[PATCH v3 0/5] misc serdev: new serdev based driver for Wi2Wi w2sg00x4 GPS module

[PATCH v3 0/5] misc serdev: new serdev based driver for Wi2Wi w2sg00x4 GPS module

[H. Nikolaus Schaller]

Changes V3:
* worked in suggestions by kbuild test robot
* added misc+serdev to the subject

2017-11-12 22:00:02: Changes V2:
* reduced to submit only w2sg00x4 GPS driver code
* add DT node for GTA04 device to make use of the driver
* split into base code and a debugging Kconfig option (brings device into false power state after boot)
* worked in comments by kbuild robot and Rob Herring

2017-05-21 12:44:07: RFC V1
* RFC concerning new serdev based drivers for Wi2Wi w2sg00x4 GPS module and w2cbw003 bluetooth

H. Nikolaus Schaller (5):
  DT: vendor prefix for Wi2Wi, Inc.
  DT: misc serdev: w2sg0004: add bindings documentation (GPS module with
    serdev UART)
  misc serdev: Add w2sg0004 (gps receiver) power control driver
  DTS: gta04: add serdev node for w2sg00x4
  misc serdev: w2sg0004: add debugging code and Kconfig

 .../devicetree/bindings/misc/wi2wi,w2sg0004.txt    |  24 +
 .../devicetree/bindings/vendor-prefixes.txt        |   1 +
 arch/arm/boot/dts/omap3-gta04.dtsi                 |   6 +
 drivers/misc/Kconfig                               |  18 +
 drivers/misc/Makefile                              |   1 +
 drivers/misc/w2sg0004.c                            | 602 +++++++++++++++++++++
 include/linux/w2sg0004.h                           |  27 +
 7 files changed, 679 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/misc/wi2wi,w2sg0004.txt
 create mode 100644 drivers/misc/w2sg0004.c
 create mode 100644 include/linux/w2sg0004.h

-- 
2.12.2

[PATCH v3 2/5] DT: misc serdev: w2sg0004: add bindings documentation (GPS module with serdev UART)

[H. Nikolaus Schaller]

add bindings documentation for Wi2Wi W2SG00x4 GPS module

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
---
 .../devicetree/bindings/misc/wi2wi,w2sg0004.txt    | 24 ++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/misc/wi2wi,w2sg0004.txt

diff --git a/Documentation/devicetree/bindings/misc/wi2wi,w2sg0004.txt b/Documentation/devicetree/bindings/misc/wi2wi,w2sg0004.txt
new file mode 100644
index 000000000000..ccec9361a1a4
--- /dev/null
+++ b/Documentation/devicetree/bindings/misc/wi2wi,w2sg0004.txt
@@ -0,0 +1,24 @@
+Wi2Wi GPS module connected through UART
+
+Should be a subnode of the SoC UART it is connected to (serdev).
+
+Required properties:
+- compatible:	should be one of (depending on precise model)
+	"wi2wi,w2sg0004"
+	"wi2wi,w2sg0084"
+- enable-gpio:	the GPIO that controls the module's power toggle
+	input. A positive impulse of sufficent length toggles the
+	power state.
+
+Optional properties:
+- lna-supply:	an (optional) LNA regulator that is enabled together with the GPS receiver
+
+Example:
+
+&uart2 {
+	w2sg0004: gps {
+		compatible = "wi2wi,w2sg0004";
+		lna-supply = <&vsim>;   /* LNA regulator */
+		enable-gpios = <&gpio5 17 GPIO_ACTIVE_HIGH>;    /* GPIO_145: trigger for turning on/off w2sg0004 */
+        };
+};
-- 
2.12.2

[PATCH v3 3/5] misc serdev: Add w2sg0004 (gps receiver) power control driver

[H. Nikolaus Schaller]

Add driver for Wi2Wi W2SG0004/84 GPS module connected through uart.

Use serdev API hooks to monitor and forward the UART traffic to /dev/GPSn
and turn on/off the module. It also detects if the module is turned on (sends data)
but should be off, e.g. if it was already turned on during boot or power-on-reset.

Additionally, rfkill block/unblock can be used to control an external LNA
(and power down the module if not needed).

The driver concept is based on code developed by NeilBrown <neilb@suse.de>
but simplified and adapted to use the new serdev API introduced in 4.11.

