linux-kernel - Re: [PATCH 4/5] i2c: qcom-cci: Add OPP table support and enforce FAST

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Message-ID: <6501e5b4-9939-4dac-991c-7a2033cfb506@oss.qualcomm.com>
Date: Thu, 4 Sep 2025 16:50:02 +0200
From: Konrad Dybcio <konrad.dybcio@....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
Subject: Re: [PATCH 4/5] i2c: qcom-cci: Add OPP table support and enforce
 FAST_PLUS requirements

On 9/4/25 4:31 PM, Konrad Dybcio wrote:
> From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> 
> The CCI clock has voltage requirements, which need to be described
> through an OPP table.
> 
> The 1 MHz FAST_PLUS mode requires the CCI core clock runs at 37,5 MHz
> (which is a value common across all SoCs), since it's not possible to
> reach the required timings with the default 19.2 MHz rate.
> 
> Address both issues by introducing an OPP table and using it to vote
> for the faster rate.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> ---
>  drivers/i2c/busses/i2c-qcom-cci.c | 33 +++++++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-qcom-cci.c b/drivers/i2c/busses/i2c-qcom-cci.c
> index 74fedfdec3ae4e034ec4d946179e963c783b5923..d6192e2a5e3bc4d908cba594d1910a41f3a41e9c 100644
> --- a/drivers/i2c/busses/i2c-qcom-cci.c
> +++ b/drivers/i2c/busses/i2c-qcom-cci.c
> @@ -10,6 +10,7 @@
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/platform_device.h>
> +#include <linux/pm_opp.h>
>  #include <linux/pm_runtime.h>
>  
>  #define CCI_HW_VERSION				0x0
> @@ -121,6 +122,7 @@ struct cci_data {
>  	struct i2c_adapter_quirks quirks;
>  	u16 queue_size[NUM_QUEUES];
>  	struct hw_params params[3];
> +	bool fast_mode_plus_supported;
>  };
>  
>  struct cci {
> @@ -466,9 +468,22 @@ static const struct i2c_algorithm cci_algo = {
>  	.functionality = cci_func,
>  };
>  
> +static unsigned long cci_desired_clk_rate(struct cci *cci)
> +{
> +	if (cci->data->fast_mode_plus_supported)
> +		return 37500000ULL;
> +
> +	return 19200000ULL;

Well this is embarrassing

ULL -> UL

Konrad