* [PATCH 1/2] hwmon: (nct6683) Report the duty cycle of NCT6687D-R system fans
2026-10-04 15:32 [PATCH 0/2] hwmon: (nct6683) Add fan control support for MSI boards with NCT6687D-R Hamza Mahfooz
@ 2026-10-04 15:32 ` Hamza Mahfooz
2026-10-04 15:32 ` [PATCH 2/2] hwmon: (nct6683) Add fan control support for MSI boards with NCT6687D-R Hamza Mahfooz
1 sibling, 0 replies; 3+ messages in thread
From: Hamza Mahfooz @ 2026-10-04 15:32 UTC (permalink / raw)
To: linux-hwmon
Cc: Guenter Roeck, Jonathan Corbet, Randy Dunlap, linux-doc,
linux-kernel, Hamza Mahfooz
Recent MSI boards (customer ID 0x20d) use an NCT6687D-R. Its system fans
are connected to channels 10-15, which have no fan output configuration
register, so their duty cycle is not reported.
According to a reverse engineered register map, the duty cycle of these
channels is reported in register (0xe00 + channel - 10). Report it for the
system fans that are present, so that pwmN matches fanN. To do so,
support up to 16 pwm channels, indexed by fan channel.
Signed-off-by: Hamza Mahfooz <someguy@effective-light.com>
---
drivers/hwmon/nct6683.c | 26 ++++++++++++++++++++++----
1 file changed, 22 insertions(+), 4 deletions(-)
diff --git a/drivers/hwmon/nct6683.c b/drivers/hwmon/nct6683.c
index e1c36c95a..a43e23c65 100644
--- a/drivers/hwmon/nct6683.c
+++ b/drivers/hwmon/nct6683.c
@@ -22,6 +22,7 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/acpi.h>
+#include <linux/bits.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/init.h>
@@ -169,6 +170,8 @@ superio_exit(int ioreg)
#define NCT6683_FAN_CFG_REQ 0x80
#define NCT6683_FAN_CFG_DONE 0x40
+#define NCT6687DR_REG_PWM_SYS(x) (0xe00 + (x) - 10) /* channels 10-15 */
+
#define NCT6683_REG_CUSTOMER_ID 0x602
#define NCT6683_CUSTOMER_ID_INTEL 0x805
#define NCT6683_CUSTOMER_ID_MITAC 0xa0e
@@ -341,8 +344,8 @@ struct nct6683_data {
u8 fanout_cfg[NCT6683_NUM_REG_FAN];
u16 have_fan; /* some fan inputs can be disabled */
- u8 have_pwm;
- u8 pwm[NCT6683_NUM_REG_PWM];
+ u16 have_pwm;
+ u8 pwm[NCT6683_NUM_REG_FAN]; /* indexed by fan channel */
#ifdef CONFIG_PM
/* Remember extra register values over suspend/resume */
@@ -588,15 +591,21 @@ static int get_temp_reg(struct nct6683_data *data, int nr, int index)
return reg;
}
+/* Channels 8-15 are only used on NCT6687D-R */
+static u16 nct6683_pwm_reg(int ch)
+{
+ return ch < 8 ? NCT6683_REG_PWM(ch) : NCT6687DR_REG_PWM_SYS(ch);
+}
+
static void nct6683_update_pwm(struct device *dev)
{
struct nct6683_data *data = dev_get_drvdata(dev);
int i;
- for (i = 0; i < NCT6683_NUM_REG_PWM; i++) {
+ for (i = 0; i < ARRAY_SIZE(data->pwm); i++) {
if (!(data->have_pwm & (1 << i)))
continue;
- data->pwm[i] = nct6683_read(data, NCT6683_REG_PWM(i));
+ data->pwm[i] = nct6683_read(data, nct6683_pwm_reg(i));
}
}
@@ -1149,6 +1158,15 @@ nct6683_setup_fans(struct nct6683_data *data)
data->have_pwm |= 1 << i;
data->fanout_cfg[i] = reg;
}
+
+ if (data->kind == nct6687 &&
+ data->customer_id == NCT6683_CUSTOMER_ID_MSI4) {
+ /*
+ * The system fan channels (10-15) have no fan output
+ * configuration register, so check their fan input instead.