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
---
 drivers/misc/Kconfig     |  10 +
 drivers/misc/Makefile    |   1 +
 drivers/misc/w2sg0004.c  | 565 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/w2sg0004.h |  27 +++
 4 files changed, 603 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 8136dc7e863d..09d171d68408 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -518,4 +518,14 @@ source "drivers/misc/mic/Kconfig"
 source "drivers/misc/genwqe/Kconfig"
 source "drivers/misc/echo/Kconfig"
 source "drivers/misc/cxl/Kconfig"
+
+config W2SG0004
+	tristate "W2SG00x4 on/off control"
+	depends on GPIOLIB && SERIAL_DEV_BUS
+	help
+          Enable on/off control of W2SG00x4 GPS moduled connected
+	  to some SoC UART to allow powering up/down if the /dev/ttyGPSn
+	  is opened/closed.
+	  It also provides a rfkill gps name to control the LNA power.
+
 endmenu
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index ad0e64fdba34..abcb667e0ff0 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -51,6 +51,7 @@ obj-$(CONFIG_SRAM_EXEC)		+= sram-exec.o
 obj-y				+= mic/
 obj-$(CONFIG_GENWQE)		+= genwqe/
 obj-$(CONFIG_ECHO)		+= echo/
+obj-$(CONFIG_W2SG0004)		+= w2sg0004.o
 obj-$(CONFIG_VEXPRESS_SYSCFG)	+= vexpress-syscfg.o
 obj-$(CONFIG_CXL_BASE)		+= cxl/
 obj-$(CONFIG_ASPEED_LPC_CTRL)	+= aspeed-lpc-ctrl.o
diff --git a/drivers/misc/w2sg0004.c b/drivers/misc/w2sg0004.c
new file mode 100644
index 000000000000..385d35c99791
--- /dev/null
+++ b/drivers/misc/w2sg0004.c
@@ -0,0 +1,565 @@
+/*
+ * w2sg0004.c
+ * Driver for power controlling the w2sg0004/w2sg0084 GPS receiver.
+ *
+ * This receiver has an ON/OFF pin which must be toggled to
+ * turn the device 'on' of 'off'.  A high->low->high toggle
+ * will switch the device on if it is off, and off if it is on.
+ *
+ * To enable receiving on/off requests we register with the
+ * UART power management notifications.
+ *
+ * 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.
+ *
+ * To detect that the power state is out of sync (e.g. if GPS
+ * was enabled before a reboot), we register for UART data received
+ * notifications.
+ *
+ * In addition we register as a rfkill client so that we can
+ * control the LNA power.
+ *
+ */
+
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/of_gpio.h>
+#include <linux/platform_device.h>
+#include <linux/rfkill.h>
+#include <linux/serdev.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/w2sg0004.h>
+#include <linux/workqueue.h>
+
+/*
+ * There seems to be 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	/* deactivate on/off impulse */
+};
+
+struct w2sg_data {
+	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;	/* the on-off gpio number */
+	struct		serdev_device *uart;	/* uart connected to the chip */
+	struct		tty_driver *tty_drv;	/* this is the user space tty */
+	struct		device *dev;	/* from tty_port_register_device() */
+	struct		tty_port port;
+	int		open_count;	/* how often we were opened */
+	enum		w2sg_state state;
+	int		requested;	/* requested state (0/1) */
+	int		suspended;
+	struct delayed_work work;
+	int		discard_count;
+};
+
+static struct w2sg_data *w2sg_by_minor[1];
+
+static int w2sg_set_lna_power(struct w2sg_data *data)
+{
+	int ret = 0;
+	int off = data->suspended || !data->requested || data->lna_blocked;
+
+	pr_debug("%s: %s\n", __func__, off ? "off" : "on");
+
+	if (off != data->lna_is_off) {
+		data->lna_is_off = off;
+		if (!IS_ERR_OR_NULL(data->lna_regulator)) {
+			if (off)
+				regulator_disable(data->lna_regulator);
+			else
+				ret = regulator_enable(data->lna_regulator);
+		}
+	}
+
+	return ret;
+}
+
+static void w2sg_set_power(void *pdata, int val)
+{
+	struct w2sg_data *data = (struct w2sg_data *) pdata;
+
+	pr_debug("%s to state=%d (requested=%d)\n", __func__, val, data->requested);
+
+	if (val && !data->requested) {
+		data->requested = true;
+	} else if (!val && data->requested) {
+		data->backoff = HZ;
+		data->requested = false;
+	} else
+		return;
+
+	pr_debug("w2sg00x4 scheduled for %d\n", data->requested);
+
+	if (!data->suspended)
+		schedule_delayed_work(&data->work, 0);
+}
+
+/* called each time data is received by the UART (i.e. sent by the w2sg0004) */
+
+static int w2sg_uart_receive_buf(struct serdev_device *serdev,
+				const unsigned char *rxdata,
+				size_t count)
+{
+	struct w2sg_data *data =
+		(struct w2sg_data *) serdev_device_get_drvdata(serdev);
+
+	if (!data->requested && !data->is_on) {
+		/*
+		 * we have received characters while the w2sg
+		 * should have been be turned off
+		 */
+		data->discard_count += count;
+		if ((data->state == W2SG_IDLE) &&
+		    time_after(jiffies,
+		    data->last_toggle + data->backoff)) {
+			/* Should be off by now, time to toggle again */
+			pr_debug("w2sg00x4 has sent %d characters data although it should be off!\n",
+				data->discard_count);
+
+			data->discard_count = 0;
+
+			data->is_on = true;
+			data->backoff *= 2;
+			if (!data->suspended)
+				schedule_delayed_work(&data->work, 0);
+		}
+	} else if (data->open_count > 0) {
+		int n;
+
+		pr_debug("w2sg00x4: push %lu chars to tty port\n", count);
+
+		/* pass to user-space */
