linux-kernel - [PATCH 7/7] dma: fsl-edma: Support source stride for interleaved DMA transfers

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Message-Id: <20251124-dma-coldfire-v1-7-dc8f93185464@yoseli.org>
Date: Mon, 24 Nov 2025 13:50:28 +0100
From: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
To: Frank Li <Frank.Li@....com>, Vinod Koul <vkoul@...nel.org>
Cc: Greg Ungerer <gerg@...ux-m68k.org>, imx@...ts.linux.dev, 
 dmaengine@...r.kernel.org, linux-m68k@...ts.linux-m68k.org, 
 linux-kernel@...r.kernel.org, 
 Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
Subject: [PATCH 7/7] dma: fsl-edma: Support source stride for interleaved
 DMA transfers

Add support for using src_port_window_size to configure the source
address stride (SOFF) in DMA transfers. This enables interleaved
memory access patterns needed for applications like stereo audio
de-interleaving.

When src_port_window_size is set, the source offset is calculated as:
  SOFF = src_port_window_size * dst_addr_width

This allows DMA to skip samples in memory while writing consecutive
samples to the device, enabling efficient stereo-to-mono de-interleaving
without CPU intervention.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
---
 drivers/dma/fsl-edma-common.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/dma/fsl-edma-common.c b/drivers/dma/fsl-edma-common.c
index 40ac6a7d8480b9ed2c6a2bdec59b4fda5fcb6271..e510cab24382fa557a2623465393c852b616fef3 100644
--- a/drivers/dma/fsl-edma-common.c
+++ b/drivers/dma/fsl-edma-common.c
@@ -647,6 +647,9 @@ struct dma_async_tx_descriptor *fsl_edma_prep_dma_cyclic(
 			doff = fsl_chan->is_multi_fifo ? 4 : 0;
 			if (fsl_chan->cfg.dst_port_window_size)
 				doff = fsl_chan->cfg.dst_addr_width;
+			if (fsl_chan->cfg.src_port_window_size)
+				soff = fsl_chan->cfg.src_port_window_size *
+					fsl_chan->cfg.dst_addr_width;
 		} else if (direction == DMA_DEV_TO_MEM) {
 			src_addr = fsl_chan->dma_dev_addr;
 			dst_addr = dma_buf_next;
@@ -714,6 +717,9 @@ struct dma_async_tx_descriptor *fsl_edma_prep_slave_sg(
 			dst_addr = fsl_chan->dma_dev_addr;
 			soff = fsl_chan->cfg.dst_addr_width;
 			doff = 0;
+			if (fsl_chan->cfg.src_port_window_size)
+				soff = fsl_chan->cfg.src_port_window_size *
+					fsl_chan->cfg.dst_addr_width;
 		} else if (direction == DMA_DEV_TO_MEM) {
 			src_addr = fsl_chan->dma_dev_addr;
 			dst_addr = sg_dma_address(sg);

-- 
2.39.5