Re: [PATCH v2] ASoC: davinci-mcasp: Choose PCM driver based on configured DMA controller

[Jyri Sarha <jsarha@ti.com>]

On 06/02/15 19:16, Misael Lopez Cruz wrote:
> Jyri,
>
> On 06/02/2015 08:49 AM, Jyri Sarha wrote:
>> Find the configured DMA controller by asking for a DMA channel in the
>> probe phase and releasing it right after. The controller device can be
>> found via the dma_chan struct and the controller is recognized from
>> the compatible property of its device node. The patch assumes EDMA if
>> there is no device node.
>>
>> Signed-off-by: Jyri Sarha <jsarha@ti.com>
>> ---
>> Changes since first patch version:
>> - Change enum names from MCASP_?DMA to PCM_?DMA
>> - Return PCM_EDMA if !mcasp->dev->of_node
>> - Do not ignore possible error code returned by
>>    davinci_mcasp_get_dma_type()
>>
>>   sound/soc/davinci/davinci-mcasp.c | 68
>> +++++++++++++++++++++++++++++++++------
>>   1 file changed, 58 insertions(+), 10 deletions(-)
>>
>> diff --git a/sound/soc/davinci/davinci-mcasp.c
>> b/sound/soc/davinci/davinci-mcasp.c
>> index d793494..3b78c3e 100644
>> --- a/sound/soc/davinci/davinci-mcasp.c
>> +++ b/sound/soc/davinci/davinci-mcasp.c
>> @@ -1565,6 +1565,49 @@ static int
>> davinci_mcasp_init_ch_constraints(struct davinci_mcasp *mcasp)
>>       return ret;
>>   }
>>
>> +enum {
>> +    PCM_EDMA,
>> +    PCM_SDMA,
>> +};
>> +static const char *sdma_prefix = "ti,omap";
>> +
>> +static int davinci_mcasp_get_dma_type(struct davinci_mcasp *mcasp)
>> +{
>> +    struct dma_chan *chan;
>> +    const char *tmp;
>> +    int ret = PCM_EDMA;
>> +
>> +    if (!mcasp->dev->of_node)
>> +        return PCM_EDMA;
>> +
>> +    tmp = mcasp->dma_data[SNDRV_PCM_STREAM_PLAYBACK].filter_data;
>> +    chan = dma_request_slave_channel_reason(mcasp->dev, tmp);
>> +    if (IS_ERR(chan)) {
>> +        if (PTR_ERR(chan) != -EPROBE_DEFER)
>> +            dev_err(mcasp->dev,
>> +                "Can't verify DMA configuration (%ld)\n",
>> +                PTR_ERR(chan));
>> +        return PTR_ERR(chan);
>> +    }
>> +    BUG_ON(!chan->device || !chan->device->dev);
>> +
>> +    if (chan->device->dev->of_node)
>> +        ret = of_property_read_string(chan->device->dev->of_node,
>> +                          "compatible", &tmp);
>
> I wonder how this is going to play out when the DMA crossbar is present
> (i.e. dra7 family).
>
> In that case, isn't the 'compatible' string here that of the DMA
> crossbar (not the one from the DMA controller)?

That is exactly why I am requesting a channel and going from there. The 
DMA router will do its thing in the middle and the device pointer found 
via the returned dma_chan is pointing at the actual DMA controller.

I have tested the code on am57xx-beagle-x15, which is also using the DMA 
crossbar.

>
>> +    else
>> +        dev_dbg(mcasp->dev, "DMA controller has no of-node\n");
>> +
>> +    dma_release_channel(chan);
>> +    if (ret)
>> +        return ret;
>> +
>> +    dev_dbg(mcasp->dev, "DMA controller compatible = \"%s\"\n", tmp);
>> +    if (!strncmp(tmp, sdma_prefix, strlen(sdma_prefix)))
>> +        return PCM_SDMA;
>> +
>> +    return PCM_EDMA;
>> +}
>> +
>>   static int davinci_mcasp_probe(struct platform_device *pdev)
>>   {
>>       struct snd_dmaengine_dai_dma_data *dma_data;
>> @@ -1763,27 +1806,32 @@ static int davinci_mcasp_probe(struct
>> platform_device *pdev)
>>       if (ret != 0)
>>           goto err;
>>
>> -    switch (mcasp->version) {
>> +    ret = davinci_mcasp_get_dma_type(mcasp);
>> +    switch (ret) {
>> +    case PCM_EDMA:
>>   #if IS_BUILTIN(CONFIG_SND_EDMA_SOC) || \
>>       (IS_MODULE(CONFIG_SND_DAVINCI_SOC_MCASP) && \
>>        IS_MODULE(CONFIG_SND_EDMA_SOC))
>> -    case MCASP_VERSION_1:
>> -    case MCASP_VERSION_2:
>> -    case MCASP_VERSION_3:
>>           ret = edma_pcm_platform_register(&pdev->dev);
>> -        break;
>> +#else
>> +        dev_err(&pdev->dev, "Missing SND_EDMA_SOC\n");
>> +        ret = -EINVAL;
>>   #endif
>> +        break;
>> +    case PCM_SDMA:
>>   #if IS_BUILTIN(CONFIG_SND_OMAP_SOC) || \
>>       (IS_MODULE(CONFIG_SND_DAVINCI_SOC_MCASP) && \
>>        IS_MODULE(CONFIG_SND_OMAP_SOC))
>> -    case MCASP_VERSION_4:
>>           ret = omap_pcm_platform_register(&pdev->dev);
>> -        break;
>> +#else
>> +        dev_err(&pdev->dev, "Missing SND_SDMA_SOC\n");
>> +        ret = -EINVAL;
>>   #endif
>> +        break;
>> +    case -EPROBE_DEFER:
>> +        break;
>>       default:
>> -        dev_err(&pdev->dev, "Invalid McASP version: %d\n",
>> -            mcasp->version);
>> -        ret = -EINVAL;
>> +        dev_err(&pdev->dev, "No DMA controller found (%d)\n", ret);
>>           break;
>>       }
>>
>>