hwmon: Add Baikal-T1 PVT sensor driver

Baikal-T1 SoC provides an embedded process, voltage and temperature
sensor to monitor an internal SoC environment (chip temperature, supply
voltage and process monitor) and on time detect critical situations,
which may cause the system instability and even damages. The IP-block
is based on the Analog Bits PVT sensor, but is equipped with a
dedicated control wrapper, which provides a MMIO registers-based access
to the sensor core functionality (APB3-bus based) and exposes an
additional functions like thresholds/data ready interrupts, its status
and masks, measurements timeout. All of these is used to create a hwmon
driver being added to the kernel by this commit.

The driver implements support for the hardware monitoring capabilities
of Baikal-T1 process, voltage and temperature sensors. PVT IP-core
consists of one temperature and four voltage sensors, each of which is
implemented as a dedicated hwmon channel config.

The driver can optionally provide the hwmon alarms for each sensor the
PVT controller supports. The alarms functionality is made compile-time
configurable due to the hardware interface implementation peculiarity,
which is connected with an ability to convert data from only one sensor
at a time. Additional limitation is that the controller performs the
thresholds checking synchronously with the data conversion procedure.
Due to these limitations in order to have the hwmon alarms
automatically detected the driver code must switch from one sensor to
another, read converted data and manually check the threshold status
bits. Depending on the measurements timeout settings this design may
cause additional burden on the system performance. By default if the
alarms kernel config is disabled the data conversion is performed by
the driver on demand when read operation is requested via corresponding
_input-file.

Co-developed-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
Signed-off-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: devicetree@vger.kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

1 files changed, 1146 insertions, 0 deletions

diff --git a/drivers/hwmon/bt1-pvt.c b/drivers/hwmon/bt1-pvt.c
new file mode 100644
index 000000000000..1a9772fb1f73
--- /dev/null
+++ b/drivers/hwmon/bt1-pvt.c
@@ -0,0 +1,1146 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
+ *
+ * Authors:
+ *   Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
+ *   Serge Semin <Sergey.Semin@baikalelectronics.ru>
+ *
+ * Baikal-T1 Process, Voltage, Temperature sensor driver
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/completion.h>
+#include <linux/device.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/hwmon.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/ktime.h>
+#include <linux/limits.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/seqlock.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+
+#include "bt1-pvt.h"
+
+/*
+ * For the sake of the code simplification we created the sensors info table
+ * with the sensor names, activation modes, threshold registers base address
+ * and the thresholds bit fields.
+ */
+static const struct pvt_sensor_info pvt_info[] = {
+	PVT_SENSOR_INFO(0, "CPU Core Temperature", hwmon_temp, TEMP, TTHRES),
+	PVT_SENSOR_INFO(0, "CPU Core Voltage", hwmon_in, VOLT, VTHRES),
+	PVT_SENSOR_INFO(1, "CPU Core Low-Vt", hwmon_in, LVT, LTHRES),
+	PVT_SENSOR_INFO(2, "CPU Core High-Vt", hwmon_in, HVT, HTHRES),
+	PVT_SENSOR_INFO(3, "CPU Core Standard-Vt", hwmon_in, SVT, STHRES),
+};
+
+/*
+ * The original translation formulae of the temperature (in degrees of Celsius)
+ * to PVT data and vice-versa are following:
+ * N = 1.8322e-8*(T^4) + 2.343e-5*(T^3) + 8.7018e-3*(T^2) + 3.9269*(T^1) +
+ *     1.7204e2,
+ * T = -1.6743e-11*(N^4) + 8.1542e-8*(N^3) + -1.8201e-4*(N^2) +
+ *     3.1020e-1*(N^1) - 4.838e1,
+ * where T = [-48.380, 147.438]C and N = [0, 1023].
+ * They must be accordingly altered to be suitable for the integer arithmetics.
+ * The technique is called 'factor redistribution', which just makes sure the
+ * multiplications and divisions are made so to have a result of the operations
+ * within the integer numbers limit. In addition we need to translate the
+ * formulae to accept millidegrees of Celsius. Here what they look like after
+ * the alterations:
+ * N = (18322e-20*(T^4) + 2343e-13*(T^3) + 87018e-9*(T^2) + 39269e-3*T +
+ *     17204e2) / 1e4,
+ * T = -16743e-12*(D^4) + 81542e-9*(D^3) - 182010e-6*(D^2) + 310200e-3*D -
+ *     48380,
+ * where T = [-48380, 147438] mC and N = [0, 1023].
+ */
+static const struct pvt_poly poly_temp_to_N = {
+	.total_divider = 10000,
+	.terms = {
+		{4, 18322, 10000, 10000},
+		{3, 2343, 10000, 10},
+		{2, 87018, 10000, 10},
+		{1, 39269, 1000, 1},
+		{0, 1720400, 1, 1}
+	}
+};
+
+static const struct pvt_poly poly_N_to_temp = {
+	.total_divider = 1,
+	.terms = {
+		{4, -16743, 1000, 1},
+		{3, 81542, 1000, 1},
+		{2, -182010, 1000, 1},
+		{1, 310200, 1000, 1},
+		{0, -48380, 1, 1}
+	}
+};
+
+/*
+ * Similar alterations are performed for the voltage conversion equations.
