PPS: pps-gpio PPS ECHO implementation

PATCH Superseded Tom Burkart 2 participants 16 messages Nov 14, 2018 – Dec 1, 2018

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Device tree bindings PPS support

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Tom Burkart

author

2018-11-14 12:55 UTC #0 lore raw

v7 cover PPS: pps-gpio PPS ECHO implementation

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.

Parts 1 and 2 of the patch change the original driver from the number based GPIO ABI to the descriptor based ABI. This has been modified to not break backward compatibility.

Parts 3 and 4 then add the PPS ECHO functionality. This is enabled if a "echo-gpios" entry is found in the devicetree.

Changes in v4:
There is a bugfix in part 2 that was returning an uninitialised variable and juggling some code that speeds up the probe by not running code when not using PPS ECHO.

Changes in v5:
Meet all requirements of checkpatch

Changes in v6:
Cosmetic changes to code layout

Changes in v7:
Also accept the DEPRECATED "gpios" devicetree entry to ensure backward compatibility.

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 there is a need.

Please install, test and comment as it is now a quite major change to the driver.
Please do send suggestions for improvement.

Tom Burkart

Tom Burkart (4):
dt-bindings: pps: descriptor-based gpio, capture-clear addition
pps: descriptor-based gpio, capture-clear addition
dt-bindings: pps: pps-gpio PPS ECHO implementation
pps: pps-gpio pps-echo implementation

 Documentation/devicetree/bindings/pps/pps-gpio.txt |  17 +-
 drivers/pps/clients/pps-gpio.c                     | 225 +++++++++++++++++----
 include/linux/pps-gpio.h                           |   6 +-
 3 files changed, 203 insertions(+), 45 deletions(-)

Signature · 1 line

2.12.3

Tom Burkart

author

2018-11-14 12:54 UTC #1 lore raw

PATCH v7 1/4 dt-bindings: pps: descriptor-based gpio, capture-clear addition

This patch changes the devicetree bindings for the pps-gpio driver from the integer based ABI to the descriptor based ABI. It also adds documentation for the device tree capture-clear option. The legacy device tree entry for the GPIO pin is supported.

Signed-off-by Tom Burkart <[email protected]>

---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Documentation/devicetree/bindings/pps/pps-gpio.txt +6 -2

index 3683874832ae..6c9fc0998d94 100644
@@ -5,19 +5,23 @@ a GPIO pin.
 
 Required properties:
 - compatible: should be "pps-gpio"
-- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+- pps-gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+Alternatively (DEPRECATED), instead of pps-gpios above, it may have:
+- gpios: one PPS GPIO as above
 
 Optional properties:
 - assert-falling-edge: when present, assert is indicated by a falling edge
                        (instead of by a rising edge)
+- capture-clear: when present, also capture the PPS clear event
 
 Example:
 	pps {
 		pinctrl-names = "default";
 		pinctrl-0 = <&pinctrl_pps>;
 
-		gpios = <&gpio1 26 GPIO_ACTIVE_HIGH>;
+		pps-gpios = <&gpio1 26 GPIO_ACTIVE_HIGH>;
 		assert-falling-edge;
+		capture-clear;
 
 		compatible = "pps-gpio";
 	};

Signature · 1 line

2.12.3

Tom Burkart

author

2018-11-14 12:55 UTC #2 lore raw

PATCH v7 2/4 pps: descriptor-based gpio, capture-clear addition

This patch changes the GPIO access for the pps-gpio driver from the integer based ABI to the descriptor based ABI. It also adds documentation for the device tree capture-clear option and device tree capture-clear extraction. The legacy device tree entry for the GPIO pin is supported.

Signed-off-by Tom Burkart <[email protected]>

---
 drivers/pps/clients/pps-gpio.c | 124 ++++++++++++++++++++++++++++-------------
 include/linux/pps-gpio.h       |   3 +-
 2 files changed, 86 insertions(+), 41 deletions(-)

drivers/pps/clients/pps-gpio.c +84 ~~-40~~

index 333ad7d5b45b..aa8b8fb0e9ab 100644
@@ -31,7 +31,8 @@
 #include <linux/slab.h>
 #include <linux/pps_kernel.h>
 #include <linux/pps-gpio.h>
-#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>	/* GPIO descriptor ABI */
+#include <linux/gpio.h>			/* GPIO integer ABI */
 #include <linux/list.h>
 #include <linux/of_device.h>
 #include <linux/of_gpio.h>

@@ -41,9 +42,11 @@ 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;
+	bool legacy_int_gpio;		/* flag for which ABI to use */
+	unsigned int gpio_pin_int;	/* GPIO integer ABI */
 };
 
 /*

@@ -61,18 +64,87 @@ static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
 
 	info = data;
 
-	rising_edge = gpio_get_value(info->gpio_pin);
+	if (info->legacy_int_gpio)
+		rising_edge = gpio_get_value(info->gpio_pin_int);
+	else
+		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);
+	const struct pps_gpio_platform_data *pdata = pdev->dev.platform_data;
+	struct device_node *np = pdev->dev.of_node;
+	const char *gpio_label;
+	int ret;
+
+	if (pdata) {
+		data->gpio_pin_int = pdata->gpio_pin_int;
+		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 {
+		if (of_get_property(np, "gpios", NULL)) { /* integer GPIO */
+			data->legacy_int_gpio = true;
+
+			ret = of_get_named_gpio(np, "gpios", 0);
+			if (ret < 0) {
+				dev_err(&pdev->dev,
+					"failed to get GPIO from device tree\n");
+				return ret;
+			}
+			data->gpio_pin_int = ret;
+			gpio_label = PPS_GPIO_NAME;
+
+		} else {	/* descriptor GPIO */
+			data->gpio_pin = devm_gpiod_get(&pdev->dev,
+				"pps",
+				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_get_property(np, "assert-falling-edge", NULL))
+			data->assert_falling_edge = true;
+
+		if (of_get_property(np, "capture-clear", NULL))
+			data->capture_clear = true;
+	}
+
+	/* GPIO setup */
+	if (data->legacy_int_gpio) {
+		ret = devm_gpio_request(&pdev->dev,
+			data->gpio_pin_int,
+			gpio_label);
+		if (ret) {
+			dev_err(&pdev->dev, "failed to request GPIO %u\n",
+				data->gpio_pin_int);
+			return ret;
+		}
+
+		ret = gpio_direction_input(data->gpio_pin_int);
+		if (ret) {
+			dev_err(&pdev->dev, "failed to set pin as input\n");
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+
 static unsigned long
 get_irqf_trigger_flags(const struct pps_gpio_device_data *data)
 {

