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SubjectRe: [PATCH v4 09/11] dmaengine: dw: Initialize min_burst capability
On Fri, May 29, 2020 at 01:29:02PM +0300, Andy Shevchenko wrote:
> On Fri, May 29, 2020 at 01:25:15PM +0300, Andy Shevchenko wrote:
> > On Fri, May 29, 2020 at 01:23:59AM +0300, Serge Semin wrote:
> > > According to the DW APB DMAC data book the minimum burst transaction
> > > length is 1 and it's true for any version of the controller since
> > > isn't parametrised in the coreAssembler so can't be changed at the
> > > IP-core synthesis stage. Let's initialise the min_burst member of the
> > > DMA controller descriptor so the DMA clients could use it to properly
> > > optimize the DMA requests.
>
> ...
>
> > > /* DMA capabilities */
> >
> > > + dw->dma.min_burst = 1;
> >
> > Perhaps then relaxed maximum, like
> >
> > dw->dma.max_burst = 256;
> >
> > (channels will update this)
> >
> > ?
>

> And forgot to mention that perhaps we need a definitions for both.

By "definitions for both" do you mean a macro with corresponding parameter
definition like it's done for the max burst length in the next patch?
Something like this:
--- include/linux/platform_data/dma-dw.h
+++ include/linux/platform_data/dma-dw.h
+#define DW_DMA_MIN_BURST 1
+#define DW_DMA_MAX_BURST 256

?

-Sergey

>
> > > dw->dma.src_addr_widths = DW_DMA_BUSWIDTHS;
> > > dw->dma.dst_addr_widths = DW_DMA_BUSWIDTHS;
>
> --
> With Best Regards,
> Andy Shevchenko
>
>

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