drivers/counter/i8254.c - pub/scm/linux/kernel/git/tnguy/next-queue - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Intel 8254 Programmable Interval Timer
  * Copyright (C) William Breathitt Gray
  */
 #include <linux/bitfield.h>
 #include <linux/bits.h>
 #include <linux/counter.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/export.h>
 #include <linux/i8254.h>
 #include <linux/limits.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/regmap.h>

 #include <linux/unaligned.h>

 #define I8254_COUNTER_REG(_counter) (_counter)
 #define I8254_CONTROL_REG 0x3

 #define I8254_SC GENMASK(7, 6)
 #define I8254_RW GENMASK(5, 4)
 #define I8254_M GENMASK(3, 1)
 #define I8254_CONTROL(_sc, _rw, _m) \
 	(u8_encode_bits(_sc, I8254_SC) | u8_encode_bits(_rw, I8254_RW) | \
 	 u8_encode_bits(_m, I8254_M))

 #define I8254_RW_TWO_BYTE 0x3
 #define I8254_MODE_INTERRUPT_ON_TERMINAL_COUNT 0
 #define I8254_MODE_HARDWARE_RETRIGGERABLE_ONESHOT 1
 #define I8254_MODE_RATE_GENERATOR 2
 #define I8254_MODE_SQUARE_WAVE_MODE 3
 #define I8254_MODE_SOFTWARE_TRIGGERED_STROBE 4
 #define I8254_MODE_HARDWARE_TRIGGERED_STROBE 5

 #define I8254_COUNTER_LATCH(_counter) I8254_CONTROL(_counter, 0x0, 0x0)
 #define I8254_PROGRAM_COUNTER(_counter, _mode) I8254_CONTROL(_counter, I8254_RW_TWO_BYTE, _mode)

 #define I8254_NUM_COUNTERS 3

 /**
  * struct i8254 - I8254 device private data structure
  * @lock:	synchronization lock to prevent I/O race conditions
  * @preset:	array of Counter Register states
  * @out_mode:	array of mode configuration states
  * @map:	Regmap for the device
  */
 struct i8254 {
 	struct mutex lock;
 	u16 preset[I8254_NUM_COUNTERS];
 	u8 out_mode[I8254_NUM_COUNTERS];
 	struct regmap *map;
 };

 static int i8254_count_read(struct counter_device *const counter, struct counter_count *const count,
 			    u64 *const val)
 {
 	struct i8254 *const priv = counter_priv(counter);
 	int ret;
 	u8 value[2];

 	mutex_lock(&priv->lock);

 	ret = regmap_write(priv->map, I8254_CONTROL_REG, I8254_COUNTER_LATCH(count->id));
 	if (ret) {
 		mutex_unlock(&priv->lock);
 		return ret;
 	}
 	ret = regmap_noinc_read(priv->map, I8254_COUNTER_REG(count->id), value, sizeof(value));
 	if (ret) {
 		mutex_unlock(&priv->lock);
 		return ret;
 	}

 	mutex_unlock(&priv->lock);

 	*val = get_unaligned_le16(value);

 	return ret;
 }

 static int i8254_function_read(struct counter_device *const counter,
 			       struct counter_count *const count,
 			       enum counter_function *const function)
 {
 	*function = COUNTER_FUNCTION_DECREASE;
 	return 0;
 }

 #define I8254_SYNAPSES_PER_COUNT 2
 #define I8254_SIGNAL_ID_CLK 0
 #define I8254_SIGNAL_ID_GATE 1

 static int i8254_action_read(struct counter_device *const counter,
 			     struct counter_count *const count,
 			     struct counter_synapse *const synapse,
 			     enum counter_synapse_action *const action)
 {
 	struct i8254 *const priv = counter_priv(counter);

 	switch (synapse->signal->id % I8254_SYNAPSES_PER_COUNT) {
 	case I8254_SIGNAL_ID_CLK:
 		*action = COUNTER_SYNAPSE_ACTION_FALLING_EDGE;
 		return 0;
 	case I8254_SIGNAL_ID_GATE:
 		switch (priv->out_mode[count->id]) {
 		case I8254_MODE_HARDWARE_RETRIGGERABLE_ONESHOT:
 		case I8254_MODE_RATE_GENERATOR:
 		case I8254_MODE_SQUARE_WAVE_MODE:
 		case I8254_MODE_HARDWARE_TRIGGERED_STROBE:
 			*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
 			return 0;
 		default:
 			*action = COUNTER_SYNAPSE_ACTION_NONE;
 			return 0;
 		}
 	default:
 		/* should never reach this path */
 		return -EINVAL;
 	}
 }