+		n = tty_insert_flip_string(&data->port, rxdata, count);
+		if (n != count)
+			pr_err("w2sg00x4: did loose %lu characters\n", count - n);
+		tty_flip_buffer_push(&data->port);
+		return n;
+	}
+
+	/* assume we have processed everything */
+	return count;
+}
+
+/* try to toggle the power state by sending a pulse to the on-off GPIO */
+
+static void toggle_work(struct work_struct *work)
+{
+	struct w2sg_data *data = container_of(work, struct w2sg_data,
+					      work.work);
+
+	switch (data->state) {
+	case W2SG_IDLE:
+		if (data->requested == data->is_on)
+			return;
+
+		w2sg_set_lna_power(data);	/* update LNA power state */
+		gpio_set_value_cansleep(data->on_off_gpio, 0);
+		data->state = W2SG_PULSE;
+
+		pr_debug("w2sg: power gpio ON\n");
+
+		schedule_delayed_work(&data->work,
+				      msecs_to_jiffies(10));
+		break;
+
+	case W2SG_PULSE:
+		gpio_set_value_cansleep(data->on_off_gpio, 1);
+		data->last_toggle = jiffies;
+		data->state = W2SG_NOPULSE;
+		data->is_on = !data->is_on;
+
+		pr_debug("w2sg: power gpio OFF\n");
+
+		schedule_delayed_work(&data->work,
+				      msecs_to_jiffies(10));
+		break;
+
+	case W2SG_NOPULSE:
+		data->state = W2SG_IDLE;
+
+		pr_debug("w2sg: idle\n");
+
+		break;
+
+	}
+}
+
+static int w2sg_rfkill_set_block(void *pdata, bool blocked)
+{
+	struct w2sg_data *data = pdata;
+
+	pr_debug("%s: blocked: %d\n", __func__, blocked);
+
+	data->lna_blocked = blocked;
+
+	return w2sg_set_lna_power(data);
+}
+
+static struct rfkill_ops w2sg0004_rfkill_ops = {
+	.set_block = w2sg_rfkill_set_block,
+};
+
+static struct serdev_device_ops serdev_ops = {
+	.receive_buf = w2sg_uart_receive_buf,
+};
+
+/*
+ * we are a man-in the middle between the user-space visible tty port
+ * and the serdev tty where the chip is connected.
+ * This allows us to recognise when the device should be powered on
+ * or off and handle the "false" state that data arrives while no
+ * users-space tty client exists.
+ */
+
+static struct w2sg_data *w2sg_get_by_minor(unsigned int minor)
+{
+	return w2sg_by_minor[minor];
+}
+
+static int w2sg_tty_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+	struct w2sg_data *data;
+	int retval;
+
+	pr_debug("%s() tty = %p\n", __func__, tty);
+
+	data = w2sg_get_by_minor(tty->index);
+
+	if (!data)
+		return -ENODEV;
+
+	retval = tty_standard_install(driver, tty);
+	if (retval)
+		goto error_init_termios;
+
+	tty->driver_data = data;
+
+	return 0;
+
+error_init_termios:
+	tty_port_put(&data->port);
+	return retval;
+}
+
+static int w2sg_tty_open(struct tty_struct *tty, struct file *file)
+{
+	struct w2sg_data *data = tty->driver_data;
+
+	pr_debug("%s() data = %p open_count = ++%d\n", __func__, data, data->open_count);
+
+	w2sg_set_power(data, ++data->open_count > 0);
+
+	return tty_port_open(&data->port, tty, file);
+}
+
+static void w2sg_tty_close(struct tty_struct *tty, struct file *file)
+{
+	struct w2sg_data *data = tty->driver_data;
+
+	pr_debug("%s()\n", __func__);
+
+	w2sg_set_power(data, --data->open_count > 0);
+
+	tty_port_close(&data->port, tty, file);
+}
+
+static int w2sg_tty_write(struct tty_struct *tty,
+		const unsigned char *buffer, int count)
+{
+	struct w2sg_data *data = tty->driver_data;
+
+	/* simply pass down to UART */
+	return serdev_device_write_buf(data->uart, buffer, count);
+}
+
+
+static const struct tty_operations w2sg_serial_ops = {
+	.install = w2sg_tty_install,
+	.open = w2sg_tty_open,
+	.close = w2sg_tty_close,
+	.write = w2sg_tty_write,
+};
+
+static const struct tty_port_operations w2sg_port_ops = {
+};
+
+static int w2sg_probe(struct serdev_device *serdev)
+{
+	struct w2sg_pdata *pdata = NULL;
+	struct w2sg_data *data;
+	struct rfkill *rf_kill;
+	int err;
+	int minor;
+
+	pr_debug("%s()\n", __func__);
+
+	minor = 0;
+	if (w2sg_by_minor[minor]) {
+		pr_err("w2sg minor is already in use!\n");
+		return -ENODEV;
+	}
+
+	if (serdev->dev.of_node) {
+		struct device *dev = &serdev->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,
+							     "enable-gpios", 0,
+							     &flags);
+
+		/* defer until we have all gpios */
+		if (pdata->on_off_gpio == -EPROBE_DEFER)
+			return -EPROBE_DEFER;
+
+		pdata->lna_regulator = devm_regulator_get_optional(dev, "lna");
+		if (IS_ERR(pdata->lna_regulator)) {
+			/* defer until we can get the regulator */
+			if (PTR_ERR(pdata->lna_regulator) == -EPROBE_DEFER)
+				return -EPROBE_DEFER;
+
+			pdata->lna_regulator = NULL;
+		}
+
+		pr_debug("%s() lna_regulator = %p\n", __func__,
+			pdata->lna_regulator);
+
+		serdev->dev.platform_data = pdata;
+	}
+
+	data = devm_kzalloc(&serdev->dev, sizeof(*data), GFP_KERNEL);
+	if (data == NULL)
+		return -ENOMEM;
+
+	w2sg_by_minor[minor] = data;
+
+	serdev_device_set_drvdata(serdev, data);
+
+	data->lna_regulator = pdata->lna_regulator;
+	data->lna_blocked = true;
+	data->lna_is_off = true;
+
+	data->on_off_gpio = pdata->on_off_gpio;
+
+	data->is_on = false;
+	data->requested = false;
+	data->state = W2SG_IDLE;
+	data->last_toggle = jiffies;
+	data->backoff = HZ;
+
+	data->uart = serdev;
+
+	INIT_DELAYED_WORK(&data->work, toggle_work);
+
+	err = devm_gpio_request(&serdev->dev, data->on_off_gpio,
