[v12,3/3] hwmon: (aspeed-g6-pwm-tacho): Support for ASPEED g6 PWM/Fan tach

diff --git a/Documentation/hwmon/aspeed-g6-pwm-tach.rst b/Documentation/hwmon/aspeed-g6-pwm-tach.rst
new file mode 100644
index 000000000000..17398fe397fe
--- /dev/null
+++ b/Documentation/hwmon/aspeed-g6-pwm-tach.rst
@@ -0,0 +1,26 @@ 
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver aspeed-g6-pwm-tach
+=================================
+
+Supported chips:
+	ASPEED AST2600
+
+Authors:
+	<billy_tsai@aspeedtech.com>
+
+Description:
+------------
+This driver implements support for ASPEED AST2600 Fan Tacho controller.
+The controller supports up to 16 tachometer inputs.
+
+The driver provides the following sensor accesses in sysfs:
+
+=============== ======= ======================================================
+fanX_input	ro	provide current fan rotation value in RPM as reported
+			by the fan to the device.
+fanX_div	rw	Fan divisor: Supported value are power of 4 (1, 4, 16
+                        64, ... 4194304)
+                        The larger divisor, the less rpm accuracy and the less
+                        affected by fan signal glitch.
+=============== ======= ======================================================
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index 72f4e6065bae..f5ff380f7c9d 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -44,6 +44,7 @@  Hardware Monitoring Kernel Drivers
    aquacomputer_d5next
    asb100
    asc7621
+   aspeed-g6-pwm-tach
    aspeed-pwm-tacho
    asus_ec_sensors
    asus_wmi_sensors
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index cf27523eed5a..546a47a5880b 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -412,6 +412,17 @@  config SENSORS_ASPEED
 	  This driver can also be built as a module. If so, the module
 	  will be called aspeed_pwm_tacho.
 
+config SENSORS_ASPEED_G6
+	tristate "ASPEED g6 PWM and Fan tach driver"
+	depends on ARCH_ASPEED || COMPILE_TEST
+	depends on PWM
+	help
+	  This driver provides support for ASPEED G6 PWM and Fan Tach
+	  controllers.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called aspeed_pwm_tacho.
+
 config SENSORS_ATXP1
 	tristate "Attansic ATXP1 VID controller"
 	depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index e84bd9685b5c..92b150682828 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -55,6 +55,7 @@  obj-$(CONFIG_SENSORS_ARM_SCPI)	+= scpi-hwmon.o
 obj-$(CONFIG_SENSORS_AS370)	+= as370-hwmon.o
 obj-$(CONFIG_SENSORS_ASC7621)	+= asc7621.o
 obj-$(CONFIG_SENSORS_ASPEED)	+= aspeed-pwm-tacho.o
+obj-$(CONFIG_SENSORS_ASPEED_G6) += aspeed-g6-pwm-tach.o
 obj-$(CONFIG_SENSORS_ATXP1)	+= atxp1.o
 obj-$(CONFIG_SENSORS_AXI_FAN_CONTROL) += axi-fan-control.o
 obj-$(CONFIG_SENSORS_BT1_PVT)	+= bt1-pvt.o
diff --git a/drivers/hwmon/aspeed-g6-pwm-tach.c b/drivers/hwmon/aspeed-g6-pwm-tach.c
new file mode 100644
index 000000000000..996b77489710
--- /dev/null
+++ b/drivers/hwmon/aspeed-g6-pwm-tach.c
@@ -0,0 +1,538 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2021 Aspeed Technology Inc.
+ *
+ * PWM/TACH controller driver for Aspeed ast2600 SoCs.
+ * This drivers doesn't support earlier version of the IP.
+ *
+ * The hardware operates in time quantities of length
+ * Q := (DIV_L + 1) << DIV_H / input-clk
+ * The length of a PWM period is (DUTY_CYCLE_PERIOD + 1) * Q.
+ * The maximal value for DUTY_CYCLE_PERIOD is used here to provide
+ * a fine grained selection for the duty cycle.