+ * The original formulae are:
+ * N = 1.8658e3*V - 1.1572e3,
+ * V = (N + 1.1572e3) / 1.8658e3,
+ * where V = [0.620, 1.168] V and N = [0, 1023].
+ * After the optimization they looks as follows:
+ * N = (18658e-3*V - 11572) / 10,
+ * V = N * 10^5 / 18658 + 11572 * 10^4 / 18658.
+ */
+static const struct pvt_poly poly_volt_to_N = {
+	.total_divider = 10,
+	.terms = {
+		{1, 18658, 1000, 1},
+		{0, -11572, 1, 1}
+	}
+};
+
+static const struct pvt_poly poly_N_to_volt = {
+	.total_divider = 10,
+	.terms = {
+		{1, 100000, 18658, 1},
+		{0, 115720000, 1, 18658}
+	}
+};
+
+/*
+ * Here is the polynomial calculation function, which performs the
+ * redistributed terms calculations. It's pretty straightforward. We walk
+ * over each degree term up to the free one, and perform the redistributed
+ * multiplication of the term coefficient, its divider (as for the rationale
+ * fraction representation), data power and the rational fraction divider
+ * leftover. Then all of this is collected in a total sum variable, which
+ * value is normalized by the total divider before being returned.
+ */
+static long pvt_calc_poly(const struct pvt_poly *poly, long data)
+{
+	const struct pvt_poly_term *term = poly->terms;
+	long tmp, ret = 0;
+	int deg;
+
+	do {
+		tmp = term->coef;
+		for (deg = 0; deg < term->deg; ++deg)
+			tmp = mult_frac(tmp, data, term->divider);
+		ret += tmp / term->divider_leftover;
+	} while ((term++)->deg);
+
+	return ret / poly->total_divider;
+}
+
+static inline u32 pvt_update(void __iomem *reg, u32 mask, u32 data)
+{
+	u32 old;
+
+	old = readl_relaxed(reg);
+	writel((old & ~mask) | (data & mask), reg);
+
+	return old & mask;
+}
+
+/*
+ * Baikal-T1 PVT mode can be updated only when the controller is disabled.
+ * So first we disable it, then set the new mode together with the controller
+ * getting back enabled. The same concerns the temperature trim and
+ * measurements timeout. If it is necessary the interface mutex is supposed
+ * to be locked at the time the operations are performed.
+ */
+static inline void pvt_set_mode(struct pvt_hwmon *pvt, u32 mode)
+{
+	u32 old;
+
+	mode = FIELD_PREP(PVT_CTRL_MODE_MASK, mode);
+
+	old = pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_MODE_MASK | PVT_CTRL_EN,
+		   mode | old);
+}
+
+static inline u32 pvt_calc_trim(long temp)
+{
+	temp = clamp_val(temp, 0, PVT_TRIM_TEMP);
+
+	return DIV_ROUND_UP(temp, PVT_TRIM_STEP);
+}
+
+static inline void pvt_set_trim(struct pvt_hwmon *pvt, u32 trim)
+{
+	u32 old;
+
+	trim = FIELD_PREP(PVT_CTRL_TRIM_MASK, trim);
+
+	old = pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_TRIM_MASK | PVT_CTRL_EN,
+		   trim | old);
+}
+
+static inline void pvt_set_tout(struct pvt_hwmon *pvt, u32 tout)
+{
+	u32 old;
+
+	old = pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
+	writel(tout, pvt->regs + PVT_TTIMEOUT);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, old);
+}
+
+/*
+ * This driver can optionally provide the hwmon alarms for each sensor the PVT
+ * controller supports. The alarms functionality is made compile-time
+ * configurable due to the hardware interface implementation peculiarity
+ * described further in this comment. So in case if alarms are unnecessary in
+ * your system design it's recommended to have them disabled to prevent the PVT
+ * IRQs being periodically raised to get the data cache/alarms status up to
+ * date.
+ *
+ * Baikal-T1 PVT embedded controller is based on the Analog Bits PVT sensor,
+ * but is equipped with a dedicated control wrapper. It exposes the PVT
+ * sub-block registers space via the APB3 bus. In addition the wrapper provides
+ * a common interrupt vector of the sensors conversion completion events and
+ * threshold value alarms. Alas the wrapper interface hasn't been fully thought
+ * through. There is only one sensor can be activated at a time, for which the
+ * thresholds comparator is enabled right after the data conversion is
+ * completed. Due to this if alarms need to be implemented for all available
+ * sensors we can't just set the thresholds and enable the interrupts. We need
+ * to enable the sensors one after another and let the controller to detect
+ * the alarms by itself at each conversion. This also makes pointless to handle
+ * the alarms interrupts, since in occasion they happen synchronously with
+ * data conversion completion. The best driver design would be to have the
+ * completion interrupts enabled only and keep the converted value in the
+ * driver data cache. This solution is implemented if hwmon alarms are enabled
+ * in this driver. In case if the alarms are disabled, the conversion is
+ * performed on demand at the time a sensors input file is read.
