Merge tag 'counter-updates-for-6.5a' of...

Merge tag 'counter-updates-for-6.5a' of git://git.kernel.org/pub/scm/linux/kernel/git/wbg/counter into char-misc-next

William writes:

First set of Counter updates for the 6.5 cycle

Biggest changes in this set include the introduction of a new Intel 8254
interface library module and the refactoring of the existing 104-quad-8
modules to migrate it to the regmap API. Some other minor cleanups
touching tools/counter and stm32-timer-cnt are also present.

Changes
* 104-quad-8
  - Remove reference in Kconfig to 25-bit counter value
  - Utilize bitfield access macros
  - Refactor to buffer states for CMR, IOR, and IDR
  - Utilize helper functions to handle PR, FLAG and PSC
  - Migrate to the regmap API
* i8254
  - Introduce the Intel 8254 interface library module
* stm32-timer-cnt
  - Reset TIM_TISEL to its default value in probe
* tools/counter
  - Add .gitignore
  - Remove lingering 'include' directories on make clean

* tag 'counter-updates-for-6.5a' of git://git.kernel.org/pub/scm/linux/kernel/git/wbg/counter:
  counter: i8254: Introduce the Intel 8254 interface library module
  counter: 104-quad-8: Migrate to the regmap API
  counter: 104-quad-8: Utilize helper functions to handle PR, FLAG and PSC
  counter: 104-quad-8: Refactor to buffer states for CMR, IOR, and IDR
  counter: 104-quad-8: Utilize bitfield access macros
  tools/counter: Makefile: Remove lingering 'include' directories on make clean
  tools/counter: Add .gitignore
  counter: stm32-timer-cnt: Reset TIM_TISEL to its default value in probe
  counter: 104-quad-8: Remove reference in Kconfig to 25-bit counter value

Documentation/ABI/testing/sysfs-bus-counter

@@ -90,6 +90,60 @@ Description:
 			counter does not freeze at the boundary points, but
 			counts continuously throughout.
 
+		interrupt on terminal count:
+			The output signal is initially low, and will remain low
+			until the counter reaches zero. The output signal then
+			goes high and remains high until a new preset value is
+			set.
+
+		hardware retriggerable one-shot:
+			The output signal is initially high. The output signal
+			will go low by a trigger input signal, and will remain
+			low until the counter reaches zero. The output will then
+			go high and remain high until the next trigger. A
+			trigger results in loading the counter to the preset
+			value and setting the output signal low, thus starting
+			the one-shot pulse.
+
+		rate generator:
+			The output signal is initially high. When the counter
+			has decremented to 1, the output signal goes low for one
+			clock pulse. The output signal then goes high again, the
+			counter is reloaded to the preset value, and the process
+			repeats in a periodic manner as such.
+
+		square wave mode:
+			The output signal is initially high.
+
+			If the initial count is even, the counter is decremented
+			by two on succeeding clock pulses. When the count
+			expires, the output signal changes value and the
+			counter is reloaded to the preset value. The process
+			repeats in periodic manner as such.
+
+			If the initial count is odd, the initial count minus one
+			(an even number) is loaded and then is decremented by
+			two on succeeding clock pulses. One clock pulse after
+			the count expires, the output signal goes low and the
+			counter is reloaded to the preset value minus one.
+			Succeeding clock pulses decrement the count by two. When
+			the count expires, the output goes high again and the
+			counter is reloaded to the preset value minus one. The
+			process repeats in a periodic manner as such.
+
+		software triggered strobe:
+			The output signal is initially high. When the count
+			expires, the output will go low for one clock pulse and
+			then go high again. The counting sequence is "triggered"
+			by setting the preset value.
+
+		hardware triggered strobe:
+			The output signal is initially high. Counting is started
+			by a trigger input signal. When the count expires, the
+			output signal will go low for one clock pulse and then
+			go high again. A trigger results in loading the counter
+			to the preset value.
+
 What:		/sys/bus/counter/devices/counterX/countY/count_mode_available
 What:		/sys/bus/counter/devices/counterX/countY/error_noise_available
 What:		/sys/bus/counter/devices/counterX/countY/function_available

MAINTAINERS

@@ -10260,6 +10260,13 @@ L:	linux-fbdev@vger.kernel.org
 S:	Maintained
 F:	drivers/video/fbdev/i810/
 
+INTEL 8254 COUNTER DRIVER
+M:	William Breathitt Gray <william.gray@linaro.org>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	drivers/counter/i8254.c
+F:	include/linux/i8254.h
+
 INTEL 8255 GPIO DRIVER
 M:	William Breathitt Gray <william.gray@linaro.org>
 L:	linux-gpio@vger.kernel.org

drivers/counter/104-quad-8.c

@@ -5,10 +5,11 @@
  *
  * This driver supports the ACCES 104-QUAD-8 and ACCES 104-QUAD-4.
  */
-#include <linux/bitops.h>
+#include <linux/bitfield.h>
+#include <linux/bits.h>
 #include <linux/counter.h>
 #include <linux/device.h>
-#include <linux/errno.h>
+#include <linux/err.h>
 #include <linux/io.h>
 #include <linux/ioport.h>
 #include <linux/interrupt.h>
@@ -17,8 +18,11 @@
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
-#include <linux/types.h>
+#include <linux/regmap.h>
 #include <linux/spinlock.h>
+#include <linux/types.h>
+
+#include <asm/unaligned.h>
 
 #define QUAD8_EXTENT 32
 
@@ -34,118 +38,196 @@ MODULE_PARM_DESC(irq, "ACCES 104-QUAD-8 interrupt line numbers");
 
 #define QUAD8_NUM_COUNTERS 8
 
-/**
- * struct channel_reg - channel register structure
- * @data:	Count data
- * @control:	Channel flags and control
- */
-struct channel_reg {
-	u8 data;
-	u8 control;
-};
-
-/**
- * struct quad8_reg - device register structure
- * @channel:		quadrature counter data and control
- * @interrupt_status:	channel interrupt status
- * @channel_oper:	enable/reset counters and interrupt functions
- * @index_interrupt:	enable channel interrupts
- * @reserved:		reserved for Factory Use
- * @index_input_levels:	index signal logical input level
- * @cable_status:	differential encoder cable status
- */
-struct quad8_reg {
-	struct channel_reg channel[QUAD8_NUM_COUNTERS];
-	u8 interrupt_status;
-	u8 channel_oper;
-	u8 index_interrupt;
-	u8 reserved[3];
-	u8 index_input_levels;
-	u8 cable_status;
-};
+#define QUAD8_DATA(_channel) ((_channel) * 2)
+#define QUAD8_CONTROL(_channel) (QUAD8_DATA(_channel) + 1)
+#define QUAD8_INTERRUPT_STATUS 0x10
+#define QUAD8_CHANNEL_OPERATION 0x11
+#define QUAD8_INDEX_INTERRUPT 0x12
+#define QUAD8_INDEX_INPUT_LEVELS 0x16
+#define QUAD8_CABLE_STATUS 0x17
 
