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Date:   Sat, 2 Apr 2022 18:01:11 +0200
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Subject: Re: [PATCH v3 1/2] dt-bindings: clock: convert
 rockchip,rk3188-cru.txt to YAML
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To:     Johan Jonker <jbx6244@gmail.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        =?UTF-8?Q?Heiko_St=c3=bcbner?= <heiko@sntech.de>,
        zhangqing@rock-chips.com, Stephen Boyd <sboyd@kernel.org>
Cc:     robh+dt@kernel.org, krzk+dt@kernel.org, mturquette@baylibre.com,
        linux-clk@vger.kernel.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org
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From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <0eed395b-ca02-2308-a5c6-7c4a72720175@gmail.com>
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On 02/04/2022 14:20, Johan Jonker wrote:
> 
> 
> On 4/2/22 14:16, Krzysztof Kozlowski wrote:
>> 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@rock-chips.com>
>>>>>>> +  - Heiko Stuebner <heiko@sntech.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. :)
> 
> PX2 == rk3066
> 
> Rockchip PX2 TRM V1.0.pdf
> 
> page 30
> 
> Chip Clock Architecture Diagram 1

I found it, thanks. That's the answer, so indeed this is an input.

Answering partially to Heiko/Stephen, this could be still modeled in DTS
as a fixed-frequency clock going as input to the clock-controller. The
trouble with that approach is that it would actually duplicate the
definition (another one coming from PMIC).

Best regards,
Krzysztof