+ */
+
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+
+#define pvt_hard_isr NULL
+
+static irqreturn_t pvt_soft_isr(int irq, void *data)
+{
+	const struct pvt_sensor_info *info;
+	struct pvt_hwmon *pvt = data;
+	struct pvt_cache *cache;
+	u32 val, thres_sts, old;
+
+	/*
+	 * DVALID bit will be cleared by reading the data. We need to save the
+	 * status before the next conversion happens. Threshold events will be
+	 * handled a bit later.
+	 */
+	thres_sts = readl(pvt->regs + PVT_RAW_INTR_STAT);
+
+	/*
+	 * Then lets recharge the PVT interface with the next sampling mode.
+	 * Lock the interface mutex to serialize trim, timeouts and alarm
+	 * thresholds settings.
+	 */
+	cache = &pvt->cache[pvt->sensor];
+	info = &pvt_info[pvt->sensor];
+	pvt->sensor = (pvt->sensor == PVT_SENSOR_LAST) ?
+		      PVT_SENSOR_FIRST : (pvt->sensor + 1);
+
+	/*
+	 * For some reason we have to mask the interrupt before changing the
+	 * mode, otherwise sometimes the temperature mode doesn't get
+	 * activated even though the actual mode in the ctrl register
+	 * corresponds to one. Then we read the data. By doing so we also
+	 * recharge the data conversion. After this the mode corresponding
+	 * to the next sensor in the row is set. Finally we enable the
+	 * interrupts back.
+	 */
+	mutex_lock(&pvt->iface_mtx);
+
+	old = pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
+			 PVT_INTR_DVALID);
+
+	val = readl(pvt->regs + PVT_DATA);
+
+	pvt_set_mode(pvt, pvt_info[pvt->sensor].mode);
+
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID, old);
+
+	mutex_unlock(&pvt->iface_mtx);
+
+	/*
+	 * We can now update the data cache with data just retrieved from the
+	 * sensor. Lock write-seqlock to make sure the reader has a coherent
+	 * data.
+	 */
+	write_seqlock(&cache->data_seqlock);
+
+	cache->data = FIELD_GET(PVT_DATA_DATA_MASK, val);
+
+	write_sequnlock(&cache->data_seqlock);
+
+	/*
+	 * While PVT core is doing the next mode data conversion, we'll check
+	 * whether the alarms were triggered for the current sensor. Note that
+	 * according to the documentation only one threshold IRQ status can be
+	 * set at a time, that's why if-else statement is utilized.
+	 */
+	if ((thres_sts & info->thres_sts_lo) ^ cache->thres_sts_lo) {
+		WRITE_ONCE(cache->thres_sts_lo, thres_sts & info->thres_sts_lo);
+		hwmon_notify_event(pvt->hwmon, info->type, info->attr_min_alarm,
+				   info->channel);
+	} else if ((thres_sts & info->thres_sts_hi) ^ cache->thres_sts_hi) {
+		WRITE_ONCE(cache->thres_sts_hi, thres_sts & info->thres_sts_hi);
+		hwmon_notify_event(pvt->hwmon, info->type, info->attr_max_alarm,
+				   info->channel);
+	}
+
+	return IRQ_HANDLED;
+}
+
+inline umode_t pvt_limit_is_visible(enum pvt_sensor_type type)
+{
+	return 0644;
+}
+
+inline umode_t pvt_alarm_is_visible(enum pvt_sensor_type type)
+{
+	return 0444;
+}
+
+static int pvt_read_data(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			 long *val)
+{
+	struct pvt_cache *cache = &pvt->cache[type];
+	unsigned int seq;
+	u32 data;
+
+	do {
+		seq = read_seqbegin(&cache->data_seqlock);
+		data = cache->data;
+	} while (read_seqretry(&cache->data_seqlock, seq));
+
+	if (type == PVT_TEMP)
+		*val = pvt_calc_poly(&poly_N_to_temp, data);
+	else
+		*val = pvt_calc_poly(&poly_N_to_volt, data);
+
+	return 0;
+}
+
+static int pvt_read_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			  bool is_low, long *val)
+{
+	u32 data;
+
+	/* No need in serialization, since it is just read from MMIO. */
+	data = readl(pvt->regs + pvt_info[type].thres_base);
+
+	if (is_low)
+		data = FIELD_GET(PVT_THRES_LO_MASK, data);
+	else
+		data = FIELD_GET(PVT_THRES_HI_MASK, data);
+
+	if (type == PVT_TEMP)
+		*val = pvt_calc_poly(&poly_N_to_temp, data);
+	else