@@ -90,53 +162,26 @@ 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);
 	if (!data)
 		return -ENOMEM;
-
-	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;
-	}
+	platform_set_drvdata(pdev, data);
 
 	/* 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");
+	ret = pps_gpio_setup(pdev);
+	if (ret)
 		return -EINVAL;
-	}
 
 	/* IRQ setup */
-	ret = gpio_to_irq(data->gpio_pin);
+	if (data->legacy_int_gpio)
+		ret = gpio_to_irq(data->gpio_pin_int);
+	else
+		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 +218,6 @@ 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 +253,4 @@ MODULE_AUTHOR("Ricardo Martins <[email protected]>");
 MODULE_AUTHOR("James Nuss <[email protected]>");
 MODULE_DESCRIPTION("Use GPIO pin as PPS source");
 MODULE_LICENSE("GPL");
-MODULE_VERSION("1.0.0");
+MODULE_VERSION("1.1.0");

include/linux/pps-gpio.h +2 -1

index 56f35dd3d01d..86e2081dc7d1 100644
@@ -23,9 +23,10 @@
 #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;
+	unsigned int gpio_pin_int;
 	const char *gpio_label;
 };

Signature · 1 line

2.12.3

Tom Burkart

author

2018-11-14 12:54 UTC #3 lore raw

PATCH v7 3/4 dt-bindings: pps: pps-gpio PPS ECHO implementation

This patch implements the device tree 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.

Signed-off-by Lukas Senger <[email protected]>

Signed-off-by Tom Burkart <[email protected]>

---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 9 +++++++++
 1 file changed, 9 insertions(+)

Documentation/devicetree/bindings/pps/pps-gpio.txt +9 -0

index 6c9fc0998d94..f85dbe4ce0b3 100644
@@ -9,10 +9,15 @@ Required properties:
 Alternatively (DEPRECATED), instead of pps-gpios above, it may have:
 - gpios: one PPS GPIO as above
 
+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)
 - capture-clear: when present, also capture the PPS clear event
+- invert-pps-echo: when present, invert the PPS ECHO pulse
 
 Example:
 	pps {

@@ -23,5 +28,9 @@ Example:
 		assert-falling-edge;
 		capture-clear;
 
+		echo-gpios = <&gpio1 27 GPIO_ACTIVE_HIGH>;
+		echo-active-ms = <100>;
+		invert-pps-echo;
+
 		compatible = "pps-gpio";
 	};

Signature · 1 line

2.12.3

Tom Burkart

author

2018-11-14 12:55 UTC #4 lore raw

PATCH v7 4/4 pps: pps-gpio pps-echo implementation

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 <[email protected]>

Signed-off-by Tom Burkart <[email protected]>

---
 drivers/pps/clients/pps-gpio.c | 103 +++++++++++++++++++++++++++++++++++++++--
 include/linux/pps-gpio.h       |   3 ++
 2 files changed, 103 insertions(+), 3 deletions(-)

drivers/pps/clients/pps-gpio.c +100 -3

index aa8b8fb0e9ab..ea035399d56d 100644
@@ -36,6 +36,8 @@
 #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 {

@@ -43,10 +45,16 @@ 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;
+	bool enable_pps_echo;
+	bool invert_pps_echo;
 	bool legacy_int_gpio;		/* flag for which ABI to use */
+	unsigned int echo_active_ms;	/* PPS echo active duration */
 	unsigned int gpio_pin_int;	/* GPIO integer ABI */
+	unsigned long echo_timeout;	/* timer timeout value in jiffies */
 };
 
 /*

@@ -70,15 +78,54 @@ 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,
+				info->invert_pps_echo ? 0 : 1);
+		break;
+
+	case PPS_CAPTURECLEAR:
+		if (pps->params.mode & PPS_ECHOCLEAR)
+			gpiod_set_value(info->echo_pin,
+				info->invert_pps_echo ? 0 : 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,
+		info->invert_pps_echo ? 1 : 0);
+}
+
 static int pps_gpio_setup(struct platform_device *pdev)
 {
 	struct pps_gpio_device_data *data = platform_get_drvdata(pdev);

@@ -86,14 +133,20 @@ static int pps_gpio_setup(struct platform_device *pdev)
 	struct device_node *np = pdev->dev.of_node;
 	const char *gpio_label;
 	int ret;
+	u32 value;
 
 	if (pdata) {
 		data->gpio_pin_int = pdata->gpio_pin_int;
 		data->gpio_pin = pdata->gpio_pin;
+		data->echo_pin = pdata->echo_pin;
+		if (pdata->echo_pin != NULL)
+			data->enable_pps_echo = true;
 		gpio_label = pdata->gpio_label;
 
 		data->assert_falling_edge = pdata->assert_falling_edge;
 		data->capture_clear = pdata->capture_clear;
+		data->invert_pps_echo = pdata->invert_pps_echo;
+		data->echo_active_ms = pdata->echo_active_ms;
 	} else {
 		if (of_get_property(np, "gpios", NULL)) { /* integer GPIO */
 			data->legacy_int_gpio = true;

@@ -118,11 +171,45 @@ static int pps_gpio_setup(struct platform_device *pdev)
 			}
 		}
 
+		if (of_get_property(np, "echo-gpios", NULL)) {
+			data->enable_pps_echo = true;
+
+			data->echo_pin = devm_gpiod_get(&pdev->dev,
+				"echo",
+				GPIOD_OUT_LOW);
+			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;
+		}
+
+
 		if (of_get_property(np, "assert-falling-edge", NULL))
 			data->assert_falling_edge = true;
 
 		if (of_get_property(np, "capture-clear", NULL))
 			data->capture_clear = true;
+
+		if (of_get_property(np, "invert-pps-echo", NULL))
+			data->invert_pps_echo = true;
+	}
+	/* sanity check on echo_active_ms */
+	if (data->enable_pps_echo
+			&& (!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;
 	}
 
 	/* GPIO setup */

@@ -197,6 +284,11 @@ 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->enable_pps_echo) {
+		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;

@@ -229,6 +321,11 @@ 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->enable_pps_echo) {
+		del_timer_sync(&data->echo_timer);
+		/* reset echo pin in any case */
+		gpiod_set_value(data->echo_pin, data->invert_pps_echo ? 1 : 0);
+	}
 	dev_info(&pdev->dev, "removed IRQ %d as PPS source\n", data->irq);
 	return 0;
 }

@@ -253,4 +350,4 @@ MODULE_AUTHOR("Ricardo Martins <[email protected]>");
 MODULE_AUTHOR("James Nuss <[email protected]>");
 MODULE_DESCRIPTION("Use GPIO pin as PPS source");
 MODULE_LICENSE("GPL");
-MODULE_VERSION("1.1.0");
+MODULE_VERSION("1.2.0");

include/linux/pps-gpio.h +3 -0

index 86e2081dc7d1..21eceb90187d 100644
@@ -24,8 +24,11 @@
 
 struct pps_gpio_platform_data {
 	struct gpio_desc *gpio_pin;
+	struct gpio_desc *echo_pin;
 	bool assert_falling_edge;
 	bool capture_clear;
+	bool invert_pps_echo;
+	unsigned int echo_active_ms;
 	unsigned int gpio_pin_int;
 	const char *gpio_label;
 };

Signature · 1 line

2.12.3

Rob Herring

maintainer

2018-11-16 22:49 UTC #5 lore raw

Re: [PATCH v7 1/4] dt-bindings: pps: descriptor-based gpio, capture-clear addition

In reply to Tom Burkart

Quoted 2 lines · Tom Burkart

This patch changes the devicetree bindings for the pps-gpio driver from the integer based ABI to the descriptor based ABI.

