[PATCH v2 3/5] dmaengine: sun6i: Add 4 as a possible burst value

[Maxime Ripard]

On Fri, Mar 11, 2016 at 05:28:58PM +0100, Jean-Francois Moine wrote:
> On Fri, 11 Mar 2016 13:06:01 +0100
> Maxime Ripard <maxime.ripard at free-electrons.com> wrote:
> 
> > On Fri, Mar 11, 2016 at 12:01:29PM +0100, Jean-Francois Moine wrote:
> > > Some DMA transfers, as for H3 audio, ask for 4 as a burst value.
> 	[snip]
> > > @@ -238,6 +238,8 @@ static inline s8 convert_burst(u32 maxburst)
> > >  	switch (maxburst) {
> > >  	case 1:
> > >  		return 0;
> > > +	case 4:
> > > +		return 1;
> > 
> > This is true only for the H3.
> > 
> > For the other SoCs that we support, the only valid values are 0 and 2,
> > so we need to reject those values.
> > 
> > We should do that based on the compatible.
> > 
> > The easiest solution would be to expose the available burst sizes in
> > the probe, and just our new one if we match that compatible, and any
> > invalid burst size would be rejected by the framework. Vinod, any
> > objection to that?
> 
> Do you think that we should also check if the requested ports are
> valid, i.e. have a list/bitmap of the possible input/output ports per
> SoC, instead of just only the ID of the max port?

That would require having a map of the possible endpoints for a given
device, which would be quite difficult to accomplish.

I don't think customer drivers have access to that anyway, only the
provider driver is parsing the DT to retrieve the ID. And we already
trust the DT for so many things it would be a bit pointless to check
that.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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