Messages in this thread | | | Date | Mon, 9 Oct 2023 10:08:48 +0100 | From | Cristian Marussi <> | Subject | Re: [RFC v2 5/5] dt-bindings: gpio: Add bindings for pinctrl based generic gpio driver |
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On Mon, Oct 09, 2023 at 09:49:33AM +0200, Linus Walleij wrote: > On Fri, Oct 6, 2023 at 3:23 PM Rob Herring <robh@kernel.org> wrote: > > On Thu, Oct 05, 2023 at 11:58:43AM +0900, AKASHI Takahiro wrote: >
Hi Linus and all,
> > > A dt binding for pin controller based generic gpio driver is defined in > > > this commit. One usable device is Arm's SCMI. > > > > You don't need a "generic" binding to have a generic driver. Keep the > > binding specific and then decide in the OS to whether to use a generic > > or specific driver. That decision could change over time, but the > > binding can't. For example, see simple-panel. > > What you say is true for simple-panel (a word like "simple" should > always cause red flags). > > This case is more like mfd/syscon.yaml, where the singular > compatible = "syscon"; is in widespread use: > > $ git grep 'compatible = \"syscon\";' |wc -l > 50 > > I would accept adding a tuple compatible if you insist, so: > > compatible = "foo-silicon", "pin-contro-gpio"; > > One case will be something like: > > compatible = "optee-scmi-pin-control", "pin-control-gpio"; > > In this case I happen to know that we have the problem of > this being standardization work ahead of implementation on > actual hardware, and that is driven by the will known firmware > ambition to be completely abstract. It is supposed to sit on > top of pin control, or as part of pin control. Which leads me to > this thing (which I didn't think of before...) > > > + gpio0: gpio@0 { > > + compatible = "pin-control-gpio"; > > + gpio-controller; > > + #gpio-cells = <2>; > > + gpio-ranges = <&scmi_pinctrl 0 10 5>, > > + <&scmi_pinctrl 5 0 0>; > > + gpio-ranges-group-names = "", > > + "pinmux_gpio"; > > + }; >
Assuming the above &scmi_pinctrl refers to the protocol node as we usually do, I am a bit puzzled by this example in this RFC series, because usually in SCMI we DO refer to some resources using the phandle and the domain IDs as in:
scmi_sensor: protocol@15 { reg = <15>; #thermal-sensors-cells = <1>; };
...
thermal_zones { pmic { thermal-sensor = <&scmi_sensor 0>; }; }; BUT in the SCMI Pinctrl case the current v4 Oleksii series takes advantage of the existing Pinctrl bindings and naming to describe and refer to pin/groups/functions, indeed #pinctrl-cells is defined as '0' in the upcoming SCMI DT protocol node @19 in Oleksii v4, since indeed all the parsing/matching is done by resource-names following the Picntrl framework conventions. (AFAIU)
Moreover, due to how the SCMI Pinctrl protocol defines and describes the pins/groups/functions using a tuple like (<TYPE>, <ID>) , with TYPE being pin/group/function, a generic binding like the above would have to be defined by at least 2 cells to be able to identify an SCMI PinCtrl resource by index. (if that is the aim here...)
Am I right to think that such a generic SCMI PinCtrl binding is still to be defined somewhere on the SCMI side, if needed as such by this GPIO driver ?
... or I am missing something ?
Thanks, Cristian
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