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From: "yitian" <yitian.bu@tangramtek.com>
To: "'Andy Shevchenko'" <andriy.shevchenko@linux.intel.com>,
        "'Andy Shevchenko'" <andy.shevchenko@gmail.com>,
        "'Viresh Kumar'" <viresh.kumar@linaro.org>
Cc: "'Viresh Kumar'" <vireshk@kernel.org>,
        "'Vinod Koul'" <vinod.koul@intel.com>,
        "'Dan Williams'" <dan.j.williams@intel.com>,
        "'dmaengine'" <dmaengine@vger.kernel.org>,
        "'Linux Kernel Mailing List'" <linux-kernel@vger.kernel.org>
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In-Reply-To: <1443429967.8361.227.camel@linux.intel.com>
Subject: RE: [PATCH 1/1] dmaengine: dw: resolve recursion lock when audio playback
Date: Mon, 28 Sep 2015 17:14:36 +0800
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> From: Andy Shevchenko [mailto:andriy.shevchenko@linux.intel.com]
> Sent: Monday, September 28, 2015 4:46 PM
> To: yitian <yitian.bu@tangramtek.com>; 'Andy Shevchenko'
> <andy.shevchenko@gmail.com>; 'Viresh Kumar' <viresh.kumar@linaro.org>
> Cc: 'Viresh Kumar' <vireshk@kernel.org>; 'Vinod Koul'
> <vinod.koul@intel.com>; 'Dan Williams' <dan.j.williams@intel.com>;
> 'dmaengine' <dmaengine@vger.kernel.org>; 'Linux Kernel Mailing List'
> <linux-kernel@vger.kernel.org>
> Subject: Re: [PATCH 1/1] dmaengine: dw: resolve recursion lock when
> audio playback
> 
> On Mon, 2015-09-28 at 15:23 +0800, yitian wrote:
> > >
> > > From: Andy Shevchenko [mailto:andy.shevchenko@gmail.com]
> > > Sent: Monday, September 28, 2015 3:06 PM
> > > To: Viresh Kumar <viresh.kumar@linaro.org>
> > > Cc: yitian <yitian.bu@tangramtek.com>; Viresh Kumar
> > > <vireshk@kernel.org>; Andy Shevchenko
> > > <andriy.shevchenko@linux.intel.com>; Vinod Koul <
> > > vinod.koul@intel.com>;
> > > Dan Williams <dan.j.williams@intel.com>; dmaengine
> > > <dmaengine@vger.kernel.org>; Linux Kernel Mailing List
> > > <linux-kernel@vger.kernel.org>
> > > Subject: Re: [PATCH 1/1] dmaengine: dw: resolve recursion
> > > > I am not sure if this is a sane way of doing that, and we were
> > > > scanning
> > > > the descriptors for some valid reason..
> > >
> > > Actually one of the patches in a pile sitting in my private repo is
> > > also including similar change. In my case the reason is to support
> > > cyclic transfers natively.
> > >
> >
> > Yes, i am using DW DMAC to support cyclic transfer.
> > Currently it is very easy to get recursion lock crash, but
> > after this patch everything is fine on my device.
> 
> What is an actual hardware you are running kernel on?
> 
Hi Andy:

I am using a FPGA, with Cortex-A5 core, Designware I2S IP, Designware
DMAC IP. What I was done is to run tinyplay and tinycap to test the
playback and capture function on the FPGA. With my change, both of
them are okay now. I didn't push the patch which added cyclic DMA
support for dw DMAC because I didn't make it decent enough yet.