	.mmap		= ux500_pcm_mmap
 };