Received-SPF: pass (google.com: domain of linux-kernel+bounces-147994-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
Precedence: bulk
MIME-Version: 1.0
References: <20240413091942.316054-1-apatel@ventanamicro.com>
 <20240416141049.GA2148267-robh@kernel.org> <CAGETcx_Ni3MjwVHDOdre1nSqQP07=gaUtCDj31ndKcMFtm+xjg@mail.gmail.com>
In-Reply-To: <CAGETcx_Ni3MjwVHDOdre1nSqQP07=gaUtCDj31ndKcMFtm+xjg@mail.gmail.com>
From: Anup Patel <apatel@ventanamicro.com>
Date: Wed, 17 Apr 2024 12:04:20 +0530
Message-ID: <CAK9=C2WUe-JWk4QLxHNc_gSCqjBCxrVfcPcYP9-_QFoGk-vF5Q@mail.gmail.com>
Subject: Re: [PATCH v2] of: property: Add fw_devlink support for interrupt-map property
To: Saravana Kannan <saravanak@google.com>
Cc: Rob Herring <robh@kernel.org>, Palmer Dabbelt <palmer@dabbelt.com>, 
	Paul Walmsley <paul.walmsley@sifive.com>, Atish Patra <atishp@atishpatra.org>, 
	Andrew Jones <ajones@ventanamicro.com>, Sunil V L <sunilvl@ventanamicro.com>, 
	Anup Patel <anup@brainfault.org>, linux-riscv@lists.infradead.org, 
	linux-kernel@vger.kernel.org, devicetree@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Wed, Apr 17, 2024 at 6:34=E2=80=AFAM Saravana Kannan <saravanak@google.c=
om> wrote:
>
> On Tue, Apr 16, 2024 at 7:11=E2=80=AFAM Rob Herring <robh@kernel.org> wro=
te:
> >
> > 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?

The of_irq_parse_one() calls of_irq_parse_raw() only if the DT
node has "interrupts" or "interrupts-extended" DT property. This
means for most PCI host controller DT nodes, the of_irq_parse_one()
will not return any interrupts.

Here's an example PCI host DT node from the RISC-V world
(but this also applies to other architectures):

pci@30000000 {
    compatible =3D "pci-host-ecam-generic";
     device_type =3D "pci";
     #address-cells =3D <0x03>;
     #size-cells =3D <0x02>;
     #interrupt-cells =3D <0x01>;
     interrupt-map-mask =3D <0x0 0x00 0x00 0x07>;
     interrupt-map =3D <0x00 0x00 0x00 0x01 &aplic_slevel 28 0x04>,
                              <0x00 0x00 0x00 0x02 &aplic_slevel 29 0x04>,
                              <0x00 0x00 0x00 0x03 &aplic_slevel 30 0x04>,
                              <0x00 0x00 0x00 0x04 &aplic_slevel 31 0x04>;
     reg =3D <0x0 0x30000000 0x0 0x10000000>;
     ranges =3D <0x01000000 0x0 0x0 0x0 0x1fff0000 0x00000000 0x10000>,
                    <0x02000000 0x0 0x40000000 0x0 0x40000000 0x0 0x4000000=
0>,
                     <0x03000000 0x100 0x0 0x100 0x0 0x4 0x0>;
     interrupt-parent =3D <&aplic_slevel>;
     msi-parent =3D <&imsic_slevel>;
     bus-range =3D <0x00 0xff>;
     linux,pci-domain =3D <0x00>;
};

In the above example, the "interrupt-map" DT property maps a set
of PCIe endpoints to APLIC interrupt sources but this only applies
if the corresponding PCIe endpoints are actually present. Also,
which entry of "interrupt-map" DT property is used for a PCIe
endpoint also depends on the PCI requester ID (bus-device-func)
assigned to the PCIe endpoint.

Regards,
Anup

>
> -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@ventanamicro.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(st=
ruct 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 *n=
p,
> > > +                                            const char *prop_name, i=
nt 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 =3D of_node_get(np);
> > > +     do {
> > > +             if (!of_property_read_u32(ipar, "#interrupt-cells", &in=
tcells))
> > > +                     break;
> > > +             tn =3D ipar;
> > > +             ipar =3D 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 =3D of_bus_n_addr_cells(ipar);
> > > +     of_node_put(ipar);
> > > +
> > > +     imap =3D of_get_property(np, "interrupt-map", &imaplen);
> > > +     if (!imap || imaplen <=3D (addrcells + intcells))
> > > +             return NULL;
> > > +     imap_end =3D imap + imaplen;
> > > +
> > > +     sup_args.np =3D NULL;
> > > +     for (i =3D 0; i <=3D index && imap < imap_end; i++) {
> > > +             if (sup_args.np) {
> > > +                     of_node_put(sup_args.np);
> > > +                     sup_args.np =3D NULL;
> > > +             }
> > > +
> > > +             addr =3D imap;
> > > +             imap +=3D addrcells;
> > > +
> > > +             sup_args.np =3D np;
> > > +             sup_args.args_count =3D intcells;
> > > +             for (j =3D 0; j < intcells; j++)
> > > +                     sup_args.args[j] =3D be32_to_cpu(imap[j]);
> > > +             imap +=3D intcells;
> > > +
> > > +             if (of_irq_parse_raw(addr, &sup_args))
> > > +                     return NULL;
> > > +             imap +=3D 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=3D1, but
> > then exit because imap=3D=3Dimap_end. We need a put on index=3D=3D1 nod=
e.
> >
> > 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