linux-kernel - Re: [PATCH v2] of: property: Add fw_devlink support for interrupt-map property

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Message-ID: <CAGETcx_Ni3MjwVHDOdre1nSqQP07=gaUtCDj31ndKcMFtm+xjg@mail.gmail.com>
Date: Tue, 16 Apr 2024 18:03:17 -0700
From: Saravana Kannan <saravanak@...gle.com>
To: Rob Herring <robh@...nel.org>
Cc: Anup Patel <apatel@...tanamicro.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 v2] of: property: Add fw_devlink support for interrupt-map property

On Tue, Apr 16, 2024 at 7:11 AM Rob Herring <robh@...nel.org> wrote:
>
> On Sat, Apr 13, 2024 at 02:49:42PM +0530, Anup Patel 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. This the only case where
> > the interrupts are not described in DT.
> >
> > Currently, there is no fw_devlink created based on "interrupt-map"
> > DT property

parse_interrupts() calls of_irq_parse_one() that in turn calls
of_irq_parse_one() that does the "interrupts-map" handling. In fact
of_irq_parse_pci() also calls of_irq_parse_one() if the PCI device has
a DT node. So I don't think any new functionality needs to be added.
If I'm not mistaken we just need parse_interrupts to not ignore
interrupts-map? A one line change?

Why do we need all of this code you wrote below?

-Saravana

> >  so interrupt controller is not guaranteed to be probed
> > before PCI host controller. This affects every platform where both
> > PCI host controller and interrupt controllers are probed as regular
> > platform devices.
> >
> > 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>
> > ---
> > Changes since v1:
> > - Updated commit description based on Rob's suggestion
> > - Use of_irq_parse_raw() for parsing interrupt-map DT property
> > ---
> >  drivers/of/property.c | 58 +++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 58 insertions(+)
> >
> > diff --git a/drivers/of/property.c b/drivers/of/property.c
> > index a6358ee99b74..67be66384dac 100644
> > --- a/drivers/of/property.c
> > +++ b/drivers/of/property.c
> > @@ -1311,6 +1311,63 @@ static struct device_node *parse_interrupts(struct device_node *np,
> >       return of_irq_parse_one(np, index, &sup_args) ? NULL : sup_args.np;
> >  }
> >
> > +static struct device_node *parse_interrupt_map(struct device_node *np,
> > +                                            const char *prop_name, int index)
> > +{
> > +     const __be32 *imap, *imap_end, *addr;
> > +     struct of_phandle_args sup_args;
> > +     struct device_node *tn, *ipar;
> > +     u32 addrcells, intcells;
> > +     int i, j, 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);
>
> No need for this loop. We've only gotten here if 'interrupt-map' is
> present in the node and '#interrupt-cells' is required if
> 'interrupt-map' is present.
>
> > +     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;
> > +
> > +     sup_args.np = NULL;
> > +     for (i = 0; i <= index && imap < imap_end; i++) {
> > +             if (sup_args.np) {
> > +                     of_node_put(sup_args.np);
> > +                     sup_args.np = NULL;
> > +             }
> > +
> > +             addr = imap;
> > +             imap += addrcells;
> > +
> > +             sup_args.np = np;
> > +             sup_args.args_count = intcells;
> > +             for (j = 0; j < intcells; j++)
> > +                     sup_args.args[j] = be32_to_cpu(imap[j]);
> > +             imap += intcells;
> > +
> > +             if (of_irq_parse_raw(addr, &sup_args))
> > +                     return NULL;
> > +             imap += sup_args.args_count + 1;
> > +     }
>
> Doesn't this leak a ref on the last time the function is invoked? For
> example, if we have 2 entries and index is 2. We'll get index=1, but
> then exit because imap==imap_end. We need a put on index==1 node.
>
> Look at my next branch where I've converted things to use __free()
> cleanups. I don't see it helping here as-is, but maybe when it is
> correct.
>
> Rob