ASoC: dmaengine_pcm: Make FLAG_NO_RESIDUE internal

Whether residue can be reported or not is not a property of the audio
controller but of the DMA controller. The FLAG_NO_RESIDUE was initially
added when the DMAengine framework had no support for describing the residue
reporting capabilities of the controller. Support for this was added quite a
while ago and recently the DMAengine framework started to complain if a
driver does not describe its capabilities and a lot of patches have been
merged that add support for this where it was missing. So it should be safe
to assume that driver on actively used platforms properly implement the DMA
capabilities API.

This patch makes the FLAG_NO_RESIDUE internal and no longer allows audio
controller drivers to manually set the flag. If a DMA driver against
expectations does not support reporting its capabilities for now the generic
DMAengine PCM driver will now emit a warning and simply assume that residue
reporting is not supported. In the future this might be changed to aborting
with an error.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 14 insertions, 11 deletions

diff --git a/sound/soc/soc-generic-dmaengine-pcm.c b/sound/soc/soc-generic-dmaengine-pcm.c
index c9917ca5de1a..6fd1906af387 100644
--- a/sound/soc/soc-generic-dmaengine-pcm.c
+++ b/sound/soc/soc-generic-dmaengine-pcm.c
@@ -24,6 +24,12 @@
 
 #include <sound/dmaengine_pcm.h>
 
+/*
+ * The platforms dmaengine driver does not support reporting the amount of
+ * bytes that are still left to transfer.
+ */
+#define SND_DMAENGINE_PCM_FLAG_NO_RESIDUE BIT(31)
+
 struct dmaengine_pcm {
 	struct dma_chan *chan[SNDRV_PCM_STREAM_LAST + 1];
 	const struct snd_dmaengine_pcm_config *config;
@@ -222,14 +228,18 @@ static struct dma_chan *dmaengine_pcm_compat_request_channel(
 	return snd_dmaengine_pcm_request_channel(fn, dma_data->filter_data);
 }
 
-static bool dmaengine_pcm_can_report_residue(struct dma_chan *chan)
+static bool dmaengine_pcm_can_report_residue(struct device *dev,
+	struct dma_chan *chan)
 {
 	struct dma_slave_caps dma_caps;
 	int ret;
 
 	ret = dma_get_slave_caps(chan, &dma_caps);
-	if (ret != 0)
-		return true;
+	if (ret != 0) {
+		dev_warn(dev, "Failed to get DMA channel capabilities, falling back to period counting: %d\n",
+			 ret);
+		return false;
+	}
 
 	if (dma_caps.residue_granularity == DMA_RESIDUE_GRANULARITY_DESCRIPTOR)
 		return false;
@@ -289,14 +299,7 @@ static int dmaengine_pcm_new(struct snd_soc_pcm_runtime *rtd)
 		if (ret)
 			return ret;
 
-		/*
-		 * This will only return false if we know for sure that at least
-		 * one channel does not support residue reporting. If the DMA
-		 * driver does not implement the slave_caps API we rely having
-		 * the NO_RESIDUE flag set manually in case residue reporting is
-		 * not supported.
-		 */
-		if (!dmaengine_pcm_can_report_residue(pcm->chan[i]))
+		if (!dmaengine_pcm_can_report_residue(dev, pcm->chan[i]))
 			pcm->flags |= SND_DMAENGINE_PCM_FLAG_NO_RESIDUE;
 	}