[PATCH v8 3/3] thermal/drivers/imx: Add calibration offset support
From: Haoning CHENG via B4 Relay <devnull+Haoning.CHENG.cn.bosch.com@kernel.org>
Date: 2026-07-14 10:28:46
Also in:
b4-sent, imx, linux-devicetree, linux-pm, lkml
Subsystem:
the rest, thermal · Maintainers:
Linus Torvalds, Rafael J. Wysocki, Daniel Lezcano
From: Haoning CHENG <redacted>
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 <redacted>
---
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)
--
2.43.0