+				"w2sg0004-on-off");
+	if (err < 0)
+		goto out;
+
+	gpio_direction_output(data->on_off_gpio, false);
+
+	serdev_device_set_client_ops(data->uart, &serdev_ops);
+	serdev_device_open(data->uart);
+
+	serdev_device_set_baudrate(data->uart, 9600);
+	serdev_device_set_flow_control(data->uart, false);
+
+	rf_kill = rfkill_alloc("GPS", &serdev->dev, RFKILL_TYPE_GPS,
+				&w2sg0004_rfkill_ops, data);
+	if (rf_kill == NULL) {
+		err = -ENOMEM;
+		goto err_rfkill;
+	}
+
+	err = rfkill_register(rf_kill);
+	if (err) {
+		dev_err(&serdev->dev, "Cannot register rfkill device\n");
+		goto err_rfkill;
+	}
+
+	data->rf_kill = rf_kill;
+
+	/* allocate the tty driver */
+	data->tty_drv = alloc_tty_driver(1);
+	if (!data->tty_drv)
+		return -ENOMEM;
+
+	/* initialize the tty driver */
+	data->tty_drv->owner = THIS_MODULE;
+	data->tty_drv->driver_name = "w2sg0004";
+	data->tty_drv->name = "ttyGPS";
+	data->tty_drv->major = 0;
+	data->tty_drv->minor_start = 0;
+	data->tty_drv->type = TTY_DRIVER_TYPE_SERIAL;
+	data->tty_drv->subtype = SERIAL_TYPE_NORMAL;
+	data->tty_drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
+	data->tty_drv->init_termios = tty_std_termios;
+	data->tty_drv->init_termios.c_cflag = B9600 | CS8 | CREAD |
+					      HUPCL | CLOCAL;
+	/*
+	 * optional:
+	 * tty_termios_encode_baud_rate(&data->tty_drv->init_termios,
+					115200, 115200);
+	 * w2sg_tty_termios(&data->tty_drv->init_termios);
+	 */
+	tty_set_operations(data->tty_drv, &w2sg_serial_ops);
+
+	/* register the tty driver */
+	err = tty_register_driver(data->tty_drv);
+	if (err) {
+		pr_err("%s - tty_register_driver failed(%d)\n",
+			__func__, err);
+		put_tty_driver(data->tty_drv);
+		goto err_rfkill;
+	}
+
+	tty_port_init(&data->port);
+	data->port.ops = &w2sg_port_ops;
+
+/*
+ * FIXME: this appears to reenter this probe() function a second time
+ * which only fails because the gpio is already assigned
+ */
+
+	data->dev = tty_port_register_device(&data->port,
+			data->tty_drv, minor, &serdev->dev);
+
+	pr_debug("w2sg probed\n");
+
+	/* keep off until user space requests the device */
+	w2sg_set_power(data, false);
+
+	return 0;
+
+err_rfkill:
+	rfkill_destroy(rf_kill);
+	serdev_device_close(data->uart);
+out:
+	return err;
+}
+
+static void w2sg_remove(struct serdev_device *serdev)
+{
+	struct w2sg_data *data = serdev_device_get_drvdata(serdev);
+	int minor;
+
+	cancel_delayed_work_sync(&data->work);
+
+	/* what is the right sequence to avoid problems? */
+	serdev_device_close(data->uart);
+
+	minor = 0;
+	tty_unregister_device(data->tty_drv, minor);
+
+	tty_unregister_driver(data->tty_drv);
+}
+
+static int w2sg_suspend(struct device *dev)
+{
+	struct w2sg_data *data = dev_get_drvdata(dev);
+
+	data->suspended = true;
+
+	cancel_delayed_work_sync(&data->work);
+
+	w2sg_set_lna_power(data);	/* shuts down if needed */
+
+	if (data->state == W2SG_PULSE) {
+		msleep(10);
+		gpio_set_value_cansleep(data->on_off_gpio, 1);
+		data->last_toggle = jiffies;
+		data->is_on = !data->is_on;
+		data->state = W2SG_NOPULSE;
+	}
+
+	if (data->state == W2SG_NOPULSE) {
+		msleep(10);
+		data->state = W2SG_IDLE;
+	}
+
+	if (data->is_on) {
+		pr_info("GPS off for suspend %d %d %d\n", data->requested,
+			data->is_on, data->lna_is_off);
+
+		gpio_set_value_cansleep(data->on_off_gpio, 0);
+		msleep(10);
+		gpio_set_value_cansleep(data->on_off_gpio, 1);
+		data->is_on = 0;
+	}
+
+	return 0;
+}
+
+static int w2sg_resume(struct device *dev)
+{
+	struct w2sg_data *data = dev_get_drvdata(dev);
+
+	data->suspended = false;
+
+	pr_info("GPS resuming %d %d %d\n", data->requested,
+		data->is_on, data->lna_is_off);
+
+	schedule_delayed_work(&data->work, 0);	/* enables LNA if needed */
+
+	return 0;
+}
+
+#if defined(CONFIG_OF)
+static const struct of_device_id w2sg0004_of_match[] = {
+	{ .compatible = "wi2wi,w2sg0004" },
+	{ .compatible = "wi2wi,w2sg0084" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, w2sg0004_of_match);
+#endif
+
+SIMPLE_DEV_PM_OPS(w2sg_pm_ops, w2sg_suspend, w2sg_resume);
+
+static struct serdev_device_driver w2sg_driver = {
+	.probe		= w2sg_probe,
+	.remove		= w2sg_remove,
+	.driver = {
+		.name	= "w2sg0004",
+		.owner	= THIS_MODULE,
+		.pm	= &w2sg_pm_ops,
+		.of_match_table = of_match_ptr(w2sg0004_of_match)
+	},
+};
+
+module_serdev_device_driver(w2sg_driver);
+
+MODULE_ALIAS("w2sg0004");
+
+MODULE_AUTHOR("NeilBrown <neilb@suse.de>");
+MODULE_DESCRIPTION("w2sg0004 GPS power management driver");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/w2sg0004.h b/include/linux/w2sg0004.h
new file mode 100644
index 000000000000..ad0c4a18e01d
--- /dev/null
+++ b/include/linux/w2sg0004.h
@@ -0,0 +1,27 @@
+/*
+ * UART slave to allow ON/OFF control of w2sg0004 GPS receiver.
+ *
+ * Copyright (C) 2011 Neil Brown <neil@brown.name>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+
+
+#ifndef __LINUX_W2SG0004_H
+#define __LINUX_W2SG0004_H
+
+#include <linux/regulator/consumer.h>
+
+struct w2sg_pdata {
+	struct regulator *lna_regulator;	/* enable LNA power */
+	int	on_off_gpio;	/*  on-off input of the GPS module */
+};
+#endif /* __LINUX_W2SG0004_H */
-- 
2.12.2

