linux-kernel - Re: [PATCH v4] dma: imx-sdma: switch to dynamic context mode after script loaded

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Date:	Mon, 16 Mar 2015 15:55:50 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Robin Gong <b38343@...escale.com>
Cc:	dan.j.williams@...el.com, dmaengine@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] dma: imx-sdma: switch to dynamic context mode after
 script loaded

On Sun, Feb 15, 2015 at 10:00:35AM +0800, Robin Gong wrote:
> Below comments got from Page4724 of Reference Manual of i.mx6q:
> http://cache.freescale.com/files/32bit/doc/ref_manual/IMX6DQRM.pdf
> 
> --"Static context mode should be used for the first channel called
> after reset to ensure that the all context RAM for that channel is
> initialized during the context SAVE phase when the channel is
> done or yields. Subsequent calls to the same channel or
> different channels may use any of the dynamic context modes.
> This will ensure that all context locations for the bootload
> channel are initialized, and prevent undefined values in context
> RAM from being loaded during the context restore if the
> channel is re-started later"
> 
> Unfortunately, the rule was broken by commit(5b28aa319bba96987316425a1131813d87cbab35)
> .This patch just take them back.

Applied, thanks

-- 
~Vinod

> 
> Signed-off-by: Robin Gong <b38343@...escale.com>
> ---
>  drivers/dma/imx-sdma.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> index d0df198..644cfa0 100644
> --- a/drivers/dma/imx-sdma.c
> +++ b/drivers/dma/imx-sdma.c
> @@ -531,6 +531,10 @@ static int sdma_run_channel0(struct sdma_engine *sdma)
>  		dev_err(sdma->dev, "Timeout waiting for CH0 ready\n");
>  	}
>  
> +	/* Set bits of CONFIG register with dynamic context switching */
> +	if (readl(sdma->regs + SDMA_H_CONFIG) == 0)
> +		writel_relaxed(SDMA_H_CONFIG_CSM, sdma->regs + SDMA_H_CONFIG);
> +
>  	return ret ? 0 : -ETIMEDOUT;
>  }
>  
> @@ -1401,9 +1405,6 @@ static int sdma_init(struct sdma_engine *sdma)
>  
>  	writel_relaxed(ccb_phys, sdma->regs + SDMA_H_C0PTR);
>  
> -	/* Set bits of CONFIG register with given context switching mode */
> -	writel_relaxed(SDMA_H_CONFIG_CSM, sdma->regs + SDMA_H_CONFIG);
> -
>  	/* Initializes channel's priorities */
>  	sdma_set_channel_priority(&sdma->channel[0], 7);
>  
> -- 
> 1.9.1
> 
> --
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