 /**
  * struct quad8 - device private data structure
  * @lock:		lock to prevent clobbering device states during R/W ops
- * @counter:		instance of the counter_device
+ * @cmr:		array of Counter Mode Register states
+ * @ior:		array of Input / Output Control Register states
+ * @idr:		array of Index Control Register states
  * @fck_prescaler:	array of filter clock prescaler configurations
  * @preset:		array of preset values
- * @count_mode:		array of count mode configurations
- * @quadrature_mode:	array of quadrature mode configurations
- * @quadrature_scale:	array of quadrature mode scale configurations
- * @ab_enable:		array of A and B inputs enable configurations
- * @preset_enable:	array of set_to_preset_on_index attribute configurations
- * @irq_trigger:	array of current IRQ trigger function configurations
- * @synchronous_mode:	array of index function synchronous mode configurations
- * @index_polarity:	array of index function polarity configurations
  * @cable_fault_enable:	differential encoder cable status enable configurations
- * @reg:		I/O address offset for the device registers
+ * @map:		regmap for the device
  */
 struct quad8 {
 	spinlock_t lock;
+	u8 cmr[QUAD8_NUM_COUNTERS];
+	u8 ior[QUAD8_NUM_COUNTERS];
+	u8 idr[QUAD8_NUM_COUNTERS];
 	unsigned int fck_prescaler[QUAD8_NUM_COUNTERS];
 	unsigned int preset[QUAD8_NUM_COUNTERS];
-	unsigned int count_mode[QUAD8_NUM_COUNTERS];
-	unsigned int quadrature_mode[QUAD8_NUM_COUNTERS];
-	unsigned int quadrature_scale[QUAD8_NUM_COUNTERS];
-	unsigned int ab_enable[QUAD8_NUM_COUNTERS];
-	unsigned int preset_enable[QUAD8_NUM_COUNTERS];
-	unsigned int irq_trigger[QUAD8_NUM_COUNTERS];
-	unsigned int synchronous_mode[QUAD8_NUM_COUNTERS];
-	unsigned int index_polarity[QUAD8_NUM_COUNTERS];
 	unsigned int cable_fault_enable;
-	struct quad8_reg __iomem *reg;
+	struct regmap *map;
+};
+
+static const struct regmap_range quad8_wr_ranges[] = {
+	regmap_reg_range(0x0, 0xF), regmap_reg_range(0x11, 0x12), regmap_reg_range(0x17, 0x17),
+};
+static const struct regmap_range quad8_rd_ranges[] = {
+	regmap_reg_range(0x0, 0x12), regmap_reg_range(0x16, 0x18),
+};
+static const struct regmap_access_table quad8_wr_table = {
+	.yes_ranges = quad8_wr_ranges,
+	.n_yes_ranges = ARRAY_SIZE(quad8_wr_ranges),
+};
+static const struct regmap_access_table quad8_rd_table = {
+	.yes_ranges = quad8_rd_ranges,
+	.n_yes_ranges = ARRAY_SIZE(quad8_rd_ranges),
+};
+static const struct regmap_config quad8_regmap_config = {
+	.reg_bits = 8,
+	.reg_stride = 1,
+	.val_bits = 8,
+	.io_port = true,
+	.wr_table = &quad8_wr_table,
+	.rd_table = &quad8_rd_table,
 };
 
 /* Error flag */
-#define QUAD8_FLAG_E BIT(4)
+#define FLAG_E BIT(4)
 /* Up/Down flag */
-#define QUAD8_FLAG_UD BIT(5)
+#define FLAG_UD BIT(5)
+/* Counting up */
+#define UP 0x1
+
+#define REGISTER_SELECTION GENMASK(6, 5)
+
 /* Reset and Load Signal Decoders */
-#define QUAD8_CTR_RLD 0x00
+#define SELECT_RLD u8_encode_bits(0x0, REGISTER_SELECTION)
 /* Counter Mode Register */
-#define QUAD8_CTR_CMR 0x20
+#define SELECT_CMR u8_encode_bits(0x1, REGISTER_SELECTION)
 /* Input / Output Control Register */
-#define QUAD8_CTR_IOR 0x40
+#define SELECT_IOR u8_encode_bits(0x2, REGISTER_SELECTION)
 /* Index Control Register */
-#define QUAD8_CTR_IDR 0x60
+#define SELECT_IDR u8_encode_bits(0x3, REGISTER_SELECTION)
+
+/*
+ * Reset and Load Signal Decoders
+ */
+#define RESETS GENMASK(2, 1)
+#define LOADS GENMASK(4, 3)
 /* Reset Byte Pointer (three byte data pointer) */
-#define QUAD8_RLD_RESET_BP 0x01
-/* Reset Counter */
-#define QUAD8_RLD_RESET_CNTR 0x02
-/* Reset Borrow Toggle, Carry Toggle, Compare Toggle, and Sign flags */
-#define QUAD8_RLD_RESET_FLAGS 0x04
+#define RESET_BP BIT(0)
+/* Reset Borrow Toggle, Carry toggle, Compare toggle, Sign, and Index flags */
+#define RESET_BT_CT_CPT_S_IDX u8_encode_bits(0x2, RESETS)
 /* Reset Error flag */
-#define QUAD8_RLD_RESET_E 0x06
+#define RESET_E u8_encode_bits(0x3, RESETS)
 /* Preset Register to Counter */
-#define QUAD8_RLD_PRESET_CNTR 0x08
+#define TRANSFER_PR_TO_CNTR u8_encode_bits(0x1, LOADS)
 /* Transfer Counter to Output Latch */
-#define QUAD8_RLD_CNTR_OUT 0x10
+#define TRANSFER_CNTR_TO_OL u8_encode_bits(0x2, LOADS)
 /* Transfer Preset Register LSB to FCK Prescaler */
-#define QUAD8_RLD_PRESET_PSC 0x18
-#define QUAD8_CHAN_OP_RESET_COUNTERS 0x01
-#define QUAD8_CHAN_OP_ENABLE_INTERRUPT_FUNC 0x04
-#define QUAD8_CMR_QUADRATURE_X1 0x08
-#define QUAD8_CMR_QUADRATURE_X2 0x10
-#define QUAD8_CMR_QUADRATURE_X4 0x18
+#define TRANSFER_PR0_TO_PSC u8_encode_bits(0x3, LOADS)
+
+/*
+ * Counter Mode Registers
+ */
+#define COUNT_ENCODING BIT(0)
+#define COUNT_MODE GENMASK(2, 1)
+#define QUADRATURE_MODE GENMASK(4, 3)
+/* Binary count */
+#define BINARY u8_encode_bits(0x0, COUNT_ENCODING)
+/* Normal count */
+#define NORMAL_COUNT 0x0
+/* Range Limit */
+#define RANGE_LIMIT 0x1
+/* Non-recycle count */
+#define NON_RECYCLE_COUNT 0x2
+/* Modulo-N */
+#define MODULO_N 0x3
+/* Non-quadrature */
+#define NON_QUADRATURE 0x0
+/* Quadrature X1 */
+#define QUADRATURE_X1 0x1
+/* Quadrature X2 */
+#define QUADRATURE_X2 0x2
+/* Quadrature X4 */
+#define QUADRATURE_X4 0x3
+
+/*
+ * Input/Output Control Register
+ */
+#define AB_GATE BIT(0)
+#define LOAD_PIN BIT(1)
+#define FLG_PINS GENMASK(4, 3)
+/* Disable inputs A and B */
+#define DISABLE_AB u8_encode_bits(0x0, AB_GATE)
+/* Load Counter input */
+#define LOAD_CNTR 0x0
+/* FLG1 = CARRY(active low); FLG2 = BORROW(active low) */
+#define FLG1_CARRY_FLG2_BORROW 0x0
+/* FLG1 = COMPARE(active low); FLG2 = BORROW(active low) */
+#define FLG1_COMPARE_FLG2_BORROW 0x1
+/* FLG1 = Carry(active low)/Borrow(active low); FLG2 = U/D(active low) flag */
+#define FLG1_CARRYBORROW_FLG2_UD 0x2
+/* FLG1 = INDX (low pulse at INDEX pin active level); FLG2 = E flag */
+#define FLG1_INDX_FLG2_E 0x3
+
+/*
+ * INDEX CONTROL REGISTERS
+ */
+#define INDEX_MODE BIT(0)
+#define INDEX_POLARITY BIT(1)
+/* Disable Index mode */
+#define DISABLE_INDEX_MODE 0x0
+/* Enable Index mode */
+#define ENABLE_INDEX_MODE 0x1
+/* Negative Index Polarity */
+#define NEGATIVE_INDEX_POLARITY 0x0
+/* Positive Index Polarity */
+#define POSITIVE_INDEX_POLARITY 0x1
+
+/*
+ * Channel Operation Register
+ */
+#define COUNTERS_OPERATION BIT(0)
+#define INTERRUPT_FUNCTION BIT(2)
+/* Enable all Counters */
+#define ENABLE_COUNTERS u8_encode_bits(0x0, COUNTERS_OPERATION)
+/* Reset all Counters */
+#define RESET_COUNTERS u8_encode_bits(0x1, COUNTERS_OPERATION)
+/* Disable the interrupt function */
+#define DISABLE_INTERRUPT_FUNCTION u8_encode_bits(0x0, INTERRUPT_FUNCTION)
+/* Enable the interrupt function */
+#define ENABLE_INTERRUPT_FUNCTION u8_encode_bits(0x1, INTERRUPT_FUNCTION)
+/* Any write to the Channel Operation register clears any pending interrupts */
+#define CLEAR_PENDING_INTERRUPTS (ENABLE_COUNTERS | ENABLE_INTERRUPT_FUNCTION)
 