+		*val = pvt_calc_poly(&poly_N_to_volt, data);
+
+	return 0;
+}
+
+static int pvt_write_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			   bool is_low, long val)
+{
+	u32 data, limit, mask;
+	int ret;
+
+	if (type == PVT_TEMP) {
+		val = clamp(val, PVT_TEMP_MIN, PVT_TEMP_MAX);
+		data = pvt_calc_poly(&poly_temp_to_N, val);
+	} else {
+		val = clamp(val, PVT_VOLT_MIN, PVT_VOLT_MAX);
+		data = pvt_calc_poly(&poly_volt_to_N, val);
+	}
+
+	/* Serialize limit update, since a part of the register is changed. */
+	ret = mutex_lock_interruptible(&pvt->iface_mtx);
+	if (ret)
+		return ret;
+
+	/* Make sure the upper and lower ranges don't intersect. */
+	limit = readl(pvt->regs + pvt_info[type].thres_base);
+	if (is_low) {
+		limit = FIELD_GET(PVT_THRES_HI_MASK, limit);
+		data = clamp_val(data, PVT_DATA_MIN, limit);
+		data = FIELD_PREP(PVT_THRES_LO_MASK, data);
+		mask = PVT_THRES_LO_MASK;
+	} else {
+		limit = FIELD_GET(PVT_THRES_LO_MASK, limit);
+		data = clamp_val(data, limit, PVT_DATA_MAX);
+		data = FIELD_PREP(PVT_THRES_HI_MASK, data);
+		mask = PVT_THRES_HI_MASK;
+	}
+
+	pvt_update(pvt->regs + pvt_info[type].thres_base, mask, data);
+
+	mutex_unlock(&pvt->iface_mtx);
+
+	return 0;
+}
+
+static int pvt_read_alarm(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			  bool is_low, long *val)
+{
+	if (is_low)
+		*val = !!READ_ONCE(pvt->cache[type].thres_sts_lo);
+	else
+		*val = !!READ_ONCE(pvt->cache[type].thres_sts_hi);
+
+	return 0;
+}
+
+static const struct hwmon_channel_info *pvt_channel_info[] = {
+	HWMON_CHANNEL_INFO(chip,
+			   HWMON_C_REGISTER_TZ | HWMON_C_UPDATE_INTERVAL),
+	HWMON_CHANNEL_INFO(temp,
+			   HWMON_T_INPUT | HWMON_T_TYPE | HWMON_T_LABEL |
+			   HWMON_T_MIN | HWMON_T_MIN_ALARM |
+			   HWMON_T_MAX | HWMON_T_MAX_ALARM |
+			   HWMON_T_OFFSET),
+	HWMON_CHANNEL_INFO(in,
+			   HWMON_I_INPUT | HWMON_I_LABEL |
+			   HWMON_I_MIN | HWMON_I_MIN_ALARM |
+			   HWMON_I_MAX | HWMON_I_MAX_ALARM,
+			   HWMON_I_INPUT | HWMON_I_LABEL |
+			   HWMON_I_MIN | HWMON_I_MIN_ALARM |
+			   HWMON_I_MAX | HWMON_I_MAX_ALARM,
+			   HWMON_I_INPUT | HWMON_I_LABEL |
+			   HWMON_I_MIN | HWMON_I_MIN_ALARM |
+			   HWMON_I_MAX | HWMON_I_MAX_ALARM,
+			   HWMON_I_INPUT | HWMON_I_LABEL |
+			   HWMON_I_MIN | HWMON_I_MIN_ALARM |
+			   HWMON_I_MAX | HWMON_I_MAX_ALARM),
+	NULL
+};
+
+#else /* !CONFIG_SENSORS_BT1_PVT_ALARMS */
+
+static irqreturn_t pvt_hard_isr(int irq, void *data)
+{
+	struct pvt_hwmon *pvt = data;
+	struct pvt_cache *cache;
+	u32 val;
+
+	/*
+	 * Mask the DVALID interrupt so after exiting from the handler a
+	 * repeated conversion wouldn't happen.
+	 */
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
+		   PVT_INTR_DVALID);
+
+	/*
+	 * Nothing special for alarm-less driver. Just read the data, update
+	 * the cache and notify a waiter of this event.
+	 */
+	val = readl(pvt->regs + PVT_DATA);
+	if (!(val & PVT_DATA_VALID)) {
+		dev_err(pvt->dev, "Got IRQ when data isn't valid\n");
+		return IRQ_HANDLED;
+	}
+
+	cache = &pvt->cache[pvt->sensor];
+
+	WRITE_ONCE(cache->data, FIELD_GET(PVT_DATA_DATA_MASK, val));
+
+	complete(&cache->conversion);
+
+	return IRQ_HANDLED;
+}
+
+#define pvt_soft_isr NULL
+
+inline umode_t pvt_limit_is_visible(enum pvt_sensor_type type)
+{
+	return 0;
+}
+
+inline umode_t pvt_alarm_is_visible(enum pvt_sensor_type type)
+{
+	return 0;
+}
+
+static int pvt_read_data(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			 long *val)
+{
+	struct pvt_cache *cache = &pvt->cache[type];
+	u32 data;
+	int ret;
+
+	/*
+	 * Lock PVT conversion interface until data cache is updated. The
+	 * data read procedure is following: set the requested PVT sensor
+	 * mode, enable IRQ and conversion, wait until conversion is finished,
+	 * then disable conversion and IRQ, and read the cached data.
