counter: Internalize sysfs interface code

This is a reimplementation of the Generic Counter driver interface.
There are no modifications to the Counter subsystem userspace interface,
so existing userspace applications should continue to run seamlessly.

The purpose of this patch is to internalize the sysfs interface code
among the various counter drivers into a shared module. Counter drivers
pass and take data natively (i.e. u8, u64, etc.) and the shared counter
module handles the translation between the sysfs interface and the
device drivers. This guarantees a standard userspace interface for all
counter drivers, and helps generalize the Generic Counter driver ABI in
order to support the Generic Counter chrdev interface (introduced in a
subsequent patch) without significant changes to the existing counter
drivers.

Note, Counter device registration is the same as before: drivers
populate a struct counter_device with components and callbacks, then
pass the structure to the devm_counter_register function. However,
what's different now is how the Counter subsystem code handles this
registration internally.

Whereas before callbacks would interact directly with sysfs data, this
interaction is now abstracted and instead callbacks interact with native
C data types. The counter_comp structure forms the basis for Counter
extensions.

The counter-sysfs.c file contains the code to parse through the
counter_device structure and register the requested components and
extensions. Attributes are created and populated based on type, with
respective translation functions to handle the mapping between sysfs and
the counter driver callbacks.

The translation performed for each attribute is straightforward: the
attribute type and data is parsed from the counter_attribute structure,
the respective counter driver read/write callback is called, and sysfs
I/O is handled before or after the driver read/write function is called.

Cc: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Cc: Patrick Havelange <patrick.havelange@essensium.com>
Cc: Kamel Bouhara <kamel.bouhara@bootlin.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Syed Nayyar Waris <syednwaris@gmail.com>
Reviewed-by: David Lechner <david@lechnology.com>
Tested-by: David Lechner <david@lechnology.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Reviewed-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com> # for stm32
Link: https://lore.kernel.org/r/c68b4a1ffb195c1a2f65e8dd5ad7b7c14e79c6ef.1630031207.git.vilhelm.gray@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

1 files changed, 68 insertions, 111 deletions

diff --git a/drivers/counter/stm32-timer-cnt.c b/drivers/counter/stm32-timer-cnt.c
index 1fbc46f4ee66..0546e932db0c 100644
--- a/drivers/counter/stm32-timer-cnt.c
+++ b/drivers/counter/stm32-timer-cnt.c
@@ -13,6 +13,7 @@
 #include <linux/module.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/platform_device.h>
+#include <linux/types.h>
 
 #define TIM_CCMR_CCXS	(BIT(8) | BIT(0))
 #define TIM_CCMR_MASK	(TIM_CCMR_CC1S | TIM_CCMR_CC2S | \
@@ -36,29 +37,15 @@ struct stm32_timer_cnt {
 	struct stm32_timer_regs bak;
 };
 
-/**
- * enum stm32_count_function - enumerates stm32 timer counter encoder modes
- * @STM32_COUNT_SLAVE_MODE_DISABLED: counts on internal clock when CEN=1
- * @STM32_COUNT_ENCODER_MODE_1: counts TI1FP1 edges, depending on TI2FP2 level
- * @STM32_COUNT_ENCODER_MODE_2: counts TI2FP2 edges, depending on TI1FP1 level
- * @STM32_COUNT_ENCODER_MODE_3: counts on both TI1FP1 and TI2FP2 edges
- */
-enum stm32_count_function {
-	STM32_COUNT_SLAVE_MODE_DISABLED,
-	STM32_COUNT_ENCODER_MODE_1,
-	STM32_COUNT_ENCODER_MODE_2,
-	STM32_COUNT_ENCODER_MODE_3,
-};
-
 static const enum counter_function stm32_count_functions[] = {
-	[STM32_COUNT_SLAVE_MODE_DISABLED] = COUNTER_FUNCTION_INCREASE,
-	[STM32_COUNT_ENCODER_MODE_1] = COUNTER_FUNCTION_QUADRATURE_X2_A,
-	[STM32_COUNT_ENCODER_MODE_2] = COUNTER_FUNCTION_QUADRATURE_X2_B,
-	[STM32_COUNT_ENCODER_MODE_3] = COUNTER_FUNCTION_QUADRATURE_X4,
+	COUNTER_FUNCTION_INCREASE,
+	COUNTER_FUNCTION_QUADRATURE_X2_A,
+	COUNTER_FUNCTION_QUADRATURE_X2_B,
+	COUNTER_FUNCTION_QUADRATURE_X4,
 };
 
