Re: [PATCH RFC v2 1/8] spi: dt-bindings: spi-peripheral-props: add spi-offloads property

[Nuno Sá <noname.nuno@xxxxxxxxx>]

On Thu, 2024-05-23 at 10:09 -0500, David Lechner wrote:
> On 5/23/24 9:57 AM, Nuno Sá wrote:
> > On Thu, 2024-05-23 at 09:28 -0500, David Lechner wrote:
> > > On 5/22/24 1:24 PM, Conor Dooley wrote:
> > > > On Tue, May 21, 2024 at 09:54:39AM -0500, David Lechner wrote:
> > > > > On Sun, May 19, 2024 at 7:53 AM Conor Dooley <conor@xxxxxxxxxx> wrote:
> > > > > > 
> > > > > > On Fri, May 17, 2024 at 11:51:58AM -0500, David Lechner wrote:
> > > > > > > On Thu, May 16, 2024 at 4:32 PM Conor Dooley <conor@xxxxxxxxxx> wrote:
> > > > > > > > On Tue, May 14, 2024 at 05:56:47PM -0500, David Lechner wrote:
> > > > > > 
> > > 
> > 
> > ...
> > 
> > > 
> > > controller:
> > > #spi-offload-cells = <2>: /* 1st cell = offload instance
> > >                            * 2nd cell = trigger provider */
> > > 
> > 
> > What about things like DMA? I'm mentioning it a lot because it's way more complex
> > having it on the controller (from a SW perspective). But from an HW point of
> > view,
> > it's always very similar (if not the same) as your case A.
> > 
> 
> If we had a setup where there was more than one place that, e.g. the
> RX stream from the offload could be piped, then I would add a 3rd
> cell to describe that. If the hardware is fixed and the RX stream
> always goes to a specific DMA channel, then it doesn't seem like we
> need to describe that in the SPI controller node because the hardware
> is fixed.
> 

Well, yes, still the DMA channel is connected on the controller and not the
peripheral. Same deal as we discussed on the IIO backends stuff. But there, since
it's all IIO it was easy to make the DMA a property of the backend device. That said,
I can surely see having the property in the peripheral.

Another thing that came to mind for the trigger case. What about an additional spi
interface for configuring/setting the trigger rate? Sounds generic and then we would
not really need the trigger on the peripheral right (did not checked the CRC issue
you mentioned so not sure if it's somehow trigger related)?

Hmm but sometimes there's other things than rate/period (like offset) to care about
so maybe not doable... Bah!

- Nuno Sá