From: Rob Herring <robh@kernel.org>
To: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Wolfram Sang <wsa@the-dreams.de>,
linux-i2c@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
linux-doc@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Arnd Bergmann <arnd@arndb.de>,
Przemyslaw Sroka <psroka@cadence.com>,
Arkadiusz Golec <agolec@cadence.com>,
Alan Douglas <adouglas@cadence.com>,
Bartosz Folta <bfolta@cadence.com>, Damian Kos <dkos@cadence.com>,
Alicja Jurasik-Urbaniak <alicja@cadence.com>,
Cyprian Wronka <cwronka@cadence.com>,
Suresh Punnoose <sureshp@cadence.com>,
Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
Nishanth Menon <nm@ti.com>, Pawel Moll <pawel.moll@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Ian Campbell <ijc+devicetree@hellion.org.uk>,
Kumar Gala <galak@codeaurora.org>,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
Vitor Soares <Vitor.Soares@synopsys.com>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Linus Walleij <linus.walleij@linaro.org>
Subject: Re: [PATCH v2 5/7] dt-bindings: i3c: Document core bindings
Date: Wed, 20 Dec 2017 12:06:45 -0600 [thread overview]
Message-ID: <20171220180645.pis34opfwawakmqc@rob-hp-laptop> (raw)
In-Reply-To: <20171216193537.0aef2e97@bbrezillon>
On Sat, Dec 16, 2017 at 07:35:37PM +0100, Boris Brezillon wrote:
> On Sat, 16 Dec 2017 11:20:40 -0600
> Rob Herring <robh@kernel.org> wrote:
>
> > On Thu, Dec 14, 2017 at 04:16:08PM +0100, Boris Brezillon wrote:
> > > A new I3C subsystem has been added and a generic description has been
> > > created to represent the I3C bus and the devices connected on it.
> > >
> > > Document this generic representation.
[...]
> > So please define the node
> > name to be "i3c-controller". That's more inline with other node names
> > than i3c-master that you used below.
>
> Hm, not sure i3c-controller is appropriate though, because you can have
> slave controllers. Maybe i3c-host, but I'd prefer to keep the term
> master since it's employed everywhere in the spec. I can also be
> i3c-master-controller if you prefer.
Okay, i3c-master is fine. Just make it explicit.
> > > +I3C devices
> > > +===========
> > > +
> > > +All I3C devices are supposed to support DAA (Dynamic Address Assignment), and
> > > +are thus discoverable. So, by default, I3C devices do not have to be described
> > > +in the device tree.
> > > +This being said, one might want to attach extra resources to these devices,
> > > +and those resources may have to be described in the device tree, which in turn
> > > +means we have to describe I3C devices.
> > > +
> > > +Another use case for describing an I3C device in the device tree is when this
> > > +I3C device has a static address and we want to assign it a specific dynamic
> > > +address before the DAA takes place (so that other devices on the bus can't
> > > +take this dynamic address).
> > > +
> > > +Required properties
> > > +-------------------
> > > +- i3c-pid: PID (Provisional ID). 64-bit property which is used to match a
> > > + device discovered during DAA with its device tree definition. The
> > > + PID is supposed to be unique on a given bus, which guarantees a 1:1
> > > + match. This property becomes optional if a reg property is defined,
> > > + meaning that the device has a static address.
> >
> > What determines this number?
>
> Part of it is fixed (manufacturer and part id) and the last few bits
> represent the device instance on the bus (so you can have several
> identical devices on the same bus). The manufacturer and part ids
> should be statically assigned during production, instance id is usually
> configurable through extra pins that you drive high or low at reset
> time.
Sounds like an I2C address at least for the pin strapping part...
> > > +
> > > +Optional properties
> > > +-------------------
> > > +- reg: static address. Only valid is the device has a static address.
> > > +- i3c-dynamic-address: dynamic address to be assigned to this device. This
> > > + property depends on the reg property.
> >
> > Perhaps "assigned-address" property would be appropriate. I'm not all
> > that familiar with it though.
>
> Again, the spec use the term "dynamic address" everywhere, and I'd like
> to stay as close as possible to the spec.
I looked at assigned-addresses a bit more and that won't really fit
because it should be the same format as reg. So I think reg should
always be the PID as that is fixed and always present. Then the DAA
address is separate and can be the i3c-dynamic-address property.
However, there's still part I don't understand...
