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

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Message-ID: <5e1b6c09-0a8f-f1d9-728b-90ffbaedae83@linaro.org>
Date:   Sat, 2 Apr 2022 14:16:39 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Johan Jonker <jbx6244@...il.com>,
        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 02/04/2022 13:45, Johan Jonker wrote:
> 
> 
> 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" };

Thanks, but that's not the answer whether it is an input to the clock
controller. It's the answer how the driver implements this. :)

Best regards,
Krzysztof