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SubjectRe: [PATCH v3 10/10] dmaengine: dw: Initialize max_sg_nents with nollp flag
On Thu, May 28, 2020 at 6:52 PM Serge Semin
<Sergey.Semin@baikalelectronics.ru> wrote:
> On Thu, May 28, 2020 at 05:56:30PM +0300, Andy Shevchenko wrote:
> > On Wed, May 27, 2020 at 01:50:21AM +0300, Serge Semin wrote:

...

> > In principal I agree, one nit below.
> > If you are okay with it, feel free to add my Rb tag.

> > > + /*
> > > + * It might be crucial for some devices to have the hardware
> > > + * accelerated multi-block transfers supported, aka LLPs in DW DMAC
> > > + * notation. So if LLPs are supported then max_sg_nents is set to
> > > + * zero which means unlimited number of SG entries can be handled in a
> > > + * single DMA transaction, otherwise it's just one SG entry.
> > > + */
> >
> > > + caps->max_sg_nents = dwc->nollp;
> >
>
> > To be on the safer side I would explicitly do it like
> >
> > if (dwc->nollp)
> > /* your nice comment */
> > = 1;
> > else
> > /* Unlimited */
> > = 0;
> >
> > type or content of nollp theoretically can be changed and this will affect maximum segments.
>
> Agree. Though I don't like formatting you suggested. If I add my nice comment
> between if-statement and assignment the the former will be look detached from
> the if-statement, which seems a bit ugly. So I'd leave the comment above the
> whole if-else statement, especially seeing I've already mentioned there about
> the unlimited number of SG entries there.
>
> /*
> * It might be crucial for some devices to have the hardware
> * accelerated multi-block transfers supported, aka LLPs in DW DMAC
> * notation. So if LLPs are supported then max_sg_nents is set to
> * zero which means unlimited number of SG entries can be handled in a
> * single DMA transaction, otherwise it's just one SG entry.
> */
> if (dwc->nollp)
> caps->max_sg_nents = 1;
> else
> caps->max_sg_nents = 0;

Fine with me, thanks!

--
With Best Regards,
Andy Shevchenko

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