[PATCH v1 0/2] add support for GPIO based counter

[PATCH v1 0/2] add support for GPIO based counter

[Oleksij Rempel]

Add support for GPIO based pulse counter. For now it can only count
pulses. With counter char device support, we will be able to attach
timestamps and measure actual pulse frequency.

Never the less, it is better to mainline this driver now (before chardev
patches go mainline), to provide developers additional use case for the counter
framework with chardev support.

Oleksij Rempel (2):
  dt-bindings: counter: add gpio-pulse-counter binding
  counter: add GPIO based pulse counters

 .../bindings/counter/gpio-pulse-counter.yaml  |  39 +++
 drivers/counter/Kconfig                       |   9 +
 drivers/counter/Makefile                      |   1 +
 drivers/counter/gpio-pulse-cnt.c              | 245 ++++++++++++++++++
 4 files changed, 294 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/counter/gpio-pulse-counter.yaml
 create mode 100644 drivers/counter/gpio-pulse-cnt.c

-- 
2.30.0

[PATCH v1 1/2] dt-bindings: counter: add gpio-pulse-counter binding

[Oleksij Rempel]

Add binding for GPIO based pulse counter node

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 .../bindings/counter/gpio-pulse-counter.yaml  | 39 +++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/counter/gpio-pulse-counter.yaml

diff --git a/Documentation/devicetree/bindings/counter/gpio-pulse-counter.yaml b/Documentation/devicetree/bindings/counter/gpio-pulse-counter.yaml
new file mode 100644
index 000000000000..dfa93956f15c
--- /dev/null
+++ b/Documentation/devicetree/bindings/counter/gpio-pulse-counter.yaml
@@ -0,0 +1,39 @@
+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/counter/gpio-pulse-counter.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: GPIO base pulse counter
+
+maintainers:
+  - Oleksij Rempel <o.rempel@pengutronix.de>
+
+properties:
+  compatible:
+    const: virtual,gpio-pulse-counter
+
+  gpios:
+    maxItems: 1
+
+required:
+  - gpios
+
+additionalProperties: false
+
+examples:
+  - |
+
+    #include <dt-bindings/gpio/gpio.h>
+
+    counter-0 {
+        compatible = "virtual,gpio-pulse-counter";
+        gpios = <&gpio 0 GPIO_ACTIVE_HIGH>;
+    };
+
+    counter-1 {
+        compatible = "virtual,gpio-pulse-counter";
+        gpios = <&gpio 1 GPIO_ACTIVE_HIGH>;
+    };
+
+...
-- 
2.30.0

[PATCH v1 2/2] counter: add GPIO based pulse counters

[Oleksij Rempel]

Add simple GPIO base pulse 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@pengutronix.de>
---
 drivers/counter/Kconfig          |   9 ++
 drivers/counter/Makefile         |   1 +
 drivers/counter/gpio-pulse-cnt.c | 245 +++++++++++++++++++++++++++++++
 3 files changed, 255 insertions(+)
 create mode 100644 drivers/counter/gpio-pulse-cnt.c

diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
index 2de53ab0dd25..9ad1d9d49dd1 100644
--- a/drivers/counter/Kconfig
+++ b/drivers/counter/Kconfig
@@ -29,6 +29,15 @@ config 104_QUAD_8
 	  The base port addresses for the devices may be configured via the base
 	  array module parameter.
 