 static int i8254_count_ceiling_read(struct counter_device *const counter,
 				    struct counter_count *const count, u64 *const ceiling)
 {
 	struct i8254 *const priv = counter_priv(counter);

 	mutex_lock(&priv->lock);

 	switch (priv->out_mode[count->id]) {
 	case I8254_MODE_RATE_GENERATOR:
 		/* Rate Generator decrements 0 by one and the counter "wraps around" */
 		*ceiling = (priv->preset[count->id] == 0) ? U16_MAX : priv->preset[count->id];
 		break;
 	case I8254_MODE_SQUARE_WAVE_MODE:
 		if (priv->preset[count->id] % 2)
 			*ceiling = priv->preset[count->id] - 1;
 		else if (priv->preset[count->id] == 0)
 			/* Square Wave Mode decrements 0 by two and the counter "wraps around" */
 			*ceiling = U16_MAX - 1;
 		else
 			*ceiling = priv->preset[count->id];
 		break;
 	default:
 		*ceiling = U16_MAX;
 		break;
 	}

 	mutex_unlock(&priv->lock);

 	return 0;
 }

 static int i8254_count_mode_read(struct counter_device *const counter,
 				 struct counter_count *const count,
 				 enum counter_count_mode *const count_mode)
 {
 	const struct i8254 *const priv = counter_priv(counter);

 	switch (priv->out_mode[count->id]) {
 	case I8254_MODE_INTERRUPT_ON_TERMINAL_COUNT:
 		*count_mode = COUNTER_COUNT_MODE_INTERRUPT_ON_TERMINAL_COUNT;
 		return 0;
 	case I8254_MODE_HARDWARE_RETRIGGERABLE_ONESHOT:
 		*count_mode = COUNTER_COUNT_MODE_HARDWARE_RETRIGGERABLE_ONESHOT;
 		return 0;
 	case I8254_MODE_RATE_GENERATOR:
 		*count_mode = COUNTER_COUNT_MODE_RATE_GENERATOR;
 		return 0;
 	case I8254_MODE_SQUARE_WAVE_MODE:
 		*count_mode = COUNTER_COUNT_MODE_SQUARE_WAVE_MODE;
 		return 0;
 	case I8254_MODE_SOFTWARE_TRIGGERED_STROBE:
 		*count_mode = COUNTER_COUNT_MODE_SOFTWARE_TRIGGERED_STROBE;
 		return 0;
 	case I8254_MODE_HARDWARE_TRIGGERED_STROBE:
 		*count_mode = COUNTER_COUNT_MODE_HARDWARE_TRIGGERED_STROBE;
 		return 0;
 	default:
 		/* should never reach this path */
 		return -EINVAL;
 	}
 }

 static int i8254_count_mode_write(struct counter_device *const counter,
 				  struct counter_count *const count,
 				  const enum counter_count_mode count_mode)
 {
 	struct i8254 *const priv = counter_priv(counter);
 	u8 out_mode;
 	int ret;

 	switch (count_mode) {
 	case COUNTER_COUNT_MODE_INTERRUPT_ON_TERMINAL_COUNT:
 		out_mode = I8254_MODE_INTERRUPT_ON_TERMINAL_COUNT;
 		break;
 	case COUNTER_COUNT_MODE_HARDWARE_RETRIGGERABLE_ONESHOT:
 		out_mode = I8254_MODE_HARDWARE_RETRIGGERABLE_ONESHOT;
 		break;
 	case COUNTER_COUNT_MODE_RATE_GENERATOR:
 		out_mode = I8254_MODE_RATE_GENERATOR;
 		break;
 	case COUNTER_COUNT_MODE_SQUARE_WAVE_MODE:
 		out_mode = I8254_MODE_SQUARE_WAVE_MODE;
 		break;
 	case COUNTER_COUNT_MODE_SOFTWARE_TRIGGERED_STROBE:
 		out_mode = I8254_MODE_SOFTWARE_TRIGGERED_STROBE;
 		break;
 	case COUNTER_COUNT_MODE_HARDWARE_TRIGGERED_STROBE:
 		out_mode = I8254_MODE_HARDWARE_TRIGGERED_STROBE;
 		break;
 	default:
 		/* should never reach this path */
 		return -EINVAL;
 	}

 	mutex_lock(&priv->lock);

