Re: [PATCH 01/14] dma: sun6i-dma: Add burst case of 4

Jean-Francois Moine
2016-10-04T13:46:51Z

On Tue, 4 Oct 2016 14:12:21 +0200
Thomas Petazzoni <thomas.petazzoni-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org> wrote:

> > > Add the case of a burst of 4 which is handled by the SoC.
> > >
> > > Signed-off-by: Mylène Josserand <mylene.josserand@free-electrons.com>
> > > ---
> > > drivers/dma/sun6i-dma.c | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
> > > index 8346199..0485204 100644
> > > --- a/drivers/dma/sun6i-dma.c
> > > +++ b/drivers/dma/sun6i-dma.c
> > > @@ -240,6 +240,8 @@ static inline s8 convert_burst(u32 maxburst)
> > > switch (maxburst) {
> > > case 1:
> > > return 0;
> > > + case 4:
> > > + return 1;
> > > case 8:
> > > return 2;
> > > default:
> > > --
> > > 2.9.3
> >
> > This patch has already been rejected by Maxime in the threads
> > http://www.spinics.net/lists/dmaengine/msg08610.html
> > and
> > http://www.spinics.net/lists/dmaengine/msg08719.html
> >
> > I hope you will find the way he wants for this maxburst to be added.
>
> I was about to reply to Mylene's e-mail, suggesting that she should add
> a comment in the code (and maybe in the commit log) to explain why this
> addition is needed, and also that even though the schematics say that
> value "1" (max burst size of 4 bytes) is reserved, it is in fact
> incorrect. The Allwinner BSP code is really using this value, and it's
> the value that makes audio work, so we believe the datasheet is simply
> incorrect.
>
> We already discussed it with Maxime, so I believe he should agree this
> time. But I would suggest to have such details explained in the commit
> log and in a comment in the code.

Strange. Looking at the datasheets of the A23, A31, A33, A83T and H3
(these are the SoCs using the DMA sun6i), only the H3 can have 4 as the
burst size (the doc is unclear for the A31).

Well, I was submitting for the H3, Mylène is submitting for the A33.
So, what about the A23, A31 and A83T?

--
Ken ar c'hentañ | ** Breizh ha Linux atav! **
Jef | http://moinejf.free.fr/

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