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

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Date:   Sat, 2 Apr 2022 13:45:47 +0200
From:   Johan Jonker <jbx6244@...il.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Heiko Stübner <heiko@...ech.de>,
        zhangqing@...k-chips.com, Stephen Boyd <sboyd@...nel.org>
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



On 4/2/22 13:41, Krzysztof Kozlowski wrote:
> On 01/04/2022 09:55, Heiko Stübner wrote:
>> 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.
> 
> Are you sure that xin32k (RTC) clock should be input to the clock
> controller? I would expect it is the input to the SoC RTC block, so
> there is no circular dependency.

clk-rk3188.c:

PNAME(mux_pll_p)		= { "xin24m", "xin32k" };

> 
> 
> Best regards,
> Krzysztof