Re: [PATCH] of: property: Add device link support for interrupts

[Rob Herring <robh@kernel.org>]

On Thu, Jan 7, 2021 at 12:09 PM Saravana Kannan <saravanak@google.com> wrote:
>
> On Thu, Jan 7, 2021 at 10:39 AM Rob Herring <robh@kernel.org> wrote:
> >
> > On Wed, Jan 6, 2021 at 11:53 AM Saravana Kannan <saravanak@google.com> wrote:
> > >
> > > On Sat, Jan 2, 2021 at 3:37 AM Marc Zyngier <maz@kernel.org> wrote:
> > > >
> > > > On Thu, 31 Dec 2020 21:12:40 +0000,
> > > > Rob Herring <robh@kernel.org> wrote:
> > > > >
> > > > > On Mon, Dec 21, 2020 at 09:30:45AM +0000, Marc Zyngier wrote:
> > > > > > On 2020-12-18 21:07, Saravana Kannan wrote:
> > > > > > > Add support for creating device links out of interrupts property.
> > > > > > >
> > > > > > > Cc: Marc Zyngier <maz@kernel.org>
> > > > > > > Cc: Kevin Hilman <khilman@baylibre.com>
> > > > > > > Signed-off-by: Saravana Kannan <saravanak@google.com>
> > > > > > > ---
> > > > > > > Rob/Greg,
> > > > > > >
> > > > > > > This might need to go into driver-core to avoid conflict
> > > > > > > due to fw_devlink refactor series that merged there.
> > > > > > >
> > > > > > > Thanks,
> > > > > > > Saravana
> > > > > > >
> > > > > > >
> > > > > > >  drivers/of/property.c | 17 +++++++++++++++++
> > > > > > >  1 file changed, 17 insertions(+)
> > > > > > >
> > > > > > > diff --git a/drivers/of/property.c b/drivers/of/property.c
> > > > > > > index 5f9eed79a8aa..e56a5eae0a0b 100644
> > > > > > > --- a/drivers/of/property.c
> > > > > > > +++ b/drivers/of/property.c
> > > > > > > @@ -1271,6 +1271,22 @@ static struct device_node
> > > > > > > *parse_iommu_maps(struct device_node *np,
> > > > > > >   return of_parse_phandle(np, prop_name, (index * 4) + 1);
> > > > > > >  }
> > > > > > >
> > > > > > > +static struct device_node *parse_interrupts(struct device_node *np,
> > > > > > > +                                     const char *prop_name, int index)
> > > > > > > +{
> > > > > > > + struct device_node *sup;
> > > > > > > +
> > > > > > > + if (strcmp(prop_name, "interrupts") || index)
> > > > > > > +         return NULL;
> > > > > > > +
> > > > > > > + of_node_get(np);
> > > > > > > + while (np && !(sup = of_parse_phandle(np, "interrupt-parent", 0)))
> > > > > > > +         np = of_get_next_parent(np);
> > > > > > > + of_node_put(np);
> > > > > > > +
> > > > > > > + return sup;
> > > > > > > +}
> > > > > > > +
> > > > > > >  static const struct supplier_bindings of_supplier_bindings[] = {
> > > > > > >   { .parse_prop = parse_clocks, },
> > > > > > >   { .parse_prop = parse_interconnects, },
> > > > > > > @@ -1296,6 +1312,7 @@ static const struct supplier_bindings
> > > > > > > of_supplier_bindings[] = {
> > > > > > >   { .parse_prop = parse_pinctrl6, },
> > > > > > >   { .parse_prop = parse_pinctrl7, },
> > > > > > >   { .parse_prop = parse_pinctrl8, },
> > > > > > > + { .parse_prop = parse_interrupts, },
> > > > > > >   { .parse_prop = parse_regulators, },
> > > > > > >   { .parse_prop = parse_gpio, },
> > > > > > >   { .parse_prop = parse_gpios, },
> > > > > >
> > > > > > You don't really describe what this is for so I'm only guessing
> > > > > > from the context. If you want to follow the interrupt hierarchy,
> > > > > > "interrupt-parent" isn't enough. You also need to track
> > > > > > things like interrupt-map, or anything that carries a phandle
> > > > > > to an interrupt controller.
> > > > >
> > > > > We don't need to follow the hierarchy, we just need the immediate
> > > > > dependencies.
> > > >
> > > > Indeed. I also wonder why this isn't just a irq_find_parent() call, TBH.
> > >
> > > Thanks Rob for explaining it.
> > >
> > > Marc, I wasn't sure if Rob would be okay with including of_irq.h here.
> > > Also, I'm trying to keep of/property.c independent of the framework
> > > code for now. The long term goal is to see if I can move out most of
> > > this into the frameworks. But I want to do that after I sort of some
> > > of the larger problems (like getting fw_devlink=on to work on all
> > > devices  first). Let me know if you have a strong preference for right
> > > now, if not, I'd rather keep property.c independent for now.
> > >
> > > I wasn't aware of interrupt-map until a few weeks ago and didn't know
> > > it carried phandles. I can add support for that too. There's no reason
> > > for all of them to go in one patch though.
> > >
> > > >
> > > > > But you are right that 'interrupt-map' also needs to be tracked.
> > > >
> > > > And 'interrupts-extended', while we're at it.
> > >
> > > This is already handled.
> > >
> > > > >
> > > > > I also noticed that we define 'interrupt-parent' as a dependency to
> > > > > parse, but that's wrong. The dependency is where 'interrupts' appears
> > > > > and where 'interrupt-parent' appears is irrelevant.
> > >
> > > No, the interrupt-parent parsing is correct and it's needed for
> > > interrupt controllers to probe in the right order. But
> > > interrupt-parent is also needs to be looked at for parsing
> > > "interrupts".
> >
> > If you parse 'interrupts' for interrupt controllers (which in turn
> > will use 'interrupt-parent'), then you aren't going to need to track
> > 'interrupt-parent' by itself.
>
> Do all interrupt controllers (that are not the root interrupt
> controller) need to have "interrupts" property? If yes, then yeah,
> that makes sense. But I vaguely remember that this wasn't the case for
> some DT I saw.

There are some cases of stacked controllers where it's implicit.

>
> Ah, here's one I found.
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/mt2701.dtsi#n209

Right, so this is one of several cases of custom interrupt mapping
properties (mediatek,ext-irq-range). Really, 'interrupts' or
'interrupt-map' should have been used here, but 'interrupt-map'
doesn't really scale well if you have large ranges of interrupts.

To handle the dependency with just 'interrupt-parent', you need to
find nodes that are themselves an 'interrupt-parent' and then find
their 'interrupt-parent'.

Rob