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

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Message-ID: <d05c7b0e-6edb-bc0f-5875-fc5cb8ea6b8a@quicinc.com>
Date:   Thu, 22 Jun 2023 11:55:49 +0530
From:   Devi Priya <quic_devipriy@...cinc.com>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>, <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 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.

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";