? That has nothing to do with DT.

Quoted 16 lines

It also adds
documentation for the device tree capture-clear option. The legacy device tree entry for the GPIO pin is supported.
Signed-off-by Tom Burkart <[email protected]>
---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
Documentation/devicetree/bindings/pps/pps-gpio.txt +0 -0
index 3683874832ae..6c9fc0998d94 100644
@@ -5,19 +5,23 @@ a GPIO pin.
 
 Required properties:

Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 15

Quoted 10 lines

Documentation/devicetree/bindings/pps/pps-gpio.txt +4 -1

 - compatible: should be "pps-gpio"
-- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+- pps-gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+Alternatively (DEPRECATED), instead of pps-gpios above, it may have:
+- gpios: one PPS GPIO as above
 
 Optional properties:
 - assert-falling-edge: when present, assert is indicated by a falling edge
                        (instead of by a rising edge)
+- capture-clear: when present, also capture the PPS clear event

Is this a h/w thing? or driver configuration?

Quoted 16 lines

Documentation/devicetree/bindings/pps/pps-gpio.txt +2 -1

 Example:
 	pps {
 		pinctrl-names = "default";
 		pinctrl-0 = <&pinctrl_pps>;
 
-		gpios = <&gpio1 26 GPIO_ACTIVE_HIGH>;
+		pps-gpios = <&gpio1 26 GPIO_ACTIVE_HIGH>;
 		assert-falling-edge;
+		capture-clear;
 
 		compatible = "pps-gpio";
 	};

Signature · 1 line

2.12.3

tom burkart

author

2018-11-17 10:35 UTC #6 lore raw

Re: [PATCH v7 1/4] dt-bindings: pps: descriptor-based gpio, capture-clear addition

Quoting Rob Herring <[email protected]>:

Quoted 4 lines · Tom Burkart

Quoted 2 lines
This patch changes the devicetree bindings for the pps-gpio driver from the integer based ABI to the descriptor based ABI.
? That has nothing to do with DT.

I believe it does, as the change in ABI forces a rename in the DT naming convention. This is due to the descriptor based ABI appending "-gpio" or "-gpios" (see Documentation/gpio/base.txt.)
Admittedly, I may have called it by the wrong name due to ignorance, my apologies.

Quoted 22 lines

Quoted 22 lines
It also adds
documentation for the device tree capture-clear option. The legacy device tree entry for the GPIO pin is supported.
Signed-off-by Tom Burkart <[email protected]>
---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
Documentation/devicetree/bindings/pps/pps-gpio.txt +3 -1
index 3683874832ae..6c9fc0998d94 100644
@@ -5,19 +5,23 @@ a GPIO pin.
 
 Required properties:
 - compatible: should be "pps-gpio"
-- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+- pps-gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+Alternatively (DEPRECATED), instead of pps-gpios above, it may have:
+- gpios: one PPS GPIO as above
 

Quoted 6 lines

Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 15
Quoted 4 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
 Optional properties:
 - assert-falling-edge: when present, assert is indicated by a falling edge
                        (instead of by a rising edge)
+- capture-clear: when present, also capture the PPS clear event
Is this a h/w thing? or driver configuration?

Driver configuration. Most of the code was present in the driver, yet it was not documented, or usable due to a two line (code) omission (the value was not being fetched from DT).

Quoted 18 lines

Quoted 16 lines

Documentation/devicetree/bindings/pps/pps-gpio.txt +2 -2

 Example:
 	pps {
 		pinctrl-names = "default";
 		pinctrl-0 = <&pinctrl_pps>;
 
-		gpios = <&gpio1 26 GPIO_ACTIVE_HIGH>;
+		pps-gpios = <&gpio1 26 GPIO_ACTIVE_HIGH>;
 		assert-falling-edge;
+		capture-clear;
 
 		compatible = "pps-gpio";
 	};
--

2.12.3

Rob Herring

maintainer

2018-11-17 14:22 UTC #7 lore raw

Re: [PATCH v7 1/4] dt-bindings: pps: descriptor-based gpio, capture-clear addition

Quoted 6 lines · tom burkart

Quoting Rob Herring <[email protected]>:
Quoted 3 lines · Tom Burkart
Quoted 2 lines
This patch changes the devicetree bindings for the pps-gpio driver from the integer based ABI to the descriptor based ABI.

Quoted 8 lines

Quoted 1 line
? That has nothing to do with DT.
I believe it does, as the change in ABI forces a rename in the DT naming convention.
This is due to the descriptor based ABI appending "-gpio" or "-gpios" (see Documentation/gpio/base.txt.)
Admittedly, I may have called it by the wrong name due to ignorance, my apologies.

If what you say is correct, then you can't change this driver. You'll break compatibility with any existing DT.

Changing the binding reasoning should purely be that this is the preferred form. Bindings must be independent from changing kernel APIs.

Quoted 31 lines

Quoted 24 lines
Quoted 24 lines
It also adds
documentation for the device tree capture-clear option. The legacy device tree entry for the GPIO pin is supported.
Signed-off-by Tom Burkart <[email protected]>
---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
Documentation/devicetree/bindings/pps/pps-gpio.txt +3 -1
index 3683874832ae..6c9fc0998d94 100644
@@ -5,19 +5,23 @@ a GPIO pin.
 
 Required properties:
 - compatible: should be "pps-gpio"
-- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+- pps-gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+Alternatively (DEPRECATED), instead of pps-gpios above, it may have:
+- gpios: one PPS GPIO as above
 
Quoted 6 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 15
Quoted 4 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
 Optional properties:
 - assert-falling-edge: when present, assert is indicated by a falling edge
                        (instead of by a rising edge)
+- capture-clear: when present, also capture the PPS clear event
Is this a h/w thing? or driver configuration?