Re: [PATCH v3 3/5] misc serdev: Add w2sg0004 (gps receiver) power control driver

[Arnd Bergmann]

On Wed, Nov 15, 2017 at 4:19 PM, H. Nikolaus Schaller <hns-xXXSsgcRVICgSpxsJD1C4w@public.gmane.org> wrote:
> Add driver for Wi2Wi W2SG0004/84 GPS module connected through uart.
>
> Use serdev API hooks to monitor and forward the UART traffic to /dev/GPSn
> and turn on/off the module. It also detects if the module is turned on (sends data)
> but should be off, e.g. if it was already turned on during boot or power-on-reset.
>
> Additionally, rfkill block/unblock can be used to control an external LNA
> (and power down the module if not needed).
>
> The driver concept is based on code developed by NeilBrown <neilb-l3A5Bk7waGM@public.gmane.org>
> but simplified and adapted to use the new serdev API introduced in 4.11.
>
> Signed-off-by: H. Nikolaus Schaller <hns-xXXSsgcRVICgSpxsJD1C4w@public.gmane.org>

I'm a bit confused by the concept here. Did I understand it right that this
attaches to a tty_port and then registers another tty_driver with one
tty_port for the first port?

> +static int w2sg_probe(struct serdev_device *serdev)
> +{
> +       struct w2sg_pdata *pdata = NULL;
> +       struct w2sg_data *data;
> +       struct rfkill *rf_kill;
> +       int err;
> +       int minor;
> +
> +       pr_debug("%s()\n", __func__);
> +
> +       minor = 0;
> +       if (w2sg_by_minor[minor]) {
> +               pr_err("w2sg minor is already in use!\n");
> +               return -ENODEV;
> +       }
> +
> +       if (serdev->dev.of_node) {
> +               struct device *dev = &serdev->dev;
> +               enum of_gpio_flags flags;
> +
> +               pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
> +               if (!pdata)
> +                       return -ENOMEM;

This looks like it's a leftover from pre-DT days, but it doesn't
actually work without DT in the current form. How about
merging the contents of w2sg_pdata into w2sg_data?

> +
> +       /* initialize the tty driver */
> +       data->tty_drv->owner = THIS_MODULE;
> +       data->tty_drv->driver_name = "w2sg0004";
> +       data->tty_drv->name = "ttyGPS";
> +       data->tty_drv->major = 0;
> +       data->tty_drv->minor_start = 0;
> +       data->tty_drv->type = TTY_DRIVER_TYPE_SERIAL;
> +       data->tty_drv->subtype = SERIAL_TYPE_NORMAL;
> +       data->tty_drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
> +       data->tty_drv->init_termios = tty_std_termios;
> +       data->tty_drv->init_termios.c_cflag = B9600 | CS8 | CREAD |
> +                                             HUPCL | CLOCAL;
> +       /*
> +        * optional:
> +        * tty_termios_encode_baud_rate(&data->tty_drv->init_termios,
> +                                       115200, 115200);
> +        * w2sg_tty_termios(&data->tty_drv->init_termios);
> +        */
> +       tty_set_operations(data->tty_drv, &w2sg_serial_ops);

While I'm still not sure about why we want nested tty port, it
seems that we should have only one tty_driver that gets initialized
at module load time, rather than one driver structure per port.

> +       /* register the tty driver */
> +       err = tty_register_driver(data->tty_drv);
> +       if (err) {
> +               pr_err("%s - tty_register_driver failed(%d)\n",
> +                       __func__, err);
> +               put_tty_driver(data->tty_drv);
> +               goto err_rfkill;
> +       }
> +
> +       tty_port_init(&data->port);
> +       data->port.ops = &w2sg_port_ops;
> +
> +/*
> + * FIXME: this appears to reenter this probe() function a second time
> + * which only fails because the gpio is already assigned
> + */
> +
> +       data->dev = tty_port_register_device(&data->port,
> +                       data->tty_drv, minor, &serdev->dev);

This seems to be a result of having nested tty ports, and both
ports point to the same device.

