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

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On 06/02/15 13:31, Peter Ujfalusi wrote:
On 06/02/2015 11:58 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@xxxxxx>
---
  sound/soc/davinci/davinci-mcasp.c | 61 ++++++++++++++++++++++++++++++++-------
  1 file changed, 51 insertions(+), 10 deletions(-)

diff --git a/sound/soc/davinci/davinci-mcasp.c b/sound/soc/davinci/davinci-mcasp.c
index d793494..5bc2712 100644
--- a/sound/soc/davinci/davinci-mcasp.c
+++ b/sound/soc/davinci/davinci-mcasp.c
@@ -1565,6 +1565,46 @@ static int davinci_mcasp_init_ch_constraints(struct davinci_mcasp *mcasp)
  	return ret;
  }

+enum {
+	MCASP_EDMA = 1,

Why start from 1?

This is just an implementation detail, for "if" statement below. Maybe I should restucture for better readability.

I'm not sure about the name. It somehow implies that McASP has something to do
with the dma engine.
MCASP_SERVICED_BY_E/SDMA
PLATFORM_USES_E/SDMA

I can not come up with a decent name :(


What about PCM_EDMA/PCM_SDMA? This is a local definition after all.


+	MCASP_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 = MCASP_EDMA;
+
+	tmp = mcasp->dma_data[SNDRV_PCM_STREAM_PLAYBACK].filter_data;
+	chan = dma_request_slave_channel_reason(mcasp->dev, tmp);

this will return with error in case of !dev->of_node.
The first check should be:
if (!mcasp->dev->of_node)
	return MCASP_EDMA;

since we can only boot in legacy mode with daVinci devices and they are using
eDMA.

+	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);
+	else
+		dev_dbg(mcasp->dev, "DMA controller has no of-node\n");

Now this is not likely to happen...


Not having of_node happens on am335x, but not having compatible property is unlikely...

+
+	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 MCASP_SDMA;
+
+	return MCASP_EDMA;
+}
+
  static int davinci_mcasp_probe(struct platform_device *pdev)
  {
  	struct snd_dmaengine_dai_dma_data *dma_data;
@@ -1763,27 +1803,28 @@ static int davinci_mcasp_probe(struct platform_device *pdev)
  	if (ret != 0)
  		goto err;

-	switch (mcasp->version) {
+	ret = -EINVAL;

Why? What was the problem with setting the ret in the default case?

+	switch (davinci_mcasp_get_dma_type(mcasp)) {
+	case MCASP_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");
  #endif
+		break;
+	case MCASP_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");
  #endif
+		break;
  	default:
-		dev_err(&pdev->dev, "Invalid McASP version: %d\n",
-			mcasp->version);
-		ret = -EINVAL;
+		dev_err(&pdev->dev, "No DMA controller found\n");
  		break;
  	}





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