[alsa-devel] [PATCH 2/2] ASoC: use dma_ops of parent device for acp_audio_dma

[Yu Zhao]

AMD platform device acp_audio_dma can only be created by parent PCI
device driver (drivers/gpu/drm/amd/amdgpu/amdgpu_acp.c). 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 in mfd_add_device(), 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: Yu Zhao <yuzhao at google.com>
---
 sound/soc/amd/acp-pcm-dma.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/sound/soc/amd/acp-pcm-dma.c b/sound/soc/amd/acp-pcm-dma.c
index fd3db4c37882..f4011bebc7ec 100644
--- a/sound/soc/amd/acp-pcm-dma.c
+++ b/sound/soc/amd/acp-pcm-dma.c
@@ -1146,18 +1146,21 @@ static int acp_dma_new(struct snd_soc_pcm_runtime *rtd)
 	struct snd_soc_component *component = snd_soc_rtdcom_lookup(rtd,
 								    DRV_NAME);
 	struct audio_drv_data *adata = dev_get_drvdata(component->dev);
+	struct device *parent = component->dev->parent;
 
 	switch (adata->asic_type) {
 	case CHIP_STONEY:
 		ret = snd_pcm_lib_preallocate_pages_for_all(rtd->pcm,
 							    SNDRV_DMA_TYPE_DEV,
-							    NULL, ST_MIN_BUFFER,
+							    parent,
+							    ST_MIN_BUFFER,
 							    ST_MAX_BUFFER);
 		break;
 	default:
 		ret = snd_pcm_lib_preallocate_pages_for_all(rtd->pcm,
 							    SNDRV_DMA_TYPE_DEV,
-							    NULL, MIN_BUFFER,
+							    parent,
+							    MIN_BUFFER,
 							    MAX_BUFFER);
 		break;
 	}
-- 
2.20.0.rc1.387.gf8505762e3-goog