Quoted 3 lines

Driver configuration. Most of the code was present in the driver, yet it was not documented, or usable due to a two line (code) omission (the value was not being fetched from DT).

So what determines how you want to configure this? If the user will want to change it, then it should be a sysfs attr and exposed to userspace. If it depends on h/w config for a board then it can be in DT.

Rob

tom burkart

author

2018-11-18 00:35 UTC #8 lore raw

Re: [PATCH v7 1/4] dt-bindings: pps: descriptor-based gpio, capture-clear addition

Quoting Rob Herring <[email protected]>:

Quoted 16 lines · tom burkart

Quoted 6 lines
Quoting Rob Herring <[email protected]>:
Quoted 3 lines · Tom Burkart
Quoted 2 lines
This patch changes the devicetree bindings for the pps-gpio driver from the integer based ABI to the descriptor based ABI.
Quoted 8 lines
Quoted 1 line
? That has nothing to do with DT.
I believe it does, as the change in ABI forces a rename in the DT naming convention.
This is due to the descriptor based ABI appending "-gpio" or "-gpios" (see Documentation/gpio/base.txt.)
Admittedly, I may have called it by the wrong name due to ignorance, my apologies.

Quoted 6 lines

If what you say is correct, then you can't change this driver. You'll break compatibility with any existing DT.
Changing the binding reasoning should purely be that this is the preferred form. Bindings must be independent from changing kernel APIs.

See comments from Philip Zabel. I misread the documentation and this has now been corrected in v8 of the patch. I hope that eliminates all comments made above.

Quoted 31 lines

Quoted 31 lines
Quoted 23 lines
Quoted 23 lines
It also adds
documentation for the device tree capture-clear option. The legacy device tree entry for the GPIO pin is supported.
Signed-off-by Tom Burkart <[email protected]>
---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
Documentation/devicetree/bindings/pps/pps-gpio.txt +3 -1
index 3683874832ae..6c9fc0998d94 100644
@@ -5,19 +5,23 @@ a GPIO pin.
 
 Required properties:
 - compatible: should be "pps-gpio"
-- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+- pps-gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+Alternatively (DEPRECATED), instead of pps-gpios above, it may have:
+- gpios: one PPS GPIO as above
 
Quoted 2 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 13
Quoted 2 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt +0 -0
 Optional properties:
 - assert-falling-edge: when present, assert is indicated by a  
falling edge
Quoted 4 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 15
Quoted 2 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
                        (instead of by a rising edge)
+- capture-clear: when present, also capture the PPS clear event
Is this a h/w thing? or driver configuration?

Quoted 8 lines

Quoted 3 lines
Driver configuration. Most of the code was present in the driver, yet it was not documented, or usable due to a two line (code) omission (the value was not being fetched from DT).
So what determines how you want to configure this? If the user will want to change it, then it should be a sysfs attr and exposed to userspace. If it depends on h/w config for a board then it can be in DT.

Sorry, I misled you somewhat. If the PPS pulse active transition from the hardware is on the falling edge, this flag is required to get the OS to use that as the active transition. This would not change at the user's whim but rather it is dependent on connected hardware.

Tom

Rob Herring

maintainer

2018-11-26 19:39 UTC #9 lore raw

Re: [PATCH v7 1/4] dt-bindings: pps: descriptor-based gpio, capture-clear addition

Quoted 70 lines · tom burkart

Quoting Rob Herring <[email protected]>:
Quoted 16 lines · tom burkart
Quoted 6 lines
Quoting Rob Herring <[email protected]>:
Quoted 3 lines · Tom Burkart
Quoted 2 lines
This patch changes the devicetree bindings for the pps-gpio driver from the integer based ABI to the descriptor based ABI.
Quoted 8 lines
Quoted 1 line
? That has nothing to do with DT.
I believe it does, as the change in ABI forces a rename in the DT naming convention.
This is due to the descriptor based ABI appending "-gpio" or "-gpios" (see Documentation/gpio/base.txt.)
Admittedly, I may have called it by the wrong name due to ignorance, my apologies.
Quoted 6 lines
If what you say is correct, then you can't change this driver. You'll break compatibility with any existing DT.
Changing the binding reasoning should purely be that this is the preferred form. Bindings must be independent from changing kernel APIs.
See comments from Philip Zabel. I misread the documentation and this has now been corrected in v8 of the patch. I hope that eliminates all comments made above.
Quoted 31 lines
Quoted 31 lines
Quoted 23 lines
Quoted 23 lines
It also adds
documentation for the device tree capture-clear option. The legacy device tree entry for the GPIO pin is supported.
Signed-off-by Tom Burkart <[email protected]>
---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
Documentation/devicetree/bindings/pps/pps-gpio.txt +3 -1
index 3683874832ae..6c9fc0998d94 100644
@@ -5,19 +5,23 @@ a GPIO pin.
 
 Required properties:
 - compatible: should be "pps-gpio"
-- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+- pps-gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+Alternatively (DEPRECATED), instead of pps-gpios above, it may have:
+- gpios: one PPS GPIO as above
 
Quoted 2 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 13
Quoted 2 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt +0 -0
 Optional properties:
 - assert-falling-edge: when present, assert is indicated by a
falling edge
Quoted 4 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 15
Quoted 2 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
                        (instead of by a rising edge)
+- capture-clear: when present, also capture the PPS clear event
Is this a h/w thing? or driver configuration?
Quoted 8 lines
Quoted 3 lines
Driver configuration. Most of the code was present in the driver, yet it was not documented, or usable due to a two line (code) omission (the value was not being fetched from DT).
So what determines how you want to configure this? If the user will want to change it, then it should be a sysfs attr and exposed to userspace. If it depends on h/w config for a board then it can be in DT.

Quoted 4 lines

Sorry, I misled you somewhat. If the PPS pulse active transition from the hardware is on the falling edge, this flag is required to get the OS to use that as the active transition. This would not change at the user's whim but rather it is dependent on connected hardware.

This description sounds more like 'assert-falling-edge' than 'capture-clear'.

I'm still not clear on what 'capture-clear' is.

