linux-kernel - [RFC V3 PATCH 7/8] dmaengine: xilinx_dma: Program interrupt delay timeout

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Message-ID: <20220920055119.12634-8-sarath.babu.naidu.gaddam@amd.com>
Date:   Tue, 20 Sep 2022 11:21:18 +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 7/8] dmaengine: xilinx_dma: Program interrupt delay timeout

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

Program IRQDelay for AXI DMA. The interrupt timeout mechanism causes
the DMA engine to generate an interrupt after the delay time period
has expired. It enables dmaengine to respond in real-time even though
interrupt coalescing is configured. It also remove the placeholder
for delay interrupt and merge it with frame completion interrupt.
Since by default interrupt delay timeout is disabled this feature
addition has no functional impact on VDMA and CDMA IP's.

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:
- None.

Changes in V2:
- Read irq delay timeout value from DT.
- Merge interrupt processing for frame done and delay interrupt.
---
 drivers/dma/xilinx/xilinx_dma.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
index 8126a56980f2..bd8f09837141 100644
--- a/drivers/dma/xilinx/xilinx_dma.c
+++ b/drivers/dma/xilinx/xilinx_dma.c
@@ -173,8 +173,10 @@
 #define XILINX_DMA_MAX_TRANS_LEN_MAX	23
 #define XILINX_DMA_V2_MAX_TRANS_LEN_MAX	26
 #define XILINX_DMA_CR_COALESCE_MAX	GENMASK(23, 16)
+#define XILINX_DMA_CR_DELAY_MAX		GENMASK(31, 24)
 #define XILINX_DMA_CR_CYCLIC_BD_EN_MASK	BIT(4)
 #define XILINX_DMA_CR_COALESCE_SHIFT	16
+#define XILINX_DMA_CR_DELAY_SHIFT	24
 #define XILINX_DMA_BD_SOP		BIT(27)
 #define XILINX_DMA_BD_EOP		BIT(26)
 #define XILINX_DMA_BD_COMP_MASK		BIT(31)
@@ -411,6 +413,7 @@ struct xilinx_dma_tx_descriptor {
  * @stop_transfer: Differentiate b/w DMA IP's quiesce
  * @tdest: TDEST value for mcdma
  * @has_vflip: S2MM vertical flip
+ * @irq_delay: Interrupt delay timeout
  */
 struct xilinx_dma_chan {
 	struct xilinx_dma_device *xdev;
@@ -449,6 +452,7 @@ struct xilinx_dma_chan {
 	int (*stop_transfer)(struct xilinx_dma_chan *chan);
 	u16 tdest;
 	bool has_vflip;
+	u8 irq_delay;
 };
 
 /**
@@ -1561,6 +1565,9 @@ static void xilinx_dma_start_transfer(struct xilinx_dma_chan *chan)
 	if (chan->has_sg)
 		xilinx_write(chan, XILINX_DMA_REG_CURDESC,
 			     head_desc->async_tx.phys);
+	reg  &= ~XILINX_DMA_CR_DELAY_MAX;
+	reg  |= chan->irq_delay << XILINX_DMA_CR_DELAY_SHIFT;
+	dma_ctrl_write(chan, XILINX_DMA_REG_DMACR, reg);
 
 	xilinx_dma_start(chan);
 
@@ -1896,15 +1903,8 @@ static irqreturn_t xilinx_dma_irq_handler(int irq, void *data)
 		}
 	}
 
-	if (status & XILINX_DMA_DMASR_DLY_CNT_IRQ) {
-		/*
-		 * Device takes too long to do the transfer when user requires
-		 * responsiveness.
-		 */
-		dev_dbg(chan->dev, "Inter-packet latency too long\n");
-	}
-
-	if (status & XILINX_DMA_DMASR_FRM_CNT_IRQ) {
+	if (status & (XILINX_DMA_DMASR_FRM_CNT_IRQ |
+		      XILINX_DMA_DMASR_DLY_CNT_IRQ)) {
 		spin_lock(&chan->lock);
 		xilinx_dma_complete_descriptor(chan);
 		chan->idle = true;
@@ -2831,6 +2831,8 @@ static int xilinx_dma_chan_probe(struct xilinx_dma_device *xdev,
 	/* Retrieve the channel properties from the device tree */
 	has_dre = of_property_read_bool(node, "xlnx,include-dre");
 
+	of_property_read_u8(node, "xlnx,irq-delay", &chan->irq_delay);
+
 	chan->genlock = of_property_read_bool(node, "xlnx,genlock-mode");
 
 	err = of_property_read_u32(node, "xlnx,datawidth", &value);
-- 
2.25.1