+config GPIO_PULSE_CNT
+	tristate "GPIO pulse counter driver"
+	depends on GPIOLIB
+	help
+	  Select this option to enable GPIO pulse counter driver.
+
+	  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..6a5c3fc6f2a0 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_GPIO_PULSE_CNT)	+= gpio-pulse-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/gpio-pulse-cnt.c b/drivers/counter/gpio-pulse-cnt.c
new file mode 100644
index 000000000000..e847831f4cce
--- /dev/null
+++ b/drivers/counter/gpio-pulse-cnt.c
@@ -0,0 +1,245 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2021 Pengutronix, Oleksij Rempel <kernel@pengutronix.de>
+ */
+
+#include <linux/counter.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of_gpio.h>
+#include <linux/platform_device.h>
+
+#define GPIO_PULSE_NAME		"gpio-pulse-counter"
+
+struct gpio_pulse_priv {
+	struct counter_device counter;
+	struct gpio_desc *gpio;
+	int irq;
+	bool enabled;
+	unsigned long count;
+};
+
+static irqreturn_t gpio_pulse_irq_isr(int irq, void *dev_id)
+{
+	struct gpio_pulse_priv *priv = dev_id;
+
+	if (!priv->enabled)
+		return IRQ_NONE;
+
+	priv->count++;
+
+	return IRQ_HANDLED;
+}
+
+static ssize_t gpio_pulse_count_enable_read(struct counter_device *counter,
+					    struct counter_count *count,
+					    void *private, char *buf)
+{
+	struct gpio_pulse_priv *priv = counter->priv;
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", priv->enabled);
+}
+
+static ssize_t gpio_pulse_count_enable_write(struct counter_device *counter,
+					     struct counter_count *count,
+					     void *private,
+					     const char *buf, size_t len)
+{
+	struct gpio_pulse_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)
+		enable_irq(priv->irq);
+	else
+		disable_irq(priv->irq);
+
+	priv->enabled = enable;
+
+	return len;
+}
+
+static const struct counter_count_ext gpio_pulse_count_ext[] = {
+	{
+		.name = "enable",
+		.read = gpio_pulse_count_enable_read,
+		.write = gpio_pulse_count_enable_write
+	},
+};
+
+static enum counter_synapse_action gpio_pulse_synapse_actions[] = {
+	COUNTER_SYNAPSE_ACTION_RISING_EDGE,
+};
+
+static int gpio_pulse_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 gpio_pulse_count_read(struct counter_device *counter,
+				 struct counter_count *count,
+				 unsigned long *val)
+{
+	struct gpio_pulse_priv *priv = counter->priv;
+
+	*val = priv->count;
+
+	return 0;
+}
+
+static int gpio_pulse_count_write(struct counter_device *counter,
+				  struct counter_count *count,
+				  const unsigned long val)
+{
+	struct gpio_pulse_priv *priv = counter->priv;
+
+	priv->count = val;
+
+	return 0;
+}
+
+static int gpio_pulse_count_function_get(struct counter_device *counter,
+					 struct counter_count *count,
+					 size_t *function)
+{
+	*function = COUNTER_COUNT_FUNCTION_INCREASE;
+
+	return 0;
+}
+
+static int gpio_pulse_count_signal_read(struct counter_device *counter,
+					struct counter_signal *signal,
+					enum counter_signal_value *val)
+{
+	struct gpio_pulse_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 const struct counter_ops gpio_pulse_cnt_ops = {
+	.action_get = gpio_pulse_action_get,
+	.count_read = gpio_pulse_count_read,
+	.count_write = gpio_pulse_count_write,
+	.function_get = gpio_pulse_count_function_get,
+	.signal_read  = gpio_pulse_count_signal_read,
+};
+
+static struct counter_signal gpio_pulse_signals[] = {
+	{
+		.id = 0,
+		.name = "Channel 0 signal"
+	},
+};
+
+static struct counter_synapse gpio_pulse_count_synapses[] = {
+	{
+		.actions_list = gpio_pulse_synapse_actions,
+		.num_actions = ARRAY_SIZE(gpio_pulse_synapse_actions),
+		.signal = &gpio_pulse_signals[0]
+	},
+};
+
+static enum counter_count_function gpio_pulse_count_functions[] = {
+	COUNTER_COUNT_FUNCTION_INCREASE,
+};
+
+static struct counter_count gpio_pulse_counts[] = {
+	{
+		.id = 0,
+		.name = "Channel 1 Count",
+		.functions_list = gpio_pulse_count_functions,
+		.num_functions = ARRAY_SIZE(gpio_pulse_count_functions),
+		.synapses = gpio_pulse_count_synapses,
+		.num_synapses = ARRAY_SIZE(gpio_pulse_count_synapses),
+		.ext = gpio_pulse_count_ext,
+		.num_ext = ARRAY_SIZE(gpio_pulse_count_ext)
+	},
+};
+
+static int gpio_pulse_cnt_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct device *dev = &pdev->dev;
+	struct gpio_pulse_priv *priv;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	if (of_gpio_count(np) != 1) {
+		dev_err(dev, "Error, need exactly 1 gpio for device\n");
+		return -EINVAL;
+	}
+
+	priv->gpio = devm_fwnode_gpiod_get(dev, of_fwnode_handle(np),
+					   NULL, GPIOD_IN, GPIO_PULSE_NAME);
+	if (IS_ERR(priv->gpio))
+		return dev_err_probe(dev, PTR_ERR(priv->gpio), "failed to get gpio\n");
+
+	priv->irq = gpiod_to_irq(priv->gpio);
+	if (priv->irq < 0) {
+		dev_err(dev, "failed to map GPIO to IRQ: %d\n", priv->irq);
+		return priv->irq;
+	}
+
+	priv->counter.name = dev_name(dev);
+	priv->counter.parent = dev;
+	priv->counter.ops = &gpio_pulse_cnt_ops;
+	priv->counter.counts = gpio_pulse_counts;
+	priv->counter.num_counts = ARRAY_SIZE(gpio_pulse_counts);
+	priv->counter.signals = gpio_pulse_signals;
+	priv->counter.num_signals = ARRAY_SIZE(gpio_pulse_signals);
+	priv->counter.priv = priv;
+
+	ret = devm_request_irq(dev, priv->irq, gpio_pulse_irq_isr,
+			       IRQF_TRIGGER_RISING | IRQF_NO_THREAD,
+			       GPIO_PULSE_NAME, priv);
+	if (ret)
+		return ret;
+
+	disable_irq(priv->irq);
+
+	platform_set_drvdata(pdev, priv);
+
+	return devm_counter_register(dev, &priv->counter);
+}
+
+static const struct of_device_id gpio_pulse_cnt_of_match[] = {
+	{ .compatible = "virtual,gpio-pulse-counter", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, gpio_pulse_cnt_of_match);
+
+static struct platform_driver gpio_pulse_cnt_driver = {
+	.probe = gpio_pulse_cnt_probe,
+	.driver = {
+		.name = GPIO_PULSE_NAME,
+		.of_match_table = gpio_pulse_cnt_of_match,
+	},
+};
+module_platform_driver(gpio_pulse_cnt_driver);
+
+MODULE_ALIAS("platform:gpio-pulse-counter");
+MODULE_AUTHOR("Oleksij Rempel <o.rempel@pengutronix.de>");
+MODULE_DESCRIPTION("GPIO pulse counter driver");
+MODULE_LICENSE("GPL v2");
-- 
2.30.0

