linux-kernel - Re: [PATCH] of: property: Add fw_devlink support for interrupt-map property

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Message-ID: <CAK9=C2UMP3hAmn4-QruO90E1ZKY_nMP-yt5T6hife-9hC5H92A@mail.gmail.com>
Date: Fri, 12 Apr 2024 19:20:49 +0530
From: Anup Patel <apatel@...tanamicro.com>
To: Rob Herring <robh@...nel.org>
Cc: Saravana Kannan <saravanak@...gle.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Atish Patra <atishp@...shpatra.org>, 
	Andrew Jones <ajones@...tanamicro.com>, Sunil V L <sunilvl@...tanamicro.com>, 
	Anup Patel <anup@...infault.org>, linux-riscv@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH] of: property: Add fw_devlink support for interrupt-map property

On Fri, Apr 12, 2024 at 6:07 PM Rob Herring <robh@...nel.org> wrote:
>
> On Fri, Apr 12, 2024 at 6:29 AM Anup Patel <apatel@...tanamicro.com> wrote:
> >
> > Some of the PCI controllers (such as generic PCI host controller)
> > use "interrupt-map" DT property to describe the mapping between
> > PCI endpoints and PCI interrupt pins.
>
> I would go as far as saying that's the only case as that's the only
> case where the interrupts are not described in DT.

Sure, I will update the text.

>
> > Currently, there is no fw_devlink created based on "interrupt-map"
> > DT property so interrupt controller is not guaranteed to be probed
> > before PCI host controller. This mainly affects RISC-V platforms
> > where both PCI host controller and interrupt controllers are probed
> > as regular platform devices.
>
> That's *every* system with PCI really.

Okay, I will re-word.

>
> > This creates fw_devlink between consumers (PCI host controller) and
> > supplier (interrupt controller) based on "interrupt-map" DT property.
> >
> > Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> > ---
> >  drivers/of/property.c | 53 +++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 53 insertions(+)
> >
> > diff --git a/drivers/of/property.c b/drivers/of/property.c
> > index a6358ee99b74..ccbbb651a89a 100644
> > --- a/drivers/of/property.c
> > +++ b/drivers/of/property.c
> > @@ -1311,6 +1311,58 @@ static struct device_node *parse_interrupts(struct device_node *np,
> >         return of_irq_parse_one(np, index, &sup_args) ? NULL : sup_argsnp;
> >  }
> >
> > +static struct device_node *parse_interrupt_map(struct device_node *np,
> > +                                              const char *prop_name, int index)
> > +{
> > +       struct device_node *tn, *ipar, *supnp = NULL;
> > +       u32 addrcells, intcells, cells;
> > +       const __be32 *imap, *imap_end;
> > +       int i, imaplen;
> > +
> > +       if (!IS_ENABLED(CONFIG_OF_IRQ))
> > +               return NULL;
> > +
> > +       if (strcmp(prop_name, "interrupt-map"))
> > +               return NULL;
> > +
> > +       ipar = of_node_get(np);
> > +       do {
> > +               if (!of_property_read_u32(ipar, "#interrupt-cells", &intcells))
> > +                       break;
> > +               tn = ipar;
> > +               ipar = of_irq_find_parent(ipar);
> > +               of_node_put(tn);
> > +       } while (ipar);
> > +       if (!ipar)
> > +               return NULL;
> > +       addrcells = of_bus_n_addr_cells(ipar);
> > +       of_node_put(ipar);
> > +
> > +       imap = of_get_property(np, "interrupt-map", &imaplen);
> > +       if (!imap || imaplen <= (addrcells + intcells))
> > +               return NULL;
> > +       imap_end = imap + imaplen;
> > +
> > +       for (i = 0; i <= index && imap < imap_end; i++) {
> > +               if (supnp)
> > +                       of_node_put(supnp);
> > +
> > +               imap += addrcells;
> > +               imap += intcells;
> > +
> > +               supnp = of_find_node_by_phandle(be32_to_cpu(imap[0]));
> > +               if (!supnp)
> > +                       return NULL;
> > +               imap += 1;
> > +
> > +               if (of_property_read_u32(supnp, "#interrupt-cells", &cells))
> > +                       return NULL;
> > +               imap += cells;
>
> This is wrong. Technically, you can have #address-cells too.
>
> The bigger problem I have is this creates 2 sets of 'interrupt-map'
> parsing code. Your version skips a lot of things like whether the
> interrupt controller is available and there's the list of
> 'interrupt-map' abusers to think about.
>

In my first attempt, I was trying to keep it simple but I guess I
over-simplified it.

I have an alternate approach to use of_irq_parse_raw() over
here (similar to of_irq_parse_pci() in drivers/pci/of.c). Are you
okay with this approach ?

Regards,
Anup