On 03/13/2014 12:28 PM, Lars-Peter Clausen wrote:
+int edma_pcm_platform_register(struct device *dev) +{
- if (dev->of_node)
return snd_dmaengine_pcm_register(dev,&edma_dmaengine_pcm_config,SND_DMAENGINE_PCM_FLAG_NO_RESIDUE);Since the edma dmaengine driver implements the slave cap API there is no need to manually specify SND_DMAENGINE_PCM_FLAG_NO_RESIDUE manually. But since the edma driver sets the granularity to DMA_RESIDUE_GRANULARITY_DESCRIPTOR in this case the generic dmaengine will not set SND_DMAENGINE_PCM_FLAG_NO_RESIDUE automatically since it assumes that the dmaengine driver is capable of properly reporting the DMA position.
Hrm, I see. For eDMA I think we can support DMA_RESIDUE_GRANULARITY_SEGMENT granularity. Since according to the documentation the _SEGMENT means that the DMA position will be updated per periods, which is basically the same thing what we are doing at the moment when the granularity is DMA_RESIDUE_GRANULARITY_DESCRIPTOR.
From ALSA point of view at least they are the same: neither of them can report
exact position, the DMA pointer jumps from period to period.
IMHO in the generic dmaengine PCM we should set the SNDRV_PCM_INFO_BATCH for both cases.