[PATCH] dmaengine: xilinx_dma: Fix freeup active list based on descriptor completion bit

[Pandey, Radhey Shyam]

> -----Original Message-----
> From: Marek Vasut <marex at denx.de>
> Sent: Thursday, October 31, 2024 10:28 PM
> To: dmaengine at vger.kernel.org
> Cc: Marek Vasut <marex at denx.de>; Uwe Kleine-König <u.kleine-
> koenig at baylibre.com>; Simek, Michal <michal.simek at amd.com>; Peter Korsgaard
> <peter at korsgaard.com>; Pandey, Radhey Shyam
> <radhey.shyam.pandey at amd.com>; Vinod Koul <vkoul at kernel.org>; linux-arm-
> kernel at lists.infradead.org
> Subject: [PATCH] dmaengine: xilinx_dma: Fix freeup active list based on descriptor
> completion bit
> 
> The xilinx_dma is completely broken since the referenced commit,
> because if the (seg->hw.status & XILINX_DMA_BD_COMP_MASK) is not
> set for whatever reason, the current descriptor is never moved to

I want to understand more on this failure scenario.  How to replicate it?

Why is completion bit not set ? Based on the documentation completed bit
indicates to the software that the DMA Engine has completed the transfer
as described by the associated descriptor. The DMA Engine sets this bit 
to 1 when the transfer is completed.


> the done list, and the DMA stops moving data.
> 
> Isolate the newly added check to DMA which does implement irq_delay,
> that way the new check is matching what is likely some new bit in a
> new core, without breaking the DMA for older versions of the same
> core.
> 
> Fixes: 7bcdaa658102 ("dmaengine: xilinx_dma: Freeup active list based on
> descriptor completion bit")
> Signed-off-by: Marek Vasut <marex at denx.de>
> ---
> Cc: "Uwe Kleine-König" <u.kleine-koenig at baylibre.com>
> Cc: Michal Simek <michal.simek at amd.com>
> Cc: Peter Korsgaard <peter at korsgaard.com>
> Cc: Radhey Shyam Pandey <radhey.shyam.pandey at amd.com>
> Cc: Vinod Koul <vkoul at kernel.org>
> Cc: dmaengine at vger.kernel.org
> Cc: linux-arm-kernel at lists.infradead.org
> ---
>  drivers/dma/xilinx/xilinx_dma.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
> index 1bdd57de87a6e..48647c8a64a5b 100644
> --- a/drivers/dma/xilinx/xilinx_dma.c
> +++ b/drivers/dma/xilinx/xilinx_dma.c
> @@ -1718,7 +1718,8 @@ static void xilinx_dma_complete_descriptor(struct
> xilinx_dma_chan *chan)
>  		return;
> 
>  	list_for_each_entry_safe(desc, next, &chan->active_list, node) {
> -		if (chan->xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA) {
> +		if (chan->xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA
> &&
> +		    chan->irq_delay) {
>  			struct xilinx_axidma_tx_segment *seg;
> 
>  			seg = list_last_entry(&desc->segments,
> --
> 2.45.2