linux-kernel - Re: [PATCH v3.5] dw_dmac: return proper residue value

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Message-ID: <CAHp75Vd_1iozR20gHO46fqVQMBrJ43rXbWrLKCesJcqxE5QAhA@mail.gmail.com>
Date:	Fri, 25 Jan 2013 11:19:40 +0200
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Vinod Koul <vinod.koul@...el.com>, linux-kernel@...r.kernel.org,
	spear-devel <spear-devel@...t.st.com>
Subject: Re: [PATCH v3.5] dw_dmac: return proper residue value

On Fri, Jan 25, 2013 at 11:07 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 25 January 2013 14:34, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
>> Okay, we have to have a protection here because get_sent reads two
>> registers consequentially. This means we could end up with scenario
>> with threads 1 and 2
>>
>> 1. read ctlhi
>> 2. write ctlhi
>> 2. write ctllo
>> 1. read ctllo
>
> Who is going to right on ctlhi/lo?

dwc_do_single_block()

> we write to ctlhi/lo only when we program new
> transfer. and that is not going to happen while we are in middle of a transfer.

We have got a tasklet running inside tx_status call. Isn't possible?
tasklet runs scan_descriptors, that continues transfer in soft LLP mode.

-- 
With Best Regards,
Andy Shevchenko
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