 	/* Counter Register is cleared when the counter is programmed */
 	priv->preset[count->id] = 0;
 	priv->out_mode[count->id] = out_mode;
 	ret = regmap_write(priv->map, I8254_CONTROL_REG,
 			   I8254_PROGRAM_COUNTER(count->id, out_mode));

 	mutex_unlock(&priv->lock);

 	return ret;
 }

 static int i8254_count_floor_read(struct counter_device *const counter,
 				  struct counter_count *const count, u64 *const floor)
 {
 	struct i8254 *const priv = counter_priv(counter);

 	mutex_lock(&priv->lock);

 	switch (priv->out_mode[count->id]) {
 	case I8254_MODE_RATE_GENERATOR:
 		/* counter is always reloaded after 1, but 0 is a possible reload value */
 		*floor = (priv->preset[count->id] == 0) ? 0 : 1;
 		break;
 	case I8254_MODE_SQUARE_WAVE_MODE:
 		/* counter is always reloaded after 2 for even preset values */
 		*floor = (priv->preset[count->id] % 2 || priv->preset[count->id] == 0) ? 0 : 2;
 		break;
 	default:
 		*floor = 0;
 		break;
 	}

 	mutex_unlock(&priv->lock);

 	return 0;
 }

 static int i8254_count_preset_read(struct counter_device *const counter,
 				   struct counter_count *const count, u64 *const preset)
 {
 	const struct i8254 *const priv = counter_priv(counter);

 	*preset = priv->preset[count->id];

 	return 0;
 }

 static int i8254_count_preset_write(struct counter_device *const counter,
 				    struct counter_count *const count, const u64 preset)
 {
 	struct i8254 *const priv = counter_priv(counter);
 	int ret;
 	u8 value[2];

 	if (preset > U16_MAX)
 		return -ERANGE;

 	mutex_lock(&priv->lock);

 	if (priv->out_mode[count->id] == I8254_MODE_RATE_GENERATOR ||
 	    priv->out_mode[count->id] == I8254_MODE_SQUARE_WAVE_MODE) {
 		if (preset == 1) {
 			mutex_unlock(&priv->lock);
 			return -EINVAL;
 		}
 	}

 	priv->preset[count->id] = preset;

 	put_unaligned_le16(preset, value);
 	ret = regmap_noinc_write(priv->map, I8254_COUNTER_REG(count->id), value, 2);

 	mutex_unlock(&priv->lock);

 	return ret;
 }

 static int i8254_init_hw(struct regmap *const map)
 {
 	unsigned long i;
 	int ret;

 	for (i = 0; i < I8254_NUM_COUNTERS; i++) {
 		/* Initialize each counter to Mode 0 */
 		ret = regmap_write(map, I8254_CONTROL_REG,
 				   I8254_PROGRAM_COUNTER(i, I8254_MODE_INTERRUPT_ON_TERMINAL_COUNT));
 		if (ret)
 			return ret;
 	}

 	return 0;
 }

 static const struct counter_ops i8254_ops = {
 	.count_read = i8254_count_read,
 	.function_read = i8254_function_read,
 	.action_read = i8254_action_read,
 };

 #define I8254_SIGNAL(_id, _name) {		\
 	.id = (_id),				\
 	.name = (_name),			\
 }

 static struct counter_signal i8254_signals[] = {
 	I8254_SIGNAL(0, "CLK 0"), I8254_SIGNAL(1, "GATE 0"),
 	I8254_SIGNAL(2, "CLK 1"), I8254_SIGNAL(3, "GATE 1"),
 	I8254_SIGNAL(4, "CLK 2"), I8254_SIGNAL(5, "GATE 2"),
 };

 static const enum counter_synapse_action i8254_clk_actions[] = {
 	COUNTER_SYNAPSE_ACTION_FALLING_EDGE,
 };
 static const enum counter_synapse_action i8254_gate_actions[] = {
 	COUNTER_SYNAPSE_ACTION_NONE,
 	COUNTER_SYNAPSE_ACTION_RISING_EDGE,
 };

