linux-kernel - [RFC V3 PATCH 5/8] dmaengine: xilinx_dma: Freeup active list based on descriptor completion bit

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Date:   Tue, 20 Sep 2022 11:21:16 +0530
From:   Sarath Babu Naidu Gaddam <sarath.babu.naidu.gaddam@....com>
To:     <vkoul@...nel.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <lars@...afoo.de>,
        <adrianml@...mnos.upm.es>
CC:     <dmaengine@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <michal.simek@....com>,
        <radhey.shyam.pandey@....com>, <anirudha.sarangi@....com>,
        <harini.katakam@....com>, <sarath.babu.naidu.gaddam@....com>,
        <git@...inx.com>, <git@....com>
Subject: [RFC V3 PATCH 5/8] dmaengine: xilinx_dma: Freeup active list based on descriptor completion bit

From: Radhey Shyam Pandey <radhey.shyam.pandey@...inx.com>

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 <radhey.shyam.pandey@...inx.com>
Signed-off-by: Sarath Babu Naidu Gaddam <sarath.babu.naidu.gaddam@....com>
---
Changes in V3:
- Addressed RFC V2 review comment in xilinx_dma_complete_descriptor.
  "remove hardcoding for axidma_tx_segment".

- Below review comment is in pipeline. We are facing a race issue when
  addressing it. we will fix it in the next version.
  "chan->idle = true; in xilinx_dma_irq_handler() needs to be gated on
   the active_list being empty".

Changes in V2:
- Check BD completion bit only for SG mode.
- Modify the logic to have early return path.
---
 drivers/dma/xilinx/xilinx_dma.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
index 8c6065cbda79..1488cc6a299a 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
@@ -1706,6 +1707,14 @@ 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) {
+			struct xilinx_axidma_tx_segment *seg;
+
+			seg = list_last_entry(&desc->segments,
+					      struct xilinx_axidma_tx_segment, node);
+			if (!(seg->hw.status & XILINX_DMA_BD_COMP_MASK) && chan->has_sg)
+				break;
+		}
 		if (chan->has_sg && chan->xdev->dma_config->dmatype !=
 		    XDMA_TYPE_VDMA)
 			desc->residue = xilinx_dma_get_residue(chan, desc);
-- 
2.25.1