This is a driver for the Wi2Wi GPS modules connected through an UART.
The tricky part is that the module is turned on or off by an impulse
on the control line - but it is only possible to get the real state by monitoring
the UART RX input. Since the kernel can't know in which status the module
is brought e.g. by a boot loader or after suspend, we need some logic to handle
this.
The driver allows two different methods to enable (and power up) GPS:
a) through rfkill
b) as a GPIO
The GPIO enable can be plumbed to other drivers that expect to be able to control
a GPIO. On the GTA04 board this is the DTR-gpio of the connected UART so that
opening the UART device enables the receiver and closing it shuts the receiver down.
Original implementation by Neil Brown, fixes + DT bindings by H. Nikolaus Schaller
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
Signed-off-by: Marek Belisko <marek@xxxxxxxxxxxxx>
---
drivers/misc/Kconfig | 10 +
drivers/misc/Makefile | 1 +
drivers/misc/w2sg0004.c | 512 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/w2sg0004.h | 23 +++
4 files changed, 546 insertions(+)
create mode 100644 drivers/misc/w2sg0004.c
create mode 100644 include/linux/w2sg0004.h
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index bbeb451..03af633 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -515,6 +515,16 @@ config VEXPRESS_SYSCFG
bus. System Configuration interface is one of the possible means
of generating transactions on this bus.
+config W2SG0004
+ tristate "W2SG0004 on/off control"
+ depends on GPIOLIB
+ help
+ Enable on/off control of W2SG0004 GPS using a virtual GPIO.
+ The virtual GPIO can be connected to a DTR line of a serial
+ interface to allow powering up if the /dev/tty$n is opened.
+ It also provides a rfkill gps node to control the LNA power.
+ NOTE: can't currently be compiled as module, so please choose Y.
+
source "drivers/misc/c2port/Kconfig"
source "drivers/misc/eeprom/Kconfig"
source "drivers/misc/cb710/Kconfig"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 7d5c4cd..2f83270 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -56,3 +56,4 @@ obj-$(CONFIG_GENWQE) += genwqe/
obj-$(CONFIG_ECHO) += echo/
obj-$(CONFIG_VEXPRESS_SYSCFG) += vexpress-syscfg.o
obj-$(CONFIG_CXL_BASE) += cxl/
+obj-${CONFIG_W2SG0004} += w2sg0004.o
diff --git a/drivers/misc/w2sg0004.c b/drivers/misc/w2sg0004.c
new file mode 100644
index 0000000..8f0afcf
--- /dev/null
+++ b/drivers/misc/w2sg0004.c
@@ -0,0 +1,512 @@
+/*
+ * w2sg0004.c
+ * Virtual GPIO of controlling the w2sg0004 GPS receiver.
+ *
+ * Copyright (C) 2011 Neil Brown <neil@xxxxxxxxxx>
+ *
+ * This receiver has an ON/OFF pin which must be toggled to
+ * turn the device 'on' or 'off'. A high->low->high toggle
+ * will switch the device on if it is off, and off if it is on.
+ * It is not possible to directly detect the state of the device.
+ * However when it is on it will send characters on a UART line
+ * regularly.
+ * On the OMAP3, the UART line can also be programmed as a GPIO
+ * on which we can receive interrupts.
+ * So when we want the device to be 'off' we can reprogram
+ * the line, toggle the ON/OFF pin and hope that it is off.
+ * However if an interrupt arrives we know that it is really on
+ * and can toggle again.
+ *
+ * To enable receiving on/off requests we create a gpio_chip
+ * with a single 'output' GPIO. When it is low, the
+ * GPS is turned off. When it is high, it is turned on.
+ * This can be configured as the DTR GPIO on the UART which
+ * connects the GPS. Then whenever the tty is open, the GPS
+ * will be switched on, and whenever it is closed, the GPS will
+ * be switched off.
+ *
+ * In addition we register as a rfkill client so that we can
+ * control the LNA power.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <linux/irq.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/delay.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/gpio.h>
+#include <linux/of_gpio.h>
+#include <linux/platform_device.h>
+#include <linux/w2sg0004.h>
+#include <linux/workqueue.h>
+#include <linux/rfkill.h>
+#include <linux/pinctrl/consumer.h>
+
+/*
+ * There seems to restrictions on how quickly we can toggle the
+ * on/off line. data sheets says "two rtc ticks", whatever that means.
+ * If we do it too soon it doesn't work.
+ * So we have a state machine which uses the common work queue to ensure
+ * clean transitions.