 static int stm32_count_read(struct counter_device *counter,
-			    struct counter_count *count, unsigned long *val)
+			    struct counter_count *count, u64 *val)
 {
 	struct stm32_timer_cnt *const priv = counter->priv;
 	u32 cnt;
@@ -70,8 +57,7 @@ static int stm32_count_read(struct counter_device *counter,
 }
 
 static int stm32_count_write(struct counter_device *counter,
-			     struct counter_count *count,
-			     const unsigned long val)
+			     struct counter_count *count, const u64 val)
 {
 	struct stm32_timer_cnt *const priv = counter->priv;
 	u32 ceiling;
@@ -83,9 +69,9 @@ static int stm32_count_write(struct counter_device *counter,
 	return regmap_write(priv->regmap, TIM_CNT, val);
 }
 
-static int stm32_count_function_get(struct counter_device *counter,
-				    struct counter_count *count,
-				    size_t *function)
+static int stm32_count_function_read(struct counter_device *counter,
+				     struct counter_count *count,
+				     enum counter_function *function)
 {
 	struct stm32_timer_cnt *const priv = counter->priv;
 	u32 smcr;
@@ -94,40 +80,40 @@ static int stm32_count_function_get(struct counter_device *counter,
 
 	switch (smcr & TIM_SMCR_SMS) {
 	case TIM_SMCR_SMS_SLAVE_MODE_DISABLED:
-		*function = STM32_COUNT_SLAVE_MODE_DISABLED;
+		*function = COUNTER_FUNCTION_INCREASE;
 		return 0;
 	case TIM_SMCR_SMS_ENCODER_MODE_1:
-		*function = STM32_COUNT_ENCODER_MODE_1;
+		*function = COUNTER_FUNCTION_QUADRATURE_X2_A;
 		return 0;
 	case TIM_SMCR_SMS_ENCODER_MODE_2:
-		*function = STM32_COUNT_ENCODER_MODE_2;
+		*function = COUNTER_FUNCTION_QUADRATURE_X2_B;
 		return 0;
 	case TIM_SMCR_SMS_ENCODER_MODE_3:
-		*function = STM32_COUNT_ENCODER_MODE_3;
+		*function = COUNTER_FUNCTION_QUADRATURE_X4;
 		return 0;
 	default:
 		return -EINVAL;
 	}
 }
 
-static int stm32_count_function_set(struct counter_device *counter,
-				    struct counter_count *count,
-				    size_t function)
+static int stm32_count_function_write(struct counter_device *counter,
+				      struct counter_count *count,
+				      enum counter_function function)
 {
 	struct stm32_timer_cnt *const priv = counter->priv;
 	u32 cr1, sms;
 
 	switch (function) {
-	case STM32_COUNT_SLAVE_MODE_DISABLED:
+	case COUNTER_FUNCTION_INCREASE:
 		sms = TIM_SMCR_SMS_SLAVE_MODE_DISABLED;
 		break;
-	case STM32_COUNT_ENCODER_MODE_1:
+	case COUNTER_FUNCTION_QUADRATURE_X2_A:
 		sms = TIM_SMCR_SMS_ENCODER_MODE_1;
 		break;
-	case STM32_COUNT_ENCODER_MODE_2:
+	case COUNTER_FUNCTION_QUADRATURE_X2_B:
 		sms = TIM_SMCR_SMS_ENCODER_MODE_2;
 		break;
-	case STM32_COUNT_ENCODER_MODE_3:
+	case COUNTER_FUNCTION_QUADRATURE_X4:
 		sms = TIM_SMCR_SMS_ENCODER_MODE_3;
 		break;
 	default:
@@ -150,44 +136,37 @@ static int stm32_count_function_set(struct counter_device *counter,
 	return 0;
 }
 