 /* Each Counter is 24 bits wide */
 #define LS7267_CNTR_MAX GENMASK(23, 0)
 
+static __always_inline int quad8_control_register_update(struct regmap *const map, u8 *const buf,
+							 const size_t channel, const u8 val,
+							 const u8 field)
+{
+	u8p_replace_bits(&buf[channel], val, field);
+	return regmap_write(map, QUAD8_CONTROL(channel), buf[channel]);
+}
+
 static int quad8_signal_read(struct counter_device *counter,
 			     struct counter_signal *signal,
 			     enum counter_signal_level *level)
 {
 	const struct quad8 *const priv = counter_priv(counter);
-	unsigned int state;
+	int ret;
 
 	/* Only Index signal levels can be read */
 	if (signal->id < 16)
 		return -EINVAL;
 
-	state = ioread8(&priv->reg->index_input_levels) & BIT(signal->id - 16);
+	ret = regmap_test_bits(priv->map, QUAD8_INDEX_INPUT_LEVELS, BIT(signal->id - 16));
+	if (ret < 0)
+		return ret;
 
-	*level = (state) ? COUNTER_SIGNAL_LEVEL_HIGH : COUNTER_SIGNAL_LEVEL_LOW;
+	*level = (ret) ? COUNTER_SIGNAL_LEVEL_HIGH : COUNTER_SIGNAL_LEVEL_LOW;
 
 	return 0;
 }
@@ -154,65 +236,81 @@ static int quad8_count_read(struct counter_device *counter,
 			    struct counter_count *count, u64 *val)
 {
 	struct quad8 *const priv = counter_priv(counter);
-	struct channel_reg __iomem *const chan = priv->reg->channel + count->id;
 	unsigned long irqflags;
-	int i;
-
-	*val = 0;
+	u8 value[3];
+	int ret;
 
 	spin_lock_irqsave(&priv->lock, irqflags);
 
-	/* Reset Byte Pointer; transfer Counter to Output Latch */
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP | QUAD8_RLD_CNTR_OUT,
-		 &chan->control);
-
-	for (i = 0; i < 3; i++)
-		*val |= (unsigned long)ioread8(&chan->data) << (8 * i);
+	ret = regmap_write(priv->map, QUAD8_CONTROL(count->id),
+			   SELECT_RLD | RESET_BP | TRANSFER_CNTR_TO_OL);
+	if (ret)
+		goto exit_unlock;
+	ret = regmap_noinc_read(priv->map, QUAD8_DATA(count->id), value, sizeof(value));
 
+exit_unlock:
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	return 0;
+	*val = get_unaligned_le24(value);
+
+	return ret;
+}
+
+static int quad8_preset_register_set(struct quad8 *const priv, const size_t id,
+				     const unsigned long preset)
+{
+	u8 value[3];
+	int ret;
+
+	put_unaligned_le24(preset, value);
+
+	ret = regmap_write(priv->map, QUAD8_CONTROL(id), SELECT_RLD | RESET_BP);
+	if (ret)
+		return ret;
+	return regmap_noinc_write(priv->map, QUAD8_DATA(id), value, sizeof(value));
+}
+
+static int quad8_flag_register_reset(struct quad8 *const priv, const size_t id)
+{
+	int ret;
+
+	ret = regmap_write(priv->map, QUAD8_CONTROL(id), SELECT_RLD | RESET_BT_CT_CPT_S_IDX);
+	if (ret)
+		return ret;
+	return regmap_write(priv->map, QUAD8_CONTROL(id), SELECT_RLD | RESET_E);
 }
 
 static int quad8_count_write(struct counter_device *counter,
 			     struct counter_count *count, u64 val)
 {
 	struct quad8 *const priv = counter_priv(counter);
-	struct channel_reg __iomem *const chan = priv->reg->channel + count->id;
 	unsigned long irqflags;
-	int i;
+	int ret;
 
 	if (val > LS7267_CNTR_MAX)
 		return -ERANGE;
 
 	spin_lock_irqsave(&priv->lock, irqflags);
 
-	/* Reset Byte Pointer */
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, &chan->control);
-
 	/* Counter can only be set via Preset Register */
-	for (i = 0; i < 3; i++)
-		iowrite8(val >> (8 * i), &chan->data);
+	ret = quad8_preset_register_set(priv, count->id, val);
+	if (ret)
+		goto exit_unlock;
+	ret = regmap_write(priv->map, QUAD8_CONTROL(count->id), SELECT_RLD | TRANSFER_PR_TO_CNTR);
+	if (ret)
+		goto exit_unlock;
 
-	/* Transfer Preset Register to Counter */
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_PRESET_CNTR, &chan->control);
-
-	/* Reset Byte Pointer */
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, &chan->control);
+	ret = quad8_flag_register_reset(priv, count->id);
+	if (ret)
+		goto exit_unlock;
 
 	/* Set Preset Register back to original value */
-	val = priv->preset[count->id];
-	for (i = 0; i < 3; i++)
-		iowrite8(val >> (8 * i), &chan->data);
-
-	/* Reset Borrow, Carry, Compare, and Sign flags */
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_RESET_FLAGS, &chan->control);
-	/* Reset Error flag */
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_RESET_E, &chan->control);
+	ret = quad8_preset_register_set(priv, count->id, priv->preset[count->id]);
 
+exit_unlock:
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	return 0;
+	return ret;
 }
 
 static const enum counter_function quad8_count_functions_list[] = {
@@ -225,19 +323,17 @@ static const enum counter_function quad8_count_functions_list[] = {
 static int quad8_function_get(const struct quad8 *const priv, const size_t id,
 			      enum counter_function *const function)
 {
-	if (!priv->quadrature_mode[id]) {
+	switch (u8_get_bits(priv->cmr[id], QUADRATURE_MODE)) {
+	case NON_QUADRATURE:
 		*function = COUNTER_FUNCTION_PULSE_DIRECTION;
 		return 0;
-	}
-
-	switch (priv->quadrature_scale[id]) {
-	case 0:
+	case QUADRATURE_X1:
 		*function = COUNTER_FUNCTION_QUADRATURE_X1_A;
 		return 0;
-	case 1:
+	case QUADRATURE_X2:
 		*function = COUNTER_FUNCTION_QUADRATURE_X2_A;
 		return 0;
-	case 2:
+	case QUADRATURE_X4:
 		*function = COUNTER_FUNCTION_QUADRATURE_X4;
 		return 0;
 	default:
@@ -269,60 +365,46 @@ static int quad8_function_write(struct counter_device *counter,
 {
 	struct quad8 *const priv = counter_priv(counter);
 	const int id = count->id;
-	unsigned int *const quadrature_mode = priv->quadrature_mode + id;
-	unsigned int *const scale = priv->quadrature_scale + id;
-	unsigned int *const synchronous_mode = priv->synchronous_mode + id;
-	u8 __iomem *const control = &priv->reg->channel[id].control;
 	unsigned long irqflags;
 	unsigned int mode_cfg;
-	unsigned int idr_cfg;
+	bool synchronous_mode;
+	int ret;
 