+ */
+ data->have_pwm |= data->have_fan & GENMASK(15, 10);
+ }
}
/*
--
2.56.0
^ permalink raw reply [flat|nested] 3+ messages in thread* [PATCH 2/2] hwmon: (nct6683) Add fan control support for MSI boards with NCT6687D-R
2026-10-04 15:32 [PATCH 0/2] hwmon: (nct6683) Add fan control support for MSI boards with NCT6687D-R Hamza Mahfooz
2026-10-04 15:32 ` [PATCH 1/2] hwmon: (nct6683) Report the duty cycle of NCT6687D-R system fans Hamza Mahfooz
@ 2026-10-04 15:32 ` Hamza Mahfooz
1 sibling, 0 replies; 3+ messages in thread
From: Hamza Mahfooz @ 2026-10-04 15:32 UTC (permalink / raw)
To: linux-hwmon
Cc: Guenter Roeck, Jonathan Corbet, Randy Dunlap, linux-doc,
linux-kernel, Hamza Mahfooz
The fan control registers of the NCT6687D-R used on recent MSI boards
(customer ID 0x20d) differ from the ones used on Mitac boards, and
changes must be made in a configuration phase of its fan engine.
Add fan control support for these boards, based on a reverse engineered
register map:
- Manual mode is selected with bit (channel % 8) of register 0xa00
(channels 0-7) or 0x80f (channels 8-15). In manual mode, the duty
cycle is set with register (0xa28 + channel) (channels 0-7) or
(0x260 + channel - 10) (channels 10-15). Otherwise, the fan curve
configured by the BIOS is used.
- A configuration phase is requested by setting bit 7 of register
0xa01, and is entered once register 0xcf8 reports that the fan
registers are unlocked. It is completed by setting bit 6 of register
0xa01, after which the EC checks the new configuration, locks the
registers again and reports whether the configuration was accepted.
Fan control is supported for the CPU (channel 0), pump (channel 1) and
system fan (channels 10-15) headers. Add pwmN_enable attributes for
them, with 1 selecting manual and 2 automatic mode, and make pwmN
writable in manual mode. The behaviour of the driver does not change
unless pwmN or pwmN_enable is written.
Signed-off-by: Hamza Mahfooz <someguy@effective-light.com>
---
Documentation/hwmon/nct6683.rst | 17 +++
drivers/hwmon/nct6683.c | 209 +++++++++++++++++++++++++++++++-
2 files changed, 223 insertions(+), 3 deletions(-)
diff --git a/Documentation/hwmon/nct6683.rst b/Documentation/hwmon/nct6683.rst
index c47b0709c..ffc80fad3 100644
--- a/Documentation/hwmon/nct6683.rst
+++ b/Documentation/hwmon/nct6683.rst
@@ -49,6 +49,22 @@ The driver has only been tested with the Intel firmware, and by default
only instantiates on Intel boards. To enable it on non-Intel boards,
set the 'force' module parameter to 1.
+Fan Control
+-----------
+
+Fan control is supported on MSI boards with an NCT6687D-R (customer ID
+0x20d). pwm1 and pwm2 control the CPU and pump fan headers, and pwm11 to
+pwm16 control the system fan headers that are present. pwmN controls the
+fan reported by fanN_input.
+
+pwmN_enable selects the fan control mode:
+
+ * 1: manual mode, the duty cycle is set with pwmN
+ * 2: automatic mode, using the fan curve configured in the BIOS
+
+pwmN can only be written in manual mode. Switching to manual mode keeps the
+current duty cycle.
