linux-kernel - Re: [PATCH 1/2] dma: cppi41: start tear down only if channel is busy

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Message-ID: <1393490862.28803.40.camel@smile.fi.intel.com>
Date:	Thu, 27 Feb 2014 08:47:42 +0000
From:	"Shevchenko, Andriy" <andriy.shevchenko@...el.com>
To:	George Cherian <george.cherian@...com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"balbi@...com" <balbi@...com>,
	"Williams, Dan J" <dan.j.williams@...el.com>,
	"Koul, Vinod" <vinod.koul@...el.com>,
	"msmucr@...il.com" <msmucr@...il.com>
Subject: Re: [PATCH 1/2] dma: cppi41: start tear down only if channel is busy

On Thu, 2014-02-27 at 10:44 +0530, George Cherian wrote:
> Start the channel tear down only if the channel is busy, else just
> bail out. In some cases its seen that by the time the tear down is
> initiated the cppi completes the DMA, especially in ISOCH transfers.
> 
> Signed-off-by: George Cherian <george.cherian@...com>
> ---
>  drivers/dma/cppi41.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/cppi41.c b/drivers/dma/cppi41.c
> index c18aebf..d028f36 100644
> --- a/drivers/dma/cppi41.c
> +++ b/drivers/dma/cppi41.c
> @@ -620,12 +620,15 @@ static int cppi41_stop_chan(struct dma_chan *chan)
>  	u32 desc_phys;
>  	int ret;
>  
> +	desc_phys = lower_32_bits(c->desc_phys);
> +	desc_num = (desc_phys - cdd->descs_phys) / sizeof(struct cppi41_desc);
> +	if (!cdd->chan_busy[desc_num])
> +		return 0;
> +
>  	ret = cppi41_tear_down_chan(c);
>  	if (ret)
>  		return ret;
>  
> -	desc_phys = lower_32_bits(c->desc_phys);
> -	desc_num = (desc_phys - cdd->descs_phys) / sizeof(struct cppi41_desc);
>  	WARN_ON(!cdd->chan_busy[desc_num]);

Do you still need this WARN_ON?

>  	cdd->chan_busy[desc_num] = NULL;
>  


-- 
Andy Shevchenko <andriy.shevchenko@...el.com>
Intel Finland Oy
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