> > > + /* I3C device with a static address. */
> > > + thermal_sensor: sensor@68 {
> > > + reg = <0x68>;
> > > + i3c-dynamic-address = <0xa>;
I'm confused as to how/why you have both reg and dynamic address?
> > > + };
> > > +
> > > + /*
> > > + * I3C device without a static address but requiring resources
> > > + * described in the DT.
> > > + */
> > > + sensor2 {
> >
> > It's not great that we can't follow using generic node names. Maybe the
> > PID can be used as the address? In USB for example, we use hub ports for
> > DT addresses rather than USB addresses since those are dynamic.
>
> Hm, the problem is, we may have 2 numbering schemes here: one where reg
> is used (reg representing the I2C/static address), and another one
> where the PID is used.
> If you're okay with mixing those 2 schemes, then I'm fine with that too.
Mixing I2C devices and I3C devices, yes. But you need to mix in a single
device? IOW, do I3C devices also have an I2C address?
Rob
next prev parent reply other threads:[~2017-12-20 18:06 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-14 15:16 [PATCH v2 0/7] Add the I3C subsystem Boris Brezillon
2017-12-14 15:16 ` [PATCH v2 1/7] i2c: Export of_i2c_get_board_info() Boris Brezillon
2017-12-14 15:16 ` [PATCH v2 2/7] i3c: Add core I3C infrastructure Boris Brezillon
2017-12-17 22:32 ` Randy Dunlap
2017-12-18 8:37 ` Boris Brezillon
2017-12-18 18:22 ` Randy Dunlap
2017-12-19 8:52 ` Greg Kroah-Hartman
2017-12-19 9:09 ` Boris Brezillon
2017-12-19 9:13 ` Boris Brezillon
2017-12-19 9:21 ` Greg Kroah-Hartman
2017-12-19 9:28 ` Boris Brezillon
2017-12-19 9:36 ` Greg Kroah-Hartman
2018-02-21 14:22 ` Boris Brezillon
2018-02-21 14:38 ` Greg Kroah-Hartman
2018-02-23 16:28 ` Vitor Soares
2018-02-23 16:56 ` Vitor Soares
2018-02-23 20:30 ` Boris Brezillon
2018-02-26 18:58 ` Vitor Soares
2018-02-26 20:36 ` Boris Brezillon
2018-02-26 20:40 ` Boris Brezillon
2018-02-26 21:38 ` Boris Brezillon
2018-02-27 16:03 ` Vitor Soares
2018-02-27 16:43 ` Przemyslaw Sroka
2018-02-27 17:06 ` Przemyslaw Sroka
2018-02-27 20:25 ` Boris Brezillon
2018-02-27 20:13 ` Boris Brezillon
2018-02-27 20:24 ` Przemyslaw Sroka
2018-02-27 21:14 ` Boris Brezillon
2018-02-27 19:57 ` Boris Brezillon
2018-02-23 22:45 ` Boris Brezillon
2017-12-14 15:16 ` [PATCH v2 3/7] docs: driver-api: Add I3C documentation Boris Brezillon
2017-12-14 15:16 ` [PATCH v2 4/7] i3c: Add sysfs ABI spec Boris Brezillon
2017-12-14 15:16 ` [PATCH v2 5/7] dt-bindings: i3c: Document core bindings Boris Brezillon
2017-12-14 16:24 ` Geert Uytterhoeven
2017-12-14 21:47 ` Peter Rosin
2017-12-16 17:20 ` Rob Herring
2017-12-16 18:35 ` Boris Brezillon
2017-12-20 18:06 ` Rob Herring [this message]
2017-12-21 10:41 ` Boris Brezillon
2017-12-26 18:29 ` Rob Herring
2018-01-07 14:14 ` Boris Brezillon
2018-01-22 8:47 ` Boris Brezillon
2017-12-14 15:16 ` [PATCH v2 6/7] i3c: master: Add driver for Cadence IP Boris Brezillon
2017-12-14 19:54 ` Randy Dunlap
2017-12-14 20:17 ` Boris Brezillon
2017-12-14 20:25 ` Randy Dunlap
2017-12-14 20:44 ` Boris Brezillon
2017-12-14 22:10 ` Randy Dunlap
2017-12-14 15:16 ` [PATCH v2 7/7] dt-bindings: i3c: Document Cadence I3C master bindings Boris Brezillon
2018-02-22 15:00 ` [PATCH v2 0/7] Add the I3C subsystem Vitor Soares
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