[PATCH v9 0/3] thermal: imx: Add temperature offset support

[PATCH v9 0/3] thermal: imx: Add temperature offset support

[Haoning CHENG via B4 Relay]

Some i.MX boards need the reported temperature to represent the SoC
package-surface temperature rather than the internal die temperature.
This series adds an optional DT property to specify a board-specific
conversion offset and implements the corresponding support in the
imx_thermal driver.

Patch 1 documents the new fsl,temp-calibration-offset-millicelsius
property in the i.MX thermal DT binding. The offset is board-specific,
determined through thermal characterization, and limited to ±20 °C.

Patch 2 fixes the i.MX7D alarm temperature conversion to use
ceiling division (DIV_ROUND_UP() for non-negative, plain /
for negative) and clamp() to stay within the 9-bit register range.

Patch 3 reads this property in the imx_thermal driver and applies
the offset symmetrically: it is added when reporting temperature to
the thermal framework (to produce a package-surface estimate) and
subtracted when programming hardware alarm thresholds (to keep trip
point semantics consistent). Out-of-range values are rejected with
-EINVAL at probe time. When the property is absent, the default
offset is 0.

Signed-off-by: Haoning CHENG <Haoning.CHENG@cn.bosch.com>
---
Changes in v9:
- Rephrase the series to clarify that the offset converts the internal
  TEMPMON reading to a package-surface temperature estimate, rather than
  calibrating the sensor for better die temperature accuracy (Frieder)
- dt-bindings: update the property description to explicitly state it is
  a board-specific conversion offset, not a sensor calibration
- driver commit message: distinguish die temperature from package-surface
  temperature in the symmetric offset mechanism explanation
- Pick up Reviewed-by tags from Frank Li (patches 2,3) and Lukasz Luba
  (patches 1,2,3)
- Link to v8: https://patch.msgid.link/20260714-b4-symana21-11221-imx-thermal-support-upstream-6-18-v8-0-d54d8690e16e@cn.bosch.com

Changes in v8:
- binding: s/behaviour/behavior/ (Lukasz)
- New prep patch: use ceiling division (DIV_ROUND_UP() for non-negative, plain /
  for negative) and clamp() for i.MX7D, extracted into a separate patch (Frank)
- driver commit message: add offset mechanism explanation with a +3000 m°C calculation example (Lukasz)
- probe: reject out-of-range offset with -EINVAL instead of silently clamping (Lukasz)
- prep patch: handle negative alarm_temp with plain division (C rounds toward zero)
- Link to v7: https://patch.msgid.link/20260713-b4-symana21-11221-imx-thermal-support-upstream-6-18-v7-0-09b6b7669be1@cn.bosch.com

Changes in v7:
- Align the author name with the Signed-off-by trailer.
- Link to v6: https://patch.msgid.link/20260713-b4-symana21-11221-imx-thermal-support-upstream-6-18-v6-0-88a378faeca5@cn.bosch.com

Changes in v6:
- Align the author name with the Signed-off-by trailer.
- Link to v5: https://patch.msgid.link/20260713-b4-symana21-11221-imx-thermal-support-upstream-6-18-v5-0-69405c306c6b@cn.bosch.com

Changes in v5:
- Move calibration offset application out of c2 initialization, instead
  apply it in imx_get_temp(), imx_set_alarm_temp() and imx_set_panic_temp()
  for consistent style across i.MX6 and i.MX7D
- Subtract calibration offset from alarm_temp before the if-else block in
  imx_set_alarm_temp(), simplifying both SoC branches (Frank's suggestion)
- Link to v4: https://patch.msgid.link/20260710-b4-symana21-11221-imx-thermal-support-upstream-6-18-v4-0-1fef97d1c750@cn.bosch.com

Changes in v4:
- dt-bindings: drop maxItems to allow minimum/maximum constraints for
  temp-calibration-offset-millicelsius
- Link to v3: https://patch.msgid.link/20260710-b4-symana21-11221-imx-thermal-support-upstream-6-18-v3-0-db9fc2947c55@cn.bosch.com

