[PATCH v14 0/3] PPS: pps-gpio PPS ECHO implementation

[PATCH v14 0/3] PPS: pps-gpio PPS ECHO implementation

[Tom Burkart]

Hi all,
please find attached the PPS-GPIO PPS ECHO implementation patch. The
driver claims to have echo functionality in the sysfs interface but this
functionality is not present.  This patch provides this functionality.

Part 1 of the patch change the original driver from the number
based GPIO API to the descriptor based API.

Parts 2 and 3 then add the PPS ECHO functionality.  This is enabled if a
"echo-gpios" entry is found in the devicetree.

Changes in v10:
Changes requested by Philipp Zabel:
Mostly cosmetic changes: PATCH 2/4 now reviewed.  Thanks a lot, Philipp!
(Please note that as of v11 PATCH 1 is gone so this has become PATCH 1/3)

Change in v11:
Change requested by Rob Herring:
All changes in regard to the capture-clear DT entry are gone.

Change in v12:
Change requested by Rob Herring:
Deleted superfluous use of invert-pps-echo

Change in v13:
Patch 2/3 (DT bindings) now reviewed. Thanks a lot, Rob!

Changes in v14:
Simplify code enabling PPS ECHO functionality.

On the linuxpps mailing list it was suggested to use a hrtimer for
resetting the GPIO ECHO active state to the inactive state.
Please also comment on whether a hrtimer is necessary/desirable for the
purpose of resetting the echo pin active state.  I am happy to implement
it if this is useful/desirable.

Please install, test and comment as it is now a quite major change to
the driver.
Suggestions for improvement are welcome.

Tom Burkart

Tom Burkart (3):
  pps: descriptor-based gpio
  dt-bindings: pps: pps-gpio PPS ECHO implementation
  pps: pps-gpio pps-echo implementation

 Documentation/devicetree/bindings/pps/pps-gpio.txt |   7 +
 drivers/pps/clients/pps-gpio.c                     | 154 ++++++++++++++++-----
 include/linux/pps-gpio.h                           |   5 +-
 3 files changed, 126 insertions(+), 40 deletions(-)

-- 
2.12.3

[PATCH v14 1/3] pps: descriptor-based gpio

[Tom Burkart]

This patch changes the GPIO access for the pps-gpio driver from the
integer based API to the descriptor based API.

Reviewed-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Tom Burkart <tom@aussec.com>
---
 drivers/pps/clients/pps-gpio.c | 67 +++++++++++++++++++-----------------------
 include/linux/pps-gpio.h       |  3 +-
 2 files changed, 32 insertions(+), 38 deletions(-)

diff --git a/drivers/pps/clients/pps-gpio.c b/drivers/pps/clients/pps-gpio.c
index dd5d1103e02b..4e5e9229814b 100644
--- a/drivers/pps/clients/pps-gpio.c
+++ b/drivers/pps/clients/pps-gpio.c
@@ -31,7 +31,7 @@
 #include <linux/slab.h>
 #include <linux/pps_kernel.h>
 #include <linux/pps-gpio.h>
-#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
 #include <linux/list.h>
 #include <linux/of_device.h>
 #include <linux/of_gpio.h>
@@ -41,9 +41,9 @@ struct pps_gpio_device_data {
 	int irq;			/* IRQ used as PPS source */
 	struct pps_device *pps;		/* PPS source device */
 	struct pps_source_info info;	/* PPS source information */
+	struct gpio_desc *gpio_pin;	/* GPIO port descriptors */
 	bool assert_falling_edge;
 	bool capture_clear;
-	unsigned int gpio_pin;
 };
 
 /*
@@ -61,18 +61,37 @@ static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
 
 	info = data;
 
