dma: Add max block count attribute

Adds an attribute that describes the maximum number of scatter gather
blocks that the DMA will accept. Useful in cases where DMA is used as
the abstraction for moving data around (e.g. SoF audio streams) and
variances of the hardware need to inform decisions about how to use
the DMA API.

Co-authored-by: Adrian Bonislawski <adrian.bonislawski@intel.com>
Co-authored-by: Jaska Uimonen <jaska.uimonen@intel.com>
Signed-off-by: Tom Burdick <thomas.burdick@intel.com>

drivers/dma/dma_intel_adsp_gpdma.c

@@ -292,6 +292,9 @@ int intel_adsp_gpdma_get_attribute(const struct device *dev, uint32_t type, uint
 	case DMA_ATTR_COPY_ALIGNMENT:
 		*value = DMA_COPY_ALIGNMENT(DT_COMPAT_GET_ANY_STATUS_OKAY(intel_adsp_gpdma));
 		break;
+	case DMA_ATTR_MAX_BLOCK_COUNT:
+		*value = CONFIG_DMA_DW_LLI_POOL_SIZE;
+		break;
 	default:
 		return -EINVAL;
 	}

drivers/dma/dma_intel_adsp_hda.c

@@ -280,6 +280,9 @@ int intel_adsp_hda_dma_get_attribute(const struct device *dev, uint32_t type, ui
 	case DMA_ATTR_COPY_ALIGNMENT:
 		*value = DMA_COPY_ALIGNMENT(DT_COMPAT_GET_ANY_STATUS_OKAY(intel_adsp_hda_link_out));
 		break;
+	case DMA_ATTR_MAX_BLOCK_COUNT:
+		*value = 1;
+		break;
 	default:
 		return -EINVAL;
 	}

include/zephyr/drivers/dma.h

@@ -71,6 +71,7 @@ enum dma_attribute_type {
 	DMA_ATTR_BUFFER_ADDRESS_ALIGNMENT,
 	DMA_ATTR_BUFFER_SIZE_ALIGNMENT,
 	DMA_ATTR_COPY_ALIGNMENT,
+	DMA_ATTR_MAX_BLOCK_COUNT,
 };
 
 /**