       Arnd
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Re: [PATCH v3 3/5] misc serdev: Add w2sg0004 (gps receiver) power control driver

[H. Nikolaus Schaller]

Hi Arnd,

> Am 15.11.2017 um 16:54 schrieb Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>:
> 
> On Wed, Nov 15, 2017 at 4:19 PM, H. Nikolaus Schaller <hns-xXXSsgcRVICgSpxsJD1C4w@public.gmane.org> wrote:
>> Add driver for Wi2Wi W2SG0004/84 GPS module connected through uart.
>> 
>> Use serdev API hooks to monitor and forward the UART traffic to /dev/GPSn
>> and turn on/off the module. It also detects if the module is turned on (sends data)
>> but should be off, e.g. if it was already turned on during boot or power-on-reset.
>> 
>> Additionally, rfkill block/unblock can be used to control an external LNA
>> (and power down the module if not needed).
>> 
>> The driver concept is based on code developed by NeilBrown <neilb-l3A5Bk7waGM@public.gmane.org>
>> but simplified and adapted to use the new serdev API introduced in 4.11.
>> 
>> Signed-off-by: H. Nikolaus Schaller <hns-xXXSsgcRVICgSpxsJD1C4w@public.gmane.org>
> 
> I'm a bit confused by the concept here. Did I understand it right that this
> attaches to a tty_port and then registers another tty_driver with one
> tty_port for the first port?

Yes. It attaches to a serdev (which is a tty_port hidden from user-space) and
creates its own to be accessible from user-space.

It seems that this is very difficult to understand since I have to explain
it again and again every time I submit a new version :) Maybe I should write
some document to cite :)

Basically we only want to control power on/off of the chip but need to tap
the data stream to monitor the chip as described in the commit message. But
we do not need to modify data. The ideal solution would be that serdev wouldn't
hide the original /dev/tty for the UART but I was told that this is not possible
with serdev API.

We could also run the chip without a driver and use the original /dev/tty - but
then we have no power control of a power-hungry chip in a mobile device. And
without kernel driver, we can't turn it off automatically during suspend.

BTW: we did discuss how to do this chip right for years (IMHO the first proposal
was 2012 or 2013 by Neil Brown). Nowadays, the serdev DT structure demands that it
is a serdev and nothing else. Hence we have to live with what serdev provides
as API and make it a serdev driver.

There is one more goal. Some people are dreaming about a generic GPS interface.
Then, the driver wouldn't have to register a /dev/GPS tty any more but a
gps_interface and mangle serial data as requested by that API. This will become
a simple upgrade.

So you can consider creating a new tty as sort of temporary solution. Like we
had for years for UART HCI based bluetooth devices using a user-space daemon.

> 
>> +static int w2sg_probe(struct serdev_device *serdev)
>> +{
>> +       struct w2sg_pdata *pdata = NULL;
>> +       struct w2sg_data *data;
>> +       struct rfkill *rf_kill;
>> +       int err;
>> +       int minor;
>> +
>> +       pr_debug("%s()\n", __func__);
>> +
>> +       minor = 0;
>> +       if (w2sg_by_minor[minor]) {
>> +               pr_err("w2sg minor is already in use!\n");
>> +               return -ENODEV;
>> +       }
>> +
>> +       if (serdev->dev.of_node) {
>> +               struct device *dev = &serdev->dev;
>> +               enum of_gpio_flags flags;
>> +
>> +               pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
>> +               if (!pdata)
>> +                       return -ENOMEM;
> 
> This looks like it's a leftover from pre-DT days, but it doesn't
> actually work without DT in the current form. How about
> merging the contents of w2sg_pdata into w2sg_data?

Ok. As said the driver core is very old...

I'll look into this asap.

> 
>> +
>> +       /* initialize the tty driver */
>> +       data->tty_drv->owner = THIS_MODULE;
>> +       data->tty_drv->driver_name = "w2sg0004";
>> +       data->tty_drv->name = "ttyGPS";
>> +       data->tty_drv->major = 0;
>> +       data->tty_drv->minor_start = 0;
>> +       data->tty_drv->type = TTY_DRIVER_TYPE_SERIAL;
>> +       data->tty_drv->subtype = SERIAL_TYPE_NORMAL;
>> +       data->tty_drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
>> +       data->tty_drv->init_termios = tty_std_termios;
>> +       data->tty_drv->init_termios.c_cflag = B9600 | CS8 | CREAD |
>> +                                             HUPCL | CLOCAL;
>> +       /*
>> +        * optional:
>> +        * tty_termios_encode_baud_rate(&data->tty_drv->init_termios,
>> +                                       115200, 115200);
>> +        * w2sg_tty_termios(&data->tty_drv->init_termios);
>> +        */
>> +       tty_set_operations(data->tty_drv, &w2sg_serial_ops);
> 
> While I'm still not sure about why we want nested tty port, it
> seems that we should have only one tty_driver that gets initialized
> at module load time, rather than one driver structure per port.

If we have several such chips connected to different serdev UARTs
we need different /dev/GPS to separate them in user-space.

> 
>> +       /* register the tty driver */
>> +       err = tty_register_driver(data->tty_drv);
>> +       if (err) {
>> +               pr_err("%s - tty_register_driver failed(%d)\n",
>> +                       __func__, err);
>> +               put_tty_driver(data->tty_drv);
>> +               goto err_rfkill;
>> +       }
>> +
>> +       tty_port_init(&data->port);
>> +       data->port.ops = &w2sg_port_ops;
>> +
>> +/*
>> + * FIXME: this appears to reenter this probe() function a second time
>> + * which only fails because the gpio is already assigned
>> + */
>> +
>> +       data->dev = tty_port_register_device(&data->port,
>> +                       data->tty_drv, minor, &serdev->dev);
> 
> This seems to be a result of having nested tty ports, and both
> ports point to the same device.

