Hello, On Wed Jan 24, 2024 at 6:28 PM CET, Théo Lebrun wrote: > Hello, > > On Wed Jan 24, 2024 at 4:14 PM CET, Rob Herring wrote: > > On Tue, Jan 23, 2024 at 07:46:49PM +0100, Théo Lebrun wrote: > > > Add documentation to describe the "Other Logic Block" syscon. > > > > > > Signed-off-by: Théo Lebrun <theo.lebrun@xxxxxxxxxxx> > > > --- > > > .../bindings/soc/mobileye/mobileye,eyeq5-olb.yaml | 77 ++++++++++++++++++++++ > > > MAINTAINERS | 1 + > > > 2 files changed, 78 insertions(+) > > > > > > diff --git a/Documentation/devicetree/bindings/soc/mobileye/mobileye,eyeq5-olb.yaml b/Documentation/devicetree/bindings/soc/mobileye/mobileye,eyeq5-olb.yaml > > > new file mode 100644 > > > index 000000000000..031ef6a532c1 > > > --- /dev/null > > > +++ b/Documentation/devicetree/bindings/soc/mobileye/mobileye,eyeq5-olb.yaml > > > @@ -0,0 +1,77 @@ > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) > > > +%YAML 1.2 > > > +--- > > > +$id: http://devicetree.org/schemas/soc/mobileye/mobileye,eyeq5-olb.yaml# > > > +$schema: http://devicetree.org/meta-schemas/core.yaml# > > > + > > > +title: Mobileye EyeQ5 SoC system controller > > > + > > > +maintainers: > > > + - Grégory Clement <gregory.clement@xxxxxxxxxxx> > > > + - Théo Lebrun <theo.lebrun@xxxxxxxxxxx> > > > + - Vladimir Kondratiev <vladimir.kondratiev@xxxxxxxxxxxx> > > > + > > > +description: > > > + OLB ("Other Logic Block") is a hardware block grouping smaller blocks. Clocks, > > > + resets, pinctrl are being handled from here. > > > + > > > +properties: > > > + compatible: > > > + items: > > > + - const: mobileye,eyeq5-olb > > > + - const: syscon > > > + - const: simple-mfd > > > + > > > + reg: > > > + maxItems: 1 > > > + > > > + clock-controller: > > > + $ref: /schemas/clock/mobileye,eyeq5-clk.yaml# > > > + type: object > > > + > > > + reset-controller: > > > + $ref: /schemas/reset/mobileye,eyeq5-reset.yaml# > > > + type: object > > > + > > > + pinctrl-a: > > > + $ref: /schemas/pinctrl/mobileye,eyeq5-pinctrl.yaml# > > > + type: object > > > + > > > + pinctrl-b: > > > + $ref: /schemas/pinctrl/mobileye,eyeq5-pinctrl.yaml# > > > + type: object > > > + > > > +required: > > > + - compatible > > > + - reg > > > + > > > +additionalProperties: false > > > + > > > +examples: > > > + - | > > > + system-controller@e00000 { > > > + compatible = "mobileye,eyeq5-olb", "syscon", "simple-mfd"; > > > + reg = <0xe00000 0x400>; > > > + > > > + clock-controller { > > > + compatible = "mobileye,eyeq5-clk"; > > > + #clock-cells = <1>; > > > + clocks = <&xtal>; > > > + clock-names = "ref"; > > > + }; > > > + > > > + reset-controller { > > > + compatible = "mobileye,eyeq5-reset"; > > > + #reset-cells = <2>; > > > + }; > > > + > > > + pinctrl-a { > > > + compatible = "mobileye,eyeq5-a-pinctrl"; > > > + #pinctrl-cells = <1>; > > > > Sure you need this? Generally only pinctrl-single uses this. > > You are completely right, it is useless. I naively expected it in the > same vein as other subsystems. > > > > > > + }; > > > + > > > + pinctrl-b { > > > + compatible = "mobileye,eyeq5-b-pinctrl"; > > > + #pinctrl-cells = <1>; > > > + }; > > > + }; > > > > This can all be simplified to: > > > > system-controller@e00000 { > > compatible = "mobileye,eyeq5-olb", "syscon"; > > reg = <0xe00000 0x400>; > > #reset-cells = <2>; > > #clock-cells = <1>; > > clocks = <&xtal>; > > clock-names = "ref"; > > > > pins { ... }; > > }; > > > > There is no need for sub nodes unless you have reusable blocks or each > > block has its own resources in DT. > > That is right, and it does simplify the devicetree as you have shown. > However, the split nodes gives the following advantages: > > - Devicetree-wise, it allows for one alias per function. > `clocks = <&clocks EQ5C_PLL_CPU>` is surely more intuitive > than `clocks = <&olb EQ5C_PLL_CPU>;`. Same for reset. > > - It means an MFD driver must be implemented, adding between 100 to 200 > lines of boilerplate code to the kernel. > > - It means one pinctrl device for the two banks. That addresses your > comment on [PATCH v3 10/17]. This is often done and would be doable > on this platform. However it means added logic to each individual > function of pinctrl-eyeq5. > > Overall it makes for less readable code, for code that already looks > more complex than it really is. > > My initial non-public version of pinctrl-eyeq5 was using this method > (a device handling both banks) and I've leaned away from it. I had forgotten one other reason: - Reusability does count for something. Other Mobileye platforms exist, and the system controller stuff is more complex on those. Multiple different OLB blocks, etc. But my understanding is that per-peripheral logic is reused across versions. > > Those are all minor, but I don't have the feeling a few lines and nodes > less in devicetree compensate for those. Thanks, -- Théo Lebrun, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
