[PATCH] hwmon: temperature: (EMC1403) fix hysteresis for low limit temperature

[PATCH] hwmon: temperature: (EMC1403) fix hysteresis for low limit temperature

[Marius Cristea]

Remove the hysteresis for low temperature limit, in hardware
the hysteresis is applied only to the maxim limit and the
critical limit temperature.

Signed-off-by: Marius Cristea <marius.cristea@microchip.com>
---
 Documentation/hwmon/emc1403.rst |  8 ++++----
 drivers/hwmon/emc1403.c         | 27 +++++++++++----------------
 2 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/Documentation/hwmon/emc1403.rst b/Documentation/hwmon/emc1403.rst
index 77060d515323..ce258f0fccc6 100644
--- a/Documentation/hwmon/emc1403.rst
+++ b/Documentation/hwmon/emc1403.rst
@@ -71,10 +71,10 @@ and EMC14x8 support eight sensors (one internal, seven external).
 
 The chips implement three limits for each sensor: low (tempX_min), high
 (tempX_max) and critical (tempX_crit.) The chips also implement an
-hysteresis mechanism which applies to all limits. The relative difference
-is stored in a single register on the chip, which means that the relative
-difference between the limit and its hysteresis is always the same for
-all three limits.
+hysteresis mechanism which applies to high and critical limits. The relative
+difference is stored in a single register on the chip, which means that the
+relative difference between the limit and its hysteresis is always the same
+for high and critical limits.
 
 This implementation detail implies the following:
 
diff --git a/drivers/hwmon/emc1403.c b/drivers/hwmon/emc1403.c
index cd753b38709f..2f6dadbce68a 100644
--- a/drivers/hwmon/emc1403.c
+++ b/drivers/hwmon/emc1403.c
@@ -305,10 +305,9 @@ static int emc1403_get_hyst(struct thermal_data *data, int channel,
 	ret = regmap_read(data->regmap, 0x21, &hyst);
 	if (ret < 0)
 		return ret;
-	if (map == temp_min)
-		*val = limit + hyst * 1000;
-	else
-		*val = limit - hyst * 1000;
+
+	*val = limit - hyst * 1000;
+
 	return 0;
 }
 