-	rising_edge = gpio_get_value(info->gpio_pin);
+	rising_edge = gpiod_get_value(info->gpio_pin);
 	if ((rising_edge && !info->assert_falling_edge) ||
 			(!rising_edge && info->assert_falling_edge))
 		pps_event(info->pps, &ts, PPS_CAPTUREASSERT, NULL);
 	else if (info->capture_clear &&
 			((rising_edge && info->assert_falling_edge) ||
-			 (!rising_edge && !info->assert_falling_edge)))
+			(!rising_edge && !info->assert_falling_edge)))
 		pps_event(info->pps, &ts, PPS_CAPTURECLEAR, NULL);
 
 	return IRQ_HANDLED;
 }
 
+static int pps_gpio_setup(struct platform_device *pdev)
+{
+	struct pps_gpio_device_data *data = platform_get_drvdata(pdev);
+	struct device_node *np = pdev->dev.of_node;
+
+	data->gpio_pin = devm_gpiod_get(&pdev->dev,
+		NULL,	/* request "gpios" */
+		GPIOD_IN);
+	if (IS_ERR(data->gpio_pin)) {
+		dev_err(&pdev->dev,
+			"failed to request PPS GPIO\n");
+		return PTR_ERR(data->gpio_pin);
+	}
+
+	if (of_property_read_bool(np, "assert-falling-edge"))
+		data->assert_falling_edge = true;
+	return 0;
+}
+
 static unsigned long
 get_irqf_trigger_flags(const struct pps_gpio_device_data *data)
 {
@@ -90,53 +109,30 @@ get_irqf_trigger_flags(const struct pps_gpio_device_data *data)
 static int pps_gpio_probe(struct platform_device *pdev)
 {
 	struct pps_gpio_device_data *data;
-	const char *gpio_label;
 	int ret;
 	int pps_default_params;
 	const struct pps_gpio_platform_data *pdata = pdev->dev.platform_data;
-	struct device_node *np = pdev->dev.of_node;
 
 	/* allocate space for device info */
-	data = devm_kzalloc(&pdev->dev, sizeof(struct pps_gpio_device_data),
-			GFP_KERNEL);
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
 	if (!data)
 		return -ENOMEM;
+	platform_set_drvdata(pdev, data);
 
+	/* GPIO setup */
 	if (pdata) {
 		data->gpio_pin = pdata->gpio_pin;
-		gpio_label = pdata->gpio_label;
 
 		data->assert_falling_edge = pdata->assert_falling_edge;
 		data->capture_clear = pdata->capture_clear;
 	} else {
-		ret = of_get_gpio(np, 0);
-		if (ret < 0) {
-			dev_err(&pdev->dev, "failed to get GPIO from device tree\n");
-			return ret;
-		}
-		data->gpio_pin = ret;
-		gpio_label = PPS_GPIO_NAME;
-
-		if (of_get_property(np, "assert-falling-edge", NULL))
-			data->assert_falling_edge = true;
-	}
-
-	/* GPIO setup */
-	ret = devm_gpio_request(&pdev->dev, data->gpio_pin, gpio_label);
-	if (ret) {
-		dev_err(&pdev->dev, "failed to request GPIO %u\n",
-			data->gpio_pin);
-		return ret;
-	}
-
-	ret = gpio_direction_input(data->gpio_pin);
-	if (ret) {
-		dev_err(&pdev->dev, "failed to set pin direction\n");
-		return -EINVAL;
+		ret = pps_gpio_setup(pdev);
+		if (ret)
+			return -EINVAL;
 	}
 
 	/* IRQ setup */
-	ret = gpio_to_irq(data->gpio_pin);
+	ret = gpiod_to_irq(data->gpio_pin);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "failed to map GPIO to IRQ: %d\n", ret);
 		return -EINVAL;
@@ -173,7 +169,6 @@ static int pps_gpio_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
-	platform_set_drvdata(pdev, data);
 	dev_info(data->pps->dev, "Registered IRQ %d as PPS source\n",
 		 data->irq);
 
@@ -209,4 +204,4 @@ MODULE_AUTHOR("Ricardo Martins <rasm@fe.up.pt>");
 MODULE_AUTHOR("James Nuss <jamesnuss@nanometrics.ca>");
 MODULE_DESCRIPTION("Use GPIO pin as PPS source");
 MODULE_LICENSE("GPL");
-MODULE_VERSION("1.0.0");
+MODULE_VERSION("1.1.0");
diff --git a/include/linux/pps-gpio.h b/include/linux/pps-gpio.h
index 56f35dd3d01d..f028d2cda6f5 100644
--- a/include/linux/pps-gpio.h
+++ b/include/linux/pps-gpio.h
@@ -23,10 +23,9 @@
 #define _PPS_GPIO_H
 
 struct pps_gpio_platform_data {
+	struct gpio_desc *gpio_pin;
 	bool assert_falling_edge;
 	bool capture_clear;
-	unsigned int gpio_pin;
-	const char *gpio_label;
 };
 
 #endif /* _PPS_GPIO_H */
-- 
2.12.3

[PATCH v14 2/3] dt-bindings: pps: pps-gpio PPS ECHO implementation

[Tom Burkart]

This patch implements the device tree binding changes required for the
pps echo functionality for pps-gpio, that sysfs claims is available
already.

