Index: src/sys/dev/i2c/dbcool.c
===================================================================
RCS file: /cvsroot/src/sys/dev/i2c/dbcool.c,v
retrieving revision 1.69
diff -u -r1.69 dbcool.c
--- src/sys/dev/i2c/dbcool.c	7 Jul 2026 12:42:58 -0000	1.69
+++ src/sys/dev/i2c/dbcool.c	29 Jul 2026 11:11:01 -0000
@@ -73,7 +73,7 @@
 
 /* Sensor read functions */
 static void dbcool_refresh(struct sysmon_envsys *, envsys_data_t *);
-static int dbcool_read_rpm(struct dbcool_softc *, uint8_t);
+static int dbcool_read_rpm(struct dbcool_softc *, uint8_t, int);
 static int dbcool_read_temp(struct dbcool_softc *, uint8_t, bool);
 static int dbcool_read_volt(struct dbcool_softc *, uint8_t, int, bool);
 
@@ -107,8 +107,10 @@
 static int sysctl_dbcool_thyst(SYSCTLFN_PROTO);
 
 /* Set-up subroutines */
+static int  dbcool_set_fan_divider(struct dbcool_softc *, prop_dictionary_t,
+	int);
 static void dbcool_setup_controllers(struct dbcool_softc *);
-static int  dbcool_setup_sensors(struct dbcool_softc *);
+static int  dbcool_setup_sensors(struct dbcool_softc *, prop_dictionary_t);
 static int  dbcool_attach_sensor(struct dbcool_softc *, int);
 static int  dbcool_attach_temp_control(struct dbcool_softc *, int,
 	struct chip_id *);
@@ -538,6 +540,12 @@
 	{ DBC_EOF,  {0, 0, 0 }, 0, 0, 0 }
 };
 
+struct dbcool_fan_div ADM1030_fan_div_table[] = {
+	{ 0x08, 0x20 },
+	{ 0x09, 0x21 },
+	{ 0, 0 }
+};
+
 struct dbcool_power_control ADM1030_power_table[] = {
 	{ { DBCOOL_ADM1030_CFG1,  DBCOOL_NO_REG, DBCOOL_NO_REG,
 	    DBCOOL_ADM1030_FAN_SPEED_CFG },
@@ -1004,7 +1012,7 @@
 }
 
 static int
-dbcool_read_rpm(struct dbcool_softc *sc, uint8_t reg)
+dbcool_read_rpm(struct dbcool_softc *sc, uint8_t reg, int fan_div)
 {
 	int rpm;
 	uint8_t rpm_lo, rpm_hi;
@@ -1020,7 +1028,8 @@
 		return 0;	/* 0xffff indicates stalled/failed fan */
 
 	/* don't divide by zero */
-	return (rpm == 0)? 0 : (sc->sc_dc.dc_chip->rpm_dividend / rpm);
+	return (rpm == 0)? 0 :
+	    (sc->sc_dc.dc_chip->rpm_dividend / rpm / fan_div);
 }
 
 /* Provide chip's supply voltage, in microvolts */
@@ -1536,7 +1545,7 @@
 
 	/* Create the sensors for this device */
 	sc->sc_sme = sysmon_envsys_create();
-	if (dbcool_setup_sensors(sc))
+	if (dbcool_setup_sensors(sc, device_properties(self)))
 		goto out;
 
 	if (sc->sc_root_sysctl_num != 0) {
@@ -1602,13 +1611,67 @@
 }
 
 static int
-dbcool_setup_sensors(struct dbcool_softc *sc)
+dbcool_set_fan_divider(struct dbcool_softc *sc, prop_dictionary_t props,
+    int sensor)
+{
+	uint8_t fanchar_reg, val;
+	uint16_t props_fan_div, div_val;
+	int i, div;
+
+	div = 1;
+
+	/* ADM1030/1031 have a fan characteristics register with a divider */
+	if (sc->sc_dc.dc_chip->flags & DBCFLAG_ADM1030) {
+		fanchar_reg = 0;
+		for (i = 0; ADM1030_fan_div_table[i].fan_reg != 0; i++) {
+			if (sc->sc_dc.dc_chip->table[sensor].reg.val_reg ==
+			    ADM1030_fan_div_table[i].fan_reg)
+				fanchar_reg = ADM1030_fan_div_table[i].char_reg;
+		}
+		if (fanchar_reg) {
+			val = sc->sc_dc.dc_readreg(&sc->sc_dc, fanchar_reg);
+			val &= DBCOOL_ADM1030_FANDIV_MASK;
+			switch (val)
+			{
+				case DBCOOL_ADM1030_FANDIV_8:
+					div = 8;
+					break;
+				case DBCOOL_ADM1030_FANDIV_4:
+					div = 4;
+					break;
+				case DBCOOL_ADM1030_FANDIV_2:
+					div = 2;
+					break;
+				case DBCOOL_ADM1030_FANDIV_1:
+				default:
+					div = 1;
+					break;
+			}
+		}
+	}
+	/*
+	 * Do we have a fan divider property?
+	 * Each 4 bits contains a divider for that fan.
+	 * We only accept dividers up to 8x
+	 */
+	if (prop_dictionary_get_uint16(props,
+	    "fan_div", &props_fan_div) != 0) {
+		div_val = (props_fan_div >> (sc->sc_fan_num * 4)) & 0x0f;
+		if (div_val > 1 && div_val < 9)
+			div *= div_val;
+	}
+	return div;
+}
+
+static int
+dbcool_setup_sensors(struct dbcool_softc *sc, prop_dictionary_t props)
 {
 	int i;
 	int error = 0;
 	uint8_t	vid_reg, vid_val;
 	struct chip_id *chip = sc->sc_dc.dc_chip;
 
