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From:   Pankaj Bansal <pankaj.bansal@nxp.com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
CC:     Marc Zyngier <maz@kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Makarand Pawagi <makarand.pawagi@nxp.com>,
        Calvin Johnson <calvin.johnson@nxp.com>,
        "stuyoder@gmail.com" <stuyoder@gmail.com>,
        "nleeder@codeaurora.org" <nleeder@codeaurora.org>,
        Ioana Ciornei <ioana.ciornei@nxp.com>,
        Cristi Sovaiala <cristian.sovaiala@nxp.com>,
        Hanjun Guo <guohanjun@huawei.com>,
        Will Deacon <will@kernel.org>,
        "jon@solid-run.com" <jon@solid-run.com>,
        Russell King <linux@armlinux.org.uk>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        Len Brown <lenb@kernel.org>,
        Jason Cooper <jason@lakedaemon.net>,
        Andy Wang <Andy.Wang@arm.com>, Varun Sethi <V.Sethi@nxp.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Laurentiu Tudor <laurentiu.tudor@nxp.com>,
        Paul Yang <Paul.Yang@arm.com>,
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        Shameerali Kolothum Thodi 
        <shameerali.kolothum.thodi@huawei.com>,
        Sudeep Holla <sudeep.holla@arm.com>,
        Robin Murphy <robin.murphy@arm.com>
Subject: RE: [EXT] Re: [PATCH] bus: fsl-mc: Add ACPI support for fsl-mc
Thread-Topic: [EXT] Re: [PATCH] bus: fsl-mc: Add ACPI support for fsl-mc
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Date:   Mon, 17 Feb 2020 12:35:12 +0000
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> -----Original Message-----
> From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Sent: Friday, February 14, 2020 11:20 PM
> To: Pankaj Bansal <pankaj.bansal@nxp.com>
> Cc: Marc Zyngier <maz@kernel.org>; Ard Biesheuvel
> <ard.biesheuvel@linaro.org>; Makarand Pawagi <makarand.pawagi@nxp.com>;
> Calvin Johnson <calvin.johnson@nxp.com>; stuyoder@gmail.com;
> nleeder@codeaurora.org; Ioana Ciornei <ioana.ciornei@nxp.com>; Cristi
> Sovaiala <cristian.sovaiala@nxp.com>; Hanjun Guo <guohanjun@huawei.com>;
> Will Deacon <will@kernel.org>; jon@solid-run.com; Russell King
> <linux@armlinux.org.uk>; ACPI Devel Maling List <linux-acpi@vger.kernel.o=
rg>;
> Len Brown <lenb@kernel.org>; Jason Cooper <jason@lakedaemon.net>; Andy
> Wang <Andy.Wang@arm.com>; Varun Sethi <V.Sethi@nxp.com>; Thomas
> Gleixner <tglx@linutronix.de>; linux-arm-kernel <linux-arm-
> kernel@lists.infradead.org>; Laurentiu Tudor <laurentiu.tudor@nxp.com>; P=
aul
> Yang <Paul.Yang@arm.com>; netdev@vger.kernel.org; Rafael J. Wysocki
> <rjw@rjwysocki.net>; Linux Kernel Mailing List <linux-kernel@vger.kernel.=
org>;
> Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>;
> Sudeep Holla <sudeep.holla@arm.com>; Robin Murphy
> <robin.murphy@arm.com>
> Subject: Re: [EXT] Re: [PATCH] bus: fsl-mc: Add ACPI support for fsl-mc
>=20
> On Fri, Feb 14, 2020 at 04:35:10PM +0000, Pankaj Bansal wrote:
>=20
> [...]
>=20
> > > -----Original Message-----
> > > From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> > > Sent: Friday, February 14, 2020 9:50 PM
> > > To: Pankaj Bansal <pankaj.bansal@nxp.com>
> > > Cc: Marc Zyngier <maz@kernel.org>; Ard Biesheuvel
> > > <ard.biesheuvel@linaro.org>; Makarand Pawagi
> <makarand.pawagi@nxp.com>;
> > > Calvin Johnson <calvin.johnson@nxp.com>; stuyoder@gmail.com;
> > > nleeder@codeaurora.org; Ioana Ciornei <ioana.ciornei@nxp.com>; Cristi
> > > Sovaiala <cristian.sovaiala@nxp.com>; Hanjun Guo
> <guohanjun@huawei.com>;
> > > Will Deacon <will@kernel.org>; jon@solid-run.com; Russell King
> > > <linux@armlinux.org.uk>; ACPI Devel Maling List <linux-
> acpi@vger.kernel.org>;
> > > Len Brown <lenb@kernel.org>; Jason Cooper <jason@lakedaemon.net>;
> Andy
> > > Wang <Andy.Wang@arm.com>; Varun Sethi <V.Sethi@nxp.com>; Thomas
> > > Gleixner <tglx@linutronix.de>; linux-arm-kernel <linux-arm-
> > > kernel@lists.infradead.org>; Laurentiu Tudor <laurentiu.tudor@nxp.com=
>;
> Paul
> > > Yang <Paul.Yang@arm.com>; netdev@vger.kernel.org; Rafael J. Wysocki
> > > <rjw@rjwysocki.net>; Linux Kernel Mailing List <linux-
> kernel@vger.kernel.org>;
> > > Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>;
> > > Sudeep Holla <sudeep.holla@arm.com>; Robin Murphy
> > > <robin.murphy@arm.com>
> > > Subject: Re: [EXT] Re: [PATCH] bus: fsl-mc: Add ACPI support for fsl-=
mc
> Side note: would you mind removing the email headers (as above) in your
> replies please ?
>=20
> > > On Fri, Feb 14, 2020 at 03:58:14PM +0000, Pankaj Bansal wrote:
> > >
> > > [...]
> > >
> > > > > Why should the device know about its own ID? That's a bus/interco=
nnect
> > > thing.
> > > > > And nothing should be passed *to* IORT. IORT is the source.
> > > >
> > > > IORT is translation between Input IDs <-> Output IDs. The Input ID =
is still
> > > expected to be passed to parse IORT table.
> > >
> > > Named components use an array of single mappings (as in entries with =
single
> > > mapping flag set) - Input ID is irrelevant.
> > >
> > > Not sure what your named component is though and what you want to do
> with
> > > it, the fact that IORT allows mapping for named components do not
> necessarily
> > > mean that it can describe what your system really is, on that you nee=
d to
> > > elaborate for us to be able to help.
> >
> > Details about MC bus can be read from here:
> >
> https://eur01.safelinks.protection.outlook.com/?url=3Dhttps%3A%2F%2Felixi=
r.boo
> tlin.com%2Flinux%2Flatest%2Fsource%2FDocumentation%2Fnetworking%2Fdev
> ice_drivers%2Ffreescale%2Fdpaa2%2Foverview.rst%23L324&amp;data=3D02%7C0
> 1%7Cpankaj.bansal%40nxp.com%7Cf1bcfc907a42463b617408d7b1764f0f%7C6
> 86ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637172993997763634&am
> p;sdata=3DfPcC2UfsHoS25oYGmxJmsbPXxb1brKxP1i2qJfPdRpk%3D&amp;reserved
> =3D0
> >
> > As stated above, in Linux MC is a bus (just like PCI bus, AMBA bus etc)
> > There can be multiple devices attached to this bus. Moreover, we can
> dynamically create/destroy these devices.
> > Now, we want to represent this BUS (not individual devices connected to=
 bus)
> in IORT table.
> > The only possible way right now we see is that we describe it as Named
> components having a pool of ID mappings.
> > As and when devices are created and attached to bus, we sift through th=
is pool
> to correctly determine the output ID for the device.
> > Now the input ID that we provide, can come from device itself.
> > Then we can use the Platform MSI framework for MC bus devices.
>=20
> So are you asking me if that's OK ? Or there is something you can't
> describe with IORT ?

