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SubjectRe: [PATCH 16/18] dmaengine/ambhe rest oa-pl08x: Add support for sg len greater than one for slave transfers
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On Fri, 2011-09-09 at 03:24 +0530, Vinod Koul wrote:
> On Thu, 2011-09-08 at 12:29 +0200, Linus Walleij wrote:
> > On Thu, Sep 8, 2011 at 5:50 AM, Viresh Kumar <viresh.kumar@st.com> wrote:
> >
> > > If i am getting this clearly, the concern is "why to queue separate transfers for
> > > individual sg's? Better would be to prepare the complete list at once and
> > > start the transfer, so that DMA stops only after finishing all sg's
> > > passed from user." Is this what you are pointing at?
> >
> > Yes.
> >
> > > If yes, then the same is done in this patch too. An array for llis is allocated at
> > > the start, then for each sg i prepare lli list from this array. Last lli from one sg
> > > is followed by first lli from next sg. And so i get a continuous chain of llis.
> >
> > OK so I guess I was lost in the code ...
> >
> > So this is mainy cached as txd->dsg_list so you can quickly retrieve the
> > number of bytes pending in the LLI by traversing that sglist.
> >
> > This is better than what the coh901318 does, because that driver
> > resorts to going into the physical LLIs themselves to retrieve this
> > info.
> >
> > It also seems like this will play nice with Per Forlin's MMC
> > speed-up patches, so that will become effective for your MMC
> > usecases.
> >
> > Now I really like this patch.
> >
> > Sorry for being such a slow learner!
> > Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> Okay, great. I will check the rest of the series (i think 3 patches) and
> apply then next week.
Applied the remaining two patches for the series to my next

--
~Vinod



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