+ * When a change is requested we record that request and only act on it
+ * once the previous change has completed.
+ * A change involves a 10ms low pulse, and a 990ms raised level, so only
+ * one change per second.
+ */
+
+enum w2sg_state {
+ W2SG_IDLE, /* is not changing state */
+ W2SG_PULSE, /* activate on/off impulse */
+ W2SG_NOPULSE /* desctivate on/off impulse */
+};
+
+struct gpio_w2sg {
+ struct rfkill *rf_kill;
+ struct regulator *lna_regulator;
+ int lna_blocked; /* rfkill block gps active */
+ int lna_is_off; /* LNA is currently off */
+ int is_on; /* current state (0/1) */
+ unsigned long last_toggle;
+ unsigned long backoff; /* time to wait since last_toggle */
+ int on_off_gpio;
+ int rx_irq;
+
+ struct pinctrl *p;
+ struct pinctrl_state *default_state; /* should be UART mode */
+ struct pinctrl_state *monitor_state; /* monitor RX as GPIO */
+ enum w2sg_state state;
+ int requested; /* requested state (0/1) */
+ int suspended;
+ int rx_redirected;
+ spinlock_t lock;
+#ifdef CONFIG_GPIOLIB
+ struct gpio_chip gpio;
+ const char *gpio_name[1];
+#endif
+ struct delayed_work work;
+};
+
+static int gpio_w2sg_set_lna_power(struct gpio_w2sg *gw2sg)
+{
+ int ret = 0;
+ int off = gw2sg->suspended || !gw2sg->requested || gw2sg->lna_blocked;
+
+ pr_debug("gpio_w2sg_set_lna_power: %s\n", off ? "off" : "on");
+
+ if (off != gw2sg->lna_is_off) {
+ gw2sg->lna_is_off = off;
+ if (!IS_ERR_OR_NULL(gw2sg->lna_regulator)) {
+ if (off)
+ regulator_disable(gw2sg->lna_regulator);
+ else
+ ret = regulator_enable(gw2sg->lna_regulator);
+ }
+ }
+
+ return ret;
+}
+
+static void toggle_work(struct work_struct *work)
+{
+ struct gpio_w2sg *gw2sg = container_of(work, struct gpio_w2sg,
+ work.work);
+
+ gpio_w2sg_set_lna_power(gw2sg); /* update LNA power state */
+
+ switch (gw2sg->state) {
+ case W2SG_NOPULSE:
+ gw2sg->state = W2SG_IDLE;
+ pr_debug("GPS idle\n");
+ break;
+
+ case W2SG_IDLE:
+ spin_lock_irq(&gw2sg->lock);
+ if (gw2sg->requested == gw2sg->is_on) {
+ if (!gw2sg->is_on && !gw2sg->rx_redirected) {
+ /* not yet redirected in off state */
+ gw2sg->rx_redirected = 1;
+ pinctrl_select_state(gw2sg->p,
+ gw2sg->monitor_state);
+ enable_irq(gw2sg->rx_irq);
+ }
+ spin_unlock_irq(&gw2sg->lock);
+ return;
+ }
+ spin_unlock_irq(&gw2sg->lock);
+ gpio_set_value_cansleep(gw2sg->on_off_gpio, 0);
+ gw2sg->state = W2SG_PULSE;
+
+ pr_debug("GPS pulse\n");
+
+ schedule_delayed_work(&gw2sg->work,
+ msecs_to_jiffies(10));
+ break;
+
+ case W2SG_PULSE:
+ gpio_set_value_cansleep(gw2sg->on_off_gpio, 1);
+ gw2sg->last_toggle = jiffies;
+ gw2sg->state = W2SG_NOPULSE;
+
+ pr_debug("GPS nopulse\n");
+
+ gw2sg->is_on = !gw2sg->is_on;
+ schedule_delayed_work(&gw2sg->work,
+ msecs_to_jiffies(10));
+ break;
+ }
+}
+
+static irqreturn_t gpio_w2sg_isr(int irq, void *dev_id)
+{
+ struct gpio_w2sg *gw2sg = dev_id;
+ unsigned long flags;
+
+ /* we have received a RX signal while GPS should be off */
+ pr_debug("!");
+
+ if (!gw2sg->requested && !gw2sg->is_on &&
+ (gw2sg->state == W2SG_IDLE) &&
+ time_after(jiffies,
