[LinuxPPS] [PATCH v2 2/2] pps: pps-gpio pps-echo implementation
Tom Burkart
tom at aussec.com
Wed Sep 26 12:56:36 CEST 2018
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 at fridolin.com>
Signed-off-by: Tom Burkart <tom at aussec.com>
---
Documentation/devicetree/bindings/pps/pps-gpio.txt | 5 +
drivers/pps/clients/pps-gpio.c | 116 ++++++++++++++++++++-
include/linux/pps-gpio.h | 3 +
3 files changed, 121 insertions(+), 3 deletions(-)
diff --git a/Documentation/devicetree/bindings/pps/pps-gpio.txt b/Documentation/devicetree/bindings/pps/pps-gpio.txt
index 60d3b6e1957d..1ee02c9d0add 100644
--- a/Documentation/devicetree/bindings/pps/pps-gpio.txt
+++ b/Documentation/devicetree/bindings/pps/pps-gpio.txt
@@ -7,10 +7,15 @@ 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)
- capture-clear: when present, also capture the PPS clear event
+- invert-pps-echo: when present, invert the PPS ECHO pulse
Example:
pps {
diff --git a/drivers/pps/clients/pps-gpio.c b/drivers/pps/clients/pps-gpio.c
index 78d8fbbb4733..cfc48a5cff9e 100644
--- a/drivers/pps/clients/pps-gpio.c
+++ b/drivers/pps/clients/pps-gpio.c
@@ -35,15 +35,23 @@
#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 {
int irq; /* IRQ used as PPS source */
struct pps_device *pps; /* PPS source device */
struct pps_source_info info; /* PPS source information */
+ struct timer_list echo_timer; /* timer for resetting echo active edge */
bool assert_falling_edge;
bool capture_clear;
+ bool enable_pps_echo;
+ bool invert_pps_echo;
+ unsigned long echo_timeout; /* timer timeout value in jiffies */
unsigned int gpio_pin;
+ unsigned int echo_pin;
+ unsigned int echo_active_ms; /* PPS echo active duration */
};
/*
@@ -64,15 +72,56 @@ static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
rising_edge = gpio_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)
+ gpio_set_value(info->echo_pin, info->invert_pps_echo? 0 : 1);
+ break;
+
+ case PPS_CAPTURECLEAR:
+ if (pps->params.mode & PPS_ECHOCLEAR)
+ gpio_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);
+ }
+}
+
+
+/*
+ * If we sent an echo pulse, we set the output pin back to low. This results in
+ * an echo pulse of roughly echo_active_ms ms length.
+ */
+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);
+
+ gpio_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 +144,7 @@ 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),
@@ -104,12 +154,17 @@ static int pps_gpio_probe(struct platform_device *pdev)
if (pdata) {
data->gpio_pin = pdata->gpio_pin;
+ data->echo_pin = pdata->echo_pin;
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;
+ if (of_get_property(np, "echo-gpios", NULL))
+ data->enable_pps_echo = true;
} else {
- ret = of_get_gpio(np, 0);
+ 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;
@@ -117,11 +172,41 @@ static int pps_gpio_probe(struct platform_device *pdev)
data->gpio_pin = ret;
gpio_label = PPS_GPIO_NAME;
+ ret = of_get_named_gpio(np, "echo-gpios", 0);
+ /*
+ * Since we only enable the echo function if echo-gpios is enabled
+ * in the device tree, there is no possibility of error checking
+ */
+ if (ret >= 0) {
+ data->enable_pps_echo = true;
+ data->echo_pin = ret;
+
+ 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;
+ } else {
+ 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 ret;
}
/* GPIO setup */
@@ -138,6 +223,21 @@ static int pps_gpio_probe(struct platform_device *pdev)
return -EINVAL;
}
+ if (data->enable_pps_echo) {
+ ret = devm_gpio_request(&pdev->dev, data->echo_pin, gpio_label);
+ if (ret) {
+ dev_err(&pdev->dev, "failed to request GPIO %u\n",
+ data->echo_pin);
+ return ret;
+ }
+
+ ret = gpio_direction_output(data->echo_pin, 0);
+ if (ret) {
+ dev_err(&pdev->dev, "failed to set pin as output\n");
+ return -EINVAL;
+ }
+ }
+
/* IRQ setup */
ret = gpio_to_irq(data->gpio_pin);
if (ret < 0) {
@@ -155,6 +255,11 @@ 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;
@@ -187,6 +292,11 @@ static int pps_gpio_remove(struct platform_device *pdev)
{
struct pps_gpio_device_data *data = platform_get_drvdata(pdev);
+ if (data->enable_pps_echo) {
+ del_timer_sync(&data->echo_timer);
+ /* reset echo pin in any case */
+ gpio_set_value(data->echo_pin, data->invert_pps_echo? 1 : 0);
+ }
pps_unregister_source(data->pps);
dev_info(&pdev->dev, "removed IRQ %d as PPS source\n", data->irq);
return 0;
diff --git a/include/linux/pps-gpio.h b/include/linux/pps-gpio.h
index 56f35dd3d01d..e64a35b48ed7 100644
--- a/include/linux/pps-gpio.h
+++ b/include/linux/pps-gpio.h
@@ -25,7 +25,10 @@
struct pps_gpio_platform_data {
bool assert_falling_edge;
bool capture_clear;
+ bool invert_pps_echo;
unsigned int gpio_pin;
+ unsigned int echo_pin;
+ unsigned int echo_active_ms;
const char *gpio_label;
};
--
2.12.3
More information about the discussions
mailing list