linux-kernel - Re: [PATCH 6/7] k3dma: Fix occasional DMA ERR issue by using proper dma api

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Date:	Thu, 21 Jul 2016 12:26:48 +0800
From:	zhangfei <zhangfei.gao@...aro.org>
To:	John Stultz <john.stultz@...aro.org>,
	lkml <linux-kernel@...r.kernel.org>
CC:	Jingoo Han <jg1.han@...sung.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Mark Brown <broonie@...nel.org>, Andy Green <andy@...mcat.com>
Subject: Re: [PATCH 6/7] k3dma: Fix occasional DMA ERR issue by using proper
 dma api



On 07/21/2016 11:53 AM, John Stultz wrote:
> After lots of debugging on an occasional DMA ERR issue, I realized
> that the desc structures which we point the dma hardware are being
> allocated out of regular memory. This means when we fill the desc
> structures, that data doesn't always get flushed out to memory by
> the time we start the dma transfer, resulting in the dma engine getting
> some null values, resulting in a DMA ERR on the first irq.

How about using wmb() flush before start dma to sync desc?

I remember I used dma_pool first, then do some optimization referring 
Russell's driver.

Thanks