On Monday 16 March 2009, Nori, Sekhar wrote:
>
> From: David Brownell
> Sent: Monday, March 16, 2009 1:50 PM
> > On Sunday 15 March 2009, nar...@ti.com wrote:
> > > @@ -167,6 +175,8 @@ enum fifo_width {
> > > enum dma_event_q {
> > > EVENTQ_0 = 0,
> > > EVENTQ_1 = 1,
> > > + EVENTQ_2 = 2,
> > > + EVENTQ_3 = 3,
> > > EVENTQ_DEFAULT = -1
> > > };
> > >
> >
> > It'd be good to get rid of that enum entirely ... just use the
> > TC number, except maybe for
> >
> > EVENTQ_HI_PRIORITY ... maybe higher priority than ARM
> > EVENTQ_LO_PRIORITY ... low priority, e.g. for bulk
> > EVENTQ_DEFAULT ...
> >
> > Expecting drivers to deal with TC queues in anything other than
> > generic terms is a losing game; except maybe for SoC-specific
> > code, which should be rare.
>
> Factors like FIFOSIZE may also play role in using a particular TC for
> a particular peripheral (eg. on DM648, TC 2 & 3 are optimized for
> video because of high FIFOSIZE). Not having fine grained control can
> be a problem in such cases.
The DM648 doesn't include an ARM to run Linux. :)
But an ARM leveraging that kind of rig would fall
into the category of SoC-specific code.
> But agreed that drivers should not be making the choice as the choice
> is not generic. I think TC to be used should be coming from platform data?
If it needs that type of optimization. I think most
can just use HI priority (audio, say) or LO/bulk.
(With LO/bulk being the default.)
Yes, I had thought that video might want more choice
there ... though as I write this, the only drivers to
use EDMA are in sound/soc/davinci and drivers/mmc/host
(at least, in the DaVinci GIT tree) so there aren't
many examples to choose from. Pretty much anything
using DMA without FIFO (like SPI) seems like it should
use HI priority.
- Dave
>
> Thanks,
> Sekhar
>
> >
> > - Dave
> >
> >
> >
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>
>
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