-static ssize_t stm32_count_direction_read(struct counter_device *counter,
+static int stm32_count_direction_read(struct counter_device *counter,
 				      struct counter_count *count,
-				      void *private, char *buf)
+				      enum counter_count_direction *direction)
 {
 	struct stm32_timer_cnt *const priv = counter->priv;
-	const char *direction;
 	u32 cr1;
 
 	regmap_read(priv->regmap, TIM_CR1, &cr1);
-	direction = (cr1 & TIM_CR1_DIR) ? "backward" : "forward";
+	*direction = (cr1 & TIM_CR1_DIR) ? COUNTER_COUNT_DIRECTION_BACKWARD :
+		COUNTER_COUNT_DIRECTION_FORWARD;
 
-	return scnprintf(buf, PAGE_SIZE, "%s\n", direction);
+	return 0;
 }
 
-static ssize_t stm32_count_ceiling_read(struct counter_device *counter,
-					struct counter_count *count,
-					void *private, char *buf)
+static int stm32_count_ceiling_read(struct counter_device *counter,
+				    struct counter_count *count, u64 *ceiling)
 {
 	struct stm32_timer_cnt *const priv = counter->priv;
 	u32 arr;
 
 	regmap_read(priv->regmap, TIM_ARR, &arr);
 
-	return snprintf(buf, PAGE_SIZE, "%u\n", arr);
+	*ceiling = arr;
+
+	return 0;
 }
 
-static ssize_t stm32_count_ceiling_write(struct counter_device *counter,
-					 struct counter_count *count,
-					 void *private,
-					 const char *buf, size_t len)
+static int stm32_count_ceiling_write(struct counter_device *counter,
+				     struct counter_count *count, u64 ceiling)
 {
 	struct stm32_timer_cnt *const priv = counter->priv;
-	unsigned int ceiling;
-	int ret;
-
-	ret = kstrtouint(buf, 0, &ceiling);
-	if (ret)
-		return ret;
 
 	if (ceiling > priv->max_arr)
 		return -ERANGE;
@@ -196,34 +175,27 @@ static ssize_t stm32_count_ceiling_write(struct counter_device *counter,
 	regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_ARPE, 0);
 	regmap_write(priv->regmap, TIM_ARR, ceiling);
 
-	return len;
+	return 0;
 }
 
-static ssize_t stm32_count_enable_read(struct counter_device *counter,
-				       struct counter_count *count,
-				       void *private, char *buf)
+static int stm32_count_enable_read(struct counter_device *counter,
+				   struct counter_count *count, u8 *enable)
 {
 	struct stm32_timer_cnt *const priv = counter->priv;
 	u32 cr1;
 
 	regmap_read(priv->regmap, TIM_CR1, &cr1);
 
-	return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)(cr1 & TIM_CR1_CEN));
+	*enable = cr1 & TIM_CR1_CEN;
+
+	return 0;
 }
 
-static ssize_t stm32_count_enable_write(struct counter_device *counter,
-					struct counter_count *count,
-					void *private,
-					const char *buf, size_t len)
+static int stm32_count_enable_write(struct counter_device *counter,
+				    struct counter_count *count, u8 enable)
 {
 	struct stm32_timer_cnt *const priv = counter->priv;
-	int err;
 	u32 cr1;
-	bool enable;
-
-	err = kstrtobool(buf, &enable);
-	if (err)
-		return err;
 
 	if (enable) {
 		regmap_read(priv->regmap, TIM_CR1, &cr1);
@@ -242,70 +214,55 @@ static ssize_t stm32_count_enable_write(struct counter_device *counter,
 	/* Keep enabled state to properly handle low power states */
 	priv->enabled = enable;
 