 #define I8254_SYNAPSES_BASE(_id) ((_id) * I8254_SYNAPSES_PER_COUNT)
 #define I8254_SYNAPSE_CLK(_id) {					\
 	.actions_list	= i8254_clk_actions,				\
 	.num_actions	= ARRAY_SIZE(i8254_clk_actions),		\
 	.signal		= &i8254_signals[I8254_SYNAPSES_BASE(_id) + 0],	\
 }
 #define I8254_SYNAPSE_GATE(_id) {					\
 	.actions_list	= i8254_gate_actions,				\
 	.num_actions	= ARRAY_SIZE(i8254_gate_actions),		\
 	.signal		= &i8254_signals[I8254_SYNAPSES_BASE(_id) + 1],	\
 }

 static struct counter_synapse i8254_synapses[] = {
 	I8254_SYNAPSE_CLK(0), I8254_SYNAPSE_GATE(0),
 	I8254_SYNAPSE_CLK(1), I8254_SYNAPSE_GATE(1),
 	I8254_SYNAPSE_CLK(2), I8254_SYNAPSE_GATE(2),
 };

 static const enum counter_function i8254_functions_list[] = {
 	COUNTER_FUNCTION_DECREASE,
 };

 static const enum counter_count_mode i8254_count_modes[] = {
 	COUNTER_COUNT_MODE_INTERRUPT_ON_TERMINAL_COUNT,
 	COUNTER_COUNT_MODE_HARDWARE_RETRIGGERABLE_ONESHOT,
 	COUNTER_COUNT_MODE_RATE_GENERATOR,
 	COUNTER_COUNT_MODE_SQUARE_WAVE_MODE,
 	COUNTER_COUNT_MODE_SOFTWARE_TRIGGERED_STROBE,
 	COUNTER_COUNT_MODE_HARDWARE_TRIGGERED_STROBE,
 };

 static DEFINE_COUNTER_AVAILABLE(i8254_count_modes_available, i8254_count_modes);

 static struct counter_comp i8254_count_ext[] = {
 	COUNTER_COMP_CEILING(i8254_count_ceiling_read, NULL),
 	COUNTER_COMP_COUNT_MODE(i8254_count_mode_read, i8254_count_mode_write,
 				i8254_count_modes_available),
 	COUNTER_COMP_FLOOR(i8254_count_floor_read, NULL),
 	COUNTER_COMP_PRESET(i8254_count_preset_read, i8254_count_preset_write),
 };

 #define I8254_COUNT(_id, _name) {				\
 	.id = (_id),						\
 	.name = (_name),					\
 	.functions_list = i8254_functions_list,			\
 	.num_functions = ARRAY_SIZE(i8254_functions_list),	\
 	.synapses = &i8254_synapses[I8254_SYNAPSES_BASE(_id)],	\
 	.num_synapses =	I8254_SYNAPSES_PER_COUNT,		\
 	.ext = i8254_count_ext,					\
 	.num_ext = ARRAY_SIZE(i8254_count_ext)			\
 }

 static struct counter_count i8254_counts[I8254_NUM_COUNTERS] = {
 	I8254_COUNT(0, "Counter 0"), I8254_COUNT(1, "Counter 1"), I8254_COUNT(2, "Counter 2"),
 };

 /**
  * devm_i8254_regmap_register - Register an i8254 Counter device
  * @dev: device that is registering this i8254 Counter device
  * @config: configuration for i8254_regmap_config
  *
  * Registers an Intel 8254 Programmable Interval Timer Counter device. Returns 0 on success and
  * negative error number on failure.
  */
 int devm_i8254_regmap_register(struct device *const dev,
 			       const struct i8254_regmap_config *const config)
 {
 	struct counter_device *counter;
 	struct i8254 *priv;
 	int err;

 	if (!config->parent)
 		return -EINVAL;

 	if (!config->map)
 		return -EINVAL;

 	counter = devm_counter_alloc(dev, sizeof(*priv));
 	if (!counter)
 		return -ENOMEM;
 	priv = counter_priv(counter);
 	priv->map = config->map;

 	counter->name = dev_name(config->parent);
 	counter->parent = config->parent;
 	counter->ops = &i8254_ops;
 	counter->counts = i8254_counts;
 	counter->num_counts = ARRAY_SIZE(i8254_counts);
 	counter->signals = i8254_signals;
 	counter->num_signals = ARRAY_SIZE(i8254_signals);

 	mutex_init(&priv->lock);

 	err = i8254_init_hw(priv->map);
 	if (err)
 		return err;

 	err = devm_counter_add(dev, counter);
 	if (err < 0)
 		return dev_err_probe(dev, err, "Failed to add counter\n");

 	return 0;
 }
 EXPORT_SYMBOL_NS_GPL(devm_i8254_regmap_register, "I8254");