+ *
+ * This driver uses DUTY_CYCLE_RISING_POINT = 0, so from the start of a
+ * period the output is active until DUTY_CYCLE_FALLING_POINT * Q. Note
+ * that if DUTY_CYCLE_RISING_POINT = DUTY_CYCLE_FALLING_POINT the output is
+ * always active.
+ *
+ * Register usage:
+ * PIN_ENABLE: When it is unset the pwm controller will emit inactive level to the external.
+ * Use to determine whether the PWM channel is enabled or disabled
+ * CLK_ENABLE: When it is unset the pwm controller will assert the duty counter reset and
+ * emit inactive level to the PIN_ENABLE mux after that the driver can still change the pwm period
+ * and duty and the value will apply when CLK_ENABLE be set again.
+ * Use to determine whether duty_cycle bigger than 0.
+ * PWM_ASPEED_CTRL_INVERSE: When it is toggled the output value will inverse immediately.
+ * PWM_ASPEED_DUTY_CYCLE_FALLING_POINT/PWM_ASPEED_DUTY_CYCLE_RISING_POINT: When these two
+ * values are equal it means the duty cycle = 100%.
+ *
+ * The glitch may generate at:
+ * - Enabled changing when the duty_cycle bigger than 0% and less than 100%.
+ * - Polarity changing when the duty_cycle bigger than 0% and less than 100%.
+ *
+ * Limitations:
+ * - When changing both duty cycle and period, we cannot prevent in
+ *   software that the output might produce a period with mixed
+ *   settings.
+ * - Disabling the PWM doesn't complete the current period.
+ *
+ * Improvements:
+ * - When only changing one of duty cycle or period, our pwm controller will not
+ *   generate the glitch, the configure will change at next cycle of pwm.
+ *   This improvement can disable/enable through PWM_ASPEED_CTRL_DUTY_SYNC_DISABLE.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/hwmon.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/math64.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/reset.h>
+#include <linux/sysfs.h>
+
+/* The channel number of Aspeed pwm controller */
+#define PWM_ASPEED_NR_PWMS			16
+/* PWM Control Register */
+#define PWM_ASPEED_CTRL(ch)			((ch) * 0x10 + 0x00)
+#define PWM_ASPEED_CTRL_LOAD_SEL_RISING_AS_WDT	BIT(19)
+#define PWM_ASPEED_CTRL_DUTY_LOAD_AS_WDT_ENABLE	BIT(18)
+#define PWM_ASPEED_CTRL_DUTY_SYNC_DISABLE	BIT(17)
+#define PWM_ASPEED_CTRL_CLK_ENABLE		BIT(16)
+#define PWM_ASPEED_CTRL_LEVEL_OUTPUT		BIT(15)
+#define PWM_ASPEED_CTRL_INVERSE			BIT(14)
+#define PWM_ASPEED_CTRL_OPEN_DRAIN_ENABLE	BIT(13)
+#define PWM_ASPEED_CTRL_PIN_ENABLE		BIT(12)
+#define PWM_ASPEED_CTRL_CLK_DIV_H		GENMASK(11, 8)
+#define PWM_ASPEED_CTRL_CLK_DIV_L		GENMASK(7, 0)
+
+/* PWM Duty Cycle Register */
+#define PWM_ASPEED_DUTY_CYCLE(ch)		((ch) * 0x10 + 0x04)
+#define PWM_ASPEED_DUTY_CYCLE_PERIOD		GENMASK(31, 24)
