On Tue, Aug 25, 2020 at 4:02 PM Nicolas Pitre <nico@xxxxxxxxxxx> 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@xxxxxxxxxxxx> > > > > > > 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@xxxxxxxxxxxx> > > > --- > > > .../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@xxxxxxxxxxxx> > > > + > > > +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
