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Subject[PATCH v6 4/4] pps: pps-gpio pps-echo implementation
Date
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 | 104 +++++++++++++++++++++++++++++++++++++++--
include/linux/pps-gpio.h | 3 ++
2 files changed, 103 insertions(+), 4 deletions(-)

diff --git a/drivers/pps/clients/pps-gpio.c b/drivers/pps/clients/pps-gpio.c
index d25710883794..f5ffa2dc67b5 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 +44,14 @@ 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;
+ unsigned int echo_active_ms; /* PPS echo active duration */
+ unsigned long echo_timeout; /* timer timeout value in jiffies */
};

/*
@@ -64,15 +72,54 @@ 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);
+ (!rising_edge && !info->assert_falling_edge)))
+ 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 unsigned long
get_irqf_trigger_flags(const struct pps_gpio_device_data *data)
{
@@ -95,6 +142,7 @@ static int pps_gpio_probe(struct platform_device *pdev)
int pps_default_params;
const struct pps_gpio_platform_data *pdata = pdev->dev.platform_data;
struct device_node *np = pdev->dev.of_node;
+ u32 value;

/* allocate space for device info */
data = devm_kzalloc(&pdev->dev, sizeof(struct pps_gpio_device_data),
@@ -104,10 +152,15 @@ static int pps_gpio_probe(struct platform_device *pdev)

if (pdata) {
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 {
/* GPIO setup */
data->gpio_pin = devm_gpiod_get(&pdev->dev, "pps", GPIOD_IN);
@@ -117,11 +170,44 @@ static int pps_gpio_probe(struct platform_device *pdev)
}
gpio_label = PPS_GPIO_NAME;

+ 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;
}

/* IRQ setup */
@@ -141,6 +227,11 @@ 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;
@@ -174,6 +265,11 @@ 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;
}
@@ -198,4 +294,4 @@ 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 671a029fc80b..81c13d32ad0d 100644
--- a/include/linux/pps-gpio.h
+++ b/include/linux/pps-gpio.h
@@ -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;
const char *gpio_label;
};

--
2.12.3
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