[PATCH v5 2/2] counter: add IRQ or GPIO based event counter

[Oleksij Rempel]

Add simple IRQ or GPIO base event counter. This device is used to measure
rotation speed of some agricultural devices, so no high frequency on the
counter pin is expected.

The maximal measurement frequency depends on the CPU and system load. On
the idle iMX6S I was able to measure up to 20kHz without count drops.

Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
Reviewed-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
---
 drivers/counter/Kconfig     |  10 ++
 drivers/counter/Makefile    |   1 +
 drivers/counter/event-cnt.c | 250 ++++++++++++++++++++++++++++++++++++
 3 files changed, 261 insertions(+)
 create mode 100644 drivers/counter/event-cnt.c

diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
index 2de53ab0dd25..3284987e070a 100644
--- a/drivers/counter/Kconfig
+++ b/drivers/counter/Kconfig
@@ -29,6 +29,16 @@ config 104_QUAD_8
 	  The base port addresses for the devices may be configured via the base
 	  array module parameter.
 
+config EVENT_CNT
+	tristate "Event counter driver"
+	depends on GPIOLIB
+	help
+	  Select this option to enable event counter driver. Any interrupt source
+	  can be used by this driver as the event source.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called gpio-pulse-cnt.
+
 config STM32_TIMER_CNT
 	tristate "STM32 Timer encoder counter driver"
 	depends on MFD_STM32_TIMERS || COMPILE_TEST
diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
index 0a393f71e481..6626900468f6 100644
--- a/drivers/counter/Makefile
+++ b/drivers/counter/Makefile
@@ -6,6 +6,7 @@
 obj-$(CONFIG_COUNTER) += counter.o
 
 obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
+obj-$(CONFIG_EVENT_CNT)		+= event-cnt.o
 obj-$(CONFIG_STM32_TIMER_CNT)	+= stm32-timer-cnt.o
 obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
 obj-$(CONFIG_TI_EQEP)		+= ti-eqep.o
diff --git a/drivers/counter/event-cnt.c b/drivers/counter/event-cnt.c
new file mode 100644
index 000000000000..a394fe72c4e4
--- /dev/null
+++ b/drivers/counter/event-cnt.c
@@ -0,0 +1,250 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2021 Pengutronix, Oleksij Rempel <kernel@xxxxxxxxxxxxxx>
+ */
+
+#include <linux/counter.h>
+#include <linux/gpio/consumer.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#define EVENT_CNT_NAME		"event-cnt"
+
+struct event_cnt_priv {
+	struct counter_device counter;
+	struct counter_ops ops;
+	struct gpio_desc *gpio;
+	int irq;
+	bool enabled;
+	atomic_t count;
+};
+
+static irqreturn_t event_cnt_isr(int irq, void *dev_id)
+{
+	struct event_cnt_priv *priv = dev_id;
+
+	atomic_inc(&priv->count);
+
+	return IRQ_HANDLED;
+}
+
+static ssize_t event_cnt_enable_read(struct counter_device *counter,
+				     struct counter_count *count, void *private,
+				     char *buf)
+{
+	struct event_cnt_priv *priv = counter->priv;
+
+	return sysfs_emit(buf, "%d\n", priv->enabled);
+}
+
+static ssize_t event_cnt_enable_write(struct counter_device *counter,
+				      struct counter_count *count,
+				      void *private, const char *buf,
+				      size_t len)
+{
+	struct event_cnt_priv *priv = counter->priv;
+	bool enable;
+	ssize_t ret;
+
+	ret = kstrtobool(buf, &enable);
+	if (ret)
+		return ret;
+
+	if (priv->enabled == enable)
+		return len;
+
+	if (enable) {
+		priv->enabled = enable;
+		enable_irq(priv->irq);
+	} else {
+		disable_irq(priv->irq);
+		priv->enabled = enable;
+	}
+
+	return len;
+}
+
+static const struct counter_count_ext event_cnt_ext[] = {
+	{
+		.name = "enable",
+		.read = event_cnt_enable_read,
+		.write = event_cnt_enable_write,
+	},
+};
+
+static enum counter_synapse_action event_cnt_synapse_actionss[] = {
+	COUNTER_SYNAPSE_ACTION_RISING_EDGE,
+};
+
+static int event_cnt_action_get(struct counter_device *counter,
+			    struct counter_count *count,
+			    struct counter_synapse *synapse,
+			    size_t *action)
+{
+	*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
+
+	return 0;
+}
+
+static int event_cnt_read(struct counter_device *counter,
+				 struct counter_count *count,
+				 unsigned long *val)
+{
+	struct event_cnt_priv *priv = counter->priv;
+
+	*val = atomic_read(&priv->count);
+
+	return 0;
+}
+
+static int event_cnt_write(struct counter_device *counter,
+				  struct counter_count *count,
+				  const unsigned long val)
+{
+	struct event_cnt_priv *priv = counter->priv;
+
+	atomic_set(&priv->count, val);
+
+	return 0;
+}
+
+static int event_cnt_function_get(struct counter_device *counter,
+				  struct counter_count *count, size_t *function)
+{
+	*function = COUNTER_COUNT_FUNCTION_INCREASE;
+
+	return 0;
+}
+
+static int event_cnt_signal_read(struct counter_device *counter,
+				 struct counter_signal *signal,
+				 enum counter_signal_value *val)
+{
+	struct event_cnt_priv *priv = counter->priv;
+	int ret;
+
+	ret = gpiod_get_value(priv->gpio);
+	if (ret < 0)
+		return ret;
+
+	*val = ret ? COUNTER_SIGNAL_HIGH : COUNTER_SIGNAL_LOW;
+
+	return 0;
+}
+
+static struct counter_signal event_cnt_signals[] = {
+	{
+		.id = 0,
+		.name = "Channel 0 signal",
+	},
+};
+
+static struct counter_synapse event_cnt_synapses[] = {
+	{
+		.actions_list = event_cnt_synapse_actionss,
+		.num_actions = ARRAY_SIZE(event_cnt_synapse_actionss),
+		.signal = &event_cnt_signals[0]
+	},
+};
+
+static enum counter_count_function event_cnt_functions[] = {
+	COUNTER_COUNT_FUNCTION_INCREASE,
+};
+
+static struct counter_count event_cnts[] = {
+	{
+		.id = 0,
+		.name = "Channel 1 Count",
+		.functions_list = event_cnt_functions,
+		.num_functions = ARRAY_SIZE(event_cnt_functions),
+		.synapses = event_cnt_synapses,
+		.num_synapses = ARRAY_SIZE(event_cnt_synapses),
+		.ext = event_cnt_ext,
+		.num_ext = ARRAY_SIZE(event_cnt_ext),
+	},
+};
+
+static int event_cnt_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct event_cnt_priv *priv;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->irq = platform_get_irq_optional(pdev,  0);
+	if (priv->irq == -ENXIO)
+		priv->irq = 0;
+	else if (priv->irq < 0)
+		return dev_err_probe(dev, priv->irq, "failed to get IRQ\n");
+
+	priv->gpio = devm_gpiod_get_optional(dev, NULL, GPIOD_IN);
+	if (IS_ERR(priv->gpio))
+		return dev_err_probe(dev, PTR_ERR(priv->gpio), "failed to get GPIO\n");
+
+	if (!priv->irq && !priv->gpio) {
+		dev_err(dev, "IRQ and GPIO are not found. At least one source should be provided\n");
+		return -ENODEV;
+	}
+
+	if (!priv->irq) {
+		int irq = gpiod_to_irq(priv->gpio);
+
+		if (irq < 0)
+			return dev_err_probe(dev, irq, "failed to get IRQ from GPIO\n");
+
+		priv->irq = irq;
+	}
+
+	priv->ops.action_get = event_cnt_action_get;
+	priv->ops.count_read = event_cnt_read;
+	priv->ops.count_write = event_cnt_write;
+	priv->ops.function_get = event_cnt_function_get;
+	if (priv->gpio)
+		priv->ops.signal_read  = event_cnt_signal_read;
+
+	priv->counter.name = dev_name(dev);
+	priv->counter.parent = dev;
+	priv->counter.ops = &priv->ops;
+	priv->counter.counts = event_cnts;
+	priv->counter.num_counts = ARRAY_SIZE(event_cnts);
+	priv->counter.signals = event_cnt_signals;
+	priv->counter.num_signals = ARRAY_SIZE(event_cnt_signals);
+	priv->counter.priv = priv;
+
+	irq_set_status_flags(priv->irq, IRQ_NOAUTOEN);
+	ret = devm_request_irq(dev, priv->irq, event_cnt_isr,
+			       IRQF_TRIGGER_RISING | IRQF_NO_THREAD,
+			       EVENT_CNT_NAME, priv);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, priv);
+
+	return devm_counter_register(dev, &priv->counter);
+}
+
+static const struct of_device_id event_cnt_of_match[] = {
+	{ .compatible = "event-counter", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, event_cnt_of_match);
+
+static struct platform_driver event_cnt_driver = {
+	.probe = event_cnt_probe,
+	.driver = {
+		.name = EVENT_CNT_NAME,
+		.of_match_table = event_cnt_of_match,
+	},
+};
+module_platform_driver(event_cnt_driver);
+
+MODULE_ALIAS("platform:event-counter");
+MODULE_AUTHOR("Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Event counter driver");
+MODULE_LICENSE("GPL v2");
-- 
2.30.0