[alsa-devel] [PATCH 4/4] ASoC: DaVinci: pcm, fix underrun by using sram

[troy.kisky at boundarydevices.com]

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 On Tue 13/07/10 6:00 AM , "Nori, Sekhar" nsekhar at ti.com sent:
	Hi Troy,
 On Tue, Nov 17, 2009 at 05:22:34, Troy Kisky wrote:
 > Fix underruns by using dma to copy 1st to sram
 > in a ping/pong buffer style and then copying from
 > the sram to the ASP. This also has the advantage
 > of tolerating very long interrupt latency on dma
 > completion.
 >
 > Signed-off-by: Troy Kisky 
 [...]
 > +static int request_ping_pong(struct snd_pcm_substream *substream,
 > + struct davinci_runtime_data *prtd,
 > + struct snd_dma_buffer *iram_dma)
 > +{
 > + dma_addr_t asp_src_ping;
 > + dma_addr_t asp_dst_ping;
 > + int link;
 > + struct davinci_pcm_dma_params *dma_data = prtd->params;
 > +
 > + /* Request ram master channel */
 > + link = prtd->ram_channel = edma_alloc_channel(EDMA_CHANNEL_ANY,
 > + davinci_pcm_dma_irq, substream,
 > + EVENTQ_1);
 What is the reason for choosing EVENTQ_1 for this channel? EVENTQ_0
 is already being used for ASP channel.
 I imagine it will be much easier to tune the queue usage in the
system
 if all of audio data was using the same queue.
 I am working on a patch which lets platform specify the event queues
 for audio DMA. I am not sure if I really need to make a provision
for
 two different queues to be specified - that's why I ask.
 Thanks,
 Sekhar
	The reason is so that the IRAM data can be fetched and used while 

	EVENTQ_1 fetches the next buffer of data from sdram into IRAM. 
	Troy