[PATCH] ASoC: soc-generic-dmaengine: report DMA channel request failures more clearly

[phucduc.bui@gmail.com]

From: bui duc phuc <phucduc.bui@gmail.com>

Currently any dma_request_chan() failure other than -EPROBE_DEFER is
silently ignored, since a missing channel is expected for devices that
only support one DMA direction. This makes two real problems
indistinguishable from that normal case:

1. If the channel name is actually present in "dma-names" but the
request still fails, that is a genuine error, not a missing direction
warn about it instead of staying silent.

2. If neither direction ends up with a channel, the PCM device is
entirely unusable. Unlike missing just one direction, this is never
expected, so fail probe with a clear error instead of registering a
non-functional PCM device.

No change for the still-silent, still-supported case of a device that
legitimately onlysupports one direction.

Signed-off-by: bui duc phuc <phucduc.bui@gmail.com>
---
 sound/soc/soc-generic-dmaengine-pcm.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/sound/soc/soc-generic-dmaengine-pcm.c b/sound/soc/soc-generic-dmaengine-pcm.c
index 467426d2b5e4..c15c2d8248fa 100644
--- a/sound/soc/soc-generic-dmaengine-pcm.c
+++ b/sound/soc/soc-generic-dmaengine-pcm.c
@@ -395,6 +395,11 @@ static int dmaengine_pcm_request_chan_of(struct dmaengine_pcm *pcm,
 			 */
 			if (PTR_ERR(chan) == -EPROBE_DEFER)
 				return -EPROBE_DEFER;
+
+			if (device_property_match_string(dev, "dma-names", name) >= 0)
+				dev_warn(dev, "dma-names has '%s' but request failed (%ld)\n",
+					 name, PTR_ERR(chan));
+
 			pcm->chan[i] = NULL;
 		} else {
 			pcm->chan[i] = chan;
@@ -406,6 +411,12 @@ static int dmaengine_pcm_request_chan_of(struct dmaengine_pcm *pcm,
 	if (pcm->flags & SND_DMAENGINE_PCM_FLAG_HALF_DUPLEX)
 		pcm->chan[1] = pcm->chan[0];
 
+	if (!pcm->chan[SNDRV_PCM_STREAM_PLAYBACK] &&
+	    !pcm->chan[SNDRV_PCM_STREAM_CAPTURE]) {
+		dev_err(dev, "no DMA chanel found for either playback or capture\n");
+		return -ENODEV;
+	}
+
 	return 0;
 }
 
-- 
2.43.0