Re: PulseAudio and SNDRV_PCM_INFO_BATCH - Lars-Peter Clausen

From: Lars-Peter Clausen <lars@metafoo.de>
To: Raymond Yau <superquad.vortex2@gmail.com>
Cc: ALSA Development Mailing List <alsa-devel@alsa-project.org>,
	Takashi Iwai <tiwai@suse.de>,
	clemens@ladisch.de, Tanu Kaskinen <tanu.kaskinen@linux.intel.com>,
	Arun Raghavan <arun@accosted.net>,
	David Henningsson <david.henningsson@canonical.com>
Subject: Re: PulseAudio and SNDRV_PCM_INFO_BATCH
Date: Mon, 22 Jun 2015 08:43:03 +0200	[thread overview]
Message-ID: <5587AE77.1020709@metafoo.de> (raw)
In-Reply-To: <CAN8ccibPTkiayx_9ETOwjw1dSF+UPsxjgcqWJR+mm149c69WBg@mail.gmail.com>

On 06/22/2015 04:35 AM, Raymond Yau wrote:
>
>  >
>  > DMA_RESIDUE_GRANULARITY_BURST means it can report the position with a
> granularity of a few samples. Typically half the audio FIFO size.
>  >
>  >
>
> How many soc driver/platform dma engine support DMA_RESIDUE_GRANULARITY_BURST ?

Not sure, maybe half of them. But most of the time it is a software 
restriction rather than a hardware restriction and more and more drivers are 
supporting it.

>
> Are all soc audio driver use cyclic dma ?

I'm not sure I understand the question. All audio drivers use some kind of 
cyclic DMA. ASoC platforms which do not have a dedicated audio DMA typically 
use dmaengine for this, while others which have dedicated audio DMA do the 
DMA as part of the audio driver.