+	 */
+	ret = mutex_lock_interruptible(&pvt->iface_mtx);
+	if (ret)
+		return ret;
+
+	pvt->sensor = type;
+	pvt_set_mode(pvt, pvt_info[type].mode);
+
+	/*
+	 * Unmask the DVALID interrupt and enable the sensors conversions.
+	 * Do the reverse procedure when conversion is done.
+	 */
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID, 0);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, PVT_CTRL_EN);
+
+	wait_for_completion(&cache->conversion);
+
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
+		   PVT_INTR_DVALID);
+
+	data = READ_ONCE(cache->data);
+
+	mutex_unlock(&pvt->iface_mtx);
+
+	if (type == PVT_TEMP)
+		*val = pvt_calc_poly(&poly_N_to_temp, data);
+	else
+		*val = pvt_calc_poly(&poly_N_to_volt, data);
+
+	return 0;
+}
+
+static int pvt_read_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			  bool is_low, long *val)
+{
+	return -EOPNOTSUPP;
+}
+
+static int pvt_write_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			   bool is_low, long val)
+{
+	return -EOPNOTSUPP;
+}
+
+static int pvt_read_alarm(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
+			  bool is_low, long *val)
+{
+	return -EOPNOTSUPP;
+}
+
+static const struct hwmon_channel_info *pvt_channel_info[] = {
+	HWMON_CHANNEL_INFO(chip,
+			   HWMON_C_REGISTER_TZ | HWMON_C_UPDATE_INTERVAL),
+	HWMON_CHANNEL_INFO(temp,
+			   HWMON_T_INPUT | HWMON_T_TYPE | HWMON_T_LABEL |
+			   HWMON_T_OFFSET),
+	HWMON_CHANNEL_INFO(in,
+			   HWMON_I_INPUT | HWMON_I_LABEL,
+			   HWMON_I_INPUT | HWMON_I_LABEL,
+			   HWMON_I_INPUT | HWMON_I_LABEL,
+			   HWMON_I_INPUT | HWMON_I_LABEL),
+	NULL
+};
+
+#endif /* !CONFIG_SENSORS_BT1_PVT_ALARMS */
+
+static inline bool pvt_hwmon_channel_is_valid(enum hwmon_sensor_types type,
+					      int ch)
+{
+	switch (type) {
+	case hwmon_temp:
+		if (ch < 0 || ch >= PVT_TEMP_CHS)
+			return false;
+		break;
+	case hwmon_in:
+		if (ch < 0 || ch >= PVT_VOLT_CHS)
+			return false;
+		break;
+	default:
+		break;
+	}
+
+	/* The rest of the types are independent from the channel number. */
+	return true;
+}
+
+static umode_t pvt_hwmon_is_visible(const void *data,
+				    enum hwmon_sensor_types type,
+				    u32 attr, int ch)
+{
+	if (!pvt_hwmon_channel_is_valid(type, ch))
+		return 0;
+
+	switch (type) {
+	case hwmon_chip:
+		switch (attr) {
+		case hwmon_chip_update_interval:
+			return 0644;
+		}
+		break;
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_input:
+		case hwmon_temp_type:
+		case hwmon_temp_label:
+			return 0444;
+		case hwmon_temp_min:
+		case hwmon_temp_max:
+			return pvt_limit_is_visible(ch);
+		case hwmon_temp_min_alarm:
+		case hwmon_temp_max_alarm:
+			return pvt_alarm_is_visible(ch);
+		case hwmon_temp_offset:
+			return 0644;
+		}
+		break;
+	case hwmon_in:
+		switch (attr) {
+		case hwmon_in_input:
+		case hwmon_in_label:
+			return 0444;
+		case hwmon_in_min:
+		case hwmon_in_max:
+			return pvt_limit_is_visible(PVT_VOLT + ch);
+		case hwmon_in_min_alarm:
+		case hwmon_in_max_alarm:
+			return pvt_alarm_is_visible(PVT_VOLT + ch);
+		}
+		break;
+	default:
+		break;
+	}
+
+	return 0;
+}
+
+static int pvt_read_trim(struct pvt_hwmon *pvt, long *val)
+{
+	u32 data;
+
+	data = readl(pvt->regs + PVT_CTRL);
+	*val = FIELD_GET(PVT_CTRL_TRIM_MASK, data) * PVT_TRIM_STEP;
+
+	return 0;
+}
+
+static int pvt_write_trim(struct pvt_hwmon *pvt, long val)
+{
+	u32 trim;
+	int ret;
+
+	/*
+	 * Serialize trim update, since a part of the register is changed and
+	 * the controller is supposed to be disabled during this operation.
+	 */
+	ret = mutex_lock_interruptible(&pvt->iface_mtx);
+	if (ret)
+		return ret;
+
+	trim = pvt_calc_trim(val);
+	pvt_set_trim(pvt, trim);
+
+	mutex_unlock(&pvt->iface_mtx);
+
+	return 0;
+}
+
+static int pvt_read_timeout(struct pvt_hwmon *pvt, long *val)
+{
+	unsigned long rate;
+	ktime_t kt;
+	u32 data;
+
+	rate = clk_get_rate(pvt->clks[PVT_CLOCK_REF].clk);
+	if (!rate)
+		return -ENODEV;
+
+	/*
+	 * Don't bother with mutex here, since we just read data from MMIO.
