linux-kernel - Re: [PATCH] dmaengine: fix balance of privatecnt inc/dec operations

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Message-id: <55C7ED03.2030000@samsung.com>
Date:	Mon, 10 Aug 2015 09:14:59 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Robert Baldyga <r.baldyga@...sung.com>, vinod.koul@...el.com
Cc:	dan.j.williams@...el.com, dmaengine@...r.kernel.org,
	linux-kernel@...r.kernel.org, m.szyprowski@...sung.com
Subject: Re: [PATCH] dmaengine: fix balance of privatecnt inc/dec operations

On 07.08.2015 19:26, Robert Baldyga wrote:
> This patch increments privatecnt value and set DMA_PRIVATE in device
> caps in dma_request_slave_channel() function. This is needed to keep
> privatecnt increment/decrement balance.
> 
> As function dma_release_channel() decrements privatecnt counter, we need
> to increment it when channel is requested. Otherwise privatecnt drops
> into negatives after few dma_release_channel() calls.
> 
> Reported-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> Signed-off-by: Robert Baldyga <r.baldyga@...sung.com>
> ---
>  drivers/dma/dmaengine.c | 4 ++++
>  1 file changed, 4 insertions(+)

Fixes issue [0] (reported after applying [1]).

Tested on Trats2 board (Exynos4412, pl330, serial with DMA)

Best regards,
Krzysztof

[0] http://www.spinics.net/lists/linux-serial/msg18369.html
[1] http://www.spinics.net/lists/linux-samsung-soc/msg45700.html


> 
> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
> index 4a4cce1..3ff284c 100644
> --- a/drivers/dma/dmaengine.c
> +++ b/drivers/dma/dmaengine.c
> @@ -689,6 +689,10 @@ struct dma_chan *dma_request_slave_channel(struct device *dev,
>  	struct dma_chan *ch = dma_request_slave_channel_reason(dev, name);
>  	if (IS_ERR(ch))
>  		return NULL;
> +
> +	dma_cap_set(DMA_PRIVATE, ch->device->cap_mask);
> +	ch->device->privatecnt++;
> +
>  	return ch;
>  }
>  EXPORT_SYMBOL_GPL(dma_request_slave_channel);
> 

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