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

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Message-ID: <877dovlgdl.wl-maz@kernel.org>
Date:   Sat, 02 Jan 2021 11:36:54 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Saravana Kannan <saravanak@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Frank Rowand <frowand.list@...il.com>,
        Kevin Hilman <khilman@...libre.com>, kernel-team@...roid.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] of: property: Add device link support for interrupts

On Thu, 31 Dec 2020 21:12:40 +0000,
Rob Herring <robh@...nel.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@...nel.org>
> > > Cc: Kevin Hilman <khilman@...libre.com>
> > > Signed-off-by: Saravana Kannan <saravanak@...gle.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.

> But you are right that 'interrupt-map' also needs to be tracked.

And 'interrupts-extended', while we're at it.

>
> 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.

Agreed. Though you need the object the dependency is on, I guess, if
you want to be able to have the dependency edge between the device and
the interrupt controller. But since the commit message doesn't say
much about what this is trying to achieve, I'm only guessing the
purpose of this patch.

	M.

-- 
Without deviation from the norm, progress is not possible.