-	spin_lock_irqsave(&priv->lock, irqflags);
-
-	mode_cfg = priv->count_mode[id] << 1;
-	idr_cfg = priv->index_polarity[id] << 1;
-
-	if (function == COUNTER_FUNCTION_PULSE_DIRECTION) {
-		*quadrature_mode = 0;
-
-		/* Quadrature scaling only available in quadrature mode */
-		*scale = 0;
+	switch (function) {
+	case COUNTER_FUNCTION_PULSE_DIRECTION:
+		mode_cfg = NON_QUADRATURE;
+		break;
+	case COUNTER_FUNCTION_QUADRATURE_X1_A:
+		mode_cfg = QUADRATURE_X1;
+		break;
+	case COUNTER_FUNCTION_QUADRATURE_X2_A:
+		mode_cfg = QUADRATURE_X2;
+		break;
+	case COUNTER_FUNCTION_QUADRATURE_X4:
+		mode_cfg = QUADRATURE_X4;
+		break;
+	default:
+		/* should never reach this path */
+		return -EINVAL;
+	}
 
-		/* Synchronous function not supported in non-quadrature mode */
-		if (*synchronous_mode) {
-			*synchronous_mode = 0;
-			/* Disable synchronous function mode */
-			iowrite8(QUAD8_CTR_IDR | idr_cfg, control);
-		}
-	} else {
-		*quadrature_mode = 1;
+	spin_lock_irqsave(&priv->lock, irqflags);
 
-		switch (function) {
-		case COUNTER_FUNCTION_QUADRATURE_X1_A:
-			*scale = 0;
-			mode_cfg |= QUAD8_CMR_QUADRATURE_X1;
-			break;
-		case COUNTER_FUNCTION_QUADRATURE_X2_A:
-			*scale = 1;
-			mode_cfg |= QUAD8_CMR_QUADRATURE_X2;
-			break;
-		case COUNTER_FUNCTION_QUADRATURE_X4:
-			*scale = 2;
-			mode_cfg |= QUAD8_CMR_QUADRATURE_X4;
-			break;
-		default:
-			/* should never reach this path */
-			spin_unlock_irqrestore(&priv->lock, irqflags);
-			return -EINVAL;
-		}
+	/* Synchronous function not supported in non-quadrature mode */
+	synchronous_mode = u8_get_bits(priv->idr[id], INDEX_MODE) == ENABLE_INDEX_MODE;
+	if (synchronous_mode && mode_cfg == NON_QUADRATURE) {
+		ret = quad8_control_register_update(priv->map, priv->idr, id, DISABLE_INDEX_MODE,
+						    INDEX_MODE);
+		if (ret)
+			goto exit_unlock;
 	}
 
-	/* Load mode configuration to Counter Mode Register */
-	iowrite8(QUAD8_CTR_CMR | mode_cfg, control);
+	ret = quad8_control_register_update(priv->map, priv->cmr, id, mode_cfg, QUADRATURE_MODE);
 
+exit_unlock:
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	return 0;
+	return ret;
 }
 
 static int quad8_direction_read(struct counter_device *counter,
@@ -330,13 +412,13 @@ static int quad8_direction_read(struct counter_device *counter,
 				enum counter_count_direction *direction)
 {
 	const struct quad8 *const priv = counter_priv(counter);
-	unsigned int ud_flag;
-	u8 __iomem *const flag_addr = &priv->reg->channel[count->id].control;
-
-	/* U/D flag: nonzero = up, zero = down */
-	ud_flag = ioread8(flag_addr) & QUAD8_FLAG_UD;
+	unsigned int flag;
+	int ret;
 
-	*direction = (ud_flag) ? COUNTER_COUNT_DIRECTION_FORWARD :
+	ret = regmap_read(priv->map, QUAD8_CONTROL(count->id), &flag);
+	if (ret)
+		return ret;
+	*direction = (u8_get_bits(flag, FLAG_UD) == UP) ? COUNTER_COUNT_DIRECTION_FORWARD :
 		COUNTER_COUNT_DIRECTION_BACKWARD;
 
 	return 0;
@@ -366,13 +448,13 @@ static int quad8_action_read(struct counter_device *counter,
 	const size_t signal_a_id = count->synapses[0].signal->id;
 	enum counter_count_direction direction;
 
+	/* Default action mode */
+	*action = COUNTER_SYNAPSE_ACTION_NONE;
+
 	/* Handle Index signals */
 	if (synapse->signal->id >= 16) {
-		if (!priv->preset_enable[count->id])
+		if (u8_get_bits(priv->ior[count->id], LOAD_PIN) == LOAD_CNTR)
 			*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
-		else
-			*action = COUNTER_SYNAPSE_ACTION_NONE;
-
 		return 0;
 	}
 
@@ -392,9 +474,6 @@ static int quad8_action_read(struct counter_device *counter,
 
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	/* Default action mode */
-	*action = COUNTER_SYNAPSE_ACTION_NONE;
-
 	/* Determine action mode based on current count function mode */
 	switch (function) {
 	case COUNTER_FUNCTION_PULSE_DIRECTION:
@@ -422,67 +501,57 @@ static int quad8_action_read(struct counter_device *counter,
 	}
 }
 
-enum {
-	QUAD8_EVENT_CARRY = 0,
-	QUAD8_EVENT_COMPARE = 1,
-	QUAD8_EVENT_CARRY_BORROW = 2,
-	QUAD8_EVENT_INDEX = 3,
-};
-
 static int quad8_events_configure(struct counter_device *counter)
 {
 	struct quad8 *const priv = counter_priv(counter);
 	unsigned long irq_enabled = 0;
 	unsigned long irqflags;
 	struct counter_event_node *event_node;
-	unsigned int next_irq_trigger;
-	unsigned long ior_cfg;
+	u8 flg_pins;
+	int ret;
 
 	spin_lock_irqsave(&priv->lock, irqflags);
 
 	list_for_each_entry(event_node, &counter->events_list, l) {
 		switch (event_node->event) {
 		case COUNTER_EVENT_OVERFLOW:
-			next_irq_trigger = QUAD8_EVENT_CARRY;
+			flg_pins = FLG1_CARRY_FLG2_BORROW;
 			break;
 		case COUNTER_EVENT_THRESHOLD:
-			next_irq_trigger = QUAD8_EVENT_COMPARE;
+			flg_pins = FLG1_COMPARE_FLG2_BORROW;
 			break;
 		case COUNTER_EVENT_OVERFLOW_UNDERFLOW:
-			next_irq_trigger = QUAD8_EVENT_CARRY_BORROW;
+			flg_pins = FLG1_CARRYBORROW_FLG2_UD;
 			break;
 		case COUNTER_EVENT_INDEX:
-			next_irq_trigger = QUAD8_EVENT_INDEX;
+			flg_pins = FLG1_INDX_FLG2_E;
 			break;
 		default:
 			/* should never reach this path */
-			spin_unlock_irqrestore(&priv->lock, irqflags);
-			return -EINVAL;
+			ret = -EINVAL;
+			goto exit_unlock;
 		}
 
 		/* Enable IRQ line */
 		irq_enabled |= BIT(event_node->channel);
 
 		/* Skip configuration if it is the same as previously set */
-		if (priv->irq_trigger[event_node->channel] == next_irq_trigger)
+		if (flg_pins == u8_get_bits(priv->ior[event_node->channel], FLG_PINS))
 			continue;
 
 		/* Save new IRQ function configuration */
-		priv->irq_trigger[event_node->channel] = next_irq_trigger;
-
-		/* Load configuration to I/O Control Register */
-		ior_cfg = priv->ab_enable[event_node->channel] |
-			  priv->preset_enable[event_node->channel] << 1 |
-			  priv->irq_trigger[event_node->channel] << 3;
-		iowrite8(QUAD8_CTR_IOR | ior_cfg,
-			 &priv->reg->channel[event_node->channel].control);
+		ret = quad8_control_register_update(priv->map, priv->ior, event_node->channel,
+						    flg_pins, FLG_PINS);
+		if (ret)
+			goto exit_unlock;
 	}
 
-	iowrite8(irq_enabled, &priv->reg->index_interrupt);
+	ret = regmap_write(priv->map, QUAD8_INDEX_INTERRUPT, irq_enabled);
 