+ gw2sg->last_toggle + gw2sg->backoff)) {
+ /* Should be off by now, time to toggle again */
+ gw2sg->is_on = 1;
+ gw2sg->backoff *= 2;
+ spin_lock_irqsave(&gw2sg->lock, flags);
+ if (!gw2sg->suspended)
+ schedule_delayed_work(&gw2sg->work, 0);
+ spin_unlock_irqrestore(&gw2sg->lock, flags);
+ }
+
+ return IRQ_HANDLED;
+}
+
+static void gpio_w2sg_set_power(struct gpio_w2sg *gw2sg, int val)
+{
+ unsigned long flags;
+
+ pr_debug("GPS SET to %d\n", val);
+
+ spin_lock_irqsave(&gw2sg->lock, flags);
+
+ if (val && !gw2sg->requested) {
+ if (gw2sg->rx_redirected) {
+ gw2sg->rx_redirected = 0;
+ disable_irq(gw2sg->rx_irq);
+ pinctrl_select_state(gw2sg->p, gw2sg->default_state);
+ }
+ gw2sg->requested = 1;
+ } else if (!val && gw2sg->requested) {
+ gw2sg->backoff = HZ;
+ gw2sg->requested = 0;
+ } else
+ goto unlock;
+
+ if (!gw2sg->suspended)
+ schedule_delayed_work(&gw2sg->work, 0);
+unlock:
+ spin_unlock_irqrestore(&gw2sg->lock, flags);
+}
+
+static int gpio_w2sg_get_value(struct gpio_chip *gc, unsigned offset)
+{
+ struct gpio_w2sg *gw2sg = container_of(gc, struct gpio_w2sg, gpio);
+
+ return gw2sg->is_on;
+}
+
+static void gpio_w2sg_set_value(struct gpio_chip *gc, unsigned offset, int val)
+{
+ struct gpio_w2sg *gw2sg = container_of(gc, struct gpio_w2sg, gpio);
+
+ gpio_w2sg_set_power(gw2sg, val);
+}
+
+static int gpio_w2sg_direction_output(struct gpio_chip *gc,
+ unsigned offset, int val)
+{
+ gpio_w2sg_set_value(gc, offset, val);
+
+ return 0;
+}
+
+static int gpio_w2sg_rfkill_set_block(void *data, bool blocked)
+{
+ struct gpio_w2sg *gw2sg = data;
+
+ pr_debug("%s: blocked: %d\n", __func__, blocked);
+
+ gw2sg->lna_blocked = blocked;
+
+ return gpio_w2sg_set_lna_power(gw2sg);
+}
+
+static struct rfkill_ops gpio_w2sg0004_rfkill_ops = {
+ .set_block = gpio_w2sg_rfkill_set_block,
+};
+
+static int gpio_w2sg_probe(struct platform_device *pdev)
+{
+ struct gpio_w2sg_data *pdata = dev_get_platdata(&pdev->dev);
+ struct gpio_w2sg *gw2sg;
+ struct rfkill *rf_kill;
+ int err;
+
+ pr_debug("gpio_w2sg_probe()\n");
+
+#ifdef CONFIG_OF
+ if (pdev->dev.of_node) {
+ struct device *dev = &pdev->dev;
+ enum of_gpio_flags flags;
+
+ pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
+ if (!pdata)
+ return -ENOMEM;
+
+ pdata->on_off_gpio = of_get_named_gpio_flags(dev->of_node,
+ "on-off-gpio", 0, &flags);
+
+ pdata->rx_irq = irq_of_parse_and_map(dev->of_node, 0);
+ if (!pdata->rx_irq) {
+ dev_err(dev, "no IRQ found\n");
+ return -ENODEV;
+ }
+
+ if (pdata->on_off_gpio == -EPROBE_DEFER)
+ return -EPROBE_DEFER;
+
+ pdata->lna_regulator = devm_regulator_get_optional(dev, "lna");
+
+ pr_debug("lna_regulator = %p\n", pdata->lna_regulator);
+
+ if (IS_ERR(pdata->lna_regulator))
+ return PTR_ERR(pdata->lna_regulator);
+
+ pdata->gpio_base = -1;
+ pdev->dev.platform_data = pdata;
+ }
+#endif
+
+ gw2sg = devm_kzalloc(&pdev->dev, sizeof(*gw2sg), GFP_KERNEL);
+ if (gw2sg == NULL)
+ return -ENOMEM;
+
+ gw2sg->lna_regulator = pdata->lna_regulator;
+ gw2sg->lna_blocked = true;
+ gw2sg->lna_is_off = true;
+
