linux-kernel - Re: [PATCH] arm64: dts: qcom: ipq9574: Use assigned-clock-rates for QUP I2C core clks

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Date:   Thu, 22 Jun 2023 10:53:24 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Devi Priya <quic_devipriy@...cinc.com>, agross@...nel.org,
        andersson@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     quic_srichara@...cinc.com, quic_sjaganat@...cinc.com,
        quic_kathirav@...cinc.com, quic_anusha@...cinc.com
Subject: Re: [PATCH] arm64: dts: qcom: ipq9574: Use assigned-clock-rates for
 QUP I2C core clks

On 22.06.2023 08:25, Devi Priya wrote:
> 
> 
> On 6/15/2023 2:21 PM, Konrad Dybcio wrote:
>> On 15.06.2023 10:48, Devi Priya wrote:
>>> Use assigned-clock-rates property for configuring the QUP I2C core clocks
>>> to operate at nominal frequency.
>>>
>>> Signed-off-by: Devi Priya <quic_devipriy@...cinc.com>
>>> ---
>> There's probably some logic behind this, and it almost sounds like
>> it'd be fitting to introduce an OPP table for I2C hosts, especially
>> given the voltage requirements.
>>
>> Konrad
> The qup i2c core clocks are not scalable and operate at fixed frequency.
> The assigned-clock-rates are used to configure the clock frequency
> if it is not done by the bootloaders.
OPP tables with a single entry are totally fine.

Konrad
> 
> Thanks,
> Devi Priya
>>>   arch/arm64/boot/dts/qcom/ipq9574.dtsi | 8 ++++++++
>>>   1 file changed, 8 insertions(+)
>>>
>>> diff --git a/arch/arm64/boot/dts/qcom/ipq9574.dtsi b/arch/arm64/boot/dts/qcom/ipq9574.dtsi
>>> index 0baeb10bbdae..78bf7f9c455a 100644
>>> --- a/arch/arm64/boot/dts/qcom/ipq9574.dtsi
>>> +++ b/arch/arm64/boot/dts/qcom/ipq9574.dtsi
>>> @@ -361,6 +361,8 @@
>>>               clocks = <&gcc GCC_BLSP1_QUP2_I2C_APPS_CLK>,
>>>                    <&gcc GCC_BLSP1_AHB_CLK>;
>>>               clock-names = "core", "iface";
>>> +            assigned-clocks = <&gcc GCC_BLSP1_QUP2_I2C_APPS_CLK>;
>>> +            assigned-clock-rates = <50000000>;
>>>               dmas = <&blsp_dma 14>, <&blsp_dma 15>;
>>>               dma-names = "tx", "rx";
>>>               status = "disabled";
>>> @@ -389,6 +391,8 @@
>>>               clocks = <&gcc GCC_BLSP1_QUP3_I2C_APPS_CLK>,
>>>                    <&gcc GCC_BLSP1_AHB_CLK>;
>>>               clock-names = "core", "iface";
>>> +            assigned-clocks = <&gcc GCC_BLSP1_QUP3_I2C_APPS_CLK>;
>>> +            assigned-clock-rates = <50000000>;
>>>               dmas = <&blsp_dma 16>, <&blsp_dma 17>;
>>>               dma-names = "tx", "rx";
>>>               status = "disabled";
>>> @@ -417,6 +421,8 @@
>>>               clocks = <&gcc GCC_BLSP1_QUP4_I2C_APPS_CLK>,
>>>                    <&gcc GCC_BLSP1_AHB_CLK>;
>>>               clock-names = "core", "iface";
>>> +            assigned-clocks = <&gcc GCC_BLSP1_QUP4_I2C_APPS_CLK>;
>>> +            assigned-clock-rates = <50000000>;
>>>               dmas = <&blsp_dma 18>, <&blsp_dma 19>;
>>>               dma-names = "tx", "rx";
>>>               status = "disabled";
>>> @@ -446,6 +452,8 @@
>>>               clocks = <&gcc GCC_BLSP1_QUP5_I2C_APPS_CLK>,
>>>                    <&gcc GCC_BLSP1_AHB_CLK>;
>>>               clock-names = "core", "iface";
>>> +            assigned-clocks = <&gcc GCC_BLSP1_QUP5_I2C_APPS_CLK>;
>>> +            assigned-clock-rates = <50000000>;
>>>               dmas = <&blsp_dma 20>, <&blsp_dma 21>;
>>>               dma-names = "tx", "rx";
>>>               status = "disabled";