[alsa-devel] [PATCH 2/3] ASoC: amd: use dma_ops of parent device for acp3x dma driver

[Ravulapati Vishnu vardhan rao]

AMD platform device acp_audio_dma can only be created by parent PCI
device driver. Pass struct device of the parent
to snd_pcm_lib_preallocate_pages() so dma_alloc_coherent()
can use correct dma_ops. Otherwise, it will
use default dma_ops which is nommu_dma_ops on x86_64 even when
IOMMU is enabled and set to non passthrough mode.

Though platform device inherits some dma related fields during its
creation, we can't simply pass its struct device
to snd_pcm_lib_preallocate_pages() because dma_ops is not among the
inherited fields. Even it were, drivers/iommu/amd_iommu.c would
ignore it because get_device_id() doesn't handle platform device.

This change shouldn't give us any trouble even struct device of the
parent becomes null or represents some non PCI device in the future,
because get_dma_ops() correctly handles null struct device or uses
the default dma_ops if struct device doesn't have it set.

Signed-off-by: Vijendar Mukunda <vijendar.mukunda at amd.com>
Tested-by: Ravulapati, Vishnu vardhan rao <Vishnuvardhanrao.Ravulapati at amd.com>
---
 sound/soc/amd/raven/acp3x-pcm-dma.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/sound/soc/amd/raven/acp3x-pcm-dma.c b/sound/soc/amd/raven/acp3x-pcm-dma.c
index 49c4872..c74b094b 100644
--- a/sound/soc/amd/raven/acp3x-pcm-dma.c
+++ b/sound/soc/amd/raven/acp3x-pcm-dma.c
@@ -384,9 +384,14 @@ static snd_pcm_uframes_t acp3x_dma_pointer(struct snd_pcm_substream *substream)
 
 static int acp3x_dma_new(struct snd_soc_pcm_runtime *rtd)
 {
-	snd_pcm_lib_preallocate_pages_for_all(rtd->pcm, SNDRV_DMA_TYPE_DEV,
-					      rtd->pcm->card->dev,
-					      MIN_BUFFER, MAX_BUFFER);
+	struct snd_soc_component *component = snd_soc_rtdcom_lookup(rtd,
+								    DRV_NAME);
+	struct device *parent = component->dev->parent;
+
+	snd_pcm_lib_preallocate_pages_for_all(rtd->pcm,
+							SNDRV_DMA_TYPE_DEV,
+							parent, MIN_BUFFER,
+							MAX_BUFFER);
 	return 0;
 }
 
-- 
2.7.4