linux-kernel - Re: [PATCH V2 6/6] dmaengine: xilinx_dma: Program interrupt delay timeout

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Date:   Wed, 28 Dec 2022 16:30:45 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Sarath Babu Naidu Gaddam <sarath.babu.naidu.gaddam@....com>
Cc:     robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        lars@...afoo.de, adrianml@...mnos.upm.es,
        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, git@....com
Subject: Re: [PATCH V2 6/6] dmaengine: xilinx_dma: Program interrupt delay
 timeout

On 24-11-22, 15:57, Sarath Babu Naidu Gaddam wrote:
> 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>
> ---
>  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 ce0c151d8f61..333d68ee3559 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_COALESCE_MAX		255
> @@ -410,6 +412,7 @@ 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;
> @@ -448,6 +451,7 @@ struct xilinx_dma_chan {
>  	int (*stop_transfer)(struct xilinx_dma_chan *chan);
>  	u16 tdest;
>  	bool has_vflip;
> +	u8 irq_delay;
>  };
>  
>  /**
> @@ -1560,6 +1564,9 @@ 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);
>  
> @@ -1887,15 +1894,8 @@ 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;
> @@ -2822,6 +2822,8 @@ 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);

Same question here too

> +
>  	chan->genlock = of_property_read_bool(node, "xlnx,genlock-mode");
>  
>  	err = of_property_read_u32(node, "xlnx,datawidth", &value);
> -- 
> 2.25.1

-- 
~Vinod