Re: [PATCH V6 2/4] dmaengine: xilinx_dma: Move descriptors to done list based on completion bit

[Frank Li]

On Tue, Aug 18, 2026 at 11:11:49PM +0530, Srinivas Neeli wrote:
> In AXI MCDMA, xilinx_dma_complete_descriptor() walks the channel's
> active_list and unconditionally moves every entry to the done_list. The
> MCDMA IOC interrupt handler invokes this function on every
> interrupt-on-completion, but with interrupt coalescing (IRQThreshold > 1)
> an IOC interrupt may fire after only a subset of the queued descriptors
> have actually been processed by the hardware. As a result, descriptors
> whose completion bit is not yet set in the BD status were being reported
> as completed to client drivers.
>
> Add a check for the descriptor completion bit before moving entries from
> the active list to the done list, using the appropriate direction-
> specific status field (s2mm_status for DMA_DEV_TO_MEM, mm2s_status for
> DMA_MEM_TO_DEV).
>
> This mirrors the AXIDMA fix in commit 7bcdaa658102 ("dmaengine:
> xilinx_dma: Freeup active list based on descriptor completion bit").
>
> Fixes: 6ccd692bfb7f ("dmaengine: xilinx_dma: Add Xilinx AXI MCDMA Engine driver support")
> Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xxxxxxx>
> Signed-off-by: Srinivas Neeli <srinivas.neeli@xxxxxxx>
> ---

Reviewed-by: Frank Li <Frank.Li@xxxxxxx>

> Changes in V6:
>  - No change.
>
> Changes in V5:
>  - No change.
>
> Changes in V4:
>  - Reworded commit message to reference the AXIDMA fix it mirrors
>    (commit 7bcdaa658102).
>  - Added Reviewed-by: Radhey Shyam Pandey.
>
> Changes in V3:
>  - Added Fixes tag.
>  - Expanded commit message to explain the interrupt coalescing scenario
>    and why the has_sg guard is omitted for MCDMA.
>  - Changed local variable from 'bool completed' to 'u32 status' for
>    cleaner status field access.
>  - Simplified completion check logic.
>
> Changes in V2:
>  - No change.
> ---
>  drivers/dma/xilinx/xilinx_dma.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
> index 2319101be778..506ce1ec29bc 100644
> --- a/drivers/dma/xilinx/xilinx_dma.c
> +++ b/drivers/dma/xilinx/xilinx_dma.c
> @@ -1784,6 +1784,17 @@ static void xilinx_dma_complete_descriptor(struct xilinx_dma_chan *chan)
>  					      struct xilinx_axidma_tx_segment, node);
>  			if (!(seg->hw.status & XILINX_DMA_BD_COMP_MASK) && chan->has_sg)
>  				break;
> +		} else if (chan->xdev->dma_config->dmatype == XDMA_TYPE_AXIMCDMA) {
> +			struct xilinx_aximcdma_tx_segment *seg;
> +			u32 status;
> +
> +			seg = list_last_entry(&desc->segments,
> +					      struct xilinx_aximcdma_tx_segment,
> +					      node);
> +			status = (chan->direction == DMA_DEV_TO_MEM) ?
> +				seg->hw.s2mm_status : seg->hw.mm2s_status;
> +			if (!(status & XILINX_DMA_BD_COMP_MASK))
> +				break;
>  		}
>  		if (chan->has_sg && chan->xdev->dma_config->dmatype !=
>  		    XDMA_TYPE_VDMA)
> --
> 2.43.0
>