Re: [PATCH 2/3] k3dma: add support to reserved minimum channels

[Vinod]

On 06-07-18, 11:05, Guodong Xu wrote:
> On Thu, Jun 28, 2018 at 2:02 PM Vinod <vkoul@xxxxxxxxxx> wrote:
> >
> > On 22-06-18, 11:24, Guodong Xu wrote:
> > > From: Li Yu <liyu65@xxxxxxxxxxxxx>
> > >
> > > On k3 series of SoC, DMA controller reserves some channels for
> > > other on-chip coprocessors. By adding support to dma_min_chan, kernel
> > > will not be able to use these reserved channels.
> > >
> > > One example is on Hi3660 platform, channel 0 is reserved to lpm3.
> > >
> > > Please also refer to Documentation/devicetree/bindings/dma/k3dma.txt
> >
> > and if some other platform has channel X marked for co-processor, maybe
> > a last channel or something in middle, how will this work then?
> >
> Hiï Vinod
> 
> Sorry for delayed response. We checked with Kirin hardware design
> team, so far their design strategy is all Kirin SoC series reserve
> only from minimum side, saying channel 0, then 1, then 2. That impacts
> the current SoC in upstreaming, Kirin960 (Hi3660), and next versions
> in Kirin SoC, Kirin970 and 980, which may hit upstream later.

And what guarantees that they will not change their mind..

> > I am thinking this should be a mask, rather than min.
> >
> 
> So, since this driver k3dma.c is only used by Kirin SoC DMA
> controllers, I would prefer to keep the current design dma_min_chan
> unchanged.
> 
> What do you think?

I would still prefer bitmask to expose the channels you are supposed to
use

-- 
~Vinod