+	 * We also have to scale the ticks timeout up to compensate the
+	 * ms-ns-data translations.
+	 */
+	data = readl(pvt->regs + PVT_TTIMEOUT) + 1;
+
+	/*
+	 * Calculate ref-clock based delay (Ttotal) between two consecutive
+	 * data samples of the same sensor. So we first must calculate the
+	 * delay introduced by the internal ref-clock timer (Tref * Fclk).
+	 * Then add the constant timeout cuased by each conversion latency
+	 * (Tmin). The basic formulae for each conversion is following:
+	 *   Ttotal = Tref * Fclk + Tmin
+	 * Note if alarms are enabled the sensors are polled one after
+	 * another, so in order to have the delay being applicable for each
+	 * sensor the requested value must be equally redistirbuted.
+	 */
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+	kt = ktime_set(PVT_SENSORS_NUM * (u64)data, 0);
+	kt = ktime_divns(kt, rate);
+	kt = ktime_add_ns(kt, PVT_SENSORS_NUM * PVT_TOUT_MIN);
+#else
+	kt = ktime_set(data, 0);
+	kt = ktime_divns(kt, rate);
+	kt = ktime_add_ns(kt, PVT_TOUT_MIN);
+#endif
+
+	/* Return the result in msec as hwmon sysfs interface requires. */
+	*val = ktime_to_ms(kt);
+
+	return 0;
+}
+
+static int pvt_write_timeout(struct pvt_hwmon *pvt, long val)
+{
+	unsigned long rate;
+	ktime_t kt;
+	u32 data;
+	int ret;
+
+	rate = clk_get_rate(pvt->clks[PVT_CLOCK_REF].clk);
+	if (!rate)
+		return -ENODEV;
+
+	/*
+	 * If alarms are enabled, the requested timeout must be divided
+	 * between all available sensors to have the requested delay
+	 * applicable to each individual sensor.
+	 */
+	kt = ms_to_ktime(val);
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+	kt = ktime_divns(kt, PVT_SENSORS_NUM);
+#endif
+
+	/*
+	 * Subtract a constant lag, which always persists due to the limited
+	 * PVT sampling rate. Make sure the timeout is not negative.
+	 */
+	kt = ktime_sub_ns(kt, PVT_TOUT_MIN);
+	if (ktime_to_ns(kt) < 0)
+		kt = ktime_set(0, 0);
+
+	/*
+	 * Finally recalculate the timeout in terms of the reference clock
+	 * period.
+	 */
+	data = ktime_divns(kt * rate, NSEC_PER_SEC);
+
+	/*
+	 * Update the measurements delay, but lock the interface first, since
+	 * we have to disable PVT in order to have the new delay actually
+	 * updated.
+	 */
+	ret = mutex_lock_interruptible(&pvt->iface_mtx);
+	if (ret)
+		return ret;
+
+	pvt_set_tout(pvt, data);
+
+	mutex_unlock(&pvt->iface_mtx);
+
+	return 0;
+}
+
+static int pvt_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
+			  u32 attr, int ch, long *val)
+{
+	struct pvt_hwmon *pvt = dev_get_drvdata(dev);
+
+	if (!pvt_hwmon_channel_is_valid(type, ch))
+		return -EINVAL;
+
+	switch (type) {
+	case hwmon_chip:
+		switch (attr) {
+		case hwmon_chip_update_interval:
+			return pvt_read_timeout(pvt, val);
+		}
+		break;
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_input:
+			return pvt_read_data(pvt, ch, val);
+		case hwmon_temp_type:
+			*val = 1;
+			return 0;
+		case hwmon_temp_min:
+			return pvt_read_limit(pvt, ch, true, val);
+		case hwmon_temp_max:
+			return pvt_read_limit(pvt, ch, false, val);
+		case hwmon_temp_min_alarm:
+			return pvt_read_alarm(pvt, ch, true, val);
+		case hwmon_temp_max_alarm:
+			return pvt_read_alarm(pvt, ch, false, val);
+		case hwmon_temp_offset:
+			return pvt_read_trim(pvt, val);
+		}
+		break;
+	case hwmon_in:
+		switch (attr) {
+		case hwmon_in_input:
+			return pvt_read_data(pvt, PVT_VOLT + ch, val);
+		case hwmon_in_min:
+			return pvt_read_limit(pvt, PVT_VOLT + ch, true, val);
+		case hwmon_in_max:
+			return pvt_read_limit(pvt, PVT_VOLT + ch, false, val);
+		case hwmon_in_min_alarm:
+			return pvt_read_alarm(pvt, PVT_VOLT + ch, true, val);
+		case hwmon_in_max_alarm:
+			return pvt_read_alarm(pvt, PVT_VOLT + ch, false, val);
+		}
+		break;
+	default:
+		break;
+	}
+
+	return -EOPNOTSUPP;
+}
+
+static int pvt_hwmon_read_string(struct device *dev,
+				 enum hwmon_sensor_types type,
+				 u32 attr, int ch, const char **str)
+{
+	if (!pvt_hwmon_channel_is_valid(type, ch))
+		return -EINVAL;
+
+	switch (type) {
