Re: [PATCH v1 2/2] dmaengine: dw: implement per-channel protection control setting

Andy Shevchenko
2018-11-05T16:23:30Z

On Mon, Nov 05, 2018 at 05:06:20PM +0100, Christian Lamparter wrote:
> On Monday, November 5, 2018 3:27:41 PM CET Andy Shevchenko wrote:
> > On Mon, Nov 05, 2018 at 04:22:54PM +0200, Andy Shevchenko wrote:
> > > On Sun, Nov 04, 2018 at 06:01:39PM +0100, Christian Lamparter wrote:
> >
> > > > + struct dw_dma *dw = to_dw_dma(dwc->chan.device);
> > > > + size_t chanidx = (size_t)(dwc - dw->chan);
> > >
> > > We have mask field, so, index is a first set bit out of mask, __ffs(mask).
> > >
> > > unsigned int protctl = dw->pdata->protctl[__ffs(mask)];
> >
> > dwc->mask, of course.
> Ok, will do. I'll sent a v2 later this week.
>
> > Also, it's possible to use (though better to check) dwc->chan.chan_id,
> > though I dunno if it's reliable.
> dwc->chan.chan_id is subjected to the chan_allocation setting.
> So, if it's set to CHAN_ALLOCATION_DESCENDING the dt prop array values
> for the protctl would need to be reversed as well in order to match the
> other per-channel settings (for example multiblock).
> So, let's not do that since this gets very confusing.

Yes, that's what I suspected. So, __ffs(dwc->mask) seems feasible approach.

--
With Best Regards,
Andy Shevchenko