+exit_unlock:
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	return 0;
+	return ret;
 }
 
 static int quad8_watch_validate(struct counter_device *counter,
@@ -531,7 +600,7 @@ static int quad8_index_polarity_get(struct counter_device *counter,
 	const struct quad8 *const priv = counter_priv(counter);
 	const size_t channel_id = signal->id - 16;
 
-	*index_polarity = priv->index_polarity[channel_id];
+	*index_polarity = u8_get_bits(priv->idr[channel_id], INDEX_POLARITY);
 
 	return 0;
 }
@@ -542,22 +611,17 @@ static int quad8_index_polarity_set(struct counter_device *counter,
 {
 	struct quad8 *const priv = counter_priv(counter);
 	const size_t channel_id = signal->id - 16;
-	u8 __iomem *const control = &priv->reg->channel[channel_id].control;
 	unsigned long irqflags;
-	unsigned int idr_cfg = index_polarity << 1;
+	int ret;
 
 	spin_lock_irqsave(&priv->lock, irqflags);
 
-	idr_cfg |= priv->synchronous_mode[channel_id];
-
-	priv->index_polarity[channel_id] = index_polarity;
-
-	/* Load Index Control configuration to Index Control Register */
-	iowrite8(QUAD8_CTR_IDR | idr_cfg, control);
+	ret = quad8_control_register_update(priv->map, priv->idr, channel_id, index_polarity,
+					    INDEX_POLARITY);
 
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	return 0;
+	return ret;
 }
 
 static int quad8_polarity_read(struct counter_device *counter,
@@ -571,7 +635,7 @@ static int quad8_polarity_read(struct counter_device *counter,
 	if (err)
 		return err;
 
-	*polarity = (index_polarity) ? COUNTER_SIGNAL_POLARITY_POSITIVE :
+	*polarity = (index_polarity == POSITIVE_INDEX_POLARITY) ? COUNTER_SIGNAL_POLARITY_POSITIVE :
 		COUNTER_SIGNAL_POLARITY_NEGATIVE;
 
 	return 0;
@@ -581,7 +645,8 @@ static int quad8_polarity_write(struct counter_device *counter,
 				struct counter_signal *signal,
 				enum counter_signal_polarity polarity)
 {
-	const u32 pol = (polarity == COUNTER_SIGNAL_POLARITY_POSITIVE) ? 1 : 0;
+	const u32 pol = (polarity == COUNTER_SIGNAL_POLARITY_POSITIVE) ? POSITIVE_INDEX_POLARITY :
+									 NEGATIVE_INDEX_POLARITY;
 
 	return quad8_index_polarity_set(counter, signal, pol);
 }
@@ -598,7 +663,7 @@ static int quad8_synchronous_mode_get(struct counter_device *counter,
 	const struct quad8 *const priv = counter_priv(counter);
 	const size_t channel_id = signal->id - 16;
 
-	*synchronous_mode = priv->synchronous_mode[channel_id];
+	*synchronous_mode = u8_get_bits(priv->idr[channel_id], INDEX_MODE);
 
 	return 0;
 }
@@ -609,28 +674,26 @@ static int quad8_synchronous_mode_set(struct counter_device *counter,
 {
 	struct quad8 *const priv = counter_priv(counter);
 	const size_t channel_id = signal->id - 16;
-	u8 __iomem *const control = &priv->reg->channel[channel_id].control;
+	u8 quadrature_mode;
 	unsigned long irqflags;
-	unsigned int idr_cfg = synchronous_mode;
+	int ret;
 
 	spin_lock_irqsave(&priv->lock, irqflags);
 
-	idr_cfg |= priv->index_polarity[channel_id] << 1;
-
 	/* Index function must be non-synchronous in non-quadrature mode */
-	if (synchronous_mode && !priv->quadrature_mode[channel_id]) {
-		spin_unlock_irqrestore(&priv->lock, irqflags);
-		return -EINVAL;
+	quadrature_mode = u8_get_bits(priv->idr[channel_id], QUADRATURE_MODE);
+	if (synchronous_mode && quadrature_mode == NON_QUADRATURE) {
+		ret = -EINVAL;
+		goto exit_unlock;
 	}
 
-	priv->synchronous_mode[channel_id] = synchronous_mode;
-
-	/* Load Index Control configuration to Index Control Register */
-	iowrite8(QUAD8_CTR_IDR | idr_cfg, control);
+	ret = quad8_control_register_update(priv->map, priv->idr, channel_id, synchronous_mode,
+					    INDEX_MODE);
 
+exit_unlock:
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	return 0;
+	return ret;
 }
 
 static int quad8_count_floor_read(struct counter_device *counter,
@@ -648,18 +711,17 @@ static int quad8_count_mode_read(struct counter_device *counter,
 {
 	const struct quad8 *const priv = counter_priv(counter);
 
-	/* Map 104-QUAD-8 count mode to Generic Counter count mode */
-	switch (priv->count_mode[count->id]) {
-	case 0:
+	switch (u8_get_bits(priv->cmr[count->id], COUNT_MODE)) {
+	case NORMAL_COUNT:
 		*cnt_mode = COUNTER_COUNT_MODE_NORMAL;
 		break;
-	case 1:
+	case RANGE_LIMIT:
 		*cnt_mode = COUNTER_COUNT_MODE_RANGE_LIMIT;
 		break;
-	case 2:
+	case NON_RECYCLE_COUNT:
 		*cnt_mode = COUNTER_COUNT_MODE_NON_RECYCLE;
 		break;
-	case 3:
+	case MODULO_N:
 		*cnt_mode = COUNTER_COUNT_MODE_MODULO_N;
 		break;
 	}
@@ -673,23 +735,21 @@ static int quad8_count_mode_write(struct counter_device *counter,
 {
 	struct quad8 *const priv = counter_priv(counter);
 	unsigned int count_mode;
-	unsigned int mode_cfg;
-	u8 __iomem *const control = &priv->reg->channel[count->id].control;
 	unsigned long irqflags;
+	int ret;
 
-	/* Map Generic Counter count mode to 104-QUAD-8 count mode */
 	switch (cnt_mode) {
 	case COUNTER_COUNT_MODE_NORMAL:
-		count_mode = 0;
+		count_mode = NORMAL_COUNT;
 		break;
 	case COUNTER_COUNT_MODE_RANGE_LIMIT:
-		count_mode = 1;
+		count_mode = RANGE_LIMIT;
 		break;
 	case COUNTER_COUNT_MODE_NON_RECYCLE:
-		count_mode = 2;
+		count_mode = NON_RECYCLE_COUNT;
 		break;
 	case COUNTER_COUNT_MODE_MODULO_N:
-		count_mode = 3;
+		count_mode = MODULO_N;
 		break;
 	default:
 		/* should never reach this path */
@@ -698,21 +758,12 @@ static int quad8_count_mode_write(struct counter_device *counter,
 
 	spin_lock_irqsave(&priv->lock, irqflags);
 
-	priv->count_mode[count->id] = count_mode;
-
-	/* Set count mode configuration value */
-	mode_cfg = count_mode << 1;
-
-	/* Add quadrature mode configuration */
-	if (priv->quadrature_mode[count->id])
-		mode_cfg |= (priv->quadrature_scale[count->id] + 1) << 3;
-
-	/* Load mode configuration to Counter Mode Register */
-	iowrite8(QUAD8_CTR_CMR | mode_cfg, control);
+	ret = quad8_control_register_update(priv->map, priv->cmr, count->id, count_mode,
+					    COUNT_MODE);
 
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	return 0;
+	return ret;
 }
 
 static int quad8_count_enable_read(struct counter_device *counter,
@@ -720,7 +771,7 @@ static int quad8_count_enable_read(struct counter_device *counter,
 {
 	const struct quad8 *const priv = counter_priv(counter);
 
