-----Original Message-----
From: Lars-Peter Clausen <lars@metafoo.de>
Sent: Thursday, April 15, 2021 12:56 PM
To: Radhey Shyam Pandey <redacted>; vkoul@kernel.org;
robh+dt@kernel.org; Michal Simek [off-list ref]
Cc: dmaengine@vger.kernel.org; devicetree@vger.kernel.org; linux-arm-
kernel@lists.infradead.org; linux-kernel@vger.kernel.org; git
[off-list ref]
Subject: Re: [RFC v2 PATCH 5/7] dmaengine: xilinx_dma: Freeup active list
based on descriptor completion bit

On 4/9/21 7:56 PM, Radhey Shyam Pandey wrote:

quoted

AXIDMA IP in SG mode sets completion bit to 1 when the transfer is
completed. Read this bit to move descriptor from active list to the
done list. This feature is needed when interrupt delay timeout and
IRQThreshold is enabled i.e Dly_IrqEn is triggered w/o completing
interrupt threshold.

Signed-off-by: Radhey Shyam Pandey <redacted>
---
- Check BD completion bit only for SG mode.
- Modify the logic to have early return path.
---
  drivers/dma/xilinx/xilinx_dma.c | 7 +++++++
  1 file changed, 7 insertions(+)

diff --git a/drivers/dma/xilinx/xilinx_dma.c

b/drivers/dma/xilinx/xilinx_dma.c index 890bf46b36e5..f2305a73cb91
100644

--- a/drivers/dma/xilinx/xilinx_dma.c
+++ b/drivers/dma/xilinx/xilinx_dma.c

@@ -177,6 +177,7 @@
  #define XILINX_DMA_CR_COALESCE_SHIFT	16
  #define XILINX_DMA_BD_SOP		BIT(27)
  #define XILINX_DMA_BD_EOP		BIT(26)
+#define XILINX_DMA_BD_COMP_MASK		BIT(31)
  #define XILINX_DMA_COALESCE_MAX		255
  #define XILINX_DMA_NUM_DESCS		512
  #define XILINX_DMA_NUM_APP_WORDS	5

@@ -1683,12 +1684,18 @@ static void xilinx_dma_issue_pending(struct

dma_chan *dchan)

quoted

  static void xilinx_dma_complete_descriptor(struct xilinx_dma_chan

*chan)

quoted

  {
  	struct xilinx_dma_tx_descriptor *desc, *next;
+	struct xilinx_axidma_tx_segment *seg;

  	/* This function was invoked with lock held */
  	if (list_empty(&chan->active_list))
  		return;

  	list_for_each_entry_safe(desc, next, &chan->active_list, node) {
+		/* TODO: remove hardcoding for axidma_tx_segment */
+		seg = list_last_entry(&desc->segments,
+				      struct xilinx_axidma_tx_segment, node);
+		if (!(seg->hw.status & XILINX_DMA_BD_COMP_MASK) &&

chan->has_sg)

quoted

+			break;
  		if (chan->has_sg && chan->xdev->dma_config->dmatype !=
  		    XDMA_TYPE_VDMA)
  			desc->residue = xilinx_dma_get_residue(chan, desc);

Since not all descriptors will be completed in this function the `chan->idle =
true;` in xilinx_dma_irq_handler() needs to be gated on the active_list being
empty.

Thanks for pointing it out. Agree to it, will fix it in the next version.

xilinx_dma_complete_descriptor