linux-kernel - Re: [LINUX PATCH 2/4] dmaengine: xilinx_dma: Fix race condition in the driver for cdma

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Message-ID: <20180103035845.GG18649@localhost>
Date:   Wed, 3 Jan 2018 09:28:45 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Kedareswara rao Appana <appana.durga.rao@...inx.com>
Cc:     dan.j.williams@...el.com, michal.simek@...inx.com,
        appanad@...inx.com, lars@...afoo.de, akinobu.mita@...il.com,
        joabreu@...opsys.com, mike.looijmans@...ic.nl, kedare06@...il.com,
        dmaengine@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [LINUX PATCH 2/4] dmaengine: xilinx_dma: Fix race condition in
 the driver for cdma

On Thu, Dec 21, 2017 at 03:41:36PM +0530, Kedareswara rao Appana wrote:

same issue for patch title here too

> when hardware is idle we need to toggle the SG bit
> in the control register, inorder to update new value to the
> current descriptor register other wise undefined
> results will occur.

can you try making it bit more clear..

> 
> This patch updates the same.
> 
> Signed-off-by: Kedareswara rao Appana <appanad@...inx.com>
> ---
>  drivers/dma/xilinx/xilinx_dma.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
> index 21ac954..8467671 100644
> --- a/drivers/dma/xilinx/xilinx_dma.c
> +++ b/drivers/dma/xilinx/xilinx_dma.c
> @@ -1204,6 +1204,12 @@ static void xilinx_cdma_start_transfer(struct xilinx_dma_chan *chan)
>  	}
>  
>  	if (chan->has_sg) {
> +		dma_ctrl_clr(chan, XILINX_DMA_REG_DMACR,
> +			     XILINX_CDMA_CR_SGMODE);
> +
> +		dma_ctrl_set(chan, XILINX_DMA_REG_DMACR,
> +			     XILINX_CDMA_CR_SGMODE);
> +
>  		xilinx_write(chan, XILINX_DMA_REG_CURDESC,
>  			     head_desc->async_tx.phys);
>  
> @@ -2052,6 +2058,10 @@ static int xilinx_dma_terminate_all(struct dma_chan *dchan)
>  		chan->cyclic = false;
>  	}
>  
> +	if ((chan->xdev->dma_config->dmatype == XDMA_TYPE_CDMA) && chan->has_sg)
> +		dma_ctrl_clr(chan, XILINX_DMA_REG_DMACR,
> +			     XILINX_CDMA_CR_SGMODE);
> +
>  	return 0;
>  }
>  
> -- 
> 2.7.4
> 

-- 
~Vinod