[PATCH v3 2/5] dmaengine: sun6i: Add 4 as a possible burst value for the H3

[Jean-Francois Moine]

On Tue, 29 Mar 2016 08:46:50 +0200
Maxime Ripard <maxime.ripard at free-electrons.com> wrote:

> On Mon, Mar 21, 2016 at 09:35:33AM +0100, Jean-Francois Moine wrote:
> > On Mon, 21 Mar 2016 08:29:18 +0100
> > Maxime Ripard <maxime.ripard at free-electrons.com> wrote:
> > 
> > > > @@ -470,6 +473,10 @@ static int set_config(struct sun6i_dma_dev *sdev,
> > > >  {
> > > >  	s8 src_width, dst_width, src_burst, dst_burst;
> > > >  
> > > > +	if (!sdev->cfg->burst_4 &&
> > > > +	    (sconfig->src_maxburst == 4 || sconfig->dst_maxburst == 4))
> > > > +		return -EINVAL;
> > > > +
> > > 
> > > I still believe this should be dealt with at the framework level.
> > 
> > What do you mean? In the DMA clients?
> 
> No, in the dmaengine framework.
> 
> A driver should register the burst size they support, and
> dmaengine_slave_config would reject any invalid burst size based on
> that.

Maybe you are right, but this does not seem to be very easy: the max
burst size is on a u32 value, and, as a bit map (256Mb) is forbidden,
the DMA drivers should declare a list of (min, max) authorized values.

Well, I will not start such a development for just testing if 4 is a
good burst size when calling the sun6i DMA driver...

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