Changes in v3:
- dt-bindings: add minimum/maximum (-28580/+28580) for
  temp-calibration-offset-millicelsius, as suggested by Conor Dooley
- Link to v2: https://patch.msgid.link/20260709-b4-symana21-11221-imx-thermal-support-upstream-6-18-v2-0-00ff72495e24@cn.bosch.com

Changes in v2:
- dt-bindings: Removed explicit `$ref: /schemas/types.yaml#/definitions/int32`
  for fsl,temp-calibration-offset-millicelsius; the `-millicelsius` suffix
  already resolves to int32-array via property-units.yaml (Rob).
- dt-bindings: Fixed example indentation.
- driver: Replaced C integer division (/) with DIV_ROUND_CLOSEST() in
  imx_set_alarm_temp() to prevent off-by-one alarm threshold mismatch that
  could cause IRQ storms on i.MX7D.
- driver: Added clamp() bounds check for alarm_value [0, 0x1ff] to avoid
  corrupting adjacent register fields (PANIC_ALARM).
- Link to v1: https://patch.msgid.link/20260709-b4-symana21-11221-imx-thermal-support-upstream-6-18-v1-0-00f88f42930b@cn.bosch.com

To: "Rafael J. Wysocki" <rafael@kernel.org>
To: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Zhang Rui <rui.zhang@intel.com>
To: Lukasz Luba <lukasz.luba@arm.com>
To: Rob Herring <robh@kernel.org>
To: Krzysztof Kozlowski <krzk+dt@kernel.org>
To: Conor Dooley <conor+dt@kernel.org>
To: Shawn Guo <shawnguo@kernel.org>
To: Sascha Hauer <s.hauer@pengutronix.de>
To: Pengutronix Kernel Team <kernel@pengutronix.de>
To: Fabio Estevam <festevam@gmail.com>
Cc: linux-pm@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: imx@lists.linux.dev
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org

---
Haoning CHENG (3):
      dt-bindings: thermal: imx: Document temperature offset property
      thermal/drivers/imx: Fix rounding and clamp for i.MX7D alarm
      thermal/drivers/imx: Add temperature offset support

 .../devicetree/bindings/thermal/imx-thermal.yaml   | 15 +++++++++
 drivers/thermal/imx_thermal.c                      | 39 ++++++++++++++++++++--
 2 files changed, 51 insertions(+), 3 deletions(-)
---
base-commit: c50a940dcde35c647e097e89a9150003abd48329
change-id: 20260709-b4-symana21-11221-imx-thermal-support-upstream-6-18-a084984deb76

Best regards,
--  
Haoning Cheng <Haoning.CHENG@cn.bosch.com>

[PATCH v9 1/3] dt-bindings: thermal: imx: Document temperature offset property

[Haoning CHENG via B4 Relay]

From: Haoning CHENG <Haoning.CHENG@cn.bosch.com>

Some boards need the reported temperature to reflect the SoC
package-surface temperature rather than the internal die temperature.

Document the optional fsl,temp-calibration-offset-millicelsius property,
a signed offset in millicelsius applied to the internally measured
temperature to make it better correspond to the package-surface
temperature. The offset is board-specific and is determined through
thermal characterization. When absent, the offset is zero.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Haoning CHENG <Haoning.CHENG@cn.bosch.com>
---
 .../devicetree/bindings/thermal/imx-thermal.yaml          | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/Documentation/devicetree/bindings/thermal/imx-thermal.yaml b/Documentation/devicetree/bindings/thermal/imx-thermal.yaml
index 949b154856c5..6c268d56291b 100644
--- a/Documentation/devicetree/bindings/thermal/imx-thermal.yaml
+++ b/Documentation/devicetree/bindings/thermal/imx-thermal.yaml
@@ -59,6 +59,20 @@ properties:
   clocks:
     maxItems: 1
 
+  fsl,temp-calibration-offset-millicelsius:
+    minimum: -20000
+    maximum: 20000
+    description:
+      A signed offset, in millicelsius, added to the calculated
+      sensor temperature to make the TEMPMON reading better correspond
+      to the SoC package-surface temperature observed during board-level
+      thermal characterization. This is not a sensor calibration offset;
+      it is a board-specific conversion offset derived from the
+      relationship between the internal sensor reading and the
+      package-surface temperature, which depends on the package, PCB
+      layout, cooling arrangement, and operating environment. The range
+      is limited to ±20 °C. When absent, no offset is applied.
+
   "#thermal-sensor-cells":
     const: 0
 