+	sc->sc_fan_num = 0;
 	for (i=0; chip->table[i].type != DBC_EOF; i++) {
 		if (i < DBCOOL_MAXSENSORS)
 			sc->sc_sysctl_num[i] = -1;
@@ -1642,11 +1705,15 @@
 			error = dbcool_attach_sensor(sc, i);
 			break;
 		case DBC_FAN:
+			sc->sc_fan_div[i] = dbcool_set_fan_divider(sc,
+			    props, i);
+
 			sc->sc_sensor[i].units = ENVSYS_SFANRPM;
 			sc->sc_sensor[i].state = ENVSYS_SINVALID;
 			sc->sc_sensor[i].flags |= ENVSYS_FMONLIMITS;
 			sc->sc_sensor[i].flags |= ENVSYS_FHAS_ENTROPY;
 			error = dbcool_attach_sensor(sc, i);
+			sc->sc_fan_num++;
 			break;
 		case DBC_VID:
 			sc->sc_sensor[i].units = ENVSYS_INTEGER;
@@ -1811,7 +1878,7 @@
 dbcool_refresh(struct sysmon_envsys *sme, envsys_data_t *edata)
 {
 	struct dbcool_softc *sc=sme->sme_cookie;
-	int i, nom_volt_idx, cur;
+	int i, nom_volt_idx, fan_div, cur;
 	struct reg_list *reg;
 
 	i = edata->sensor;
@@ -1829,7 +1896,8 @@
 						true);
 			break;
 		case ENVSYS_SFANRPM:
-			cur = dbcool_read_rpm(sc, reg->val_reg);
+			fan_div = sc->sc_fan_div[i];
+			cur = dbcool_read_rpm(sc, reg->val_reg, fan_div);
 			break;
 		case ENVSYS_INTEGER:
 			return;
@@ -2015,9 +2083,10 @@
 		      sysmon_envsys_lim_t *lims, uint32_t *props)
 {
 	struct reg_list *reg = sc->sc_regs[idx];
+	int fan_div = sc->sc_fan_div[idx];
 	int32_t	limit;
 
-	limit = dbcool_read_rpm(sc, reg->lo_lim_reg);
+	limit = dbcool_read_rpm(sc, reg->lo_lim_reg, fan_div);
 	if (limit) {
 		lims->sel_critmin = limit;
 		*props |= PROP_CRITMIN;
Index: src/sys/dev/i2c/dbcool_reg.h
===================================================================
RCS file: /cvsroot/src/sys/dev/i2c/dbcool_reg.h,v
retrieving revision 1.9
diff -u -r1.9 dbcool_reg.h
--- src/sys/dev/i2c/dbcool_reg.h	16 Apr 2020 23:29:53 -0000	1.9
+++ src/sys/dev/i2c/dbcool_reg.h	29 Jul 2026 11:11:01 -0000
@@ -362,6 +362,13 @@
 #define	DBCOOL_ADM1030_COMPANYID	DBCOOL_COMPANYID_REG
 #define	DBCOOL_ADM1030_REVISION		DBCOOL_REVISION_REG
 
+/* ADM1030 fan characteristics registers 0x20/0x21: fan speed range (divider) */
+#define DBCOOL_ADM1030_FANDIV_MASK	0xc0
+#define DBCOOL_ADM1030_FANDIV_1		0x00
+#define DBCOOL_ADM1030_FANDIV_2		0x40
+#define DBCOOL_ADM1030_FANDIV_4		0x80
+#define DBCOOL_ADM1030_FANDIV_8		0xc0
+
 /*      
  * Macros to locate limit registers for the various sensor types
  */     
Index: src/sys/dev/i2c/dbcool_var.h
===================================================================
RCS file: /cvsroot/src/sys/dev/i2c/dbcool_var.h,v
retrieving revision 1.18
diff -u -r1.18 dbcool_var.h
--- src/sys/dev/i2c/dbcool_var.h	21 Sep 2025 13:54:56 -0000	1.18
+++ src/sys/dev/i2c/dbcool_var.h	29 Jul 2026 11:11:01 -0000
@@ -95,6 +95,11 @@
 	int nom_volt_index;
 };
 
+struct dbcool_fan_div {
+	uint8_t fan_reg;
+	uint8_t char_reg;
+};
+
 /*
  * The members of dbcool_power_control need to stay in the same order
  * as the enum dbc_pwm_params above
@@ -125,6 +130,8 @@
 	int sc_sysctl_num[DBCOOL_MAXSENSORS];
 	struct reg_list *sc_regs[DBCOOL_MAXSENSORS];
 	int sc_nom_volt[DBCOOL_MAXSENSORS];
+	int sc_fan_num;
+	int sc_fan_div[DBCOOL_MAXSENSORS];
 	int sc_temp_offset;
 	int64_t sc_supply_voltage;
 	bool sc_suspend;