This patch was originally written by Lukas Senger as part of a masters
thesis project and modified for inclusion into the linux kernel by Tom
Burkart.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lukas Senger <lukas@fridolin.com>
Signed-off-by: Tom Burkart <tom@aussec.com>
---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/devicetree/bindings/pps/pps-gpio.txt b/Documentation/devicetree/bindings/pps/pps-gpio.txt
index 3683874832ae..9012a2a02e14 100644
--- a/Documentation/devicetree/bindings/pps/pps-gpio.txt
+++ b/Documentation/devicetree/bindings/pps/pps-gpio.txt
@@ -7,6 +7,10 @@ Required properties:
 - compatible: should be "pps-gpio"
 - gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
 
+Additional required properties for the PPS ECHO functionality:
+- echo-gpios: one PPS ECHO GPIO in the format described by ../gpio/gpio.txt
+- echo-active-ms: duration in ms of the active portion of the echo pulse
+
 Optional properties:
 - assert-falling-edge: when present, assert is indicated by a falling edge
                        (instead of by a rising edge)
@@ -19,5 +23,8 @@ Example:
 		gpios = <&gpio1 26 GPIO_ACTIVE_HIGH>;
 		assert-falling-edge;
 
+		echo-gpios = <&gpio1 27 GPIO_ACTIVE_HIGH>;
+		echo-active-ms = <100>;
+
 		compatible = "pps-gpio";
 	};
-- 
2.12.3

[PATCH v14 3/3] pps: pps-gpio pps-echo implementation

[Tom Burkart]

This patch implements the pps echo functionality for pps-gpio, that
sysfs claims is available already.

Configuration is done via device tree bindings.

This patch was originally written by Lukas Senger as part of a masters
thesis project and modified for inclusion into the linux kernel by Tom
Burkart.

Signed-off-by: Lukas Senger <lukas@fridolin.com>
Signed-off-by: Tom Burkart <tom@aussec.com>
---
 drivers/pps/clients/pps-gpio.c | 89 ++++++++++++++++++++++++++++++++++++++++--
 include/linux/pps-gpio.h       |  2 +
 2 files changed, 88 insertions(+), 3 deletions(-)

diff --git a/drivers/pps/clients/pps-gpio.c b/drivers/pps/clients/pps-gpio.c
index 4e5e9229814b..f00f5ca9f9ad 100644
--- a/drivers/pps/clients/pps-gpio.c
+++ b/drivers/pps/clients/pps-gpio.c
@@ -35,6 +35,8 @@
 #include <linux/list.h>
 #include <linux/of_device.h>
 #include <linux/of_gpio.h>
+#include <linux/timer.h>
+#include <linux/jiffies.h>
 
 /* Info for each registered platform device */
 struct pps_gpio_device_data {
@@ -42,8 +44,12 @@ struct pps_gpio_device_data {
 	struct pps_device *pps;		/* PPS source device */
 	struct pps_source_info info;	/* PPS source information */
 	struct gpio_desc *gpio_pin;	/* GPIO port descriptors */
+	struct gpio_desc *echo_pin;
+	struct timer_list echo_timer;	/* timer to reset echo active state */
 	bool assert_falling_edge;
 	bool capture_clear;
+	unsigned int echo_active_ms;	/* PPS echo active duration */
+	unsigned long echo_timeout;	/* timer timeout value in jiffies */
 };
 