+
Tested Boards and Firmware Versions
-----------------------------------
@@ -71,6 +87,7 @@ MSI B550M NCT6687D EC firmware version 1.0 build 05/07/20
MSI B650 NCT6687D EC firmware version 0.0 build 09/27/22
MSI B650M NCT6687D EC firmware version 0.0 build 09/27/22
MSI B850M NCT6687D EC firmware version 0.0 build 03/10/25
+MSI B850-P NCT6687D EC firmware version 0.0 build 04/18/25
MSI X670-P NCT6687D EC firmware version 0.0 build 09/27/22
MSI X870E NCT6687D EC firmware version 0.0 build 11/13/24
=============================== ===============================================
diff --git a/drivers/hwmon/nct6683.c b/drivers/hwmon/nct6683.c
index a43e23c65..769a1eec9 100644
--- a/drivers/hwmon/nct6683.c
+++ b/drivers/hwmon/nct6683.c
@@ -27,6 +27,7 @@
#include <linux/err.h>
#include <linux/init.h>
#include <linux/io.h>
+#include <linux/iopoll.h>
#include <linux/jiffies.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
@@ -166,11 +167,22 @@ superio_exit(int ioreg)
#define NCT6683_REG_FAN_MIN(x) (0x3b8 + (x) * 2) /* 16 bit */
+#define NCT6683_REG_FAN_MODE 0xa00 /* channels 0-7 */
#define NCT6683_REG_FAN_CFG_CTRL 0xa01
#define NCT6683_FAN_CFG_REQ 0x80
#define NCT6683_FAN_CFG_DONE 0x40
+#define NCT6687DR_REG_FAN_MODE_SYS 0x80f /* channels 8-15 */
#define NCT6687DR_REG_PWM_SYS(x) (0xe00 + (x) - 10) /* channels 10-15 */
+#define NCT6687DR_REG_PWM_CMD_SYS(x) (0x260 + (x) - 10) /* channels 10-15 */
+
+#define NCT6687DR_FAN_CTRL_MASK (BIT(0) | BIT(1) | GENMASK(15, 10))
+
+#define NCT6687DR_REG_FAN_ENGINE_STS 0xcf8
+#define NCT6687DR_FAN_ENGINE_PHASE BIT(3)
+#define NCT6687DR_FAN_ENGINE_INVALID BIT(4)
+#define NCT6687DR_FAN_ENGINE_CHECK_DONE BIT(5)
+#define NCT6687DR_FAN_ENGINE_LOCK BIT(6)
#define NCT6683_REG_CUSTOMER_ID 0x602
#define NCT6683_CUSTOMER_ID_INTEL 0x805
@@ -347,6 +359,8 @@ struct nct6683_data {
u16 have_pwm;
u8 pwm[NCT6683_NUM_REG_FAN]; /* indexed by fan channel */
+ u16 have_fan_ctrl; /* channels supporting fan control */
+
#ifdef CONFIG_PM
/* Remember extra register values over suspend/resume */
u8 hwm_cfg;
@@ -925,6 +939,136 @@ static const struct sensor_template_group nct6683_temp_template_group = {
.base = 1,
};
+static u16 nct6683_mode_reg(int ch)
+{
+ return ch < 8 ? NCT6683_REG_FAN_MODE : NCT6687DR_REG_FAN_MODE_SYS;
+}
+
+static u16 nct6683_cmd_reg(int ch)
+{
+ return ch < 8 ? NCT6683_REG_PWM_WRITE(ch) : NCT6687DR_REG_PWM_CMD_SYS(ch);
+}
+
+static bool nct6683_pwm_manual(struct nct6683_data *data, int ch)
+{
+ return nct6683_read(data, nct6683_mode_reg(ch)) & BIT(ch % 8);
+}
+
+static bool nct6683_fan_cfg_idle(struct nct6683_data *data)
+{
+ return !(nct6683_read(data, NCT6687DR_REG_FAN_ENGINE_STS) &
+ NCT6687DR_FAN_ENGINE_PHASE) &&
+ !(nct6683_read(data, NCT6683_REG_FAN_CFG_CTRL) &
+ NCT6683_FAN_CFG_REQ);
+}
+
+static bool nct6687dr_fan_cfg_accessible(u16 sts)
+{
+ return (sts & (NCT6687DR_FAN_ENGINE_PHASE | NCT6687DR_FAN_ENGINE_LOCK)) ==
+ NCT6687DR_FAN_ENGINE_PHASE;
+}
+