Rob

tom burkart

author

2018-11-27 03:57 UTC #10 lore raw

Re: [PATCH v7 1/4] dt-bindings: pps: descriptor-based gpio, capture-clear addition

Hi Rob,

Quoting Rob Herring <[email protected]>:

Quoted 72 lines · tom burkart

Quoted 71 lines
Quoting Rob Herring <[email protected]>:
Quoted 12 lines · tom burkart
Quoted 11 lines
Quoting Rob Herring <[email protected]>:
Quoted 4 lines · Tom Burkart
Quoted 2 lines
This patch changes the devicetree bindings for the pps-gpio driver from the integer based ABI to the descriptor based ABI.
? That has nothing to do with DT.
I believe it does, as the change in ABI forces a rename in the DT naming convention.
This is due to the descriptor based ABI appending "-gpio" or
"-gpios" (see
Quoted 10 lines
Quoted 3 lines
Documentation/gpio/base.txt.)
Admittedly, I may have called it by the wrong name due to ignorance, my apologies.
If what you say is correct, then you can't change this driver. You'll break compatibility with any existing DT.
Changing the binding reasoning should purely be that this is the preferred form. Bindings must be independent from changing kernel APIs.
See comments from Philip Zabel. I misread the documentation and this has now been corrected in v8 of the patch. I hope that eliminates all comments made above.
Quoted 39 lines
Quoted 26 lines
Quoted 23 lines
Quoted 23 lines
It also adds
documentation for the device tree capture-clear option. The legacy device tree entry for the GPIO pin is supported.
Signed-off-by Tom Burkart <[email protected]>
---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
Documentation/devicetree/bindings/pps/pps-gpio.txt +3 -1
index 3683874832ae..6c9fc0998d94 100644
@@ -5,19 +5,23 @@ a GPIO pin.
 
 Required properties:
 - compatible: should be "pps-gpio"
-- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+- pps-gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+Alternatively (DEPRECATED), instead of pps-gpios above, it may have:
+- gpios: one PPS GPIO as above
 
Quoted 2 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 13
Quoted 2 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt +0 -0
 Optional properties:
 - assert-falling-edge: when present, assert is indicated by a
falling edge
Quoted 8 lines
Quoted 4 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 15
Quoted 2 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
                        (instead of by a rising edge)
+- capture-clear: when present, also capture the PPS clear event
Is this a h/w thing? or driver configuration?
Driver configuration. Most of the code was present in the driver, yet it was not documented, or usable due to a two line (code) omission (the value was not being fetched from DT).
So what determines how you want to configure this? If the user will want to change it, then it should be a sysfs attr and exposed to userspace. If it depends on h/w config for a board then it can be in DT.

Quoted 8 lines

Quoted 4 lines
Sorry, I misled you somewhat. If the PPS pulse active transition from the hardware is on the falling edge, this flag is required to get the OS to use that as the active transition. This would not change at the user's whim but rather it is dependent on connected hardware.
This description sounds more like 'assert-falling-edge' than 'capture-clear'.
I'm still not clear on what 'capture-clear' is.

Ignoring my patch for a minute, the pps_gpio_irq_handler will only report a pps PPS_CAPTURECLEAR event if 'capture-clear' is set. As the current pps-gpio driver is not able to set this flag, it cannot ever report a PPS_CAPTURECLEAR event.

My patch adds the ability to set this flag and adds the documentation to go with it.
Admittedly, I do not require this functionality for what I want, but working with the code, I noticed the omission and decided to add it for someone else to use it, if they need it.

I am happy to remove this out of my patch, if you feel this to be the best way forward.

Tom

Rob Herring

maintainer

2018-11-28 17:13 UTC #11 lore raw

Re: [PATCH v7 1/4] dt-bindings: pps: descriptor-based gpio, capture-clear addition

Quoted 91 lines · tom burkart

Hi Rob,
Quoting Rob Herring <[email protected]>:
Quoted 72 lines · tom burkart
Quoted 71 lines
Quoting Rob Herring <[email protected]>:
Quoted 12 lines · tom burkart
Quoted 11 lines
Quoting Rob Herring <[email protected]>:
Quoted 4 lines · Tom Burkart
Quoted 2 lines
This patch changes the devicetree bindings for the pps-gpio driver from the integer based ABI to the descriptor based ABI.
? That has nothing to do with DT.
I believe it does, as the change in ABI forces a rename in the DT naming convention.
This is due to the descriptor based ABI appending "-gpio" or
"-gpios" (see
Quoted 10 lines
Quoted 3 lines
Documentation/gpio/base.txt.)
Admittedly, I may have called it by the wrong name due to ignorance, my apologies.
If what you say is correct, then you can't change this driver. You'll break compatibility with any existing DT.
Changing the binding reasoning should purely be that this is the preferred form. Bindings must be independent from changing kernel APIs.
See comments from Philip Zabel. I misread the documentation and this has now been corrected in v8 of the patch. I hope that eliminates all comments made above.
Quoted 39 lines
Quoted 26 lines
Quoted 23 lines
Quoted 23 lines
It also adds
documentation for the device tree capture-clear option. The legacy device tree entry for the GPIO pin is supported.
Signed-off-by Tom Burkart <[email protected]>
---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
Documentation/devicetree/bindings/pps/pps-gpio.txt +3 -1
index 3683874832ae..6c9fc0998d94 100644
@@ -5,19 +5,23 @@ a GPIO pin.
 
 Required properties:
 - compatible: should be "pps-gpio"
-- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+- pps-gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+Alternatively (DEPRECATED), instead of pps-gpios above, it may have:
+- gpios: one PPS GPIO as above
 
Quoted 2 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 13
Quoted 2 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt +0 -0
 Optional properties:
 - assert-falling-edge: when present, assert is indicated by a
falling edge
Quoted 8 lines
Quoted 4 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 15
Quoted 2 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
                        (instead of by a rising edge)
+- capture-clear: when present, also capture the PPS clear event
Is this a h/w thing? or driver configuration?
Driver configuration. Most of the code was present in the driver, yet it was not documented, or usable due to a two line (code) omission (the value was not being fetched from DT).
So what determines how you want to configure this? If the user will want to change it, then it should be a sysfs attr and exposed to userspace. If it depends on h/w config for a board then it can be in DT.
Quoted 8 lines
Quoted 4 lines
Sorry, I misled you somewhat. If the PPS pulse active transition from the hardware is on the falling edge, this flag is required to get the OS to use that as the active transition. This would not change at the user's whim but rather it is dependent on connected hardware.
This description sounds more like 'assert-falling-edge' than 'capture-clear'.
I'm still not clear on what 'capture-clear' is.
Ignoring my patch for a minute, the pps_gpio_irq_handler will only report a pps PPS_CAPTURECLEAR event if 'capture-clear' is set. As the current pps-gpio driver is not able to set this flag, it cannot ever report a PPS_CAPTURECLEAR event.

Quoted 8 lines

My patch adds the ability to set this flag and adds the documentation to go with it.
Admittedly, I do not require this functionality for what I want, but working with the code, I noticed the omission and decided to add it for someone else to use it, if they need it.
I am happy to remove this out of my patch, if you feel this to be the best way forward.

I found this prior discussion on adding this[1]. Seems to me this should be userspace configurable if the GPIO line can interrupt on both edges. We shouldn't need a DT property to determine that.