+#define PWM_ASPEED_DUTY_CYCLE_POINT_AS_WDT	GENMASK(23, 16)
+#define PWM_ASPEED_DUTY_CYCLE_FALLING_POINT	GENMASK(15, 8)
+#define PWM_ASPEED_DUTY_CYCLE_RISING_POINT	GENMASK(7, 0)
+
+/* PWM fixed value */
+#define PWM_ASPEED_FIXED_PERIOD			FIELD_MAX(PWM_ASPEED_DUTY_CYCLE_PERIOD)
+
+/* The channel number of Aspeed tach controller */
+#define TACH_ASPEED_NR_TACHS		16
+/* TACH Control Register */
+#define TACH_ASPEED_CTRL(ch)		(((ch) * 0x10) + 0x08)
+#define TACH_ASPEED_IER			BIT(31)
+#define TACH_ASPEED_INVERS_LIMIT	BIT(30)
+#define TACH_ASPEED_LOOPBACK		BIT(29)
+#define TACH_ASPEED_ENABLE		BIT(28)
+#define TACH_ASPEED_DEBOUNCE_MASK	GENMASK(27, 26)
+#define TACH_ASPEED_DEBOUNCE_BIT	26
+#define TACH_ASPEED_IO_EDGE_MASK	GENMASK(25, 24)
+#define TACH_ASPEED_IO_EDGE_BIT		24
+#define TACH_ASPEED_CLK_DIV_T_MASK	GENMASK(23, 20)
+#define TACH_ASPEED_CLK_DIV_BIT		20
+#define TACH_ASPEED_THRESHOLD_MASK	GENMASK(19, 0)
+/* [27:26] */
+#define DEBOUNCE_3_CLK			0x00
+#define DEBOUNCE_2_CLK			0x01
+#define DEBOUNCE_1_CLK			0x02
+#define DEBOUNCE_0_CLK			0x03
+/* [25:24] */
+#define F2F_EDGES			0x00
+#define R2R_EDGES			0x01
+#define BOTH_EDGES			0x02
+/* [23:20] */
+/* divisor = 4 to the nth power, n = register value */
+#define DEFAULT_TACH_DIV		1024
+#define DIV_TO_REG(divisor)		(ilog2(divisor) >> 1)
+
+/* TACH Status Register */
+#define TACH_ASPEED_STS(ch)		(((ch) * 0x10) + 0x0C)
+
+/*PWM_TACH_STS */
+#define TACH_ASPEED_ISR			BIT(31)
+#define TACH_ASPEED_PWM_OUT		BIT(25)
+#define TACH_ASPEED_PWM_OEN		BIT(24)
+#define TACH_ASPEED_DEB_INPUT		BIT(23)
+#define TACH_ASPEED_RAW_INPUT		BIT(22)
+#define TACH_ASPEED_VALUE_UPDATE	BIT(21)
+#define TACH_ASPEED_FULL_MEASUREMENT	BIT(20)
+#define TACH_ASPEED_VALUE_MASK		GENMASK(19, 0)
+/**********************************************************
+ * Software setting
+ *********************************************************/
+#define DEFAULT_FAN_PULSE_PR		2
+
+struct aspeed_pwm_tach_data {
+	struct device *dev;
+	void __iomem *base;
+	struct clk *clk;
+	struct reset_control *reset;
+	unsigned long clk_rate;
+	struct pwm_chip chip;
+	bool tach_present[TACH_ASPEED_NR_TACHS];
+	u32 tach_divisor;
+};
+
+static inline struct aspeed_pwm_tach_data *
+aspeed_pwm_chip_to_data(struct pwm_chip *chip)
+{
+	return container_of(chip, struct aspeed_pwm_tach_data, chip);
+}
+
+static int aspeed_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				struct pwm_state *state)
+{
+	struct aspeed_pwm_tach_data *priv = aspeed_pwm_chip_to_data(chip);
+	u32 hwpwm = pwm->hwpwm;
+	bool polarity, pin_en, clk_en;
+	u32 duty_pt, val;
+	u64 div_h, div_l, duty_cycle_period, dividend;
+
+	val = readl(priv->base + PWM_ASPEED_CTRL(hwpwm));
+	polarity = FIELD_GET(PWM_ASPEED_CTRL_INVERSE, val);