The UART tty would be e.g. /dev/ttyO2 (on OMAP3) if no driver is
installed. And the new one that is registered is /dev/GPS0. So the
tty subsystem doesn't (or shouldn't) know they are related. They
are only related/connected inside this driver. So I assume that
some locking or reentrancy happens in tty_port_register_device().

BR and thanks,
Nikolaus Schaller

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Re: [PATCH v3 3/5] misc serdev: Add w2sg0004 (gps receiver) power control driver

[Arnd Bergmann]

On Wed, Nov 15, 2017 at 5:27 PM, H. Nikolaus Schaller <hns-xXXSsgcRVICgSpxsJD1C4w@public.gmane.org> wrote:
>> Am 15.11.2017 um 16:54 schrieb Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>:
>> On Wed, Nov 15, 2017 at 4:19 PM, H. Nikolaus Schaller <hns-xXXSsgcRVICgSpxsJD1C4w@public.gmane.org> wrote:
>>> Add driver for Wi2Wi W2SG0004/84 GPS module connected through uart.
>
> There is one more goal. Some people are dreaming about a generic GPS interface.
> Then, the driver wouldn't have to register a /dev/GPS tty any more but a
> gps_interface and mangle serial data as requested by that API. This will become
> a simple upgrade.
>
> So you can consider creating a new tty as sort of temporary solution. Like we
> had for years for UART HCI based bluetooth devices using a user-space daemon.

It shouldn't be hard to split out the tty_driver portion of your file from the
part that registers the port, basically getting two files that each handle
half of the work, and the second one would be generic from the start.

>>> +       /* initialize the tty driver */
>>> +       data->tty_drv->owner = THIS_MODULE;
>>> +       data->tty_drv->driver_name = "w2sg0004";
>>> +       data->tty_drv->name = "ttyGPS";
>>> +       data->tty_drv->major = 0;
>>> +       data->tty_drv->minor_start = 0;
>>> +       data->tty_drv->type = TTY_DRIVER_TYPE_SERIAL;
>>> +       data->tty_drv->subtype = SERIAL_TYPE_NORMAL;
>>> +       data->tty_drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
>>> +       data->tty_drv->init_termios = tty_std_termios;
>>> +       data->tty_drv->init_termios.c_cflag = B9600 | CS8 | CREAD |
>>> +                                             HUPCL | CLOCAL;
>>> +       /*
>>> +        * optional:
>>> +        * tty_termios_encode_baud_rate(&data->tty_drv->init_termios,
>>> +                                       115200, 115200);
>>> +        * w2sg_tty_termios(&data->tty_drv->init_termios);
>>> +        */
>>> +       tty_set_operations(data->tty_drv, &w2sg_serial_ops);
>>
>> While I'm still not sure about why we want nested tty port, it
>> seems that we should have only one tty_driver that gets initialized
>> at module load time, rather than one driver structure per port.
>
> If we have several such chips connected to different serdev UARTs
> we need different /dev/GPS to separate them in user-space.

I understand that you need multiple devices, but I don't see
what having multiple drivers that all share the same name
"w2sg0004" helps. I would have expected that to fail in
tty_register_driver() when you get to the second driver,
but looking at the code, it doesn't actually try to make the name
unique proc_tty_register_driver() will fail to create the second
procfs file, but we ignore that failure.

Why not call tty_register_driver() in the init function rather than probe()?

>>> +       /* register the tty driver */
>>> +       err = tty_register_driver(data->tty_drv);
>>> +       if (err) {
>>> +               pr_err("%s - tty_register_driver failed(%d)\n",
>>> +                       __func__, err);
>>> +               put_tty_driver(data->tty_drv);
>>> +               goto err_rfkill;
>>> +       }
>>> +
>>> +       tty_port_init(&data->port);
>>> +       data->port.ops = &w2sg_port_ops;
>>> +
>>> +/*
>>> + * FIXME: this appears to reenter this probe() function a second time
>>> + * which only fails because the gpio is already assigned
>>> + */
>>> +
>>> +       data->dev = tty_port_register_device(&data->port,
>>> +                       data->tty_drv, minor, &serdev->dev);
>>
>> This seems to be a result of having nested tty ports, and both
>> ports point to the same device.
>
> The UART tty would be e.g. /dev/ttyO2 (on OMAP3) if no driver is
> installed. And the new one that is registered is /dev/GPS0. So the
> tty subsystem doesn't (or shouldn't) know they are related. They
> are only related/connected inside this driver. So I assume that
> some locking or reentrancy happens in tty_port_register_device().

I meant the serdev->dev pointer that you pass into
tty_port_register_device() seems to be the same one that
got passed into the first tty_port_register_device() in the
parent uart_port.

I just checked the current mainline code, and it doesn't seem
to actually call serdev_tty_port_register() from
tty_port_register_device(), so maybe the comment was
based on an older version of the serdev framework?

It seems like something that should be fixed, so maybe
put a WARN_ON() at the beginning of the probe
function to see where we come from.

      Arnd
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Re: [PATCH v3 3/5] misc serdev: Add w2sg0004 (gps receiver) power control driver

[H. Nikolaus Schaller]

Hi Arnd,

> Am 15.11.2017 um 18:03 schrieb Arnd Bergmann <arnd@arndb.de>:
> 
> On Wed, Nov 15, 2017 at 5:27 PM, H. Nikolaus Schaller <hns@goldelico.com> wrote:
>>> Am 15.11.2017 um 16:54 schrieb Arnd Bergmann <arnd@arndb.de>:
>>> On Wed, Nov 15, 2017 at 4:19 PM, H. Nikolaus Schaller <hns@goldelico.com> wrote:
>>>> Add driver for Wi2Wi W2SG0004/84 GPS module connected through uart.
>> 
>> There is one more goal. Some people are dreaming about a generic GPS interface.
>> Then, the driver wouldn't have to register a /dev/GPS tty any more but a
>> gps_interface and mangle serial data as requested by that API. This will become
>> a simple upgrade.
>> 
>> So you can consider creating a new tty as sort of temporary solution. Like we
>> had for years for UART HCI based bluetooth devices using a user-space daemon.
> 
> It shouldn't be hard to split out the tty_driver portion of your file from the
> part that registers the port, basically getting two files that each handle
> half of the work, and the second one would be generic from the start.