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_label:
+			*str = pvt_info[ch].label;
+			return 0;
+		}
+		break;
+	case hwmon_in:
+		switch (attr) {
+		case hwmon_in_label:
+			*str = pvt_info[PVT_VOLT + ch].label;
+			return 0;
+		}
+		break;
+	default:
+		break;
+	}
+
+	return -EOPNOTSUPP;
+}
+
+static int pvt_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
+			   u32 attr, int ch, long val)
+{
+	struct pvt_hwmon *pvt = dev_get_drvdata(dev);
+
+	if (!pvt_hwmon_channel_is_valid(type, ch))
+		return -EINVAL;
+
+	switch (type) {
+	case hwmon_chip:
+		switch (attr) {
+		case hwmon_chip_update_interval:
+			return pvt_write_timeout(pvt, val);
+		}
+		break;
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_min:
+			return pvt_write_limit(pvt, ch, true, val);
+		case hwmon_temp_max:
+			return pvt_write_limit(pvt, ch, false, val);
+		case hwmon_temp_offset:
+			return pvt_write_trim(pvt, val);
+		}
+		break;
+	case hwmon_in:
+		switch (attr) {
+		case hwmon_in_min:
+			return pvt_write_limit(pvt, PVT_VOLT + ch, true, val);
+		case hwmon_in_max:
+			return pvt_write_limit(pvt, PVT_VOLT + ch, false, val);
+		}
+		break;
+	default:
+		break;
+	}
+
+	return -EOPNOTSUPP;
+}
+
+static const struct hwmon_ops pvt_hwmon_ops = {
+	.is_visible = pvt_hwmon_is_visible,
+	.read = pvt_hwmon_read,
+	.read_string = pvt_hwmon_read_string,
+	.write = pvt_hwmon_write
+};
+
+static const struct hwmon_chip_info pvt_hwmon_info = {
+	.ops = &pvt_hwmon_ops,
+	.info = pvt_channel_info
+};
+
+static void pvt_clear_data(void *data)
+{
+	struct pvt_hwmon *pvt = data;
+#if !defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+	int idx;
+
+	for (idx = 0; idx < PVT_SENSORS_NUM; ++idx)
+		complete_all(&pvt->cache[idx].conversion);
+#endif
+
+	mutex_destroy(&pvt->iface_mtx);
+}
+
+static struct pvt_hwmon *pvt_create_data(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct pvt_hwmon *pvt;
+	int ret, idx;
+
+	pvt = devm_kzalloc(dev, sizeof(*pvt), GFP_KERNEL);
+	if (!pvt)
+		return ERR_PTR(-ENOMEM);
+
+	ret = devm_add_action(dev, pvt_clear_data, pvt);
+	if (ret) {
+		dev_err(dev, "Can't add PVT data clear action\n");
+		return ERR_PTR(ret);
+	}
+
+	pvt->dev = dev;
+	pvt->sensor = PVT_SENSOR_FIRST;
+	mutex_init(&pvt->iface_mtx);
+
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+	for (idx = 0; idx < PVT_SENSORS_NUM; ++idx)
+		seqlock_init(&pvt->cache[idx].data_seqlock);
+#else
+	for (idx = 0; idx < PVT_SENSORS_NUM; ++idx)
+		init_completion(&pvt->cache[idx].conversion);
+#endif
+
+	return pvt;
+}
+
+static int pvt_request_regs(struct pvt_hwmon *pvt)
+{
+	struct platform_device *pdev = to_platform_device(pvt->dev);
+	struct resource *res;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(pvt->dev, "Couldn't find PVT memresource\n");
+		return -EINVAL;
+	}
+
+	pvt->regs = devm_ioremap_resource(pvt->dev, res);
+	if (IS_ERR(pvt->regs)) {
+		dev_err(pvt->dev, "Couldn't map PVT registers\n");
+		return PTR_ERR(pvt->regs);
+	}
+
+	return 0;
+}
+
+static void pvt_disable_clks(void *data)
+{
+	struct pvt_hwmon *pvt = data;
+
+	clk_bulk_disable_unprepare(PVT_CLOCK_NUM, pvt->clks);
+}
+
+static int pvt_request_clks(struct pvt_hwmon *pvt)
+{
+	int ret;
+
+	pvt->clks[PVT_CLOCK_APB].id = "pclk";
+	pvt->clks[PVT_CLOCK_REF].id = "ref";
+
+	ret = devm_clk_bulk_get(pvt->dev, PVT_CLOCK_NUM, pvt->clks);
+	if (ret) {
+		dev_err(pvt->dev, "Couldn't get PVT clocks descriptors\n");
+		return ret;
+	}
+
+	ret = clk_bulk_prepare_enable(PVT_CLOCK_NUM, pvt->clks);
+	if (ret) {
+		dev_err(pvt->dev, "Couldn't enable the PVT clocks\n");
+		return ret;
+	}
+
+	ret = devm_add_action_or_reset(pvt->dev, pvt_disable_clks, pvt);
+	if (ret) {
+		dev_err(pvt->dev, "Can't add PVT clocks disable action\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static void pvt_init_iface(struct pvt_hwmon *pvt)
+{
+	u32 trim, temp;
+
+	/*
+	 * Make sure all interrupts and controller are disabled so not to
+	 * accidentally have ISR executed before the driver data is fully
+	 * initialized. Clear the IRQ status as well.
