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

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Message-ID: <b7d81122-6da4-405e-a370-c621131ff90a@linaro.org>
Date: Thu, 4 Sep 2025 15:55:09 +0100
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
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>, 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 4/5] i2c: qcom-cci: Add OPP table support and enforce
 FAST_PLUS requirements

On 04/09/2025 15:31, 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;

that is a very long name for a flag

>   };
>   
>   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;

what's 32 bits between friends ?

> +}
> +
>   static int __maybe_unused cci_suspend_runtime(struct device *dev)
>   {
>   	struct cci *cci = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = dev_pm_opp_set_rate(dev, 0);
> +	if (ret)
> +		return ret;
>   
>   	clk_bulk_disable_unprepare(cci->nclocks, cci->clocks);
>   
> @@ -484,6 +499,10 @@ static int __maybe_unused cci_resume_runtime(struct device *dev)
>   	if (ret)
>   		return ret;
>   
> +	ret = dev_pm_opp_set_rate(dev, cci_desired_clk_rate(cci));
> +	if (ret)
> +		return ret;
> +
>   	cci_init(cci);
>   
>   	return 0;
> @@ -588,6 +607,19 @@ static int cci_probe(struct platform_device *pdev)
>   	if (ret < 0)
>   		return ret;
>   
> +	ret = devm_pm_opp_set_clkname(dev, "cci");
> +	if (ret)
> +		return ret;
> +
> +	/* OPP table is optional */
> +	ret = devm_pm_opp_of_add_table(dev);
> +	if (ret && ret != -ENODEV)
> +		return dev_err_probe(dev, ret, "invalid OPP table in device tree\n");
> +
> +	ret = dev_pm_opp_set_rate(dev, cci_desired_clk_rate(cci));
> +	if (ret)
> +		return ret;
> +
>   	/* Interrupt */
>   
>   	ret = platform_get_irq(pdev, 0);
> @@ -775,6 +807,7 @@ static const struct cci_data cci_v2_data = {
>   		.trdhld = 3,
>   		.tsp = 3
>   	},
> +	.fast_mode_plus_supported = true,
>   };
>   
>   static const struct of_device_id cci_dt_match[] = {
> 

LGTM

Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>