+ gw2sg->on_off_gpio = pdata->on_off_gpio;
+
+ gw2sg->is_on = false;
+ gw2sg->requested = true;
+ gw2sg->state = W2SG_IDLE;
+ gw2sg->last_toggle = jiffies;
+ gw2sg->backoff = HZ;
+
+ /* label of controlling GPIO */
+ gw2sg->gpio_name[0] = "gpio-w2sg0004-enable";
+ gw2sg->gpio.label = "w2sg0004";
+ gw2sg->gpio.names = gw2sg->gpio_name;
+ gw2sg->gpio.ngpio = 1;
+ gw2sg->gpio.base = pdata->gpio_base;
+ gw2sg->gpio.owner = THIS_MODULE;
+ gw2sg->gpio.direction_output = gpio_w2sg_direction_output;
+ gw2sg->gpio.get = gpio_w2sg_get_value;
+ gw2sg->gpio.set = gpio_w2sg_set_value;
+ gw2sg->gpio.can_sleep = 0;
+ gw2sg->rx_irq = pdata->rx_irq;
+
+#ifdef CONFIG_OF_GPIO
+ gw2sg->gpio.of_node = pdev->dev.of_node;
+#endif
+
+#ifdef CONFIG_OF
+ if (pdev->dev.of_node) {
+ gw2sg->p = devm_pinctrl_get(&pdev->dev);
+ if (IS_ERR(gw2sg->p)) {
+ err = PTR_ERR(gw2sg->p);
+ dev_err(&pdev->dev, "Cannot get pinctrl: %d\n", err);
+ goto out;
+ }
+
+ gw2sg->default_state = pinctrl_lookup_state(gw2sg->p,
+ PINCTRL_STATE_DEFAULT);
+ if (IS_ERR(gw2sg->default_state)) {
+ err = PTR_ERR(gw2sg->default_state);
+ dev_err(&pdev->dev, "Cannot look up pinctrl state %s: %d\n",
+ PINCTRL_STATE_DEFAULT, err);
+ goto out;
+ }
+
+ gw2sg->monitor_state = pinctrl_lookup_state(gw2sg->p,
+ "monitor");
+ if (IS_ERR(gw2sg->monitor_state)) {
+ err = PTR_ERR(gw2sg->monitor_state);
+ dev_err(&pdev->dev,
+ "Cannot look up pinctrl state %s: %d\n",
+ "monitor", err);
+ goto out;
+ }
+ /* choose UART state as default */
+ err = pinctrl_select_state(gw2sg->p, gw2sg->default_state);
+ if (err < 0)
+ goto out;
+ }
+#endif
+
+ INIT_DELAYED_WORK(&gw2sg->work, toggle_work);
+ spin_lock_init(&gw2sg->lock);
+
+ err = devm_gpio_request(&pdev->dev, gw2sg->on_off_gpio,
+ "w2sg0004-on-off");
+ if (err < 0)
+ goto out;
+
+ gpio_direction_output(gw2sg->on_off_gpio, false);
+
+ err = devm_request_threaded_irq(&pdev->dev, gw2sg->rx_irq, NULL,
+ gpio_w2sg_isr,
+ IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+ "w2sg0004-rx",
+ gw2sg);
+ if (err < 0) {
+ dev_err(&pdev->dev, "Unable to claim irq %d; error %d\n",
+ gw2sg->rx_irq, err);
+ goto out;
+ }
+
+ disable_irq(gw2sg->rx_irq);
+
+ err = gpiochip_add(&gw2sg->gpio);
+ if (err)
+ goto out;
+
+ rf_kill = rfkill_alloc("GPS", &pdev->dev, RFKILL_TYPE_GPS,
+ &gpio_w2sg0004_rfkill_ops, gw2sg);
+ if (rf_kill == NULL) {
+ err = -ENOMEM;
+ goto err_rfkill;
+ }
+
+ err = rfkill_register(rf_kill);
+ if (err) {
+ dev_err(&pdev->dev, "Cannot register rfkill device\n");
+ goto err_rfkill;
+ }
+
+ gw2sg->rf_kill = rf_kill;
+
+ platform_set_drvdata(pdev, gw2sg);
+
+ pr_debug("w2sg0004 probed\n");
+
+ return 0;
+
+err_rfkill:
+ rfkill_destroy(rf_kill);
+ gpiochip_remove(&gw2sg->gpio);
+out:
+ return err;
+}
+
+static int gpio_w2sg_remove(struct platform_device *pdev)
+{
+ struct gpio_w2sg *gw2sg = platform_get_drvdata(pdev);
+
+ cancel_delayed_work_sync(&gw2sg->work);
+ gpiochip_remove(&gw2sg->gpio);
+
+ return 0;
+}
+
+static int gpio_w2sg_suspend(struct device *dev)
+{
+ /* Ignore the GPIO and just turn device off.