 MODULE_AUTHOR("William Breathitt Gray");
 MODULE_DESCRIPTION("Intel 8254 Programmable Interval Timer");
 MODULE_LICENSE("GPL");
 MODULE_IMPORT_NS("COUNTER");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Intel 8254 Programmable Interval Timer
	* Copyright (C) William Breathitt Gray
	*/
	#include <linux/bitfield.h>
	#include <linux/bits.h>
	#include <linux/counter.h>
	#include <linux/device.h>
	#include <linux/err.h>
	#include <linux/export.h>
	#include <linux/i8254.h>
	#include <linux/limits.h>
	#include <linux/module.h>
	#include <linux/mutex.h>
	#include <linux/regmap.h>

	#include <linux/unaligned.h>

	#define I8254_COUNTER_REG(_counter) (_counter)
	#define I8254_CONTROL_REG 0x3

	#define I8254_SC GENMASK(7, 6)
	#define I8254_RW GENMASK(5, 4)
	#define I8254_M GENMASK(3, 1)
	#define I8254_CONTROL(_sc, _rw, _m) \
	(u8_encode_bits(_sc, I8254_SC) \| u8_encode_bits(_rw, I8254_RW) \| \
	u8_encode_bits(_m, I8254_M))

	#define I8254_RW_TWO_BYTE 0x3
	#define I8254_MODE_INTERRUPT_ON_TERMINAL_COUNT 0
	#define I8254_MODE_HARDWARE_RETRIGGERABLE_ONESHOT 1
	#define I8254_MODE_RATE_GENERATOR 2
	#define I8254_MODE_SQUARE_WAVE_MODE 3
	#define I8254_MODE_SOFTWARE_TRIGGERED_STROBE 4
	#define I8254_MODE_HARDWARE_TRIGGERED_STROBE 5

	#define I8254_COUNTER_LATCH(_counter) I8254_CONTROL(_counter, 0x0, 0x0)
	#define I8254_PROGRAM_COUNTER(_counter, _mode) I8254_CONTROL(_counter, I8254_RW_TWO_BYTE, _mode)

	#define I8254_NUM_COUNTERS 3

	/**
	* struct i8254 - I8254 device private data structure
	* @lock: synchronization lock to prevent I/O race conditions
	* @preset: array of Counter Register states
	* @out_mode: array of mode configuration states
	* @map: Regmap for the device
	*/
	struct i8254 {
	struct mutex lock;
	u16 preset[I8254_NUM_COUNTERS];
	u8 out_mode[I8254_NUM_COUNTERS];
	struct regmap *map;
	};

	static int i8254_count_read(struct counter_device const counter, struct counter_count const count,
	u64 *const val)
	{
	struct i8254 *const priv = counter_priv(counter);
	int ret;
	u8 value[2];

	mutex_lock(&priv->lock);

	ret = regmap_write(priv->map, I8254_CONTROL_REG, I8254_COUNTER_LATCH(count->id));
	if (ret) {
	mutex_unlock(&priv->lock);
	return ret;
	}
	ret = regmap_noinc_read(priv->map, I8254_COUNTER_REG(count->id), value, sizeof(value));
	if (ret) {
	mutex_unlock(&priv->lock);
	return ret;
	}

	mutex_unlock(&priv->lock);

	*val = get_unaligned_le16(value);

	return ret;
	}

	static int i8254_function_read(struct counter_device *const counter,
	struct counter_count *const count,
	enum counter_function *const function)
	{
	*function = COUNTER_FUNCTION_DECREASE;
	return 0;
	}

	#define I8254_SYNAPSES_PER_COUNT 2
	#define I8254_SIGNAL_ID_CLK 0
	#define I8254_SIGNAL_ID_GATE 1

	static int i8254_action_read(struct counter_device *const counter,
	struct counter_count *const count,
	struct counter_synapse *const synapse,
	enum counter_synapse_action *const action)
	{
	struct i8254 *const priv = counter_priv(counter);