-	*enable = priv->ab_enable[count->id];
+	*enable = u8_get_bits(priv->ior[count->id], AB_GATE);
 
 	return 0;
 }
@@ -729,23 +780,16 @@ static int quad8_count_enable_write(struct counter_device *counter,
 				    struct counter_count *count, u8 enable)
 {
 	struct quad8 *const priv = counter_priv(counter);
-	u8 __iomem *const control = &priv->reg->channel[count->id].control;
 	unsigned long irqflags;
-	unsigned int ior_cfg;
+	int ret;
 
 	spin_lock_irqsave(&priv->lock, irqflags);
 
-	priv->ab_enable[count->id] = enable;
-
-	ior_cfg = enable | priv->preset_enable[count->id] << 1 |
-		  priv->irq_trigger[count->id] << 3;
-
-	/* Load I/O control configuration */
-	iowrite8(QUAD8_CTR_IOR | ior_cfg, control);
+	ret = quad8_control_register_update(priv->map, priv->ior, count->id, enable, AB_GATE);
 
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	return 0;
+	return ret;
 }
 
 static const char *const quad8_noise_error_states[] = {
@@ -757,9 +801,13 @@ static int quad8_error_noise_get(struct counter_device *counter,
 				 struct counter_count *count, u32 *noise_error)
 {
 	const struct quad8 *const priv = counter_priv(counter);
-	u8 __iomem *const flag_addr = &priv->reg->channel[count->id].control;
+	unsigned int flag;
+	int ret;
 
-	*noise_error = !!(ioread8(flag_addr) & QUAD8_FLAG_E);
+	ret = regmap_read(priv->map, QUAD8_CONTROL(count->id), &flag);
+	if (ret)
+		return ret;
+	*noise_error = u8_get_bits(flag, FLAG_E);
 
 	return 0;
 }
@@ -774,38 +822,24 @@ static int quad8_count_preset_read(struct counter_device *counter,
 	return 0;
 }
 
-static void quad8_preset_register_set(struct quad8 *const priv, const int id,
-				      const unsigned int preset)
-{
-	struct channel_reg __iomem *const chan = priv->reg->channel + id;
-	int i;
-
-	priv->preset[id] = preset;
-
-	/* Reset Byte Pointer */
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, &chan->control);
-
-	/* Set Preset Register */
-	for (i = 0; i < 3; i++)
-		iowrite8(preset >> (8 * i), &chan->data);
-}
-
 static int quad8_count_preset_write(struct counter_device *counter,
 				    struct counter_count *count, u64 preset)
 {
 	struct quad8 *const priv = counter_priv(counter);
 	unsigned long irqflags;
+	int ret;
 
 	if (preset > LS7267_CNTR_MAX)
 		return -ERANGE;
 
 	spin_lock_irqsave(&priv->lock, irqflags);
 
-	quad8_preset_register_set(priv, count->id, preset);
+	priv->preset[count->id] = preset;
+	ret = quad8_preset_register_set(priv, count->id, preset);
 
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	return 0;
+	return ret;
 }
 
 static int quad8_count_ceiling_read(struct counter_device *counter,
@@ -817,9 +851,9 @@ static int quad8_count_ceiling_read(struct counter_device *counter,
 	spin_lock_irqsave(&priv->lock, irqflags);
 
 	/* Range Limit and Modulo-N count modes use preset value as ceiling */
-	switch (priv->count_mode[count->id]) {
-	case 1:
-	case 3:
+	switch (u8_get_bits(priv->cmr[count->id], COUNT_MODE)) {
+	case RANGE_LIMIT:
+	case MODULO_N:
 		*ceiling = priv->preset[count->id];
 		break;
 	default:
@@ -837,6 +871,7 @@ static int quad8_count_ceiling_write(struct counter_device *counter,
 {
 	struct quad8 *const priv = counter_priv(counter);
 	unsigned long irqflags;
+	int ret;
 
 	if (ceiling > LS7267_CNTR_MAX)
 		return -ERANGE;
@@ -844,17 +879,20 @@ static int quad8_count_ceiling_write(struct counter_device *counter,
 	spin_lock_irqsave(&priv->lock, irqflags);
 
 	/* Range Limit and Modulo-N count modes use preset value as ceiling */
-	switch (priv->count_mode[count->id]) {
-	case 1:
-	case 3:
-		quad8_preset_register_set(priv, count->id, ceiling);
-		spin_unlock_irqrestore(&priv->lock, irqflags);
-		return 0;
+	switch (u8_get_bits(priv->cmr[count->id], COUNT_MODE)) {
+	case RANGE_LIMIT:
+	case MODULO_N:
+		priv->preset[count->id] = ceiling;
+		ret = quad8_preset_register_set(priv, count->id, ceiling);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
 	}
 
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	return -EINVAL;
+	return ret;
 }
 
 static int quad8_count_preset_enable_read(struct counter_device *counter,
@@ -863,7 +901,8 @@ static int quad8_count_preset_enable_read(struct counter_device *counter,
 {
 	const struct quad8 *const priv = counter_priv(counter);
 
-	*preset_enable = !priv->preset_enable[count->id];
+	/* Preset enable is active low in Input/Output Control register */
+	*preset_enable = !u8_get_bits(priv->ior[count->id], LOAD_PIN);
 
 	return 0;
 }
@@ -873,26 +912,18 @@ static int quad8_count_preset_enable_write(struct counter_device *counter,
 					   u8 preset_enable)
 {
 	struct quad8 *const priv = counter_priv(counter);
-	u8 __iomem *const control = &priv->reg->channel[count->id].control;
 	unsigned long irqflags;
-	unsigned int ior_cfg;
-
-	/* Preset enable is active low in Input/Output Control register */
-	preset_enable = !preset_enable;
+	int ret;
 
 	spin_lock_irqsave(&priv->lock, irqflags);
 
-	priv->preset_enable[count->id] = preset_enable;
-
-	ior_cfg = priv->ab_enable[count->id] | preset_enable << 1 |
-		  priv->irq_trigger[count->id] << 3;
-
-	/* Load I/O control configuration to Input / Output Control Register */
-	iowrite8(QUAD8_CTR_IOR | ior_cfg, control);
+	/* Preset enable is active low in Input/Output Control register */
+	ret = quad8_control_register_update(priv->map, priv->ior, count->id, !preset_enable,
+					    LOAD_PIN);
 
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	return 0;
+	return ret;
 }
 
 static int quad8_signal_cable_fault_read(struct counter_device *counter,
@@ -903,7 +934,7 @@ static int quad8_signal_cable_fault_read(struct counter_device *counter,
 	const size_t channel_id = signal->id / 2;
 	unsigned long irqflags;
 	bool disabled;
-	unsigned int status;
+	int ret;
 
 	spin_lock_irqsave(&priv->lock, irqflags);
 
@@ -914,13 +945,16 @@ static int quad8_signal_cable_fault_read(struct counter_device *counter,
 		return -EINVAL;
 	}
 
-	/* Logic 0 = cable fault */
-	status = ioread8(&priv->reg->cable_status);
+	ret = regmap_test_bits(priv->map, QUAD8_CABLE_STATUS, BIT(channel_id));
+	if (ret < 0) {
+		spin_unlock_irqrestore(&priv->lock, irqflags);
+		return ret;
+	}
 
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	/* Mask respective channel and invert logic */
-	*cable_fault = !(status & BIT(channel_id));
+	/* Logic 0 = cable fault */
+	*cable_fault = !ret;
 
 	return 0;
 }
@@ -945,6 +979,7 @@ static int quad8_signal_cable_fault_enable_write(struct counter_device *counter,
 	const size_t channel_id = signal->id / 2;
 	unsigned long irqflags;
 	unsigned int cable_fault_enable;
+	int ret;
 
 	spin_lock_irqsave(&priv->lock, irqflags);
 
@@ -956,11 +991,11 @@ static int quad8_signal_cable_fault_enable_write(struct counter_device *counter,
 	/* Enable is active low in Differential Encoder Cable Status register */
 	cable_fault_enable = ~priv->cable_fault_enable;
 
-	iowrite8(cable_fault_enable, &priv->reg->cable_status);
+	ret = regmap_write(priv->map, QUAD8_CABLE_STATUS, cable_fault_enable);
 
