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Date: Wed, 17 Oct 2018 08:49:25 -0500
From: Rob Herring <robh@...nel.org>
To: Nishanth Menon <nm@...com>
Cc: Lokesh Vutla <lokeshvutla@...com>, Tero Kristo <t-kristo@...com>,
tglx@...utronix.de, jason@...edaemon.net, marc.zyngier@....com,
Santosh Shilimkar <ssantosh@...nel.org>,
Device Tree Mailing List <devicetree@...r.kernel.org>,
Linux ARM Mailing List <linux-arm-kernel@...ts.infradead.org>,
linux-kernel@...r.kernel.org, Sekhar Nori <nsekhar@...com>
Subject: Re: [PATCH 1/2] dt-bindings: irqchip: Introduce TISCI Interrupt
router bindings
On Sat, Oct 06, 2018 at 11:29:29AM -0500, Nishanth Menon wrote:
> On 12:58-20181006, Lokesh Vutla wrote:
> > Add the DT binding documentation for Interrupt router driver.
> >
> > Signed-off-by: Lokesh Vutla <lokeshvutla@...com>
> > ---
> > .../interrupt-controller/ti,sci-intr.txt | 83 +++++++++++++++++++
> > MAINTAINERS | 1 +
> > 2 files changed, 84 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/interrupt-controller/ti,sci-intr.txt
> >
> > diff --git a/Documentation/devicetree/bindings/interrupt-controller/ti,sci-intr.txt b/Documentation/devicetree/bindings/interrupt-controller/ti,sci-intr.txt
> > new file mode 100644
> > index 000000000000..681ca53cc5fb
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/interrupt-controller/ti,sci-intr.txt
> > @@ -0,0 +1,83 @@
> > +Texas Instruments K3 Interrupt Router
> > +=====================================
> > +
> > +The Interrupt Router (INTR) module provides a mechanism to mux M
> > +interrupt inputs to N interrupt outputs, where all M inputs are selectable
> > +to be driven per N output. There is one register per output (MUXCNTL_N) that
> > +controls the selection.
> > +
> > +
> > + Interrupt Router
> > + +----------------------+
> > + | Inputs Outputs |
> > + +-------+ | +------+ |
> > + | GPIO |----------->| | irq0 | | Host IRQ
> > + +-------+ | +------+ | controller
> > + | . +-----+ | +-------+
> > + +-------+ | . | 0 | |----->| GIC |
> > + | INTA |----------->| . +-----+ | +-------+
> > + +-------+ | . . |
> > + | +------+ . |
> > + | | irqM | +-----+ |
> > + | +------+ | N | |
> > + | +-----+ |
> > + +----------------------+
> > +
> > +Configuration of these MUXCNTL_N registers is done by a system controller
> > +(like the Device Memory and Security Controller on K3 AM654 SoC). System
> > +controller will keep track of the used and unused registers within the Router.
> > +Driver should request the system controller to get the range of GIC IRQs
> > +assigned to the requesting hosts. It is the drivers responsibility to keep
> > +track of GIC IRQs.
> > +
> > +Communication between the host processor running an OS and the system
> > +controller happens through a protocol called TI System Control Interface
> > +(TISCI protocol). For more details refer:
> > +Documentation/devicetree/bindings/arm/keystone/ti,sci.txt
> > +
> > +TISCI Interrupt Router Node:
> > +----------------------------
> > +- compatible: Must be "ti,sci-intr".
> > +- interrupt-controller: Identifies the node as an interrupt controller
> > +- #interrupt-cells: Specifies the number of cells needed to encode an
> > + interrupt source. The value should be 3.
> > + First cell should contain the TISCI device ID of source
> > + Second cell should contain the interrupt source offset
> > + within the device
> > + Third cell specifies the trigger type as defined
> > + in interrupts.txt in this directory.
> > +- interrupt-parent: phandle of irq parent for TISCI intr. The parent must
> > + use the same interrupt-cells format as GIC.
> > +- ti,sci: Phandle to TI-SCI compatible System controller node.
> > +- ti,sci-dst-id: TISCI device ID of the destination IRQ controller.
> > +- ti,sci-rm-range-girq: Tuple corresponding to unique TISCI resource type that
> > + defines the dst host irq ranges assigned to this
> > + interrupt router from this host context.
> > + Tuple should be of format <type subtype>.
> > +
>
> Rob, DT maintainers,
>
> I'd like a feedback from DT maintainers on this 'range' topic.
>
> TISCI Firmware [1] currently seems to define a type corresponding to a
> device ID[2]. in AM6 device, for example, this is different, however
> have a 1 to 1 correspondence. However, there is expectation that type will
> end up as device ID in a future SoC.
>
> While this is subject to much debate internally, I'd like some feedback if this
> is OK from Device tree representation - it is true that Firmware does
> look at it as type, however in some future SoC, it could be that the
> values themselves may correspond one to one with a device id -> The
> original wish was that types might be something reusable across SoCs,
> but that is turning out to be more of a theoretical wish than any thing
> practical.
I'm not sure I follow all the terminology here of type, subtype, "dst
host irq", etc. It looks to me like you should be using interrupt-map property.
Rob
>
> [1]http://software-dl.ti.com/tisci/esd/latest/5_soc_doc/am6x/resasg_types.html
> [2]http://software-dl.ti.com/tisci/esd/latest/5_soc_doc/am6x/devices.html
> --
> Regards,
> Nishanth Menon
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