linux-kernel - Re: [PATCH 0/5] Qualcomm CCI I2C clock requirements enforcement

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Message-ID: <d7937258-9cf9-4887-a117-58ac3d4473de@oss.qualcomm.com>
Date: Wed, 10 Sep 2025 16:27:12 +0530
From: Mukesh Savaliya <mukesh.savaliya@....qualcomm.com>
To: Konrad Dybcio <konradybcio@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Loic Poulain <loic.poulain@....qualcomm.com>,
        Robert Foss
 <rfoss@...nel.org>, Andi Shyti <andi.shyti@...nel.org>
Cc: Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH 0/5] Qualcomm CCI I2C clock requirements enforcement



On 9/4/2025 8:01 PM, Konrad Dybcio wrote:
> The hardware requires the faster of the two (37.5 MHz as opposed to
> 19.2 MHz) clock rates to hit the required timings for I2C Fast+ Mode.
Should mention "source clock rates" to not confuse with derived 
frequency/timings for Fast+ mode.>
> Additionally, the magic presets for electrical tuning registers on SoCs
> supporting that faster mode ("cci_v2" in the driver) are calculated
are/is calculated> based on that faster frequency.
> 
> Moreover, while its unlikely that it would ever exhibit as an issue
> given CCI is a slow & tiny core, we do need to express a minimal voltage
> level for any given clock rate, which is where the (optional -
> backwards compat) OPP table addition comes in.
> 
> This series helps ensure all these requirements are met.
> 
> Patch 1 is a related but independent fix, can be picked right away
> Patch 5 can be functionally merged as-is, but depends on patch 2 for
> bindings
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> ---
> Konrad Dybcio (5):
>        arm64: dts: qcom: sc8280xp: Fix CCI3 interrupt
>        dt-bindings: i2c: qcom-cci: Allow operating-points-v2
>        i2c: qcom-cci: Drop single-line wrappers
>        i2c: qcom-cci: Add OPP table support and enforce FAST_PLUS requirements
>        arm64: dts: qcom: sc8280xp: Add OPP table for CCI hosts
> 
>   .../devicetree/bindings/i2c/qcom,i2c-cci.yaml      |  2 +
>   arch/arm64/boot/dts/qcom/sc8280xp.dtsi             | 16 +++++++-
>   drivers/i2c/busses/i2c-qcom-cci.c                  | 45 +++++++++++++++++-----
>   3 files changed, 52 insertions(+), 11 deletions(-)
> ---
> base-commit: 4ac65880ebca1b68495bd8704263b26c050ac010
> change-id: 20250904-topic-cci_updates-800fdc9bada4
> 
> Best regards,