Rob

[1] https://lore.kernel.org/patchwork/patch/557781/

tom burkart

author

2018-11-29 00:29 UTC #12 lore raw

Re: [PATCH v7 1/4] dt-bindings: pps: descriptor-based gpio, capture-clear addition

Quoting Rob Herring <[email protected]>:

Quoted 102 lines · tom burkart

Quoted 92 lines
Quoting Rob Herring <[email protected]>:
Quoted 48 lines · tom burkart
Quoted 47 lines
Quoting Rob Herring <[email protected]>:
Quoted 12 lines · tom burkart
Quoted 11 lines
Quoting Rob Herring <[email protected]>:
Quoted 4 lines · Tom Burkart
Quoted 2 lines
This patch changes the devicetree bindings for the pps-gpio driver from the integer based ABI to the descriptor based ABI.
? That has nothing to do with DT.
I believe it does, as the change in ABI forces a rename in the DT naming convention.
This is due to the descriptor based ABI appending "-gpio" or
"-gpios" (see
Quoted 10 lines
Quoted 3 lines
Documentation/gpio/base.txt.)
Admittedly, I may have called it by the wrong name due to ignorance, my apologies.
If what you say is correct, then you can't change this driver. You'll break compatibility with any existing DT.
Changing the binding reasoning should purely be that this is the preferred form. Bindings must be independent from changing kernel APIs.
See comments from Philip Zabel. I misread the documentation and this has now been corrected in v8 of the patch. I hope that eliminates all comments made above.
Quoted 16 lines
Quoted 16 lines
Quoted 16 lines
Quoted 16 lines
It also adds
documentation for the device tree capture-clear option. The legacy device tree entry for the GPIO pin is supported.
Signed-off-by Tom Burkart <[email protected]>
---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
Documentation/devicetree/bindings/pps/pps-gpio.txt +0 -0
index 3683874832ae..6c9fc0998d94 100644
@@ -5,19 +5,23 @@ a GPIO pin.
 
Quoted 4 lines
Quoted 4 lines
Quoted 4 lines
Quoted 4 lines
Quoted 4 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 8
Quoted 4 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -1
 Required properties:
 - compatible: should be "pps-gpio"
-- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+- pps-gpios: one PPS GPIO in the format described by  
../gpio/gpio.txt
Quoted 1 line
Quoted 1 line
Quoted 1 line
Quoted 1 line
Quoted 1 line
Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 9
Quoted 1 line
Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
+Alternatively (DEPRECATED), instead of pps-gpios above,  
it may have:
Quoted 19 lines
Quoted 19 lines
Quoted 18 lines
Quoted 5 lines
Quoted 4 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 13
Quoted 4 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
+- gpios: one PPS GPIO as above
 
 Optional properties:
 - assert-falling-edge: when present, assert is indicated by a
falling edge
Quoted 8 lines
Quoted 4 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 15
Quoted 2 lines
Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
                        (instead of by a rising edge)
+- capture-clear: when present, also capture the PPS clear event
Is this a h/w thing? or driver configuration?
Driver configuration. Most of the code was present in the driver, yet it was not documented, or usable due to a two line (code) omission (the value was not being fetched from DT).
So what determines how you want to configure this? If the user will want to change it, then it should be a sysfs attr and exposed to userspace. If it depends on h/w config for a board then it can be in DT.
Quoted 6 lines
Quoted 4 lines
Sorry, I misled you somewhat. If the PPS pulse active transition from the hardware is on the falling edge, this flag is required to get the OS to use that as the active transition. This would not change at the user's whim but rather it is dependent on connected hardware.
This description sounds more like 'assert-falling-edge' than
'capture-clear'.
Quoted 2 lines
I'm still not clear on what 'capture-clear' is.
Ignoring my patch for a minute, the pps_gpio_irq_handler will only report a pps PPS_CAPTURECLEAR event if 'capture-clear' is set. As the current pps-gpio driver is not able to set this flag, it cannot ever report a PPS_CAPTURECLEAR event.
Quoted 8 lines
My patch adds the ability to set this flag and adds the documentation to go with it.
Admittedly, I do not require this functionality for what I want, but working with the code, I noticed the omission and decided to add it for someone else to use it, if they need it.
I am happy to remove this out of my patch, if you feel this to be the best way forward.

Quoted 7 lines

I found this prior discussion on adding this[1]. Seems to me this should be userspace configurable if the GPIO line can interrupt on both edges. We shouldn't need a DT property to determine that.
Rob
[1] https://lore.kernel.org/patchwork/patch/557781/

Patch v11 has just been sent that has no changes to the capture-clear DT option.

Tom

tom burkart

author

2018-11-29 02:05 UTC #13 lore raw

Re: [PATCH v7 1/4] dt-bindings: pps: descriptor-based gpio, capture-clear addition

In reply to Rob Herring

Quoting Rob Herring <[email protected]>:

Quoted 102 lines · tom burkart

Quoted 92 lines
Quoting Rob Herring <[email protected]>:
Quoted 48 lines · tom burkart
Quoted 47 lines
Quoting Rob Herring <[email protected]>:
Quoted 12 lines · tom burkart
Quoted 11 lines
Quoting Rob Herring <[email protected]>:
Quoted 4 lines · Tom Burkart
Quoted 2 lines
This patch changes the devicetree bindings for the pps-gpio driver from the integer based ABI to the descriptor based ABI.
? That has nothing to do with DT.
I believe it does, as the change in ABI forces a rename in the DT naming convention.
This is due to the descriptor based ABI appending "-gpio" or
"-gpios" (see
Quoted 10 lines
Quoted 3 lines
Documentation/gpio/base.txt.)
Admittedly, I may have called it by the wrong name due to ignorance, my apologies.
If what you say is correct, then you can't change this driver. You'll break compatibility with any existing DT.
Changing the binding reasoning should purely be that this is the preferred form. Bindings must be independent from changing kernel APIs.
See comments from Philip Zabel. I misread the documentation and this has now been corrected in v8 of the patch. I hope that eliminates all comments made above.
Quoted 16 lines
Quoted 16 lines
Quoted 16 lines
Quoted 16 lines
It also adds
documentation for the device tree capture-clear option. The legacy device tree entry for the GPIO pin is supported.
Signed-off-by Tom Burkart <[email protected]>
---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
Documentation/devicetree/bindings/pps/pps-gpio.txt +0 -0
index 3683874832ae..6c9fc0998d94 100644
@@ -5,19 +5,23 @@ a GPIO pin.
 
