Messages in this thread | | | Date | Thu, 13 Mar 2014 11:28:05 +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 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?
> + > +static const struct snd_dmaengine_pcm_config edma_dmaengine_pcm_config = { > + .pcm_hardware = &edma_pcm_hardware, > + .prepare_slave_config = snd_dmaengine_pcm_prepare_slave_config, > + .prealloc_buffer_size = 128 * 1024,
Unless there is a very good reason for exactly this size, just leave it 0 and let the generic dmaengine driver use the default.
> +}; > + > +static const struct snd_dmaengine_pcm_config edma_compat_dmaengine_pcm_config = { > + .pcm_hardware = &edma_pcm_hardware, > + .prepare_slave_config = snd_dmaengine_pcm_prepare_slave_config, > + .compat_filter_fn = edma_filter_fn, > + .prealloc_buffer_size = 128 * 1024, > +};
There is no need for different configs for DT and non-DT.
> + > +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.
> + else > + return snd_dmaengine_pcm_register(dev, > + &edma_compat_dmaengine_pcm_config, > + SND_DMAENGINE_PCM_FLAG_NO_RESIDUE | > + SND_DMAENGINE_PCM_FLAG_NO_DT | > + SND_DMAENGINE_PCM_FLAG_COMPAT);
If you set the flags to just SND_DMAENGINE_PCM_FLAG_COMPAT it will do the right thing in the generic dmaengine driver depending on whether dev->of_node is set or not.
There is also a devm_ version of snd_dmaengine_pcm_register() it probably makes sense to use it here.
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