Re: [PATCH 3/3] i2c: qcom-cci: Fix CCI clock rate enforcement

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 7/21/26 4:58 PM, Loic Poulain wrote:
> The hw_params timing values (thigh, tlow, etc.) are in CCI clock ticks
> and were calibrated for a specific clock rate per hardware variant. If
> the clock is running at a different rate the I2C timings will be wrong,
> potentially violating the I2C specification.
> 
> Rather than just warning about a mismatch, actively set the clock to the
> expected rate at probe time. Warn if the rate could not be applied so the
> user is informed that timings may be incorrect.
> 
> Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> ---
>  drivers/i2c/busses/i2c-qcom-cci.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-qcom-cci.c b/drivers/i2c/busses/i2c-qcom-cci.c
> index 5f74edde8558382e63e2c3d0fbe19489f325e8ce..e001c0d565cebd386fd67b1d9d532360b29c67d0 100644
> --- a/drivers/i2c/busses/i2c-qcom-cci.c
> +++ b/drivers/i2c/busses/i2c-qcom-cci.c
> @@ -519,6 +519,7 @@ static int cci_probe(struct platform_device *pdev)
>  	struct device *dev = &pdev->dev;
>  	struct device_node *child;
>  	struct resource *r;
> +	struct clk *cci_clk;
>  	struct cci *cci;
>  	int ret, i;
>  	u32 val;
> @@ -587,6 +588,15 @@ static int cci_probe(struct platform_device *pdev)
>  		return dev_err_probe(dev, -EINVAL, "not enough clocks in DT\n");
>  	cci->nclocks = ret;
>  
> +	cci_clk = devm_clk_get(dev, "cci");
> +	if (IS_ERR(cci_clk))
> +		return dev_err_probe(dev, PTR_ERR(cci_clk), "failed to get CCI clock\n");
> +
> +	clk_set_rate(cci_clk, cci->data->cci_clk_rate);
> +	if (clk_get_rate(cci_clk) != cci->data->cci_clk_rate)
> +		dev_warn(dev, "CCI clock is not at expected %lu Hz\n",
> +			 cci->data->cci_clk_rate);

This needs to go through OPP.

Feel free to take over and refresh:

https://lore.kernel.org/linux-arm-msm/20250904-topic-cci_updates-v1-0-d38559692703@oss.qualcomm.com/

Konrad