+	pin_en = FIELD_GET(PWM_ASPEED_CTRL_PIN_ENABLE, val);
+	clk_en = FIELD_GET(PWM_ASPEED_CTRL_CLK_ENABLE, val);
+	div_h = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_H, val);
+	div_l = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_L, val);
+	val = readl(priv->base + PWM_ASPEED_DUTY_CYCLE(hwpwm));
+	duty_pt = FIELD_GET(PWM_ASPEED_DUTY_CYCLE_FALLING_POINT, val);
+	duty_cycle_period = FIELD_GET(PWM_ASPEED_DUTY_CYCLE_PERIOD, val);
+	/*
+	 * This multiplication doesn't overflow, the upper bound is
+	 * 1000000000 * 256 * 256 << 15 = 0x1dcd650000000000
+	 */
+	dividend = (u64)NSEC_PER_SEC * (div_l + 1) * (duty_cycle_period + 1)
+		       << div_h;
+	state->period = DIV_ROUND_UP_ULL(dividend, priv->clk_rate);
+
+	if (clk_en && duty_pt) {
+		dividend = (u64)NSEC_PER_SEC * (div_l + 1) * duty_pt
+				 << div_h;
+		state->duty_cycle = DIV_ROUND_UP_ULL(dividend, priv->clk_rate);
+	} else {
+		state->duty_cycle = clk_en ? state->period : 0;
+	}
+	state->polarity = polarity ? PWM_POLARITY_INVERSED : PWM_POLARITY_NORMAL;
+	state->enabled = pin_en;
+	return 0;
+}
+
+static int aspeed_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			    const struct pwm_state *state)
+{
+	struct aspeed_pwm_tach_data *priv = aspeed_pwm_chip_to_data(chip);
+	u32 hwpwm = pwm->hwpwm, duty_pt, val;
+	u64 div_h, div_l, divisor, expect_period;
+	bool clk_en;
+
+	expect_period = div64_u64(ULLONG_MAX, (u64)priv->clk_rate);
+	expect_period = min(expect_period, state->period);
+	dev_dbg(chip->dev, "expect period: %lldns, duty_cycle: %lldns",
+		expect_period, state->duty_cycle);
+	/*
+	 * Pick the smallest value for div_h so that div_l can be the biggest
+	 * which results in a finer resolution near the target period value.
+	 */
+	divisor = (u64)NSEC_PER_SEC * (PWM_ASPEED_FIXED_PERIOD + 1) *
+		  (FIELD_MAX(PWM_ASPEED_CTRL_CLK_DIV_L) + 1);
+	div_h = order_base_2(DIV64_U64_ROUND_UP(priv->clk_rate * expect_period, divisor));
+	if (div_h > 0xf)
+		div_h = 0xf;
+
+	divisor = ((u64)NSEC_PER_SEC * (PWM_ASPEED_FIXED_PERIOD + 1)) << div_h;
+	div_l = div64_u64(priv->clk_rate * expect_period, divisor);
+
+	if (div_l == 0)
+		return -ERANGE;
+
+	div_l -= 1;
+
+	if (div_l > 255)
+		div_l = 255;
+
+	dev_dbg(chip->dev, "clk source: %ld div_h %lld, div_l : %lld\n",
+		priv->clk_rate, div_h, div_l);
+	/* duty_pt = duty_cycle * (PERIOD + 1) / period */
+	duty_pt = div64_u64(state->duty_cycle * priv->clk_rate,
+			    (u64)NSEC_PER_SEC * (div_l + 1) << div_h);
+	dev_dbg(chip->dev, "duty_cycle = %lld, duty_pt = %d\n",
+		state->duty_cycle, duty_pt);
+
+	/*
+	 * Fixed DUTY_CYCLE_PERIOD to its max value to get a
+	 * fine-grained resolution for duty_cycle at the expense of a
+	 * coarser period resolution.
