This driver supports Hardware monitor functionality for NCT6694 MFD
device based on USB interface.

Signed-off-by: Ming Yu <tmyu0@nuvoton.com>
---
 MAINTAINERS                   |   1 +
 drivers/hwmon/Kconfig         |  10 +
 drivers/hwmon/Makefile        |   1 +
 drivers/hwmon/nct6694-hwmon.c | 768 ++++++++++++++++++++++++++++++++++
 4 files changed, 780 insertions(+)
 create mode 100644 drivers/hwmon/nct6694-hwmon.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 496fe7d5a23f..d6414eea0463 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -16546,6 +16546,7 @@ M:      Ming Yu <tmyu0@nuvoton.com>
 L:     linux-kernel@vger.kernel.org
 S:     Supported
 F:     drivers/gpio/gpio-nct6694.c
+F:     drivers/hwmon/nct6694-hwmon.c
 F:     drivers/i2c/busses/i2c-nct6694.c
 F:     drivers/mfd/nct6694.c
 F:     drivers/net/can/nct6694_canfd.c

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index dd376602f3f1..df40986424bd 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig

@@ -1636,6 +1636,16 @@ config SENSORS_NCT6683
          This driver can also be built as a module. If so, the module
          will be called nct6683.

+config SENSORS_NCT6694
+       tristate "Nuvoton NCT6694 Hardware Monitor support"
+       depends on MFD_NCT6694
+       help
+         Say Y here to support Nuvoton NCT6694 hardware monitoring
+         functionality.
+
+         This driver can also be built as a module. If so, the module
+         will be called nct6694-hwmon.
+
 config SENSORS_NCT6775_CORE
        tristate
        select REGMAP

diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index b827b92f2a78..27a43e67cdb7 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile

@@ -168,6 +168,7 @@ obj-$(CONFIG_SENSORS_MLXREG_FAN) += mlxreg-fan.o
 obj-$(CONFIG_SENSORS_MENF21BMC_HWMON) += menf21bmc_hwmon.o
 obj-$(CONFIG_SENSORS_MR75203)  += mr75203.o
 obj-$(CONFIG_SENSORS_NCT6683)  += nct6683.o
+obj-$(CONFIG_SENSORS_NCT6694)  += nct6694-hwmon.o
 obj-$(CONFIG_SENSORS_NCT6775_CORE) += nct6775-core.o
 nct6775-objs                   := nct6775-platform.o
 obj-$(CONFIG_SENSORS_NCT6775)  += nct6775.o

diff --git a/drivers/hwmon/nct6694-hwmon.c b/drivers/hwmon/nct6694-hwmon.c
new file mode 100644
index 000000000000..b2320d64090b
--- /dev/null
+++ b/drivers/hwmon/nct6694-hwmon.c

@@ -0,0 +1,768 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Nuvoton NCT6694 HWMON driver based on USB interface.
+ *
+ * Copyright (C) 2024 Nuvoton Technology Corp.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/hwmon.h>
+#include <linux/kernel.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/nct6694.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+/* Host interface */
+#define NCT6694_RPT_MOD                        0xFF
+#define NCT6694_HWMON_MOD              0x00
+#define NCT6694_PWM_MOD                        0x01
+
+/* Report Channel */
+#define NCT6694_VIN_IDX(x)             (0x00 + (x))
+#define NCT6694_TIN_IDX(x)                     \
+       ({ typeof(x) (_x) = (x);                \
+        ((_x) < 10) ? (0x10 + ((_x) * 2)) :    \
+        (0x30 + (((_x) - 10) * 2)); })
+#define NCT6694_FIN_IDX(x)             (0x50 + ((x) * 2))
+#define NCT6694_PWM_IDX(x)             (0x70 + (x))
+#define NCT6694_VIN_STS(x)             (0x68 + (x))
+#define NCT6694_TIN_STS(x)             (0x6A + (x))
+#define NCT6694_FIN_STS(x)             (0x6E + (x))
+
+/* Message Channel*/
+/* HWMON Command */
+/* Command 00h */
+#define NCT6694_HWMON_CMD0_LEN         0x40
+#define NCT6694_HWMON_CMD0_OFFSET      0x0000  /* OFFSET = SEL|CMD */
+#define NCT6694_VIN_EN(x)              (0x00 + (x))
+#define NCT6694_TIN_EN(x)              (0x02 + (x))
+#define NCT6694_FIN_EN(x)              (0x04 + (x))
+#define NCT6694_PWM_EN(x)              (0x06 + (x))
+#define NCT6694_PWM_FREQ_IDX(x)                (0x30 + (x))
+/* Command 02h */
+#define NCT6694_HWMON_CMD2_LEN         0x90
+#define NCT6694_HWMON_CMD2_OFFSET      0x0002  /* OFFSET = SEL|CMD */
+#define NCT6694_SMI_CTRL_IDX           0x00
+#define NCT6694_VIN_HL(x)              (0x10 + ((x) * 2))
+#define NCT6694_VIN_LL(x)              (0x11 + ((x) * 2))
+#define NCT6694_TIN_HYST(x)            (0x30 + ((x) * 2))
+#define NCT6694_TIN_HL(x)              (0x31 + ((x) * 2))
+#define NCT6694_FIN_HL(x)              (0x70 + ((x) * 2))
+#define NCT6694_FIN_LL(x)              (0x71 + ((x) * 2))
+/* PWM Command */
+#define NCT6694_PWM_CMD1_LEN           0x18
+#define NCT6694_PWM_CMD1_OFFSET                0x0001
+#define NCT6694_MAL_VAL(x)             (0x02 + (x))
+
+#define NCT6694_FREQ_FROM_REG(reg)     ((reg) * 25000 / 255)
+#define NCT6694_FREQ_TO_REG(val)       \
+       (DIV_ROUND_CLOSEST(clamp_val((val), 100, 25000) * 255, 25000))
+
+#define NCT6694_LSB_REG_MASK           GENMASK(7, 5)
+#define NCT6694_TIN_HYST_MASK          GENMASK(7, 5)
+
+static inline long in_from_reg(u8 reg)
+{
+       return reg * 16;
+}
+
+static inline u8 in_to_reg(long val)
+{
+       if (val <= 0)
+               return 0;
+       return val / 16;
+}
+
+static inline long temp_from_reg(u8 reg)
+{
+       return reg * 1000;
+}
+
+static inline u8 temp_to_reg(long val)
+{
+       return val / 1000;
+}
+
+struct nct6694_hwmon_data {
+       struct nct6694 *nct6694;
+       struct mutex lock;
+       unsigned char *xmit_buf;
+       unsigned char hwmon_en[NCT6694_HWMON_CMD0_LEN];
+};