+ * we cannot really wait for a separate thread to
+ * do things, so we disable that and do it all
+ * here
+ */
+ struct gpio_w2sg *gw2sg = dev_get_drvdata(dev);
+
+ spin_lock_irq(&gw2sg->lock);
+ gw2sg->suspended = 1;
+ spin_unlock_irq(&gw2sg->lock);
+
+ cancel_delayed_work_sync(&gw2sg->work);
+
+ gpio_w2sg_set_lna_power(gw2sg); /* shut down if needed */
+
+ if (gw2sg->state == W2SG_PULSE) {
+ usleep_range(10000, 15000);
+ gpio_set_value_cansleep(gw2sg->on_off_gpio, 1);
+ gw2sg->last_toggle = jiffies;
+ gw2sg->is_on = !gw2sg->is_on;
+ gw2sg->state = W2SG_NOPULSE;
+ }
+
+ if (gw2sg->state == W2SG_NOPULSE) {
+ usleep_range(10000, 15000);
+ gw2sg->state = W2SG_IDLE;
+ }
+
+ if (gw2sg->is_on) {
+ pr_info("GPS off for suspend %d %d %d\n",
+ gw2sg->requested, gw2sg->is_on, gw2sg->lna_is_off);
+
+ gpio_set_value_cansleep(gw2sg->on_off_gpio, 0);
+ usleep_range(10000, 15000);
+ gpio_set_value_cansleep(gw2sg->on_off_gpio, 1);
+ gw2sg->is_on = 0;
+ }
+
+ return 0;
+}
+
+static int gpio_w2sg_resume(struct device *dev)
+{
+ struct gpio_w2sg *gw2sg = dev_get_drvdata(dev);
+
+ spin_lock_irq(&gw2sg->lock);
+ gw2sg->suspended = 0;
+ spin_unlock_irq(&gw2sg->lock);
+
+ pr_info("GPS resuming %d %d %d\n",
+ gw2sg->requested, gw2sg->is_on, gw2sg->lna_is_off);
+
+ schedule_delayed_work(&gw2sg->work, 0); /* enables LNA if needed */
+
+ return 0;
+}
+
+#if defined(CONFIG_OF)
+static const struct of_device_id w2sg0004_of_match[] = {
+ { .compatible = "wi2wi,w2sg0004" },
+ {},
+};
+MODULE_DEVICE_TABLE(of, w2sg0004_of_match);
+#endif
+
+SIMPLE_DEV_PM_OPS(w2sg_pm_ops, gpio_w2sg_suspend, gpio_w2sg_resume);
+
+static struct platform_driver gpio_w2sg_driver = {
+ .probe = gpio_w2sg_probe,
+ .remove = gpio_w2sg_remove,
+ .driver = {
+ .name = "w2sg0004",
+ .owner = THIS_MODULE,
+ .pm = &w2sg_pm_ops,
+ .of_match_table = of_match_ptr(w2sg0004_of_match)
+ },
+};
+
+module_platform_driver(gpio_w2sg_driver);
+
+MODULE_ALIAS("w2sg0004");
+
+MODULE_AUTHOR("NeilBrown <neilb@xxxxxxx>");
+MODULE_DESCRIPTION("w2sg0004 GPS virtual GPIO driver");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/w2sg0004.h b/include/linux/w2sg0004.h
new file mode 100644
index 0000000..f20e90c
--- /dev/null
+++ b/include/linux/w2sg0004.h
@@ -0,0 +1,23 @@
+/*
+ * Virtual gpio to allow ON/OFF control of w2sg0004 GPS receiver.
+ *
+ * Copyright (C) 2011 Neil Brown <neil@xxxxxxxxxx>
+ *
+ */
+
+
+#ifndef __LINUX_W2SG0004_H
+#define __LINUX_W2SG0004_H
+
+#include <linux/regulator/consumer.h>
+
+struct gpio_w2sg_data {
+ int gpio_base; /* (not used by DT) - defines the gpio.base */
+ struct regulator *lna_regulator; /* enable LNA power */
+ int on_off_gpio; /* connected to the on-off input of the GPS module */
+ int rx_irq; /* the rx irq - we track to check for module activity */
+ unsigned short on_state; /* Mux state when GPS is on */
+ unsigned short off_state; /* Mux state when GPS is off */
+};
+
+#endif /* __LINUX_W2SG0004_H */
--
1.9.1
--
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