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Date:   Tue, 30 Apr 2019 22:48:56 +0530
From:   Vinod Koul <vkoul@kernel.org>
To:     Arnaud Pouliquen <arnaud.pouliquen@st.com>
Cc:     Dan Williams <dan.j.williams@intel.com>,
        Pierre-Yves MORDRET <pierre-yves.mordret@st.com>,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org
Subject: Re: [PATCH] dmaengine: stm32-dma: fix residue calculation in
 stm32-dma
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On 30-04-19, 16:58, Arnaud Pouliquen wrote:

> >> Hope that will help to clarify.
> > 
> > Yes that helps, maybe we should add these bits in code and changelog..
> > :)I will update the comments and commit message in a V2 in this way
> > 
> > And how does this impact non cyclic case where N descriptors maybe
> > issued. The driver seems to support non cyclic too...
> 
> Correct it supports SG as well, but double buffer mode is not used in
> such case. Hw is programmed under IT for every descriptors : no
> automatic register reloaded as in cyclic mode. We won't end up in the
> situation depicted below.

Okay sounds good then. Can you add a bit more of this in the code (this
was very helpful) not as a fix but documentation so that people (or you
down the line) will remember why this was done like this

Thanks

-- 
~Vinod