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	return 0;
+	return ret;
 }
 
 static int quad8_signal_fck_prescaler_read(struct counter_device *counter,
@@ -974,30 +1009,37 @@ static int quad8_signal_fck_prescaler_read(struct counter_device *counter,
 	return 0;
 }
 
+static int quad8_filter_clock_prescaler_set(struct quad8 *const priv, const size_t id,
+					    const u8 prescaler)
+{
+	int ret;
+
+	ret = regmap_write(priv->map, QUAD8_CONTROL(id), SELECT_RLD | RESET_BP);
+	if (ret)
+		return ret;
+	ret = regmap_write(priv->map, QUAD8_DATA(id), prescaler);
+	if (ret)
+		return ret;
+	return regmap_write(priv->map, QUAD8_CONTROL(id), SELECT_RLD | TRANSFER_PR0_TO_PSC);
+}
+
 static int quad8_signal_fck_prescaler_write(struct counter_device *counter,
 					    struct counter_signal *signal,
 					    u8 prescaler)
 {
 	struct quad8 *const priv = counter_priv(counter);
 	const size_t channel_id = signal->id / 2;
-	struct channel_reg __iomem *const chan = priv->reg->channel + channel_id;
 	unsigned long irqflags;
+	int ret;
 
 	spin_lock_irqsave(&priv->lock, irqflags);
 
 	priv->fck_prescaler[channel_id] = prescaler;
-
-	/* Reset Byte Pointer */
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, &chan->control);
-
-	/* Set filter clock factor */
-	iowrite8(prescaler, &chan->data);
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP | QUAD8_RLD_PRESET_PSC,
-		 &chan->control);
+	ret = quad8_filter_clock_prescaler_set(priv, channel_id, prescaler);
 
 	spin_unlock_irqrestore(&priv->lock, irqflags);
 
-	return 0;
+	return ret;
 }
 
 static struct counter_comp quad8_signal_ext[] = {
@@ -1150,77 +1192,93 @@ static irqreturn_t quad8_irq_handler(int irq, void *private)
 {
 	struct counter_device *counter = private;
 	struct quad8 *const priv = counter_priv(counter);
+	unsigned int status;
 	unsigned long irq_status;
 	unsigned long channel;
+	unsigned int flg_pins;
 	u8 event;
+	int ret;
 
-	irq_status = ioread8(&priv->reg->interrupt_status);
-	if (!irq_status)
+	ret = regmap_read(priv->map, QUAD8_INTERRUPT_STATUS, &status);
+	if (ret)
+		return ret;
+	if (!status)
 		return IRQ_NONE;
 
+	irq_status = status;
 	for_each_set_bit(channel, &irq_status, QUAD8_NUM_COUNTERS) {
-		switch (priv->irq_trigger[channel]) {
-		case QUAD8_EVENT_CARRY:
+		flg_pins = u8_get_bits(priv->ior[channel], FLG_PINS);
+		switch (flg_pins) {
+		case FLG1_CARRY_FLG2_BORROW:
 			event = COUNTER_EVENT_OVERFLOW;
 				break;
-		case QUAD8_EVENT_COMPARE:
+		case FLG1_COMPARE_FLG2_BORROW:
 			event = COUNTER_EVENT_THRESHOLD;
 				break;
-		case QUAD8_EVENT_CARRY_BORROW:
+		case FLG1_CARRYBORROW_FLG2_UD:
 			event = COUNTER_EVENT_OVERFLOW_UNDERFLOW;
 				break;
-		case QUAD8_EVENT_INDEX:
+		case FLG1_INDX_FLG2_E:
 			event = COUNTER_EVENT_INDEX;
 				break;
 		default:
 			/* should never reach this path */
 			WARN_ONCE(true, "invalid interrupt trigger function %u configured for channel %lu\n",
-				  priv->irq_trigger[channel], channel);
+				  flg_pins, channel);
 			continue;
 		}
 
 		counter_push_event(counter, event, channel);
 	}
 
-	/* Clear pending interrupts on device */
-	iowrite8(QUAD8_CHAN_OP_ENABLE_INTERRUPT_FUNC, &priv->reg->channel_oper);
+	ret = regmap_write(priv->map, QUAD8_CHANNEL_OPERATION, CLEAR_PENDING_INTERRUPTS);
+	if (ret)
+		return ret;
 
 	return IRQ_HANDLED;
 }
 
-static void quad8_init_counter(struct channel_reg __iomem *const chan)
+static int quad8_init_counter(struct quad8 *const priv, const size_t channel)
 {
-	unsigned long i;
+	int ret;
+
+	ret = quad8_filter_clock_prescaler_set(priv, channel, 0);
+	if (ret)
+		return ret;
+	ret = quad8_preset_register_set(priv, channel, 0);
+	if (ret)
+		return ret;
+	ret = quad8_flag_register_reset(priv, channel);
+	if (ret)
+		return ret;
 
-	/* Reset Byte Pointer */
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, &chan->control);
-	/* Reset filter clock factor */
-	iowrite8(0, &chan->data);
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP | QUAD8_RLD_PRESET_PSC,
-		 &chan->control);
-	/* Reset Byte Pointer */
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, &chan->control);
-	/* Reset Preset Register */
-	for (i = 0; i < 3; i++)
-		iowrite8(0x00, &chan->data);
-	/* Reset Borrow, Carry, Compare, and Sign flags */
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_RESET_FLAGS, &chan->control);
-	/* Reset Error flag */
-	iowrite8(QUAD8_CTR_RLD | QUAD8_RLD_RESET_E, &chan->control);
 	/* Binary encoding; Normal count; non-quadrature mode */
-	iowrite8(QUAD8_CTR_CMR, &chan->control);
+	priv->cmr[channel] = SELECT_CMR | BINARY | u8_encode_bits(NORMAL_COUNT, COUNT_MODE) |
+			     u8_encode_bits(NON_QUADRATURE, QUADRATURE_MODE);
+	ret = regmap_write(priv->map, QUAD8_CONTROL(channel), priv->cmr[channel]);
+	if (ret)
+		return ret;
+
 	/* Disable A and B inputs; preset on index; FLG1 as Carry */
-	iowrite8(QUAD8_CTR_IOR, &chan->control);
+	priv->ior[channel] = SELECT_IOR | DISABLE_AB | u8_encode_bits(LOAD_CNTR, LOAD_PIN) |
+			     u8_encode_bits(FLG1_CARRY_FLG2_BORROW, FLG_PINS);
+	ret = regmap_write(priv->map, QUAD8_CONTROL(channel), priv->ior[channel]);
+	if (ret)
+		return ret;
+
 	/* Disable index function; negative index polarity */
-	iowrite8(QUAD8_CTR_IDR, &chan->control);
+	priv->idr[channel] = SELECT_IDR | u8_encode_bits(DISABLE_INDEX_MODE, INDEX_MODE) |
+			     u8_encode_bits(NEGATIVE_INDEX_POLARITY, INDEX_POLARITY);
+	return regmap_write(priv->map, QUAD8_CONTROL(channel), priv->idr[channel]);
 }
 
 static int quad8_probe(struct device *dev, unsigned int id)
 {
 	struct counter_device *counter;
 	struct quad8 *priv;
+	void __iomem *regs;
 	unsigned long i;
-	int err;
+	int ret;
 
 	if (!devm_request_region(dev, base[id], QUAD8_EXTENT, dev_name(dev))) {
 		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
@@ -1233,10 +1291,15 @@ static int quad8_probe(struct device *dev, unsigned int id)
 		return -ENOMEM;
 	priv = counter_priv(counter);
 
-	priv->reg = devm_ioport_map(dev, base[id], QUAD8_EXTENT);
-	if (!priv->reg)
+	regs = devm_ioport_map(dev, base[id], QUAD8_EXTENT);
+	if (!regs)
 		return -ENOMEM;
 