Quoted 4 lines
Quoted 4 lines
Quoted 4 lines
Quoted 4 lines
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Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 8
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Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -1
 Required properties:
 - compatible: should be "pps-gpio"
-- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+- pps-gpios: one PPS GPIO in the format described by  
../gpio/gpio.txt
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Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 9
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Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
+Alternatively (DEPRECATED), instead of pps-gpios above,  
it may have:
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Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 13
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Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
+- gpios: one PPS GPIO as above
 
 Optional properties:
 - assert-falling-edge: when present, assert is indicated by a
falling edge
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Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 15
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Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
                        (instead of by a rising edge)
+- capture-clear: when present, also capture the PPS clear event
Is this a h/w thing? or driver configuration?
Driver configuration. Most of the code was present in the driver, yet it was not documented, or usable due to a two line (code) omission (the value was not being fetched from DT).
So what determines how you want to configure this? If the user will want to change it, then it should be a sysfs attr and exposed to userspace. If it depends on h/w config for a board then it can be in DT.
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Sorry, I misled you somewhat. If the PPS pulse active transition from the hardware is on the falling edge, this flag is required to get the OS to use that as the active transition. This would not change at the user's whim but rather it is dependent on connected hardware.
This description sounds more like 'assert-falling-edge' than
'capture-clear'.
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I'm still not clear on what 'capture-clear' is.
Ignoring my patch for a minute, the pps_gpio_irq_handler will only report a pps PPS_CAPTURECLEAR event if 'capture-clear' is set. As the current pps-gpio driver is not able to set this flag, it cannot ever report a PPS_CAPTURECLEAR event.
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My patch adds the ability to set this flag and adds the documentation to go with it.
Admittedly, I do not require this functionality for what I want, but working with the code, I noticed the omission and decided to add it for someone else to use it, if they need it.
I am happy to remove this out of my patch, if you feel this to be the best way forward.

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I found this prior discussion on adding this[1]. Seems to me this should be userspace configurable if the GPIO line can interrupt on both edges. We shouldn't need a DT property to determine that.
Rob
[1] https://lore.kernel.org/patchwork/patch/557781/

Hi Rob,
the fact that prior knowledge of board/CPU/SOC specifics is required is the most compelling argument for this to be in the DT. This is not something a user should need to know or remember.

Userspace is already asking for what they need via the time_pps_setparams call, but to do that they have to first call time_pps_getparams. Time_pps_getparams will not return PPS_CAPTURECLEAR as it is never set in the driver due to it being hardware specific/unable to be set.

Tom

Rob Herring

maintainer

2018-11-29 18:00 UTC #14 lore raw

Re: [PATCH v7 1/4] dt-bindings: pps: descriptor-based gpio, capture-clear addition

Quoted 118 lines · tom burkart

Quoting Rob Herring <[email protected]>:
Quoted 102 lines · tom burkart
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Quoting Rob Herring <[email protected]>:
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Quoting Rob Herring <[email protected]>:
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Quoting Rob Herring <[email protected]>:
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This patch changes the devicetree bindings for the pps-gpio driver from the integer based ABI to the descriptor based ABI.
? That has nothing to do with DT.
I believe it does, as the change in ABI forces a rename in the DT naming convention.
This is due to the descriptor based ABI appending "-gpio" or
"-gpios" (see
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Documentation/gpio/base.txt.)
Admittedly, I may have called it by the wrong name due to ignorance, my apologies.
If what you say is correct, then you can't change this driver. You'll break compatibility with any existing DT.
Changing the binding reasoning should purely be that this is the preferred form. Bindings must be independent from changing kernel APIs.
See comments from Philip Zabel. I misread the documentation and this has now been corrected in v8 of the patch. I hope that eliminates all comments made above.
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It also adds
documentation for the device tree capture-clear option. The legacy device tree entry for the GPIO pin is supported.
Signed-off-by Tom Burkart <[email protected]>
---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
Documentation/devicetree/bindings/pps/pps-gpio.txt +0 -0
index 3683874832ae..6c9fc0998d94 100644
@@ -5,19 +5,23 @@ a GPIO pin.
 
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Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 8
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Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -1
 Required properties:
 - compatible: should be "pps-gpio"
-- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
+- pps-gpios: one PPS GPIO in the format described by
../gpio/gpio.txt
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Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 9
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Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
+Alternatively (DEPRECATED), instead of pps-gpios above,
it may have:
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Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 13
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Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
+- gpios: one PPS GPIO as above
 
 Optional properties:
 - assert-falling-edge: when present, assert is indicated by a
falling edge
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Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 15
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Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
                        (instead of by a rising edge)
+- capture-clear: when present, also capture the PPS clear event
Is this a h/w thing? or driver configuration?
Driver configuration. Most of the code was present in the driver, yet it was not documented, or usable due to a two line (code) omission (the value was not being fetched from DT).
So what determines how you want to configure this? If the user will want to change it, then it should be a sysfs attr and exposed to userspace. If it depends on h/w config for a board then it can be in DT.
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Sorry, I misled you somewhat. If the PPS pulse active transition from the hardware is on the falling edge, this flag is required to get the OS to use that as the active transition. This would not change at the user's whim but rather it is dependent on connected hardware.
This description sounds more like 'assert-falling-edge' than
'capture-clear'.
Quoted 2 lines
I'm still not clear on what 'capture-clear' is.
Ignoring my patch for a minute, the pps_gpio_irq_handler will only report a pps PPS_CAPTURECLEAR event if 'capture-clear' is set. As the current pps-gpio driver is not able to set this flag, it cannot ever report a PPS_CAPTURECLEAR event.
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My patch adds the ability to set this flag and adds the documentation to go with it.
Admittedly, I do not require this functionality for what I want, but working with the code, I noticed the omission and decided to add it for someone else to use it, if they need it.
I am happy to remove this out of my patch, if you feel this to be the best way forward.
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I found this prior discussion on adding this[1]. Seems to me this should be userspace configurable if the GPIO line can interrupt on both edges. We shouldn't need a DT property to determine that.
Rob
[1] https://lore.kernel.org/patchwork/patch/557781/
Hi Rob,
the fact that prior knowledge of board/CPU/SOC specifics is required is the most compelling argument for this to be in the DT. This is not something a user should need to know or remember.

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Userspace is already asking for what they need via the time_pps_setparams call, but to do that they have to first call time_pps_getparams. Time_pps_getparams will not return PPS_CAPTURECLEAR as it is never set in the driver due to it being hardware specific/unable to be set.

My understanding is it is a 2 step process. The capability is exposed to the user if the hardware supports it, but it is still a user decision whether or not to enable it. So as far as DT bindings are concerned, we're only concerned with the first part. Whether the hardware supports capture clear in the GPIO PPS case just depends on whether the GPIO controller can support both edge interrupts (or emulate that by switching between rising/falling edge interrupts). Do we agree on that part?

