linux-i3c.lists.infradead.org archive mirror
 help / color / mirror / Atom feed
From: Rob Herring <robh@kernel.org>
To: Nicolas Pitre <nico@fluxnic.net>
Cc: devicetree@vger.kernel.org, Robert Gough <robert.gough@intel.com>,
	Laura Nixon <laura.nixon@team.mipi.org>,
	Boris Brezillon <boris.brezillon@collabora.com>,
	Matthew Schnoor <matthew.schnoor@intel.com>,
	linux-i3c@lists.infradead.org
Subject: Re: [PATCH v2 1/2] dt-bindings: i3c: MIPI I3C Host Controller Interface
Date: Tue, 25 Aug 2020 17:06:15 -0600	[thread overview]
Message-ID: <CAL_JsqKJByNNwgP34_=G3bdVaZiM1OCUY94N1pTRzgNvqHjcWw@mail.gmail.com> (raw)
In-Reply-To: <nycvar.YSQ.7.78.906.2008251732430.1479@knanqh.ubzr>

On Tue, Aug 25, 2020 at 4:02 PM Nicolas Pitre <nico@fluxnic.net> wrote:
>
> On Tue, 25 Aug 2020, Rob Herring wrote:
>
> > On Tue, Aug 18, 2020 at 11:17:22PM -0400, Nicolas Pitre wrote:
> > > From: Nicolas Pitre <npitre@baylibre.com>
> > >
> > > The MIPI I3C HCI (Host Controller Interface) specification defines
> > > a common software driver interface to support compliant MIPI I3C
> > > host controller hardware implementations from multiple vendors.
> > >
> > > Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
> > > ---
> > >  .../devicetree/bindings/i3c/mipi-i3c-hci.yaml | 41 +++++++++++++++++++
> > >  1 file changed, 41 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/i3c/mipi-i3c-hci.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/i3c/mipi-i3c-hci.yaml b/Documentation/devicetree/bindings/i3c/mipi-i3c-hci.yaml
> > > new file mode 100644
> > > index 0000000000..8fc18ea922
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/i3c/mipi-i3c-hci.yaml
> > > @@ -0,0 +1,41 @@
> > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: "http://devicetree.org/schemas/i3c/mipi-i3c-hci.yaml#"
> > > +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> > > +
> > > +title: MIPI I3C HCI Device Tree Bindings
> > > +
> > > +maintainers:
> > > +  - Nicolas Pitre <npitre@baylibre.com>
> > > +
> > > +description: |
> > > +  MIPI I3C Host Controller Interface
> > > +
> > > +  The MIPI I3C HCI (Host Controller Interface) specification defines
> > > +  a common software driver interface to support compliant MIPI I3C
> > > +  host controller hardware implementations from multiple vendors.
> > > +
> > > +  For details, please see:
> > > +  https://www.mipi.org/specifications/i3c-hci
> > > +
> > > +properties:
> > > +  compatible:
> > > +    const: mipi-i3c-hci
> >
> > What about my comments on v1? Pasted again:
>
> Oops, sorry, I missed them.
>
> > A register interface (or protocol) spec is never complete enough to
> > capture all the details about a specific h/w implementation. One just
> > has to go look at AHCI, EHCI, OHCI, XHCI, UFS, 8250, etc. bindings.
> > Let's not start with pretending that here. Fine for this to be a
> > fallback, but it must have a compatible for a specific implementation.
>
> You might have to indulge me a bit as I don't
> understand what you're asking.
>
> Currently there are very few implementations. One of them lives in an
> FPGA and the example below is actually the DT entry I use for it. I'm
> guessing specific vendor implementations will have their own tweaks
> eventually, such as clock sources and whatnot.

Yes, exactly. And bugs too.

> But that is outside of
> the spec (actually the spec defines a register area for eventual vendor
> specific usage). But I have no visibility into that and of course the
> code has no provision for that yet either.
>
> So I imagine there will be something like this in dts files eventually:
>
>         compatibvle = "intel,foobar_soc_i3c_hci", "mipi-i3c-hci";
>
> Is that what you mean?

Yes. Even your FPGA is tied to some implementation...

> > Also, which version of the spec does this compatible correspond to?
>
> All of them.
>
> > Or are there not HCI differences in the spec versions you mention in
> > the cover letter?
>
> The hardware is self advertising per the spec. So there is no need to
> carry such distinction in the DT compatible. Even vendor extensions are
> tagged with MIPI vendor IDs in the hardware directly.

Oh good, folks are learning. :)

Is the vendor ID (and revision) discoverable even if no vendor
extensions? If so, then I'm more comfortable with "mipi-i3c-hci" on
it's own. The exception will be if there's setup needed to discover
the h/w which seems likely. In that case, we should probably do
compatible strings based on VID/PID like PCI, USB, etc. No need to
define that now I guess, but please add some sort of summary of the
above about the discoverability of the HCI implementer and features.

Rob

-- 
linux-i3c mailing list
linux-i3c@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-i3c

  reply	other threads:[~2020-08-25 23:06 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-19  3:17 [PATCH v2 1/2] MIPI I3c HCI (Host Controller Interface) driver Nicolas Pitre
2020-08-19  3:17 ` [PATCH v2 1/2] dt-bindings: i3c: MIPI I3C Host Controller Interface Nicolas Pitre
2020-08-25 21:29   ` Rob Herring
2020-08-25 22:02     ` Nicolas Pitre
2020-08-25 23:06       ` Rob Herring [this message]
2020-08-26  0:40         ` Nicolas Pitre
2020-08-19  3:17 ` [PATCH v2 2/2] i3c/master: add the mipi-i3c-hci driver Nicolas Pitre
2020-10-01 12:31   ` Sakari Ailus
2020-10-05 22:15     ` Nicolas Pitre
2020-10-07 10:17       ` Sakari Ailus
2020-10-07 16:30         ` Nicolas Pitre
2020-10-09 12:01           ` Sakari Ailus
2020-08-19  3:21 ` [PATCH v2 1/2] MIPI I3c HCI (Host Controller Interface) driver Nicolas Pitre

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAL_JsqKJByNNwgP34_=G3bdVaZiM1OCUY94N1pTRzgNvqHjcWw@mail.gmail.com' \
    --to=robh@kernel.org \
    --cc=boris.brezillon@collabora.com \
    --cc=devicetree@vger.kernel.org \
    --cc=laura.nixon@team.mipi.org \
    --cc=linux-i3c@lists.infradead.org \
    --cc=matthew.schnoor@intel.com \
    --cc=nico@fluxnic.net \
    --cc=robert.gough@intel.com \
    --subject='Re: [PATCH v2 1/2] dt-bindings: i3c: MIPI I3C Host Controller Interface' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).