Messages in this thread | | | Date | Thu, 13 Mar 2014 13:09:30 +0100 | From | Lars-Peter Clausen <> | Subject | Re: [alsa-devel] [PATCH 14/18] ASoC: davinci: Add edma dmaengine platform driver |
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On 03/13/2014 12:56 PM, Peter Ujfalusi wrote: > On 03/13/2014 12:28 PM, Lars-Peter Clausen wrote: >> On 03/13/2014 10:18 AM, Peter Ujfalusi wrote: [...] >>> +static const struct snd_pcm_hardware edma_pcm_hardware = { + .info >>> = SNDRV_PCM_INFO_MMAP | + SNDRV_PCM_INFO_MMAP_VALID | + >>> SNDRV_PCM_INFO_BATCH | + SNDRV_PCM_INFO_PAUSE | >>> SNDRV_PCM_INFO_RESUME | + SNDRV_PCM_INFO_INTERLEAVED, + >>> .buffer_bytes_max = 128 * 1024, + .period_bytes_min = 32, + >>> .period_bytes_max = 64 * 1024, + .periods_min = 2, + >>> .periods_max = 19, /* Limit by edma dmaengine driver */ +}; >> >> The idea is that we can auto-discover all the things using the >> dma_slave_caps API. Too bad we removed the possibility to specify the >> maximum number of segments from the API. Maybe we need to add it back. Is >> the 19 a hard-limit or could it be worked around by software in the >> dmaengine driver? > > The edma dmaengine driver will refuse to configure more than 20 paRAM slots (1 > for the channel + 19 for the periods). Depending on the SoC we might have > different number of paRAM entries available. The intention with the limit was > to prevent cases when we run out of paRAM entires for other devices because > audio took most of them.
The reason why we removed the max_segments field from the slave_caps struct was because we though it should be possible to, even when the hardware only supports a fixed amount of segments, emulate support for more in software. If this is not the case with the edma, we need to bring this field back.
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