	switch (synapse->signal->id % I8254_SYNAPSES_PER_COUNT) {
	case I8254_SIGNAL_ID_CLK:
	*action = COUNTER_SYNAPSE_ACTION_FALLING_EDGE;
	return 0;
	case I8254_SIGNAL_ID_GATE:
	switch (priv->out_mode[count->id]) {
	case I8254_MODE_HARDWARE_RETRIGGERABLE_ONESHOT:
	case I8254_MODE_RATE_GENERATOR:
	case I8254_MODE_SQUARE_WAVE_MODE:
	case I8254_MODE_HARDWARE_TRIGGERED_STROBE:
	*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
	return 0;
	default:
	*action = COUNTER_SYNAPSE_ACTION_NONE;
	return 0;
	}
	default:
	/* should never reach this path */
	return -EINVAL;
	}
	}

	static int i8254_count_ceiling_read(struct counter_device *const counter,
	struct counter_count const count, u64 const ceiling)
	{
	struct i8254 *const priv = counter_priv(counter);

	mutex_lock(&priv->lock);

	switch (priv->out_mode[count->id]) {
	case I8254_MODE_RATE_GENERATOR:
	/* Rate Generator decrements 0 by one and the counter "wraps around" */
	*ceiling = (priv->preset[count->id] == 0) ? U16_MAX : priv->preset[count->id];
	break;
	case I8254_MODE_SQUARE_WAVE_MODE:
	if (priv->preset[count->id] % 2)
	*ceiling = priv->preset[count->id] - 1;
	else if (priv->preset[count->id] == 0)
	/* Square Wave Mode decrements 0 by two and the counter "wraps around" */
	*ceiling = U16_MAX - 1;
	else
	*ceiling = priv->preset[count->id];
	break;
	default:
	*ceiling = U16_MAX;
	break;
	}

	mutex_unlock(&priv->lock);

	return 0;
	}

	static int i8254_count_mode_read(struct counter_device *const counter,
	struct counter_count *const count,
	enum counter_count_mode *const count_mode)
	{
	const struct i8254 *const priv = counter_priv(counter);

	switch (priv->out_mode[count->id]) {
	case I8254_MODE_INTERRUPT_ON_TERMINAL_COUNT:
	*count_mode = COUNTER_COUNT_MODE_INTERRUPT_ON_TERMINAL_COUNT;
	return 0;
	case I8254_MODE_HARDWARE_RETRIGGERABLE_ONESHOT:
	*count_mode = COUNTER_COUNT_MODE_HARDWARE_RETRIGGERABLE_ONESHOT;
	return 0;
	case I8254_MODE_RATE_GENERATOR:
	*count_mode = COUNTER_COUNT_MODE_RATE_GENERATOR;
	return 0;
	case I8254_MODE_SQUARE_WAVE_MODE:
	*count_mode = COUNTER_COUNT_MODE_SQUARE_WAVE_MODE;
	return 0;
	case I8254_MODE_SOFTWARE_TRIGGERED_STROBE:
	*count_mode = COUNTER_COUNT_MODE_SOFTWARE_TRIGGERED_STROBE;
	return 0;
	case I8254_MODE_HARDWARE_TRIGGERED_STROBE:
	*count_mode = COUNTER_COUNT_MODE_HARDWARE_TRIGGERED_STROBE;
	return 0;
	default:
	/* should never reach this path */
	return -EINVAL;
	}
	}

	static int i8254_count_mode_write(struct counter_device *const counter,
	struct counter_count *const count,
	const enum counter_count_mode count_mode)
	{
	struct i8254 *const priv = counter_priv(counter);
	u8 out_mode;
	int ret;

	switch (count_mode) {
	case COUNTER_COUNT_MODE_INTERRUPT_ON_TERMINAL_COUNT:
	out_mode = I8254_MODE_INTERRUPT_ON_TERMINAL_COUNT;
	break;
	case COUNTER_COUNT_MODE_HARDWARE_RETRIGGERABLE_ONESHOT:
	out_mode = I8254_MODE_HARDWARE_RETRIGGERABLE_ONESHOT;
	break;
	case COUNTER_COUNT_MODE_RATE_GENERATOR:
	out_mode = I8254_MODE_RATE_GENERATOR;
	break;
	case COUNTER_COUNT_MODE_SQUARE_WAVE_MODE:
	out_mode = I8254_MODE_SQUARE_WAVE_MODE;
	break;
	case COUNTER_COUNT_MODE_SOFTWARE_TRIGGERED_STROBE:
	out_mode = I8254_MODE_SOFTWARE_TRIGGERED_STROBE;
	break;
	case COUNTER_COUNT_MODE_HARDWARE_TRIGGERED_STROBE:
	out_mode = I8254_MODE_HARDWARE_TRIGGERED_STROBE;
	break;
	default:
	/* should never reach this path */
	return -EINVAL;
	}

	mutex_lock(&priv->lock);