Needing to know GPIO interrupt capabilities is hardly specific to PPS. There is not any explicit property in DT for this capability because it is implicit based on the GPIO controller's compatible string (or driver capabilities if emulated). Therefore, it is up to the GPIO driver and API to expose this information to client drivers like PPS.

Rob

tom burkart

author

2018-12-01 22:24 UTC #15 lore raw

Re: [PATCH v7 1/4] dt-bindings: pps: descriptor-based gpio, capture-clear addition

Quoting Rob Herring <[email protected]>:

Quoted 131 lines · tom burkart

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Quoting Rob Herring <[email protected]>:
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This patch changes the devicetree bindings for the
pps-gpio driver
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from the integer based ABI to the descriptor based ABI.
? That has nothing to do with DT.
I believe it does, as the change in ABI forces a rename in the DT naming convention.
This is due to the descriptor based ABI appending "-gpio" or
"-gpios" (see
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Documentation/gpio/base.txt.)
Admittedly, I may have called it by the wrong name due to
ignorance,
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my apologies.
If what you say is correct, then you can't change this
driver. You'll
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break compatibility with any existing DT.
Changing the binding reasoning should purely be that this is the preferred form. Bindings must be independent from changing kernel APIs.
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See comments from Philip Zabel. I misread the documentation and this has now been corrected in v8 of the patch. I hope that eliminates all comments made above.
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It also adds
documentation for the device tree capture-clear option.
The legacy
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device tree entry for the GPIO pin is supported.
Signed-off-by Tom Burkart <[email protected]>
---
 Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
Documentation/devicetree/bindings/pps/pps-gpio.txt +0 -0
index 3683874832ae..6c9fc0998d94 100644
@@ -5,19 +5,23 @@ a GPIO pin.
 
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Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 8
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Documentation/devicetree/bindings/pps/pps-gpio.txt +0 -1
 Required properties:
 - compatible: should be "pps-gpio"
-- gpios: one PPS GPIO in the format described by  
../gpio/gpio.txt
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Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 8
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Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
+- pps-gpios: one PPS GPIO in the format described by
../gpio/gpio.txt
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Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 9
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Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
+Alternatively (DEPRECATED), instead of pps-gpios above,
it may have:
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Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
+- gpios: one PPS GPIO as above
 
 Optional properties:
 - assert-falling-edge: when present, assert is indicated by a
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falling edge
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Documentation/devicetree/bindings/pps/pps-gpio.txt a GPIO pin. · line 15
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Documentation/devicetree/bindings/pps/pps-gpio.txt +1 -0
                        (instead of by a rising edge)
+- capture-clear: when present, also capture the PPS clear event
Is this a h/w thing? or driver configuration?
Driver configuration. Most of the code was present in the
driver, yet
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it was not documented, or usable due to a two line (code) omission (the value was not being fetched from DT).
So what determines how you want to configure this? If the user will want to change it, then it should be a sysfs attr and exposed to userspace. If it depends on h/w config for a board then it can be in DT.
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Sorry, I misled you somewhat. If the PPS pulse active transition from the hardware is on the falling edge, this flag is required to get the OS to use that as the active transition. This would not change at the user's whim but rather it is dependent on connected hardware.
This description sounds more like 'assert-falling-edge' than
'capture-clear'.
Quoted 2 lines
I'm still not clear on what 'capture-clear' is.
Ignoring my patch for a minute, the pps_gpio_irq_handler will only report a pps PPS_CAPTURECLEAR event if 'capture-clear' is set. As the current pps-gpio driver is not able to set this flag, it cannot ever report a PPS_CAPTURECLEAR event.
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My patch adds the ability to set this flag and adds the documentation to go with it.
Admittedly, I do not require this functionality for what I want, but working with the code, I noticed the omission and decided to add it for someone else to use it, if they need it.
I am happy to remove this out of my patch, if you feel this to be the best way forward.
Quoted 7 lines
I found this prior discussion on adding this[1]. Seems to me this should be userspace configurable if the GPIO line can interrupt on both edges. We shouldn't need a DT property to determine that.
Rob
[1] https://lore.kernel.org/patchwork/patch/557781/
Hi Rob,
the fact that prior knowledge of board/CPU/SOC specifics is required is the most compelling argument for this to be in the DT. This is not something a user should need to know or remember.
Quoted 5 lines
Userspace is already asking for what they need via the time_pps_setparams call, but to do that they have to first call time_pps_getparams. Time_pps_getparams will not return PPS_CAPTURECLEAR as it is never set in the driver due to it being hardware specific/unable to be set.

Quoted 8 lines

My understanding is it is a 2 step process. The capability is exposed to the user if the hardware supports it, but it is still a user decision whether or not to enable it. So as far as DT bindings are concerned, we're only concerned with the first part. Whether the hardware supports capture clear in the GPIO PPS case just depends on whether the GPIO controller can support both edge interrupts (or emulate that by switching between rising/falling edge interrupts). Do we agree on that part?

Yes and no. While it is desirable to have a complete separation of the two parts as described above, we do live in a world that isn't perfect and we do need to compromise to maximise the benefit to all. See explanation below.

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Needing to know GPIO interrupt capabilities is hardly specific to PPS. There is not any explicit property in DT for this capability because it is implicit based on the GPIO controller's compatible string (or driver capabilities if emulated). Therefore, it is up to the GPIO driver and API to expose this information to client drivers like PPS.

Let me pose the following scenario: Say, the GPIO driver/API tell the PPS driver that both edges are indeed supported. This then means that the PPS driver will blindly configure itself for returning data for both the ASSERT and DEASSERT edges of the PPS pulse. However, say, the user only wants the ASSERT edge (as would be the case in most instances). As the kernel currently stands, there is no way for the PPS driver to reconfigure itself after the pps_gpio_probe function exits. This then means that you will automatically be servicing two interrupts per PPS cycle, even though the user only wants one (for PPS this is probably not a big deal...)

The reason for the PPS driver to have to blindly configure itself is that there is always going to be a delay between the driver being loaded and the userspace program becoming active and actually requesting what it wants. On a modern x86 system this may be in the order of milliseconds, but on an embedded system this would be in the order of seconds as some systems load all configured modules at boot, before userspace gets control.

In the ideal case, it would be nice for the PPS driver to load and only configure itself after the time_pps_setparams function has been called by the user.

Here is the compromise: It is usually the hardware vendor/integrator who has a good idea (hopefully) as to what capabilities are going to be used by the system. Hence the devicetree would be the most logical place to put a flag that embodies the capabilities of the GPIO subsystem as well as the GPS or other peripheral device creating the PPS pulses. To me, that is what capture_clear is.

Anyway, v11 of my patch now excludes all changes made previously to the capture_clear flag.

Tom