[alsa-devel] [PATCH 03/17] ASoC: Add a generic dmaengine_pcm driver

[Stephen Warren]

On 04/15/2013 11:31 PM, Lars-Peter Clausen wrote:
> On 04/16/2013 01:15 AM, Stephen Warren wrote:
>> On 04/15/2013 11:19 AM, Lars-Peter Clausen wrote:
>>> This patch adds a generic dmaengine PCM driver. It builds on top of the
>>> dmaengine PCM library and adds the missing pieces like DMA channel management,
>>> buffer management and channel configuration. It will be able to replace the
>>> majority of the existing platform specific dmaengine based PCM drivers.
>>
>>> Devicetree is used to map the DMA channels to the PCM device.
>> ...
>>> diff --git a/sound/soc/soc-generic-dmaengine-pcm.c b/sound/soc/soc-generic-dmaengine-pcm.c
>> ...
>>> +static const char * const dmaengine_pcm_dma_channel_names[] = {
>>> +	[SNDRV_PCM_STREAM_PLAYBACK] = "tx",
>>> +	[SNDRV_PCM_STREAM_CAPTURE] = "rx",
>>> +};
>> ...
>>> +int snd_dmaengine_pcm_register(struct device *dev,
>>> +	const struct snd_dmaengine_pcm_config *config, unsigned int flags)
>> ...
>>> +	for (i = SNDRV_PCM_STREAM_PLAYBACK; i <= SNDRV_PCM_STREAM_CAPTURE; i++) {
>>> +		pcm->chan[i] = of_dma_request_slave_channel(dev->of_node,
>>> +					dmaengine_pcm_dma_channel_names[i]);
>>
>> That all means that the Tegra patch won't work yet. Tegra currently uses
>> a custom DT binding for DMA since we haven't fully converted everything
>> over the very new DT DMA bindings. So, the patches for Tegra may well be
>> fine /if/ staged in the correct order with some .dts file changes too.
>>
>> I wonder if all the other platforms this series modifies already have
>> the appropriate DMA properties set up? A very quick look implies that
>> (at least some) imx and omap do, but I'm not sure about spear, ep93xx,
>> ux500?
>>
>> Perhaps Laxman can provide appropriate DT fixes for Tegra while I'm on
>> vacation, and test out this series, if I don't get to it in the next 2
>> days before my vacation.
> 
> None of the converted platforms is changed to use DT yet, they all use the
> compat path. So there shouldn't be any functional change for them. Converting
> them to use the generic DT bindings can be done one by one later.

Ah right. So, this series works fine on Tegra20 at least:

Tested-by: Stephen Warren <swarren at nvidia.com>