+	 */
+	val = readl(priv->base + PWM_ASPEED_DUTY_CYCLE(hwpwm));
+	val &= ~PWM_ASPEED_DUTY_CYCLE_PERIOD;
+	val |= FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_PERIOD,
+			  PWM_ASPEED_FIXED_PERIOD);
+	writel(val, priv->base + PWM_ASPEED_DUTY_CYCLE(hwpwm));
+
+	if (duty_pt == 0) {
+		/* emit inactive level and assert the duty counter reset */
+		clk_en = 0;
+	} else {
+		clk_en = 1;
+		if (duty_pt >= (PWM_ASPEED_FIXED_PERIOD + 1))
+			duty_pt = 0;
+		val = readl(priv->base + PWM_ASPEED_DUTY_CYCLE(hwpwm));
+		val &= ~(PWM_ASPEED_DUTY_CYCLE_RISING_POINT |
+			 PWM_ASPEED_DUTY_CYCLE_FALLING_POINT);
+		val |= FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_FALLING_POINT, duty_pt);
+		writel(val, priv->base + PWM_ASPEED_DUTY_CYCLE(hwpwm));
+	}
+
+	val = readl(priv->base + PWM_ASPEED_CTRL(hwpwm));
+	val &= ~(PWM_ASPEED_CTRL_CLK_DIV_H | PWM_ASPEED_CTRL_CLK_DIV_L |
+		 PWM_ASPEED_CTRL_PIN_ENABLE | PWM_ASPEED_CTRL_CLK_ENABLE |
+		 PWM_ASPEED_CTRL_INVERSE);
+	val |= FIELD_PREP(PWM_ASPEED_CTRL_CLK_DIV_H, div_h) |
+	       FIELD_PREP(PWM_ASPEED_CTRL_CLK_DIV_L, div_l) |
+	       FIELD_PREP(PWM_ASPEED_CTRL_PIN_ENABLE, state->enabled) |
+	       FIELD_PREP(PWM_ASPEED_CTRL_CLK_ENABLE, clk_en) |
+	       FIELD_PREP(PWM_ASPEED_CTRL_INVERSE, state->polarity);
+	writel(val, priv->base + PWM_ASPEED_CTRL(hwpwm));
+
+	return 0;
+}
+
+static const struct pwm_ops aspeed_pwm_ops = {
+	.apply = aspeed_pwm_apply,
+	.get_state = aspeed_pwm_get_state,
+};
+
+static void aspeed_tach_ch_enable(struct aspeed_pwm_tach_data *priv, u8 tach_ch,
+				  bool enable)
+{
+	if (enable)
+		writel(readl(priv->base + TACH_ASPEED_CTRL(tach_ch)) |
+			       TACH_ASPEED_ENABLE,
+		       priv->base + TACH_ASPEED_CTRL(tach_ch));
+	else
+		writel(readl(priv->base + TACH_ASPEED_CTRL(tach_ch)) &
+			       ~TACH_ASPEED_ENABLE,
+		       priv->base + TACH_ASPEED_CTRL(tach_ch));
+}
+
+static int aspeed_tach_val_to_rpm(struct aspeed_pwm_tach_data *priv, u32 tach_val)
+{
+	u64 rpm;
+	u32 tach_div;
+
+	tach_div = tach_val * priv->tach_divisor * DEFAULT_FAN_PULSE_PR;
+
+	dev_dbg(priv->dev, "clk %ld, tach_val %d , tach_div %d\n",
+		priv->clk_rate, tach_val, tach_div);
+
+	rpm = (u64)priv->clk_rate * 60;
+	do_div(rpm, tach_div);
+
+	return (int)rpm;
+}
+
+static int aspeed_get_fan_tach_ch_rpm(struct aspeed_pwm_tach_data *priv,
+				      u8 fan_tach_ch)
+{
+	u32 val;
+
+	val = readl(priv->base + TACH_ASPEED_STS(fan_tach_ch));
+
+	if (!(val & TACH_ASPEED_FULL_MEASUREMENT))
+		return 0;
+	val = FIELD_GET(TACH_ASPEED_VALUE_MASK, val);
+	return aspeed_tach_val_to_rpm(priv, val);
+}
+
+static int aspeed_tach_hwmon_read(struct device *dev,
+				  enum hwmon_sensor_types type, u32 attr,
+				  int channel, long *val)
+{
+	struct aspeed_pwm_tach_data *priv = dev_get_drvdata(dev);
+	u32 reg_val;
+
+	switch (attr) {
+	case hwmon_fan_input:
+		*val = aspeed_get_fan_tach_ch_rpm(priv, channel);
+		break;
+	case hwmon_fan_div:
