linux-kernel - Re: Query dw_dmac driver: All descriptors done, but channel not idle!

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Message-ID: <4C1B7AF2.1060500@st.com>
Date:	Fri, 18 Jun 2010 19:26:02 +0530
From:	Viresh KUMAR <viresh.kumar@...com>
To:	Haavard Skinnemoen <haavard.skinnemoen@...el.com>
Cc:	Dan Williams <dan.j.williams@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"'Shiraz HASHIM'" <shiraz.hashim@...com>,
	Armando VISCONTI <armando.visconti@...com>
Subject: Re: Query dw_dmac driver: All descriptors done, but channel not idle!

On 6/18/2010 7:22 PM, Haavard Skinnemoen wrote:
> Viresh KUMAR <viresh.kumar@...com> wrote:
>> Can somebody please confirm, if it a known issue or not? Or if there
>> are some solutions for this problem.
> 
> I'm not aware of any such issue. The code was added as a purely
> defensive thing; when writing it, I just thought about what might
> happen if we go through all our descriptors without finding the current
> one, and added some code to report the issue and try to recover.
> 
> I suppose it might be caused by some issue with the peripheral itself,
> but I think it's more likely to be caused by some race condition in the
> driver, i.e. something goes wrong when inserting or removing
> descriptors in the chain.
> 
> What might be very good to know at this point is the value of
> the llp variable, and perhaps also the value of the CH_EN register to
> see if the channel is idle or not.
> 

Thanks Haavard,

Will debug it further.

viresh.
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