@@ -324,9 +323,6 @@ static int emc1403_temp_read(struct thermal_data *data, u32 attr, int channel, l
 	case hwmon_temp_input:
 		ret = emc1403_get_temp(data, channel, ema1403_temp_map[attr], val);
 		break;
-	case hwmon_temp_min_hyst:
-		ret = emc1403_get_hyst(data, channel, temp_min, val);
-		break;
 	case hwmon_temp_max_hyst:
 		ret = emc1403_get_hyst(data, channel, temp_max, val);
 		break;
@@ -548,7 +544,6 @@ static umode_t emc1403_temp_is_visible(const void *_data, u32 attr, int channel)
 	case hwmon_temp_max_alarm:
 	case hwmon_temp_crit_alarm:
 	case hwmon_temp_fault:
-	case hwmon_temp_min_hyst:
 	case hwmon_temp_max_hyst:
 		return 0444;
 	case hwmon_temp_min:
@@ -591,35 +586,35 @@ static const struct hwmon_channel_info * const emc1403_info[] = {
 	HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
 	HWMON_CHANNEL_INFO(temp,
 			   HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX |
-			   HWMON_T_CRIT | HWMON_T_MIN_HYST | HWMON_T_MAX_HYST |
+			   HWMON_T_CRIT | HWMON_T_MAX_HYST |
 			   HWMON_T_CRIT_HYST | HWMON_T_MIN_ALARM |
 			   HWMON_T_MAX_ALARM | HWMON_T_CRIT_ALARM,
 			   HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX |
-			   HWMON_T_CRIT | HWMON_T_MIN_HYST | HWMON_T_MAX_HYST |
+			   HWMON_T_CRIT | HWMON_T_MAX_HYST |
 			   HWMON_T_CRIT_HYST | HWMON_T_MIN_ALARM |
 			   HWMON_T_MAX_ALARM | HWMON_T_CRIT_ALARM | HWMON_T_FAULT,
 			   HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX |
-			   HWMON_T_CRIT | HWMON_T_MIN_HYST | HWMON_T_MAX_HYST |
+			   HWMON_T_CRIT | HWMON_T_MAX_HYST |
 			   HWMON_T_CRIT_HYST | HWMON_T_MIN_ALARM |
 			   HWMON_T_MAX_ALARM | HWMON_T_CRIT_ALARM | HWMON_T_FAULT,
 			   HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX |
-			   HWMON_T_CRIT | HWMON_T_MIN_HYST | HWMON_T_MAX_HYST |
+			   HWMON_T_CRIT | HWMON_T_MAX_HYST |
 			   HWMON_T_CRIT_HYST | HWMON_T_MIN_ALARM |
 			   HWMON_T_MAX_ALARM | HWMON_T_CRIT_ALARM | HWMON_T_FAULT,
 			   HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX |
-			   HWMON_T_CRIT | HWMON_T_MIN_HYST | HWMON_T_MAX_HYST |
+			   HWMON_T_CRIT | HWMON_T_MAX_HYST |
 			   HWMON_T_CRIT_HYST | HWMON_T_MIN_ALARM |
 			   HWMON_T_MAX_ALARM | HWMON_T_CRIT_ALARM | HWMON_T_FAULT,
 			   HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX |
-			   HWMON_T_CRIT | HWMON_T_MIN_HYST | HWMON_T_MAX_HYST |
+			   HWMON_T_CRIT | HWMON_T_MAX_HYST |
 			   HWMON_T_CRIT_HYST | HWMON_T_MIN_ALARM |
 			   HWMON_T_MAX_ALARM | HWMON_T_CRIT_ALARM | HWMON_T_FAULT,
 			   HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX |
-			   HWMON_T_CRIT | HWMON_T_MIN_HYST | HWMON_T_MAX_HYST |
+			   HWMON_T_CRIT | HWMON_T_MAX_HYST |
 			   HWMON_T_CRIT_HYST | HWMON_T_MIN_ALARM |
 			   HWMON_T_MAX_ALARM | HWMON_T_CRIT_ALARM | HWMON_T_FAULT,
 			   HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX |
-			   HWMON_T_CRIT | HWMON_T_MIN_HYST | HWMON_T_MAX_HYST |
+			   HWMON_T_CRIT | HWMON_T_MAX_HYST |
 			   HWMON_T_CRIT_HYST | HWMON_T_MIN_ALARM |
 			   HWMON_T_MAX_ALARM | HWMON_T_CRIT_ALARM | HWMON_T_FAULT
 			   ),

---
base-commit: db2ddb87143519e20a95aa36c60b36107b736a58
change-id: 20260811-emc1403_remove_min_hyst-3ec87495b000

Best regards,
-- 
Marius Cristea <marius.cristea@microchip.com>

Re: [PATCH] hwmon: temperature: (EMC1403) fix hysteresis for low limit temperature

[sashiko-bot]

> Remove the hysteresis for low temperature limit, in hardware
> the hysteresis is applied only to the maxim limit and the
> critical limit temperature.
> 
> Signed-off-by: Marius Cristea <marius.cristea@microchip.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260813-emc1403_remove_min_hyst-v1-1-43a0d05d9f49@microchip.com?part=1

Re: [PATCH] hwmon: temperature: (EMC1403) fix hysteresis for low limit temperature

[Guenter Roeck]

On Thu, Aug 13, 2026 at 11:40:07AM +0300, Marius Cristea wrote:
> Remove the hysteresis for low temperature limit, in hardware
> the hysteresis is applied only to the maxim limit and the
> critical limit temperature.
> 
> Signed-off-by: Marius Cristea <marius.cristea@microchip.com>

Applied.

Please use "hwmon: (emc1403) or similar (depending on the chip)
as subject prefix next time.

Thanks,
Guenter