-	return len;
+	return 0;
 }
 
-static const struct counter_count_ext stm32_count_ext[] = {
-	{
-		.name = "direction",
-		.read = stm32_count_direction_read,
-	},
-	{
-		.name = "enable",
-		.read = stm32_count_enable_read,
-		.write = stm32_count_enable_write
-	},
-	{
-		.name = "ceiling",
-		.read = stm32_count_ceiling_read,
-		.write = stm32_count_ceiling_write
-	},
-};
-
-enum stm32_synapse_action {
-	STM32_SYNAPSE_ACTION_NONE,
-	STM32_SYNAPSE_ACTION_BOTH_EDGES
+static struct counter_comp stm32_count_ext[] = {
+	COUNTER_COMP_DIRECTION(stm32_count_direction_read),
+	COUNTER_COMP_ENABLE(stm32_count_enable_read, stm32_count_enable_write),
+	COUNTER_COMP_CEILING(stm32_count_ceiling_read,
+			     stm32_count_ceiling_write),
 };
 
 static const enum counter_synapse_action stm32_synapse_actions[] = {
-	[STM32_SYNAPSE_ACTION_NONE] = COUNTER_SYNAPSE_ACTION_NONE,
-	[STM32_SYNAPSE_ACTION_BOTH_EDGES] = COUNTER_SYNAPSE_ACTION_BOTH_EDGES
+	COUNTER_SYNAPSE_ACTION_NONE,
+	COUNTER_SYNAPSE_ACTION_BOTH_EDGES
 };
 
-static int stm32_action_get(struct counter_device *counter,
-			    struct counter_count *count,
-			    struct counter_synapse *synapse,
-			    size_t *action)
+static int stm32_action_read(struct counter_device *counter,
+			     struct counter_count *count,
+			     struct counter_synapse *synapse,
+			     enum counter_synapse_action *action)
 {
-	size_t function;
+	enum counter_function function;
 	int err;
 
-	err = stm32_count_function_get(counter, count, &function);
+	err = stm32_count_function_read(counter, count, &function);
 	if (err)
 		return err;
 
 	switch (function) {
-	case STM32_COUNT_SLAVE_MODE_DISABLED:
+	case COUNTER_FUNCTION_INCREASE:
 		/* counts on internal clock when CEN=1 */
-		*action = STM32_SYNAPSE_ACTION_NONE;
+		*action = COUNTER_SYNAPSE_ACTION_NONE;
 		return 0;
-	case STM32_COUNT_ENCODER_MODE_1:
+	case COUNTER_FUNCTION_QUADRATURE_X2_A:
 		/* counts up/down on TI1FP1 edge depending on TI2FP2 level */
 		if (synapse->signal->id == count->synapses[0].signal->id)
-			*action = STM32_SYNAPSE_ACTION_BOTH_EDGES;
+			*action = COUNTER_SYNAPSE_ACTION_BOTH_EDGES;
 		else
-			*action = STM32_SYNAPSE_ACTION_NONE;
+			*action = COUNTER_SYNAPSE_ACTION_NONE;
 		return 0;
-	case STM32_COUNT_ENCODER_MODE_2:
+	case COUNTER_FUNCTION_QUADRATURE_X2_B:
 		/* counts up/down on TI2FP2 edge depending on TI1FP1 level */
 		if (synapse->signal->id == count->synapses[1].signal->id)
-			*action = STM32_SYNAPSE_ACTION_BOTH_EDGES;
+			*action = COUNTER_SYNAPSE_ACTION_BOTH_EDGES;
 		else
-			*action = STM32_SYNAPSE_ACTION_NONE;
+			*action = COUNTER_SYNAPSE_ACTION_NONE;
 		return 0;
-	case STM32_COUNT_ENCODER_MODE_3:
+	case COUNTER_FUNCTION_QUADRATURE_X4:
 		/* counts up/down on both TI1FP1 and TI2FP2 edges */
-		*action = STM32_SYNAPSE_ACTION_BOTH_EDGES;
+		*action = COUNTER_SYNAPSE_ACTION_BOTH_EDGES;
 		return 0;
 	default:
 		return -EINVAL;
@@ -315,9 +272,9 @@ static int stm32_action_get(struct counter_device *counter,
 static const struct counter_ops stm32_timer_cnt_ops = {
 	.count_read = stm32_count_read,
 	.count_write = stm32_count_write,
-	.function_get = stm32_count_function_get,
-	.function_set = stm32_count_function_set,
-	.action_get = stm32_action_get,
+	.function_read = stm32_count_function_read,
+	.function_write = stm32_count_function_write,
+	.action_read = stm32_action_read,
 };
 
 static struct counter_signal stm32_signals[] = {