 /*
@@ -64,19 +70,57 @@ static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
 	rising_edge = gpiod_get_value(info->gpio_pin);
 	if ((rising_edge && !info->assert_falling_edge) ||
 			(!rising_edge && info->assert_falling_edge))
-		pps_event(info->pps, &ts, PPS_CAPTUREASSERT, NULL);
+		pps_event(info->pps, &ts, PPS_CAPTUREASSERT, data);
 	else if (info->capture_clear &&
 			((rising_edge && info->assert_falling_edge) ||
 			(!rising_edge && !info->assert_falling_edge)))
-		pps_event(info->pps, &ts, PPS_CAPTURECLEAR, NULL);
+		pps_event(info->pps, &ts, PPS_CAPTURECLEAR, data);
 
 	return IRQ_HANDLED;
 }
 
+static void pps_gpio_echo(struct pps_device *pps, int event, void *data)
+{
+	/* add_timer() needs to write into info->echo_timer */
+	struct pps_gpio_device_data *info;
+
+	info = data;
+
+	switch (event) {
+	case PPS_CAPTUREASSERT:
+		if (pps->params.mode & PPS_ECHOASSERT)
+			gpiod_set_value(info->echo_pin, 1);
+		break;
+
+	case PPS_CAPTURECLEAR:
+		if (pps->params.mode & PPS_ECHOCLEAR)
+			gpiod_set_value(info->echo_pin, 1);
+		break;
+	}
+
+	/* fire the timer */
+	if (info->pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) {
+		info->echo_timer.expires = jiffies + info->echo_timeout;
+		add_timer(&info->echo_timer);
+	}
+}
+
+/* Timer callback to reset the echo pin to the inactive state */
+static void pps_gpio_echo_timer_callback(struct timer_list *t)
+{
+	const struct pps_gpio_device_data *info;
+
+	info = from_timer(info, t, echo_timer);
+
+	gpiod_set_value(info->echo_pin, 0);
+}
+
 static int pps_gpio_setup(struct platform_device *pdev)
 {
 	struct pps_gpio_device_data *data = platform_get_drvdata(pdev);
 	struct device_node *np = pdev->dev.of_node;
+	int ret;
+	u32 value;
 
 	data->gpio_pin = devm_gpiod_get(&pdev->dev,
 		NULL,	/* request "gpios" */
@@ -87,6 +131,33 @@ static int pps_gpio_setup(struct platform_device *pdev)
 		return PTR_ERR(data->gpio_pin);
 	}
 
+	data->echo_pin = devm_gpiod_get_optional(&pdev->dev,
+			"echo",
+			GPIOD_OUT_LOW);
+	if (data->echo_pin) {
+		if (IS_ERR(data->echo_pin)) {
+			dev_err(&pdev->dev, "failed to request ECHO GPIO\n");
+			return PTR_ERR(data->echo_pin);
+		}
+
+		ret = of_property_read_u32(np,
+			"echo-active-ms",
+			&value);
+		if (ret) {
+			dev_err(&pdev->dev,
+				"failed to get echo-active-ms from OF\n");
+			return ret;
+		}
+		data->echo_active_ms = value;
+		/* sanity check on echo_active_ms */
+		if (!data->echo_active_ms || data->echo_active_ms > 999) {
+			dev_err(&pdev->dev,
+				"echo-active-ms: %u - bad value from OF\n",
+				data->echo_active_ms);
+			return -EINVAL;
+		}
+	}
+
 	if (of_property_read_bool(np, "assert-falling-edge"))
 		data->assert_falling_edge = true;
 	return 0;
@@ -122,9 +193,11 @@ static int pps_gpio_probe(struct platform_device *pdev)
 	/* GPIO setup */
 	if (pdata) {
 		data->gpio_pin = pdata->gpio_pin;
+		data->echo_pin = pdata->echo_pin;
 
 		data->assert_falling_edge = pdata->assert_falling_edge;
 		data->capture_clear = pdata->capture_clear;
+		data->echo_active_ms = pdata->echo_active_ms;
 	} else {
 		ret = pps_gpio_setup(pdev);
 		if (ret)
@@ -148,6 +221,11 @@ static int pps_gpio_probe(struct platform_device *pdev)
 	data->info.owner = THIS_MODULE;
 	snprintf(data->info.name, PPS_MAX_NAME_LEN - 1, "%s.%d",
 		 pdev->name, pdev->id);
+	if (data->echo_pin) {
+		data->info.echo = pps_gpio_echo;
+		data->echo_timeout = msecs_to_jiffies(data->echo_active_ms);
+		timer_setup(&data->echo_timer, pps_gpio_echo_timer_callback, 0);
+	}
 
