Re: [PATCH v8 3/3] thermal/drivers/imx: Add calibration offset support

[Lukasz Luba <lukasz.luba@arm.com>]

On 7/14/26 11:28, Haoning CHENG via B4 Relay wrote:
> From: Haoning CHENG <Haoning.CHENG@cn.bosch.com>
> 
> Some boards need a small per-design correction to align the reported CPU
> temperature with board-level measurements. Read the optional
> fsl,temp-calibration-offset-millicelsius property from DT and apply it
> uniformly to the i.MX6/6SX/7D calibration formulas.
> 
> The offset is applied symmetrically at two points to ensure the thermal
> framework sees calibrated temperatures while hardware thresholds remain
> correctly positioned:
> 
> 1. In imx_set_alarm_temp() and imx_set_panic_temp(): the temperature
>     threshold is *subtracted* by the offset before being converted to a
>     hardware register value. This shifts the hardware IRQ trigger to the
>     physical temperature that corresponds to the intended threshold.
> 
> 2. In imx_get_temp(): after computing physical temperature from the
>     hardware register, the offset is *added* back. The thermal framework
>     always sees the calibrated temperature.
> 
> For example, if DT sets offset = +3000 m°C (board reads 3°C too low)
> and the passive trip is 95°C:
> 
>    imx_set_alarm_temp(95000):
>      alarm_temp = 95000 - 3000 = 92000
>      → hardware register programmed for 92°C physical
> 
>    Hardware IRQ fires at 92°C physical
> 
>    imx_get_temp():
>      reads hardware, computes 92°C physical
>      *temp = 92000 + 3000 = 95000
>      → thermal framework sees 95°C → correct trip
> 
> When the property is not present, the offset defaults to 0, preserving
> the current behavior.
> 
> Signed-off-by: Haoning CHENG <Haoning.CHENG@cn.bosch.com>
> ---
>   drivers/thermal/imx_thermal.c | 27 +++++++++++++++++++++++++++
>   1 file changed, 27 insertions(+)
> 
> diff --git a/drivers/thermal/imx_thermal.c b/drivers/thermal/imx_thermal.c
> index 7f7d1116b9d6..d471acc16bce 100644
> --- a/drivers/thermal/imx_thermal.c
> +++ b/drivers/thermal/imx_thermal.c
> @@ -85,6 +85,10 @@ enum imx_thermal_trip {
>   #define TEMPMON_IMX6SX			2
>   #define TEMPMON_IMX7D			3
>   
> +/* Calibration offset limits (±20 °C in millicelsius) */
> +#define IMX_TEMP_CALIB_OFFSET_MIN	(-20000)
> +#define IMX_TEMP_CALIB_OFFSET_MAX	20000
> +
>   struct thermal_soc_data {
>   	u32 version;
>   
> @@ -207,6 +211,7 @@ struct imx_thermal_data {
>   	struct regmap *tempmon;
>   	u32 c1, c2; /* See formula in imx_init_calib() */
>   	int temp_max;
> +	s32 calibration_offset;
>   	int alarm_temp;
>   	int last_temp;
>   	bool irq_enabled;
> @@ -223,6 +228,7 @@ static void imx_set_panic_temp(struct imx_thermal_data *data,
>   	struct regmap *map = data->tempmon;
>   	int critical_value;
>   
> +	panic_temp -= data->calibration_offset;
>   	critical_value = (data->c2 - panic_temp) / data->c1;
>   
>   	regmap_write(map, soc_data->panic_alarm_ctrl + REG_CLR,
> @@ -239,6 +245,7 @@ static void imx_set_alarm_temp(struct imx_thermal_data *data,
>   	int alarm_value;
>   
>   	data->alarm_temp = alarm_temp;
> +	alarm_temp -= data->calibration_offset;
>   
>   	if (data->socdata->version == TEMPMON_IMX7D) {
>   		if (alarm_temp >= 0)
> @@ -283,6 +290,7 @@ static int imx_get_temp(struct thermal_zone_device *tz, int *temp)
>   		*temp = (n_meas - data->c1 + 25) * 1000;
>   	else
>   		*temp = data->c2 - n_meas * data->c1;
> +	*temp += data->calibration_offset;
>   
>   	/* Update alarm value to next higher trip point for TEMPMON_IMX6Q */
>   	if (data->socdata->version == TEMPMON_IMX6Q) {
> @@ -635,6 +643,25 @@ static int imx_thermal_probe(struct platform_device *pdev)
>   
>   	platform_set_drvdata(pdev, data);
>   
> +	if (of_property_present(dev->of_node,
> +				"fsl,temp-calibration-offset-millicelsius")) {
> +		ret = of_property_read_s32(dev->of_node,
> +					   "fsl,temp-calibration-offset-millicelsius",
> +					   &data->calibration_offset);
> +		if (ret)
> +			return dev_err_probe(dev, ret,
> +					     "failed to read calibration offset\n");
> +
> +		if (data->calibration_offset < IMX_TEMP_CALIB_OFFSET_MIN ||
> +		    data->calibration_offset > IMX_TEMP_CALIB_OFFSET_MAX)
> +			return dev_err_probe(dev, -EINVAL,
> +					     "calibration offset %d millicelsius out of range\n",
> +					     data->calibration_offset);
> +
> +		dev_dbg(dev, "calibration offset: %d millicelsius\n",
> +			data->calibration_offset);
> +	}
> +
>   	if (of_property_present(dev->of_node, "nvmem-cells")) {
>   		ret = imx_init_from_nvmem_cells(pdev);
>   		if (ret)
> 


Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>