	/* Counter Register is cleared when the counter is programmed */
	priv->preset[count->id] = 0;
	priv->out_mode[count->id] = out_mode;
	ret = regmap_write(priv->map, I8254_CONTROL_REG,
	I8254_PROGRAM_COUNTER(count->id, out_mode));

	mutex_unlock(&priv->lock);

	return ret;
	}

	static int i8254_count_floor_read(struct counter_device *const counter,
	struct counter_count const count, u64 const floor)
	{
	struct i8254 *const priv = counter_priv(counter);

	mutex_lock(&priv->lock);

	switch (priv->out_mode[count->id]) {
	case I8254_MODE_RATE_GENERATOR:
	/* counter is always reloaded after 1, but 0 is a possible reload value */
	*floor = (priv->preset[count->id] == 0) ? 0 : 1;
	break;
	case I8254_MODE_SQUARE_WAVE_MODE:
	/* counter is always reloaded after 2 for even preset values */
	*floor = (priv->preset[count->id] % 2 \|\| priv->preset[count->id] == 0) ? 0 : 2;
	break;
	default:
	*floor = 0;
	break;
	}

	mutex_unlock(&priv->lock);

	return 0;
	}

	static int i8254_count_preset_read(struct counter_device *const counter,
	struct counter_count const count, u64 const preset)
	{
	const struct i8254 *const priv = counter_priv(counter);

	*preset = priv->preset[count->id];

	return 0;
	}

	static int i8254_count_preset_write(struct counter_device *const counter,
	struct counter_count *const count, const u64 preset)
	{
	struct i8254 *const priv = counter_priv(counter);
	int ret;
	u8 value[2];

	if (preset > U16_MAX)
	return -ERANGE;

	mutex_lock(&priv->lock);

	if (priv->out_mode[count->id] == I8254_MODE_RATE_GENERATOR \|\|
	priv->out_mode[count->id] == I8254_MODE_SQUARE_WAVE_MODE) {
	if (preset == 1) {
	mutex_unlock(&priv->lock);
	return -EINVAL;
	}
	}

	priv->preset[count->id] = preset;

	put_unaligned_le16(preset, value);
	ret = regmap_noinc_write(priv->map, I8254_COUNTER_REG(count->id), value, 2);

	mutex_unlock(&priv->lock);

	return ret;
	}

	static int i8254_init_hw(struct regmap *const map)
	{
	unsigned long i;
	int ret;

	for (i = 0; i < I8254_NUM_COUNTERS; i++) {
	/* Initialize each counter to Mode 0 */
	ret = regmap_write(map, I8254_CONTROL_REG,
	I8254_PROGRAM_COUNTER(i, I8254_MODE_INTERRUPT_ON_TERMINAL_COUNT));
	if (ret)
	return ret;
	}

	return 0;
	}

	static const struct counter_ops i8254_ops = {
	.count_read = i8254_count_read,
	.function_read = i8254_function_read,
	.action_read = i8254_action_read,
	};

	#define I8254_SIGNAL(_id, _name) { \
	.id = (_id), \
	.name = (_name), \
	}

	static struct counter_signal i8254_signals[] = {
	I8254_SIGNAL(0, "CLK 0"), I8254_SIGNAL(1, "GATE 0"),
	I8254_SIGNAL(2, "CLK 1"), I8254_SIGNAL(3, "GATE 1"),
	I8254_SIGNAL(4, "CLK 2"), I8254_SIGNAL(5, "GATE 2"),
	};

	static const enum counter_synapse_action i8254_clk_actions[] = {
	COUNTER_SYNAPSE_ACTION_FALLING_EDGE,
	};
	static const enum counter_synapse_action i8254_gate_actions[] = {
	COUNTER_SYNAPSE_ACTION_NONE,
	COUNTER_SYNAPSE_ACTION_RISING_EDGE,
	};

