linux-kernel - [PATCH] dmaengine: xilinx_dma: Add support for residue on direct AXIDMA S2MM

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Message-Id: <20251218-xilinx-dma-residue-fix-v1-1-7cd221d69d6b@ideasonboard.com>
Date: Thu, 18 Dec 2025 10:39:37 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Vinod Koul <vkoul@...nel.org>, Michal Simek <michal.simek@....com>, 
 Vishal Sagar <vishal.sagar@....com>
Cc: dmaengine@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, 
 Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Subject: [PATCH] dmaengine: xilinx_dma: Add support for residue on direct
 AXIDMA S2MM

AXIDMA IP supports reporting the amount of bytes transferred on the S2MM
channel in direct mode (i.e. non-SG), but the driver does not. Thus the
driver always reports that all of the buffer was filled.

Add xilinx_dma_get_residue_axidma_direct_s2mm() which gets the residue
amount for direct AXIDMA for S2MM direction.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
---
 drivers/dma/xilinx/xilinx_dma.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
index fabff602065f..64b3fba4e44f 100644
--- a/drivers/dma/xilinx/xilinx_dma.c
+++ b/drivers/dma/xilinx/xilinx_dma.c
@@ -1021,6 +1021,24 @@ static u32 xilinx_dma_get_residue(struct xilinx_dma_chan *chan,
 	return residue;
 }
 
+static u32
+xilinx_dma_get_residue_axidma_direct_s2mm(struct xilinx_dma_chan *chan,
+					  struct xilinx_dma_tx_descriptor *desc)
+{
+	struct xilinx_axidma_tx_segment *seg;
+	struct xilinx_axidma_desc_hw *hw;
+	u32 finished_len;
+
+	finished_len = dma_ctrl_read(chan, XILINX_DMA_REG_BTT);
+
+	seg = list_first_entry(&desc->segments, struct xilinx_axidma_tx_segment,
+			       node);
+
+	hw = &seg->hw;
+
+	return hw->control - finished_len;
+}
+
 /**
  * xilinx_dma_chan_handle_cyclic - Cyclic dma callback
  * @chan: Driver specific dma channel
@@ -1732,6 +1750,9 @@ static void xilinx_dma_complete_descriptor(struct xilinx_dma_chan *chan)
 		if (chan->has_sg && chan->xdev->dma_config->dmatype !=
 		    XDMA_TYPE_VDMA)
 			desc->residue = xilinx_dma_get_residue(chan, desc);
+		else if (chan->xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA &&
+			 chan->direction == DMA_DEV_TO_MEM && !chan->has_sg)
+			desc->residue = xilinx_dma_get_residue_axidma_direct_s2mm(chan, desc);
 		else
 			desc->residue = 0;
 		desc->err = chan->err;

---
base-commit: 7d0a66e4bb9081d75c82ec4957c50034cb0ea449
change-id: 20251218-xilinx-dma-residue-fix-f6e4f97ffe61

Best regards,
-- 
Tomi Valkeinen <tomi.valkeinen@...asonboard.com>