Re: [PATCHv3 2/6] irqchip/irq-pruss-intc: Add a PRUSS irqchip driver for PRUSS interrupts

[Marc Zyngier]

On 2020-07-08 08:04, Grzegorz Jaszczyk wrote:
> On Sun, 5 Jul 2020 at 22:45, Marc Zyngier <maz@xxxxxxxxxx> wrote:
> > On 2020-07-05 14:26, Grzegorz Jaszczyk wrote:
> > > On Sat, 4 Jul 2020 at 11:39, Marc Zyngier <maz@xxxxxxxxxx> wrote:
> > >>
> > >> On 2020-07-03 15:28, Grzegorz Jaszczyk wrote:
> >
> > [...]
> >
> > >> It still begs the question: if the HW can support both edge and level
> > >> triggered interrupts, why isn't the driver supporting this diversity?
> > >> I appreciate that your HW may only have level interrupts so far, but
> > >> what guarantees that this will forever be true? It would imply a
> > >> change
> > >> in the DT binding, which isn't desirable.
> > >
> > > Ok, I've got your point. I will try to come up with something later
> > > on. Probably extending interrupt-cells by one and passing interrupt
> > > type will be enough for now. Extending this driver to actually support
> > > it can be handled later if needed. Hope it works for you.
> >
> > Writing a set_type callback to deal with this should be pretty easy.
> > Don't delay doing the right thing.
>
> Ok.
>
> > [...]
> >
> > >> >> > +             hwirq = hipir & GENMASK(9, 0);
> > >> >> > +             virq = irq_linear_revmap(intc->domain, hwirq);
> > >> >>
> > >> >> And this is where I worry. You seems to have a single irqdomain
> > >> >> for all the muxes. Are you guaranteed that you will have no
> > >> >> overlap between muxes? And please use irq_find_mapping(), as
> > >> >> I have top-secret plans to kill irq_linear_revmap().
> > >> >
> > >> > Regarding irq_find_mapping - sure.
> > >> >
> > >> > Regarding irqdomains:
> > >> > It is a single irqdomain since the hwirq (system event) can be mapped
> > >> > to different irq_host (muxes). Patch #6
> > >> > https://lkml.org/lkml/2020/7/2/616 implements and describes how input
> > >> > events can be mapped to some output host interrupts through 2 levels
> > >> > of many-to-one mapping i.e. events to channel mapping and channels to
> > >> > host interrupts. Mentioned implementation ensures that specific system
> > >> > event (hwirq) can be mapped through PRUSS specific channel into a
> > >> > single host interrupt.
> > >>
> > >> Patch #6 is a nightmare of its own, and I haven't fully groked it yet.
> > >> Also, this driver seems to totally ignore the 2-level routing. Where
> > >> is it set up? map/unmap in this driver do exactly *nothing*, so
> > >> something somewhere must set it up.
> > >
> > > The map/unmap is updated in patch #6 and it deals with those 2-level
> > > routing setup. Map is responsible for programming the Channel Map
> > > Registers (CMRx) and Host-Interrupt Map Registers (HMRx) basing on
> > > provided configuration from the one parsed in the xlate function.
> > > Unmap undo whatever was done on the map. More details can be found in
> > > patch #6.
> > >
> > > Maybe it would be better to squash patch #6 with this one so it would
> > > be less confusing. What is your advice?
> >
> > So am I right in understanding that without patch #6, this driver does
> > exactly nothing? If so, it has been a waste of review time.
> >
> > Please split patch #6 so that this driver does something useful
> > for Linux, without any of the PRU interrupt routing stuff. I want
> > to see a Linux-only driver that works and doesn't rely on any other
> > exotic feature.
>
> Patch #6 provides PRU specific 2-level routing setup. This step is
> required and it is part of the entire patch-set. Theoretically routing
> setup could be done by other platform driver (not irq one) or e.g. by
> PRU firmware. In such case this driver would be functional without
> patch #6 but I do not think it would be proper.

Then this whole driver is non-functional until the last patch that
comes with the PRU-specific "value-add".

[...]

> I am open to any suggestion if there is a better way of handling
> 2-level routing. I will also appreciate if you could elaborate about
> issues that you see with patch #6.

The two level routing has to be part of this (or another) irqchip
driver (specially given that it appears to me like another set of
crossbar). There should only be a *single* binding for all interrupts,
including those targeting the PRU (you seem to have two).

And the non-CPU interrupt code has to be in its own patch, because
it is pretty borderline anyway (I'm still not completely convinced
this is Linux's job).

        N,
--
Jazz is not dead. It just smells funny...