+static int nct6687dr_fan_cfg_start(struct nct6683_data *data)
+{
+ bool idle;
+ u16 sts;
+ int err;
+
+ sts = nct6683_read(data, NCT6687DR_REG_FAN_ENGINE_STS);
+ if (nct6687dr_fan_cfg_accessible(sts))
+ return 0;
+
+ /* Wait for a pending request or configuration phase to complete */
+ err = read_poll_timeout(nct6683_fan_cfg_idle, idle, idle,
+ USEC_PER_MSEC, USEC_PER_SEC, false, data);
+ if (err)
+ return err;
+
+ nct6683_write(data, NCT6683_REG_FAN_CFG_CTRL,
+ nct6683_read(data, NCT6683_REG_FAN_CFG_CTRL) |
+ NCT6683_FAN_CFG_REQ);
+
+ return read_poll_timeout(nct6683_read, sts,
+ nct6687dr_fan_cfg_accessible(sts),
+ USEC_PER_MSEC, USEC_PER_SEC, true,
+ data, NCT6687DR_REG_FAN_ENGINE_STS);
+}
+
+static int nct6687dr_fan_cfg_finish(struct nct6683_data *data)
+{
+ u16 sts;
+ int err;
+
+ sts = nct6683_read(data, NCT6687DR_REG_FAN_ENGINE_STS);
+ if (!nct6687dr_fan_cfg_accessible(sts))
+ return -EAGAIN;
+
+ nct6683_write(data, NCT6683_REG_FAN_CFG_CTRL,
+ nct6683_read(data, NCT6683_REG_FAN_CFG_CTRL) |
+ NCT6683_FAN_CFG_DONE);
+
+ /* The registers are locked again once the configuration is checked */
+ err = read_poll_timeout(nct6683_read, sts,
+ (sts & NCT6687DR_FAN_ENGINE_LOCK) &&
+ (sts & NCT6687DR_FAN_ENGINE_CHECK_DONE),
+ USEC_PER_MSEC, USEC_PER_SEC, true,
+ data, NCT6687DR_REG_FAN_ENGINE_STS);
+ if (err)
+ return err;
+
+ return (sts & NCT6687DR_FAN_ENGINE_INVALID) ? -EAGAIN : 0;
+}
+
+/*
+ * Select manual or automatic mode for a fan channel and, if cmd is not
+ * negative, set its duty cycle for manual mode.
+ */
+static int nct6683_fan_ctrl_update(struct nct6683_data *data, int ch,
+ bool manual, int cmd)
+{
+ u16 mode_reg = nct6683_mode_reg(ch);
+ u16 cmd_reg = nct6683_cmd_reg(ch);
+ u8 mask = BIT(ch % 8);
+ int attempt, err;
+ u8 mode;
+
+ for (attempt = 0; attempt < 3; attempt++) {
+ err = nct6687dr_fan_cfg_start(data);
+ if (err)
+ return err;
+
+ mode = nct6683_read(data, mode_reg);
+ if (cmd >= 0)
+ nct6683_write(data, cmd_reg, cmd);
+ nct6683_write(data, mode_reg,
+ manual ? mode | mask : mode & ~mask);
+
+ /* Retry if the configuration phase was lost or rejected */
+ err = nct6687dr_fan_cfg_finish(data);
+ if (err != -EAGAIN)
+ return err;
+ }
+
+ return -EIO;
+}
+
+static int nct6683_set_pwm(struct nct6683_data *data, int ch, u8 val)
+{
+ int err;
+
+ mutex_lock(&data->update_lock);
+ /* The duty cycle can only be set in manual mode */
+ if (nct6683_pwm_manual(data, ch))
+ err = nct6683_fan_ctrl_update(data, ch, true, val);
+ else
+ err = -EBUSY;
+ if (!err)
+ data->pwm[ch] = val;
+ mutex_unlock(&data->update_lock);
+
+ return err;
+}
+
static ssize_t
show_pwm(struct device *dev, struct device_attribute *attr, char *buf)
{
@@ -943,10 +1087,16 @@ store_pwm(struct device *dev, struct device_attribute *attr, const char *buf,
struct nct6683_data *data = dev_get_drvdata(dev);
int index = sattr->index;
unsigned long val;
+ int err;
if (kstrtoul(buf, 10, &val) || val > 255)
return -EINVAL;
