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

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Message-ID:
 <MN0PR12MB59533CB998FCF1F6D5D343A0B71BA@MN0PR12MB5953.namprd12.prod.outlook.com>
Date: Mon, 29 Sep 2025 05:44:38 +0000
From: "Pandey, Radhey Shyam" <radhey.shyam.pandey@....com>
To: "Gupta, Suraj" <Suraj.Gupta2@....com>, "vkoul@...nel.org"
	<vkoul@...nel.org>, "Simek, Michal" <michal.simek@....com>
CC: "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 2/3] dmaengine: xilinx_dma: Enable transfer chaining by
 removing idle restriction

[AMD Official Use Only - AMD Internal Distribution Only]

> -----Original Message-----
> From: Suraj Gupta <suraj.gupta2@....com>
> Sent: Wednesday, September 17, 2025 7:06 PM
> To: vkoul@...nel.org; Pandey, Radhey Shyam <radhey.shyam.pandey@....com>;
> Simek, Michal <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.

As we already have changes ready for MCDMA - please merge it in v2.
Both axidma /mcdma will support axistream connected.

>
> 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