+		reg_val = readl(priv->base + TACH_ASPEED_CTRL(channel));
+		reg_val = FIELD_GET(TACH_ASPEED_CLK_DIV_T_MASK, reg_val);
+		*val = BIT(reg_val << 1);
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+	return 0;
+}
+
+static int aspeed_tach_hwmon_write(struct device *dev,
+				   enum hwmon_sensor_types type, u32 attr,
+				   int channel, long val)
+{
+	struct aspeed_pwm_tach_data *priv = dev_get_drvdata(dev);
+	u32 reg_val;
+
+	switch (attr) {
+	case hwmon_fan_div:
+		if (!is_power_of_2(val) || (ilog2(val) % 2) ||
+		    DIV_TO_REG(val) > 0xb)
+			return -EINVAL;
+		priv->tach_divisor = val;
+		reg_val = readl(priv->base + TACH_ASPEED_CTRL(channel));
+		reg_val &= ~TACH_ASPEED_CLK_DIV_T_MASK;
+		reg_val |= FIELD_PREP(TACH_ASPEED_CLK_DIV_T_MASK,
+				      DIV_TO_REG(priv->tach_divisor));
+		writel(reg_val, priv->base + TACH_ASPEED_CTRL(channel));
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static umode_t aspeed_tach_dev_is_visible(const void *drvdata,
+					  enum hwmon_sensor_types type,
+					  u32 attr, int channel)
+{
+	const struct aspeed_pwm_tach_data *priv = drvdata;
+
+	if (!priv->tach_present[channel])
+		return 0;
+	switch (attr) {
+	case hwmon_fan_input:
+		return 0444;
+	case hwmon_fan_div:
+		return 0644;
+	}
+	return 0;
+}
+
+static const struct hwmon_ops aspeed_tach_ops = {
+	.is_visible = aspeed_tach_dev_is_visible,
+	.read = aspeed_tach_hwmon_read,
+	.write = aspeed_tach_hwmon_write,
+};
+
+static const struct hwmon_channel_info *aspeed_tach_info[] = {
+	HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT | HWMON_F_DIV, HWMON_F_INPUT | HWMON_F_DIV,
+			   HWMON_F_INPUT | HWMON_F_DIV, HWMON_F_INPUT | HWMON_F_DIV,
+			   HWMON_F_INPUT | HWMON_F_DIV, HWMON_F_INPUT | HWMON_F_DIV,
+			   HWMON_F_INPUT | HWMON_F_DIV, HWMON_F_INPUT | HWMON_F_DIV,
+			   HWMON_F_INPUT | HWMON_F_DIV, HWMON_F_INPUT | HWMON_F_DIV,
+			   HWMON_F_INPUT | HWMON_F_DIV, HWMON_F_INPUT | HWMON_F_DIV,
+			   HWMON_F_INPUT | HWMON_F_DIV, HWMON_F_INPUT | HWMON_F_DIV,
+			   HWMON_F_INPUT | HWMON_F_DIV, HWMON_F_INPUT | HWMON_F_DIV),
+	NULL
+};
+
+static const struct hwmon_chip_info aspeed_tach_chip_info = {
+	.ops = &aspeed_tach_ops,
+	.info = aspeed_tach_info,
+};
+
+static void aspeed_present_fan_tach(struct aspeed_pwm_tach_data *priv, u8 *tach_ch, int count)
+{
+	u8 ch, index;
+	u32 val;
+
+	for (index = 0; index < count; index++) {
+		ch = tach_ch[index];
+		priv->tach_present[ch] = true;
+		priv->tach_divisor = DEFAULT_TACH_DIV;
+
+		val = readl(priv->base + TACH_ASPEED_CTRL(ch));
+		val &= ~(TACH_ASPEED_INVERS_LIMIT | TACH_ASPEED_DEBOUNCE_MASK |
+			 TACH_ASPEED_IO_EDGE_MASK | TACH_ASPEED_CLK_DIV_T_MASK |
+			 TACH_ASPEED_THRESHOLD_MASK);
+		val |= (DEBOUNCE_3_CLK << TACH_ASPEED_DEBOUNCE_BIT) |
+		       F2F_EDGES |
+		       FIELD_PREP(TACH_ASPEED_CLK_DIV_T_MASK,
+				  DIV_TO_REG(priv->tach_divisor));
+		writel(val, priv->base + TACH_ASPEED_CTRL(ch));
+
+		aspeed_tach_ch_enable(priv, ch, true);
+	}
+}
+
