[alsa-devel] ALSA DMA ping-pong

[Ran Shalit]

Hello,

I hope someone can help me understand the concept of ping-pong dma with ALSA.
I am using davinci soc: /sound/soc/davinci/davinci_pcm.c
But I am not sure if it using ping-pong dma or not.
In the header of "davinci_pcm_enqueue_dma" function it states "Not
used with ping/pong", but inside I see that it use period parameter in
order to set the offset inside the dma buffer which is used.
So, does it mean that ping-pong is used or not ?

/*
 * Not used with ping/pong
 */
static void davinci_pcm_enqueue_dma(struct snd_pcm_substream *substream)
.....

period_size = snd_pcm_lib_period_bytes(substream);
dma_offset = prtd->period * period_size;
dma_pos = runtime->dma_addr + dma_offset;
....


acnt = prtd->params->acnt;
edma_set_src(link, src, INCR, W8BIT);
edma_set_dest(link, dst, INCR, W8BIT);
......
}

Regards,
Ran