Re: [PATCH v1 2/2] counter: add GPIO based pulse counters

[Andy Shevchenko]

On Thu, Jan 21, 2021 at 4:32 PM Oleksij Rempel <o.rempel@pengutronix.de> wrote:
>
> Add simple GPIO base pulse 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.

...

> +#include <linux/of_gpio.h>

It would be better to see OF agnostic code WRT GPIOs.

...

> +static ssize_t gpio_pulse_count_enable_read(struct counter_device *counter,
> +                                           struct counter_count *count,
> +                                           void *private, char *buf)
> +{
> +       struct gpio_pulse_priv *priv = counter->priv;
> +
> +       return scnprintf(buf, PAGE_SIZE, "%d\n", priv->enabled);

sysfs_emit()

> +}
> +
> +static ssize_t gpio_pulse_count_enable_write(struct counter_device *counter,
> +                                            struct counter_count *count,
> +                                            void *private,
> +                                            const char *buf, size_t len)
> +{
> +       struct gpio_pulse_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)
> +               enable_irq(priv->irq);
> +       else
> +               disable_irq(priv->irq);

Oops, if IRQ happens here, shouldn't we have priv->enabled already set properly?

> +       priv->enabled = enable;
> +
> +       return len;
> +}
> +
> +static const struct counter_count_ext gpio_pulse_count_ext[] = {
> +       {
> +               .name = "enable",
> +               .read = gpio_pulse_count_enable_read,
> +               .write = gpio_pulse_count_enable_write

Leave the comma here.

> +       },
> +};

...

> +static struct counter_signal gpio_pulse_signals[] = {
> +       {
> +               .id = 0,
> +               .name = "Channel 0 signal"

Leave the comma.

> +       },
> +};
> +
> +static struct counter_synapse gpio_pulse_count_synapses[] = {
> +       {
> +               .actions_list = gpio_pulse_synapse_actions,
> +               .num_actions = ARRAY_SIZE(gpio_pulse_synapse_actions),
> +               .signal = &gpio_pulse_signals[0]

Ditto.

> +       },
> +};

...

> +static struct counter_count gpio_pulse_counts[] = {
> +       {
> +               .id = 0,
> +               .name = "Channel 1 Count",
> +               .functions_list = gpio_pulse_count_functions,
> +               .num_functions = ARRAY_SIZE(gpio_pulse_count_functions),
> +               .synapses = gpio_pulse_count_synapses,
> +               .num_synapses = ARRAY_SIZE(gpio_pulse_count_synapses),
> +               .ext = gpio_pulse_count_ext,
> +               .num_ext = ARRAY_SIZE(gpio_pulse_count_ext)

Ditto

> +       },
> +};
> +

...

> +       struct device_node *np = pdev->dev.of_node;

> +       if (of_gpio_count(np) != 1) {
> +               dev_err(dev, "Error, need exactly 1 gpio for device\n");
> +               return -EINVAL;
> +       }

gpiod_count() ?

> +       priv->gpio = devm_fwnode_gpiod_get(dev, of_fwnode_handle(np),
> +                                          NULL, GPIOD_IN, GPIO_PULSE_NAME);

of node to fwnode, can we avoid dragging this here to there?

Why is devm_gpiod_get() followed by a label setting not good enough?

> +       if (IS_ERR(priv->gpio))
> +               return dev_err_probe(dev, PTR_ERR(priv->gpio), "failed to get gpio\n");

...

> +static const struct of_device_id gpio_pulse_cnt_of_match[] = {
> +       { .compatible = "virtual,gpio-pulse-counter", },
> +       {},

No comma needed for real terminator entry.

> +};

-- 
With Best Regards,
Andy Shevchenko