+static int aspeed_tach_create_fan(struct device *dev, struct device_node *child,
+				  struct aspeed_pwm_tach_data *priv)
+{
+	int ret, count;
+	u8 *tach_ch;
+
+	count = of_property_count_u8_elems(child, "tach-ch");
+	if (count < 1)
+		return -EINVAL;
+	tach_ch = devm_kcalloc(dev, count, sizeof(*tach_ch), GFP_KERNEL);
+	if (!tach_ch)
+		return -ENOMEM;
+	ret = of_property_read_u8_array(child, "tach-ch", tach_ch, count);
+	if (ret)
+		return ret;
+
+	aspeed_present_fan_tach(priv, tach_ch, count);
+
+	return 0;
+}
+
+static int aspeed_pwm_tach_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev, *hwmon;
+	int ret;
+	struct device_node *child;
+	struct aspeed_pwm_tach_data *priv;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+	priv->dev = dev;
+	priv->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	priv->clk = devm_clk_get_enabled(dev, NULL);
+	if (IS_ERR(priv->clk))
+		return dev_err_probe(dev, PTR_ERR(priv->clk),
+				     "Couldn't get clock\n");
+	priv->clk_rate = clk_get_rate(priv->clk);
+	priv->reset = devm_reset_control_get_exclusive(dev, NULL);
+	if (IS_ERR(priv->reset))
+		return dev_err_probe(dev, PTR_ERR(priv->reset),
+				     "Couldn't get reset control\n");
+
+	ret = reset_control_deassert(priv->reset);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Couldn't deassert reset control\n");
+
+	priv->chip.dev = dev;
+	priv->chip.ops = &aspeed_pwm_ops;
+	priv->chip.npwm = PWM_ASPEED_NR_PWMS;
+
+	ret = devm_pwmchip_add(dev, &priv->chip);
+	if (ret < 0) {
+		reset_control_assert(priv->reset);
+		return dev_err_probe(dev, ret, "Failed to add PWM chip\n");
+	}
+
+	for_each_child_of_node(dev->of_node, child) {
+		ret = aspeed_tach_create_fan(dev, child, priv);
+		if (ret < 0) {
+			of_node_put(child);
+			dev_warn(dev, "Failed to create fan %d", ret);
+			return 0;
+		}
+	}
+
+	hwmon = devm_hwmon_device_register_with_info(dev, "aspeed_tach", priv,
+						     &aspeed_tach_chip_info, NULL);
+	ret = PTR_ERR_OR_ZERO(hwmon);
+	if (ret) {
+		reset_control_assert(priv->reset);
+		return dev_err_probe(dev, ret,
+				     "Failed to register hwmon device\n");
+	}
+
+	return 0;
+}
+
+static int aspeed_pwm_tach_remove(struct platform_device *pdev)
+{
+	struct aspeed_pwm_tach_data *priv = platform_get_drvdata(pdev);
+
+	reset_control_assert(priv->reset);
+
+	return 0;
+}
+
+static const struct of_device_id aspeed_pwm_tach_match[] = {
+	{
+		.compatible = "aspeed,ast2600-pwm-tach",
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, aspeed_pwm_tach_match);
+
+static struct platform_driver aspeed_pwm_tach_driver = {
+	.probe = aspeed_pwm_tach_probe,
+	.remove = aspeed_pwm_tach_remove,
+	.driver	= {
+		.name = "aspeed-g6-pwm-tach",
+		.of_match_table = aspeed_pwm_tach_match,
+	},
+};
+
+module_platform_driver(aspeed_pwm_tach_driver);
+
+MODULE_AUTHOR("Billy Tsai <billy_tsai@aspeedtech.com>");
+MODULE_DESCRIPTION("Aspeed ast2600 PWM and Fan Tach device driver");
+MODULE_LICENSE("GPL");