Re: [PATCH 3/3] spi: cadence-xspi: add ACMD mode support

[Conor Dooley <conor@kernel.org>]

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On Fri, Oct 30, 2026 at 04:00:46PM +0000, Nuno Sá wrote:
> On Fri, Oct 30, 2026 at 11:03:07AM +0000, Mark Brown wrote:
> > On Fri, Oct 30, 2026 at 10:16:00AM +0000, Nuno Sá wrote:
> > > On Thu, Oct 29, 2026 at 04:51:32PM +0000, Mark Brown wrote:
> > 
> > > > We need some suspend/resume handling to invalidate the configuration
> > > > when the IP power goes so we set everything up again.  I'm not seeing
> > > > anything here.
> > 
> > > Yeah, I did saw sashiko complain (and my local LLM also raised it
> > > actually) but I do wonder how can that happen? So we need to assume that
> > > in suspend we might lose power (maybe because it's regulator powers down)
> > > and need to do redo all the important initialization bits?
> > 
> > Yes, might not even be regulators - some SoCs have good internal power
> > domains and can gate parts of themselves very effectively.
> > 
> > > > > +	if (cdns_xspi_acmd_can_read(cdns_xspi, op))
> > > > > +		return 0;
> > 
> > > > That function has a minimum size but not a maximum size...
> > 
> > > > > +
> > > > >  	op->data.nbytes = clamp_val(op->data.nbytes, 0, cdns_xspi->sdmasize);
> > 
> > > > ...which we have here?
> > 
> > > For ACMD, in theory we can just configure UINT32_MAX on the register so
> > > not sure if it makes sense to clamp to that?
> > 
> > No, if that really is the limit it's fine.
> > 
> > > Conor is pushing against the new bindings and that it should be inferred
> > > from the compatible. I tested this on [1] which is not an upstream
> > > platform so I wonder if it's ok to add support for the complete
> > > integration even if the SoC is not upstream?
> > 
> > So long as it's an actual SoC that exists rather than some random FPGA
> > configuration or whatever upstreaming just the SPI driver is totally
> > fine, that's one less piece that needs doing whenever the rest of it is
> > handled.
> 
> Nice! Then v2 will bring the work for the SoC integration! Yes, real
> SoC with two A55 cores and a shark DSP.

You gotta start somewhere, often that is clock drivers and that kind of
thing because that's what's needed for bare minimum bootable systems,
but if it's spi, that's fine too.

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