I am asking if that would be acceptable?
i.e. we represent MC bus as Named component is IORT table with a pool of ID=
s (without single ID mapping flag)
and then we use the Platform MSI framework for all children devices of MC b=
us.
Note that it would require the Platform MSI layer to correctly pass an inpu=
t id for a platform device to IORT layer.
And IORT layer ought to retrieve the output id based on single ID mapping f=
lag as well as input id.

>=20
> Side note: can you explain to me please how the MSI allocation flow
> and kernel data structures/drivers are modeled in DT ? I had a quick
> look at:
>=20
> drivers/irqchip/irq-gic-v3-its-fsl-mc-msi.c
>=20
> and to start with, does that code imply that we create a
> DOMAIN_BUS_FSL_MC_MSI on ALL DT systems with an ITS device node ?

Yes. It's being done for all DT systems having ITS node.
The domain creation is handled in drivers/bus/fsl-mc/fsl-mc-msi.c

>=20
> I *think* you have a specific API to allocate MSIs for MC devices:
>=20
> fsl_mc_msi_domain_alloc_irqs()
>=20
> which hook into the IRQ domain created in the file above that handles
> the cascading to an ITS domain, correct ?

We associate the above created domain with dpaa2 device here:
https://elixir.bootlin.com/linux/latest/source/drivers/bus/fsl-mc/dprc-driv=
er.c#L640

Then fsl_mc_msi_domain_alloc_irqs, retrieves the domain associated with dev=
ice and calls the msi_prepare
API from its_fsl_mc_msi_prepare.

>=20
> Thanks,
> Lorenzo