+	priv->map = devm_regmap_init_mmio(dev, regs, &quad8_regmap_config);
+	if (IS_ERR(priv->map))
+		return dev_err_probe(dev, PTR_ERR(priv->map),
+				     "Unable to initialize register map\n");
+
 	/* Initialize Counter device and driver data */
 	counter->name = dev_name(dev);
 	counter->parent = dev;
@@ -1249,25 +1312,38 @@ static int quad8_probe(struct device *dev, unsigned int id)
 	spin_lock_init(&priv->lock);
 
 	/* Reset Index/Interrupt Register */
-	iowrite8(0x00, &priv->reg->index_interrupt);
+	ret = regmap_write(priv->map, QUAD8_INDEX_INTERRUPT, 0x00);
+	if (ret)
+		return ret;
 	/* Reset all counters and disable interrupt function */
-	iowrite8(QUAD8_CHAN_OP_RESET_COUNTERS, &priv->reg->channel_oper);
+	ret = regmap_write(priv->map, QUAD8_CHANNEL_OPERATION,
+			   RESET_COUNTERS | DISABLE_INTERRUPT_FUNCTION);
+	if (ret)
+		return ret;
 	/* Set initial configuration for all counters */
-	for (i = 0; i < QUAD8_NUM_COUNTERS; i++)
-		quad8_init_counter(priv->reg->channel + i);
+	for (i = 0; i < QUAD8_NUM_COUNTERS; i++) {
+		ret = quad8_init_counter(priv, i);
+		if (ret)
+			return ret;
+	}
 	/* Disable Differential Encoder Cable Status for all channels */
-	iowrite8(0xFF, &priv->reg->cable_status);
+	ret = regmap_write(priv->map, QUAD8_CABLE_STATUS, GENMASK(7, 0));
+	if (ret)
+		return ret;
 	/* Enable all counters and enable interrupt function */
-	iowrite8(QUAD8_CHAN_OP_ENABLE_INTERRUPT_FUNC, &priv->reg->channel_oper);
+	ret = regmap_write(priv->map, QUAD8_CHANNEL_OPERATION,
+			   ENABLE_COUNTERS | ENABLE_INTERRUPT_FUNCTION);
+	if (ret)
+		return ret;
 
-	err = devm_request_irq(&counter->dev, irq[id], quad8_irq_handler,
+	ret = devm_request_irq(&counter->dev, irq[id], quad8_irq_handler,
 			       IRQF_SHARED, counter->name, counter);
-	if (err)
-		return err;
+	if (ret)
+		return ret;
 
-	err = devm_counter_add(dev, counter);
-	if (err < 0)
-		return dev_err_probe(dev, err, "Failed to add counter\n");
+	ret = devm_counter_add(dev, counter);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to add counter\n");
 
 	return 0;
 }

drivers/counter/Kconfig

@@ -10,6 +10,21 @@ menuconfig COUNTER
 	  interface. You only need to enable this, if you also want to enable
 	  one or more of the counter device drivers below.
 
+config I8254
+	tristate
+	select COUNTER
+	select REGMAP
+	help
+	  Enables support for the i8254 interface library functions. The i8254
+	  interface library provides functions to facilitate communication with
+	  interfaces compatible with the venerable Intel 8254 Programmable
+	  Interval Timer (PIT). The Intel 825x family of chips was first
+	  released in the early 1980s but compatible interfaces are nowadays
+	  typically found embedded in larger VLSI processing chips and FPGA
+	  components.
+
+	  If built as a module its name will be i8254.
+
 if COUNTER
 
 config 104_QUAD_8
@@ -17,14 +32,15 @@ config 104_QUAD_8
 	depends on (PC104 && X86) || COMPILE_TEST
 	depends on HAS_IOPORT_MAP
 	select ISA_BUS_API
+	select REGMAP_MMIO
 	help
 	  Say yes here to build support for the ACCES 104-QUAD-8 quadrature
 	  encoder counter/interface device family (104-QUAD-8, 104-QUAD-4).
 
 	  A counter's respective error flag may be cleared by performing a write
-	  operation on the respective count value attribute. Although the
-	  104-QUAD-8 counters have a 25-bit range, only the lower 24 bits may be
-	  set, either directly or via the counter's preset attribute.
+	  operation on the respective count value attribute. The 104-QUAD-8
+	  counters may be set either directly or via the counter's preset
+	  attribute.
 
 	  The base port addresses for the devices may be configured via the base
 	  array module parameter. The interrupt line numbers for the devices may

drivers/counter/Makefile

@@ -6,6 +6,7 @@
 obj-$(CONFIG_COUNTER) += counter.o
 counter-y := counter-core.o counter-sysfs.o counter-chrdev.o
 
+obj-$(CONFIG_I8254)		+= i8254.o
 obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
 obj-$(CONFIG_INTERRUPT_CNT)		+= interrupt-cnt.o
 obj-$(CONFIG_RZ_MTU3_CNT)	+= rz-mtu3-cnt.o

drivers/counter/counter-sysfs.c

@@ -88,7 +88,13 @@ static const char *const counter_count_mode_str[] = {
 	[COUNTER_COUNT_MODE_NORMAL] = "normal",
 	[COUNTER_COUNT_MODE_RANGE_LIMIT] = "range limit",
 	[COUNTER_COUNT_MODE_NON_RECYCLE] = "non-recycle",
-	[COUNTER_COUNT_MODE_MODULO_N] = "modulo-n"
+	[COUNTER_COUNT_MODE_MODULO_N] = "modulo-n",
+	[COUNTER_COUNT_MODE_INTERRUPT_ON_TERMINAL_COUNT] = "interrupt on terminal count",
+	[COUNTER_COUNT_MODE_HARDWARE_RETRIGGERABLE_ONESHOT] = "hardware retriggerable one-shot",
+	[COUNTER_COUNT_MODE_RATE_GENERATOR] = "rate generator",
+	[COUNTER_COUNT_MODE_SQUARE_WAVE_MODE] = "square wave mode",
+	[COUNTER_COUNT_MODE_SOFTWARE_TRIGGERED_STROBE] = "software triggered strobe",
+	[COUNTER_COUNT_MODE_HARDWARE_TRIGGERED_STROBE] = "hardware triggered strobe",
 };
 
 static const char *const counter_signal_polarity_str[] = {

drivers/counter/i8254.c

+// 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 <asm/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);

drivers/counter/stm32-timer-cnt.c

@@ -342,6 +342,9 @@ static int stm32_timer_cnt_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, priv);
 
+	/* Reset input selector to its default input */
+	regmap_write(priv->regmap, TIM_TISEL, 0x0);
+
 	/* Register Counter device */
 	ret = devm_counter_add(dev, counter);
 	if (ret < 0)

include/linux/i8254.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) William Breathitt Gray */
+#ifndef _I8254_H_
+#define _I8254_H_
+
+struct device;
+struct regmap;
+
+/**
+ * struct i8254_regmap_config - Configuration for the register map of an i8254
+ * @parent:	parent device
+ * @map:	regmap for the i8254
+ */
+struct i8254_regmap_config {
+	struct device *parent;
+	struct regmap *map;
+};
+
+int devm_i8254_regmap_register(struct device *dev, const struct i8254_regmap_config *config);
+
+#endif /* _I8254_H_ */

include/uapi/linux/counter.h

@@ -127,6 +127,12 @@ enum counter_count_mode {
 	COUNTER_COUNT_MODE_RANGE_LIMIT,
 	COUNTER_COUNT_MODE_NON_RECYCLE,
 	COUNTER_COUNT_MODE_MODULO_N,
+	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,
 };
 
 /* Count function values */

tools/counter/.gitignore

+/counter_example
+/include/linux/counter.h

tools/counter/Makefile

@@ -40,6 +40,7 @@ $(OUTPUT)counter_example: $(COUNTER_EXAMPLE)
 clean:
 	rm -f $(ALL_PROGRAMS)
 	rm -rf $(OUTPUT)include/linux/counter.h
+	rmdir -p $(OUTPUT)include/linux
 	find $(or $(OUTPUT),.) -name '*.o' -delete -o -name '\.*.d' -delete
 
 install: $(ALL_PROGRAMS)