linux-kernel - [PATCH 2/3] dmaengine: xilinx_dma: Enable transfer chaining by removing idle restriction

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Message-ID: <20250917133609.231316-3-suraj.gupta2@amd.com>
Date: Wed, 17 Sep 2025 19:06:08 +0530
From: Suraj Gupta <suraj.gupta2@....com>
To: <vkoul@...nel.org>, <radhey.shyam.pandey@....com>, <michal.simek@....com>
CC: <dmaengine@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH 2/3] dmaengine: xilinx_dma: Enable transfer chaining by removing idle restriction

Remove the restrictive idle check in xilinx_dma_start_transfer() that
prevented new transfers from being queued when the channel was busy.
Additionally, only update the CURDESC register when the active list
is empty to avoid interfering with transfers already in progress.
When the active list contains transfers, the hardware tail pointer
extension mechanism handles chaining automatically.

Signed-off-by: Suraj Gupta <suraj.gupta2@....com>
---
 drivers/dma/xilinx/xilinx_dma.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
index 9f416eae33d0..7211c394cdca 100644
--- a/drivers/dma/xilinx/xilinx_dma.c
+++ b/drivers/dma/xilinx/xilinx_dma.c
@@ -1548,9 +1548,6 @@ static void xilinx_dma_start_transfer(struct xilinx_dma_chan *chan)
 	if (list_empty(&chan->pending_list))
 		return;
 
-	if (!chan->idle)
-		return;
-
 	head_desc = list_first_entry(&chan->pending_list,
 				     struct xilinx_dma_tx_descriptor, node);
 	tail_desc = list_last_entry(&chan->pending_list,
@@ -1567,7 +1564,7 @@ static void xilinx_dma_start_transfer(struct xilinx_dma_chan *chan)
 		dma_ctrl_write(chan, XILINX_DMA_REG_DMACR, reg);
 	}
 
-	if (chan->has_sg)
+	if (chan->has_sg && list_empty(&chan->active_list))
 		xilinx_write(chan, XILINX_DMA_REG_CURDESC,
 			     head_desc->async_tx.phys);
 	reg  &= ~XILINX_DMA_CR_DELAY_MAX;
-- 
2.25.1