	#define I8254_SYNAPSES_BASE(_id) ((_id) * I8254_SYNAPSES_PER_COUNT)
	#define I8254_SYNAPSE_CLK(_id) { \
	.actions_list = i8254_clk_actions, \
	.num_actions = ARRAY_SIZE(i8254_clk_actions), \
	.signal = &i8254_signals[I8254_SYNAPSES_BASE(_id) + 0], \
	}
	#define I8254_SYNAPSE_GATE(_id) { \
	.actions_list = i8254_gate_actions, \
	.num_actions = ARRAY_SIZE(i8254_gate_actions), \
	.signal = &i8254_signals[I8254_SYNAPSES_BASE(_id) + 1], \
	}

	static struct counter_synapse i8254_synapses[] = {
	I8254_SYNAPSE_CLK(0), I8254_SYNAPSE_GATE(0),
	I8254_SYNAPSE_CLK(1), I8254_SYNAPSE_GATE(1),
	I8254_SYNAPSE_CLK(2), I8254_SYNAPSE_GATE(2),
	};

	static const enum counter_function i8254_functions_list[] = {
	COUNTER_FUNCTION_DECREASE,
	};

	static const enum counter_count_mode i8254_count_modes[] = {
	COUNTER_COUNT_MODE_INTERRUPT_ON_TERMINAL_COUNT,
	COUNTER_COUNT_MODE_HARDWARE_RETRIGGERABLE_ONESHOT,
	COUNTER_COUNT_MODE_RATE_GENERATOR,
	COUNTER_COUNT_MODE_SQUARE_WAVE_MODE,
	COUNTER_COUNT_MODE_SOFTWARE_TRIGGERED_STROBE,
	COUNTER_COUNT_MODE_HARDWARE_TRIGGERED_STROBE,
	};

	static DEFINE_COUNTER_AVAILABLE(i8254_count_modes_available, i8254_count_modes);

	static struct counter_comp i8254_count_ext[] = {
	COUNTER_COMP_CEILING(i8254_count_ceiling_read, NULL),
	COUNTER_COMP_COUNT_MODE(i8254_count_mode_read, i8254_count_mode_write,
	i8254_count_modes_available),
	COUNTER_COMP_FLOOR(i8254_count_floor_read, NULL),
	COUNTER_COMP_PRESET(i8254_count_preset_read, i8254_count_preset_write),
	};

	#define I8254_COUNT(_id, _name) { \
	.id = (_id), \
	.name = (_name), \
	.functions_list = i8254_functions_list, \
	.num_functions = ARRAY_SIZE(i8254_functions_list), \
	.synapses = &i8254_synapses[I8254_SYNAPSES_BASE(_id)], \
	.num_synapses = I8254_SYNAPSES_PER_COUNT, \
	.ext = i8254_count_ext, \
	.num_ext = ARRAY_SIZE(i8254_count_ext) \
	}

	static struct counter_count i8254_counts[I8254_NUM_COUNTERS] = {
	I8254_COUNT(0, "Counter 0"), I8254_COUNT(1, "Counter 1"), I8254_COUNT(2, "Counter 2"),
	};

	/**
	* devm_i8254_regmap_register - Register an i8254 Counter device
	* @dev: device that is registering this i8254 Counter device
	* @config: configuration for i8254_regmap_config
	*
	* Registers an Intel 8254 Programmable Interval Timer Counter device. Returns 0 on success and
	* negative error number on failure.
	*/
	int devm_i8254_regmap_register(struct device *const dev,
	const struct i8254_regmap_config *const config)
	{
	struct counter_device *counter;
	struct i8254 *priv;
	int err;

	if (!config->parent)
	return -EINVAL;

	if (!config->map)
	return -EINVAL;

	counter = devm_counter_alloc(dev, sizeof(*priv));
	if (!counter)
	return -ENOMEM;
	priv = counter_priv(counter);
	priv->map = config->map;

	counter->name = dev_name(config->parent);
	counter->parent = config->parent;
	counter->ops = &i8254_ops;
	counter->counts = i8254_counts;
	counter->num_counts = ARRAY_SIZE(i8254_counts);
	counter->signals = i8254_signals;
	counter->num_signals = ARRAY_SIZE(i8254_signals);

	mutex_init(&priv->lock);

	err = i8254_init_hw(priv->map);
	if (err)
	return err;

	err = devm_counter_add(dev, counter);
	if (err < 0)
	return dev_err_probe(dev, err, "Failed to add counter\n");

	return 0;
	}
	EXPORT_SYMBOL_NS_GPL(devm_i8254_regmap_register, "I8254");

	MODULE_AUTHOR("William Breathitt Gray");
	MODULE_DESCRIPTION("Intel 8254 Programmable Interval Timer");
	MODULE_LICENSE("GPL");
	MODULE_IMPORT_NS("COUNTER");