+	 */
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_ALL, PVT_INTR_ALL);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
+	readl(pvt->regs + PVT_CLR_INTR);
+	readl(pvt->regs + PVT_DATA);
+
+	/* Setup default sensor mode, timeout and temperature trim. */
+	pvt_set_mode(pvt, pvt_info[pvt->sensor].mode);
+	pvt_set_tout(pvt, PVT_TOUT_DEF);
+
+	trim = PVT_TRIM_DEF;
+	if (!of_property_read_u32(pvt->dev->of_node,
+	     "baikal,pvt-temp-offset-millicelsius", &temp))
+		trim = pvt_calc_trim(temp);
+
+	pvt_set_trim(pvt, trim);
+}
+
+static int pvt_request_irq(struct pvt_hwmon *pvt)
+{
+	struct platform_device *pdev = to_platform_device(pvt->dev);
+	int ret;
+
+	pvt->irq = platform_get_irq(pdev, 0);
+	if (pvt->irq < 0)
+		return pvt->irq;
+
+	ret = devm_request_threaded_irq(pvt->dev, pvt->irq,
+					pvt_hard_isr, pvt_soft_isr,
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+					IRQF_SHARED | IRQF_TRIGGER_HIGH |
+					IRQF_ONESHOT,
+#else
+					IRQF_SHARED | IRQF_TRIGGER_HIGH,
+#endif
+					"pvt", pvt);
+	if (ret) {
+		dev_err(pvt->dev, "Couldn't request PVT IRQ\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int pvt_create_hwmon(struct pvt_hwmon *pvt)
+{
+	pvt->hwmon = devm_hwmon_device_register_with_info(pvt->dev, "pvt", pvt,
+		&pvt_hwmon_info, NULL);
+	if (IS_ERR(pvt->hwmon)) {
+		dev_err(pvt->dev, "Couldn't create hwmon device\n");
+		return PTR_ERR(pvt->hwmon);
+	}
+
+	return 0;
+}
+
+#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
+
+static void pvt_disable_iface(void *data)
+{
+	struct pvt_hwmon *pvt = data;
+
+	mutex_lock(&pvt->iface_mtx);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID,
+		   PVT_INTR_DVALID);
+	mutex_unlock(&pvt->iface_mtx);
+}
+
+static int pvt_enable_iface(struct pvt_hwmon *pvt)
+{
+	int ret;
+
+	ret = devm_add_action(pvt->dev, pvt_disable_iface, pvt);
+	if (ret) {
+		dev_err(pvt->dev, "Can't add PVT disable interface action\n");
+		return ret;
+	}
+
+	/*
+	 * Enable sensors data conversion and IRQ. We need to lock the
+	 * interface mutex since hwmon has just been created and the
+	 * corresponding sysfs files are accessible from user-space,
+	 * which theoretically may cause races.
+	 */
+	mutex_lock(&pvt->iface_mtx);
+	pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_DVALID, 0);
+	pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, PVT_CTRL_EN);
+	mutex_unlock(&pvt->iface_mtx);
+
+	return 0;
+}
+
+#else /* !CONFIG_SENSORS_BT1_PVT_ALARMS */
+
+static int pvt_enable_iface(struct pvt_hwmon *pvt)
+{
+	return 0;
+}
+
+#endif /* !CONFIG_SENSORS_BT1_PVT_ALARMS */
+
+static int pvt_probe(struct platform_device *pdev)
+{
+	struct pvt_hwmon *pvt;
+	int ret;
+
+	pvt = pvt_create_data(pdev);
+	if (IS_ERR(pvt))
+		return PTR_ERR(pvt);
+
+	ret = pvt_request_regs(pvt);
+	if (ret)
+		return ret;
+
+	ret = pvt_request_clks(pvt);
+	if (ret)
+		return ret;
+
+	pvt_init_iface(pvt);
+
+	ret = pvt_request_irq(pvt);
+	if (ret)
+		return ret;
+
+	ret = pvt_create_hwmon(pvt);
+	if (ret)
+		return ret;
+
+	ret = pvt_enable_iface(pvt);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static const struct of_device_id pvt_of_match[] = {
+	{ .compatible = "baikal,bt1-pvt" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, pvt_of_match);
+
+static struct platform_driver pvt_driver = {
+	.probe = pvt_probe,
+	.driver = {
+		.name = "bt1-pvt",
+		.of_match_table = pvt_of_match
+	}
+};
+module_platform_driver(pvt_driver);
+
+MODULE_AUTHOR("Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>");
+MODULE_DESCRIPTION("Baikal-T1 PVT driver");
+MODULE_LICENSE("GPL v2");