@@ -109,6 +123,7 @@ examples:
             nvmem-cells = <&tempmon_calib>, <&tempmon_temp_grade>;
             nvmem-cell-names = "calib", "temp_grade";
             clocks = <&clks IMX6SX_CLK_PLL3_USB_OTG>;
+            fsl,temp-calibration-offset-millicelsius = <(-6400)>;
             #thermal-sensor-cells = <0>;
         };
     };

-- 
2.43.0

[PATCH v9 2/3] thermal/drivers/imx: Fix rounding and clamp for i.MX7D alarm

[Haoning CHENG via B4 Relay]

From: Haoning CHENG <Haoning.CHENG@cn.bosch.com>

Convert the alarm temperature from millicelsius to degrees for i.MX7D
using ceiling division instead of integer division, ensuring rounding
errors do not cause the alarm to trigger below the intended threshold.
Use DIV_ROUND_UP() for non-negative values and plain integer division
for negative values, since C rounds toward zero which is equivalent to
ceiling when the divisor is positive.

Add clamp() to ensure the hardware register value stays within the 9-bit
range (0..0x1ff) of the i.MX7D alarm field, preventing silent truncation
if an out-of-range value is written.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Haoning Cheng <Haoning.CHENG@cn.bosch.com>
---
 drivers/thermal/imx_thermal.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/thermal/imx_thermal.c b/drivers/thermal/imx_thermal.c
index 38c993d1bcb3..7f7d1116b9d6 100644
--- a/drivers/thermal/imx_thermal.c
+++ b/drivers/thermal/imx_thermal.c
@@ -240,10 +240,16 @@ static void imx_set_alarm_temp(struct imx_thermal_data *data,
 
 	data->alarm_temp = alarm_temp;
 
-	if (data->socdata->version == TEMPMON_IMX7D)
-		alarm_value = alarm_temp / 1000 + data->c1 - 25;
-	else
+	if (data->socdata->version == TEMPMON_IMX7D) {
+		if (alarm_temp >= 0)
+			alarm_temp = DIV_ROUND_UP(alarm_temp, 1000);
+		else
+			alarm_temp /= 1000;
+		alarm_value = alarm_temp + data->c1 - 25;
+		alarm_value = clamp(alarm_value, 0, 0x1ff);
+	} else {
 		alarm_value = (data->c2 - alarm_temp) / data->c1;
+	}
 
 	regmap_write(map, soc_data->high_alarm_ctrl + REG_CLR,
 		     soc_data->high_alarm_mask);

-- 
2.43.0

[PATCH v9 3/3] thermal/drivers/imx: Add temperature offset support

[Haoning CHENG via B4 Relay]

From: Haoning CHENG <Haoning.CHENG@cn.bosch.com>

Some boards need a small per-design offset to make the TEMPMON reading
better correspond to the SoC package-surface temperature. This is not a
sensor calibration that improves the die temperature accuracy; it is a
board-specific conversion from the internal sensor reading to a
package-surface temperature estimate required by certain applications.

Read the optional fsl,temp-calibration-offset-millicelsius property from
DT and apply it uniformly to the i.MX6/6SX/7D formulas.

The offset is applied symmetrically at two points to keep the trip point
semantics consistent:

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
   die temperature that corresponds to the intended package-surface
   threshold.

2. In imx_get_temp(): after computing the die temperature from the
   hardware register, the offset is *added* to produce a value that
   better correlates with the package-surface temperature. The thermal
   framework always sees this package-surface estimate.

For example, if DT sets offset = +3000 m°C and the passive trip is 95°C:

  imx_set_alarm_temp(95000):
    alarm_temp = 95000 - 3000 = 92000
    → hardware register programmed for 92°C die temperature

  Hardware IRQ fires at 92°C die temperature

  imx_get_temp():
    reads hardware, computes 92°C die temperature
    *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.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
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)

-- 
2.43.0