+ if (data->have_fan_ctrl & BIT(index)) {
+ err = nct6683_set_pwm(data, index, val);
+ return err ? err : count;
+ }
+
mutex_lock(&data->update_lock);
nct6683_write(data, NCT6683_REG_FAN_CFG_CTRL, NCT6683_FAN_CFG_REQ);
usleep_range(1000, 2000);
@@ -959,17 +1109,67 @@ store_pwm(struct device *dev, struct device_attribute *attr, const char *buf,
SENSOR_TEMPLATE(pwm, "pwm%d", S_IRUGO, show_pwm, store_pwm, 0);
+static ssize_t
+show_pwm_enable(struct device *dev, struct device_attribute *attr, char *buf)
+{
+ struct sensor_device_attribute *sattr = to_sensor_dev_attr(attr);
+ struct nct6683_data *data = dev_get_drvdata(dev);
+ bool manual;
+
+ mutex_lock(&data->update_lock);
+ manual = nct6683_pwm_manual(data, sattr->index);
+ mutex_unlock(&data->update_lock);
+
+ return sysfs_emit(buf, "%d\n", manual ? 1 : 2);
+}
+
+static ssize_t
+store_pwm_enable(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct sensor_device_attribute *sattr = to_sensor_dev_attr(attr);
+ struct nct6683_data *data = dev_get_drvdata(dev);
+ int index = sattr->index;
+ unsigned long val;
+ int cmd, err = 0;
+ bool manual;
+
+ if (kstrtoul(buf, 10, &val) || (val != 1 && val != 2))
+ return -EINVAL;
+
+ manual = val == 1;
+
+ mutex_lock(&data->update_lock);
+ if (nct6683_pwm_manual(data, index) != manual) {
+ /* Keep the current duty cycle when switching to manual mode */
+ cmd = manual ? nct6683_read(data, nct6683_pwm_reg(index)) : -1;
+ err = nct6683_fan_ctrl_update(data, index, manual, cmd);
+ }
+ mutex_unlock(&data->update_lock);
+
+ return err ? err : count;
+}
+
+SENSOR_TEMPLATE(pwm_enable, "pwm%d_enable", 0444, show_pwm_enable,
+ store_pwm_enable, 0);
+
static umode_t nct6683_pwm_is_visible(struct kobject *kobj,
struct attribute *attr, int index)
{
struct device *dev = kobj_to_dev(kobj);
struct nct6683_data *data = dev_get_drvdata(dev);
- int pwm = index; /* pwm index */
+ int pwm = index / 2; /* pwm index */
+ int nr = index % 2; /* attribute index */
if (!(data->have_pwm & (1 << pwm)))
return 0;
- /* Only update pwm values for Mitac boards */
+ if (data->have_fan_ctrl & BIT(pwm))
+ return attr->mode | 0200;
+
+ if (nr == 1) /* pwm_enable */
+ return 0;
+
if (data->customer_id == NCT6683_CUSTOMER_ID_MITAC)
return attr->mode | S_IWUSR;
@@ -978,6 +1178,7 @@ static umode_t nct6683_pwm_is_visible(struct kobject *kobj,
static struct sensor_device_template *nct6683_attributes_pwm_template[] = {
&sensor_dev_template_pwm,
+ &sensor_dev_template_pwm_enable,
NULL
};
@@ -1165,7 +1366,9 @@ nct6683_setup_fans(struct nct6683_data *data)
* The system fan channels (10-15) have no fan output
* configuration register, so check their fan input instead.
*/
- data->have_pwm |= data->have_fan & GENMASK(15, 10);
+ data->have_fan_ctrl = NCT6687DR_FAN_CTRL_MASK &
+ (data->have_pwm | (data->have_fan & GENMASK(15, 8)));
+ data->have_pwm |= data->have_fan_ctrl;
}
}
--
2.56.0
^ permalink raw reply [flat|nested] 3+ messages in thread