// 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/delay.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/polynomial.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 polynomial __maybe_unused 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 polynomial 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 polynomial __maybe_unused poly_volt_to_N = {
        .total_divider = 10,
        .terms = {
                {1, 18658, 1000, 1},
                {0, -11572, 1, 1}
        }
};

static const struct polynomial poly_N_to_volt = {
        .total_divider = 10,
        .terms = {
                {1, 100000, 18658, 1},
                {0, 115720000, 1, 18658}
        }
};

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;
}

static inline umode_t pvt_limit_is_visible(enum pvt_sensor_type type)
{
        return 0644;
}

static 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 = polynomial_calc(&poly_N_to_temp, data);
        else
                *val = polynomial_calc(&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 = polynomial_calc(&poly_N_to_temp, data);
        else
                *val = polynomial_calc(&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 = polynomial_calc(&poly_temp_to_N, val);
        } else {
                val = clamp(val, PVT_VOLT_MIN, PVT_VOLT_MAX);
                data = polynomial_calc(&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 * const 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

static inline umode_t pvt_limit_is_visible(enum pvt_sensor_type type)
{
        return 0;
}

static 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];
        unsigned long timeout;
        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 with timeout since in case if the sensor is suddenly powered
         * down the request won't be completed and the caller will hang up on
         * this procedure until the power is back up again. Multiply the
         * timeout by the factor of two to prevent a false timeout.
         */
        timeout = 2 * usecs_to_jiffies(ktime_to_us(pvt->timeout));
        ret = wait_for_completion_timeout(&cache->conversion, timeout);

        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 (!ret)
                return -ETIMEDOUT;

        if (type == PVT_TEMP)
                *val = polynomial_calc(&poly_N_to_temp, data);
        else
                *val = polynomial_calc(&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 * const 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)
{
        int ret;

        ret = mutex_lock_interruptible(&pvt->iface_mtx);
        if (ret)
                return ret;

        /* Return the result in msec as hwmon sysfs interface requires. */
        *val = ktime_to_ms(pvt->timeout);

        mutex_unlock(&pvt->iface_mtx);

        return 0;
}

static int pvt_write_timeout(struct pvt_hwmon *pvt, long val)
{
        unsigned long rate;
        ktime_t kt, cache;
        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.
         */
        cache = 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);
        pvt->timeout = cache;

        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);

        pvt->regs = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(pvt->regs))
                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 int pvt_check_pwr(struct pvt_hwmon *pvt)
{
        unsigned long tout;
        int ret = 0;
        u32 data;

        /*
         * Test out the sensor conversion functionality. If it is not done on
         * time then the domain must have been unpowered and we won't be able
         * to use the device later in this driver.
         * Note If the power source is lost during the normal driver work the
         * data read procedure will either return -ETIMEDOUT (for the
         * alarm-less driver configuration) or just stop the repeated
         * conversion. In the later case alas we won't be able to detect the
         * problem.
         */
        pvt_update(pvt->regs + PVT_INTR_MASK, PVT_INTR_ALL, PVT_INTR_ALL);
        pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, PVT_CTRL_EN);
        pvt_set_tout(pvt, 0);
        readl(pvt->regs + PVT_DATA);

        tout = PVT_TOUT_MIN / NSEC_PER_USEC;
        usleep_range(tout, 2 * tout);

        data = readl(pvt->regs + PVT_DATA);
        if (!(data & PVT_DATA_VALID)) {
                ret = -ENODEV;
                dev_err(pvt->dev, "Sensor is powered down\n");
        }

        pvt_update(pvt->regs + PVT_CTRL, PVT_CTRL_EN, 0);

        return ret;
}

static int pvt_init_iface(struct pvt_hwmon *pvt)
{
        unsigned long rate;
        u32 trim, temp;

        rate = clk_get_rate(pvt->clks[PVT_CLOCK_REF].clk);
        if (!rate) {
                dev_err(pvt->dev, "Invalid reference clock rate\n");
                return -ENODEV;
        }

        /*
         * 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);

        /*
         * Preserve the current ref-clock based delay (Ttotal) between the
         * sensors data samples in the driver data so not to recalculate it
         * each time on the data requests and timeout reads. It consists of the
         * delay introduced by the internal ref-clock timer (N / Fclk) and the
         * constant timeout caused by each conversion latency (Tmin):
         *   Ttotal = N / Fclk + Tmin
         * If alarms are enabled the sensors are polled one after another and
         * in order to get the next measurement of a particular sensor the
         * caller will have to wait for at most until all the others are
         * polled. In that case the formulae will look a bit different:
         *   Ttotal = 5 * (N / Fclk + Tmin)
         */
#if defined(CONFIG_SENSORS_BT1_PVT_ALARMS)
        pvt->timeout = ktime_set(PVT_SENSORS_NUM * PVT_TOUT_DEF, 0);
        pvt->timeout = ktime_divns(pvt->timeout, rate);
        pvt->timeout = ktime_add_ns(pvt->timeout, PVT_SENSORS_NUM * PVT_TOUT_MIN);
#else
        pvt->timeout = ktime_set(PVT_TOUT_DEF, 0);
        pvt->timeout = ktime_divns(pvt->timeout, rate);
        pvt->timeout = ktime_add_ns(pvt->timeout, PVT_TOUT_MIN);
#endif

        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);

        return 0;
}

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;

        ret = pvt_check_pwr(pvt);
        if (ret)
                return ret;

        ret = pvt_init_iface(pvt);
        if (ret)
                return ret;

        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");