 	/* register PPS source */
 	pps_default_params = PPS_CAPTUREASSERT | PPS_OFFSETASSERT;
@@ -180,6 +258,11 @@ static int pps_gpio_remove(struct platform_device *pdev)
 	struct pps_gpio_device_data *data = platform_get_drvdata(pdev);
 
 	pps_unregister_source(data->pps);
+	if (data->echo_pin) {
+		del_timer_sync(&data->echo_timer);
+		/* reset echo pin in any case */
+		gpiod_set_value(data->echo_pin, 0);
+	}
 	dev_info(&pdev->dev, "removed IRQ %d as PPS source\n", data->irq);
 	return 0;
 }
@@ -204,4 +287,4 @@ MODULE_AUTHOR("Ricardo Martins <rasm@fe.up.pt>");
 MODULE_AUTHOR("James Nuss <jamesnuss@nanometrics.ca>");
 MODULE_DESCRIPTION("Use GPIO pin as PPS source");
 MODULE_LICENSE("GPL");
-MODULE_VERSION("1.1.0");
+MODULE_VERSION("1.2.0");
diff --git a/include/linux/pps-gpio.h b/include/linux/pps-gpio.h
index f028d2cda6f5..44171e6b7197 100644
--- a/include/linux/pps-gpio.h
+++ b/include/linux/pps-gpio.h
@@ -24,8 +24,10 @@
 
 struct pps_gpio_platform_data {
 	struct gpio_desc *gpio_pin;
+	struct gpio_desc *echo_pin;
 	bool assert_falling_edge;
 	bool capture_clear;
+	unsigned int echo_active_ms;
 };
 
 #endif /* _PPS_GPIO_H */
-- 
2.12.3

Re: [PATCH v14 2/3] dt-bindings: pps: pps-gpio PPS ECHO implementation

[Rodolfo Giometti]

On 30/12/2018 09:33, Tom Burkart wrote:
> This patch implements the device tree binding changes required for the
> pps echo functionality for pps-gpio, that sysfs claims is available
> already.
> 
> This patch was originally written by Lukas Senger as part of a masters
> thesis project and modified for inclusion into the linux kernel by Tom
> Burkart.

I think this patch it's OK but I'm asking to myself if it should be merged with 
next one... logically it describes what patch 3/3 does so why do we keep them 
separated?

Ciao,

Rodolfo

-- 
GNU/Linux Solutions                  e-mail: giometti@enneenne.com
Linux Device Driver                          giometti@linux.it
Embedded Systems                     phone:  +39 349 2432127
UNIX programming                     skype:  rodolfo.giometti

Re: [PATCH v14 3/3] pps: pps-gpio pps-echo implementation

[Rodolfo Giometti]

On 30/12/2018 09:33, Tom Burkart wrote:
> This patch implements the pps echo functionality for pps-gpio, that
> sysfs claims is available already.
> 
> Configuration is done via device tree bindings.
> 
> This patch was originally written by Lukas Senger as part of a masters
> thesis project and modified for inclusion into the linux kernel by Tom
> Burkart.

[snip]

> +static void pps_gpio_echo(struct pps_device *pps, int event, void *data)
> +{
> +	/* add_timer() needs to write into info->echo_timer */
> +	struct pps_gpio_device_data *info;
> +
> +	info = data;

Maybe you can write as below and saving two lines and having better readability:

struct pps_gpio_device_data *info = data;

> +	switch (event) {
> +	case PPS_CAPTUREASSERT:
> +		if (pps->params.mode & PPS_ECHOASSERT)
> +			gpiod_set_value(info->echo_pin, 1);
> +		break;
> +
> +	case PPS_CAPTURECLEAR:
> +		if (pps->params.mode & PPS_ECHOCLEAR)
> +			gpiod_set_value(info->echo_pin, 1);
> +		break;
> +	}
> +
> +	/* fire the timer */
> +	if (info->pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) {
> +		info->echo_timer.expires = jiffies + info->echo_timeout;
> +		add_timer(&info->echo_timer);
> +	}
> +}

I think is better firing the timer if and only if we set the echo GPIO otherwise 
it's useless...

Ciao,

Rodolfo

-- 
GNU/Linux Solutions                  e-mail: giometti@enneenne.com
Linux Device Driver                          giometti@linux.it
Embedded Systems                     phone:  +39 349 2432127
UNIX programming                     skype:  rodolfo.giometti