linux-kernel - Re: [PATCH v3 1/2] dt-bindings: clock: convert rockchip,rk3188-cru.txt to YAML

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Message-Id: <20220401182413.643DDC340EE@smtp.kernel.org>
Date:   Fri, 01 Apr 2022 11:24:11 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Heiko Stübner <heiko@...ech.de>,
        Johan Jonker <jbx6244@...il.com>, zhangqing@...k-chips.com
Cc:     robh+dt@...nel.org, krzk+dt@...nel.org, mturquette@...libre.com,
        linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] dt-bindings: clock: convert rockchip,rk3188-cru.txt to YAML

Quoting Heiko Stübner (2022-04-01 00:55:55)
> Hi Stephen,
> 
> Am Freitag, 1. April 2022, 00:51:32 CEST schrieb Stephen Boyd:
> > Quoting Johan Jonker (2022-03-29 04:13:22)
> > > diff --git a/Documentation/devicetree/bindings/clock/rockchip,rk3188-cru.yaml b/Documentation/devicetree/bindings/clock/rockchip,rk3188-cru.yaml
> > > new file mode 100644
> > > index 000000000..ddd7e46af
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/clock/rockchip,rk3188-cru.yaml
> > > @@ -0,0 +1,78 @@
> > > +# SPDX-License-Identifier: GPL-2.0
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/clock/rockchip,rk3188-cru.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Rockchip RK3188/RK3066 Clock and Reset Unit (CRU)
> > > +
> > > +maintainers:
> > > +  - Elaine Zhang <zhangqing@...k-chips.com>
> > > +  - Heiko Stuebner <heiko@...ech.de>
> > > +
> > > +description: |
> > > +  The RK3188/RK3066 clock controller generates and supplies clocks to various
> > > +  controllers within the SoC and also implements a reset controller for SoC
> > > +  peripherals.
> > > +  Each clock is assigned an identifier and client nodes can use this identifier
> > > +  to specify the clock which they consume. All available clocks are defined as
> > > +  preprocessor macros in the dt-bindings/clock/rk3188-cru.h and
> > > +  dt-bindings/clock/rk3066-cru.h headers and can be used in device tree sources.
> > > +  Similar macros exist for the reset sources in these files.
> > > +  There are several clocks that are generated outside the SoC. It is expected
> > > +  that they are defined using standard clock bindings with following
> > > +  clock-output-names:
> > > +    - "xin24m"    - crystal input                 - required
> > > +    - "xin32k"    - RTC clock                     - optional
> > > +    - "xin27m"    - 27mhz crystal input on RK3066 - optional
> > > +    - "ext_hsadc" - external HSADC clock          - optional
> > > +    - "ext_cif0"  - external camera clock         - optional
> > > +    - "ext_rmii"  - external RMII clock           - optional
> > > +    - "ext_jtag"  - external JTAG clock           - optional
> > 
> > I'd expect all these clks here to be inputs to this node.
> 
> The optional clocks are all part of a circular dependency.
> 
> So for example xin32k normally is generated by the pmic and fed
> back into the system, so to get xin32k, we need the pmic to probe,
> which needs i2c, which in turn already needs the clock controller.
> 
> Or optional clocks may not be available at all.
> 
> So for the past years we already relied on the clock-system's
> self adaptation if a clock becomes available at some point
> during later boot and hence do not have those in a clocks-property.
> 

Are you saying that we can't have these clks in the clocks property
because there's a circular driver probe dependency? I don't see how that
matters for the dt binding. What is broken if they're put in the binding
and specified in the node?