Hm. Sounds like a big hack to me instead of using existing API (serdev and tty_port)
and making the best out of it.

But I may have misunderstood what you mean by splitting out parts of
a tty (which one?) and why I need two files?

The structure of the driver is:

UART --> serdev magic ---> this device driver ---> register something to present data to user space ---> user space read()

Data should flow following this arrows.
And power control happens this way:

UART --> serdev magic ---> this device driver <--- register something to present data to user space <--- user space open()
GPIO <----------------------------+

So we need one serdev port to communicate with the device and something to present serial data to user-space (where gpsd runs).

> 
>>>> +       /* initialize the tty driver */
>>>> +       data->tty_drv->owner = THIS_MODULE;
>>>> +       data->tty_drv->driver_name = "w2sg0004";
>>>> +       data->tty_drv->name = "ttyGPS";
>>>> +       data->tty_drv->major = 0;
>>>> +       data->tty_drv->minor_start = 0;
>>>> +       data->tty_drv->type = TTY_DRIVER_TYPE_SERIAL;
>>>> +       data->tty_drv->subtype = SERIAL_TYPE_NORMAL;
>>>> +       data->tty_drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
>>>> +       data->tty_drv->init_termios = tty_std_termios;
>>>> +       data->tty_drv->init_termios.c_cflag = B9600 | CS8 | CREAD |
>>>> +                                             HUPCL | CLOCAL;
>>>> +       /*
>>>> +        * optional:
>>>> +        * tty_termios_encode_baud_rate(&data->tty_drv->init_termios,
>>>> +                                       115200, 115200);
>>>> +        * w2sg_tty_termios(&data->tty_drv->init_termios);
>>>> +        */
>>>> +       tty_set_operations(data->tty_drv, &w2sg_serial_ops);
>>> 
>>> While I'm still not sure about why we want nested tty port, it
>>> seems that we should have only one tty_driver that gets initialized
>>> at module load time, rather than one driver structure per port.
>> 
>> If we have several such chips connected to different serdev UARTs
>> we need different /dev/GPS to separate them in user-space.
> 
> I understand that you need multiple devices, but I don't see
> what having multiple drivers that all share the same name
> "w2sg0004" helps. I would have expected that to fail in
> tty_register_driver() when you get to the second driver,
> but looking at the code, it doesn't actually try to make the name
> unique

Yes, that is missing because I copied that from other drivers
and have no full understanding what is needed to make it really
work with multiple /dev/ttyGPS0 tty ports.

Therefore each probe (for each device connected to a different uart
of the SoC) should create a different /dev/ttyGPSn. Like you can have
multiple and independent i2c clients of the same type and driver.

> proc_tty_register_driver() will fail to create the second
> procfs file, but we ignore that failure.
> 
> Why not call tty_register_driver() in the init function rather than probe()?

We have no dedicated init function. Should we have one?

And if I understand correctly it would prohibit to fix the driver for the
multiple gps-devices situation. Or makes more work if the device is to be
registered as a future GPS interface.

So if the ->driver_name or ->name should have a dynamic sequence number,
please help me to get it correct.

> 
>>>> +       /* register the tty driver */
>>>> +       err = tty_register_driver(data->tty_drv);
>>>> +       if (err) {
>>>> +               pr_err("%s - tty_register_driver failed(%d)\n",
>>>> +                       __func__, err);
>>>> +               put_tty_driver(data->tty_drv);
>>>> +               goto err_rfkill;
>>>> +       }
>>>> +
>>>> +       tty_port_init(&data->port);
>>>> +       data->port.ops = &w2sg_port_ops;
>>>> +
>>>> +/*
>>>> + * FIXME: this appears to reenter this probe() function a second time
>>>> + * which only fails because the gpio is already assigned
>>>> + */
>>>> +
>>>> +       data->dev = tty_port_register_device(&data->port,
>>>> +                       data->tty_drv, minor, &serdev->dev);
>>> 
>>> This seems to be a result of having nested tty ports, and both
>>> ports point to the same device.
>> 
>> The UART tty would be e.g. /dev/ttyO2 (on OMAP3) if no driver is
>> installed. And the new one that is registered is /dev/GPS0. So the
>> tty subsystem doesn't (or shouldn't) know they are related. They
>> are only related/connected inside this driver. So I assume that
>> some locking or reentrancy happens in tty_port_register_device().
> 
> I meant the serdev->dev pointer that you pass into
> tty_port_register_device() seems to be the same one that
> got passed into the first tty_port_register_device() in the
> parent uart_port.

Ah, interesting!

Well, I copied that from other drivers registering a tty without
understanding all side-effects of everything.

Documentations of tty_port_register_device() says:
@device: parent if exists, otherwise NULL

Do we really need a "parent" here? Could we safely pass NULL?

> 
> I just checked the current mainline code, and it doesn't seem
> to actually call serdev_tty_port_register() from
> tty_port_register_device(), so maybe the comment was
> based on an older version of the serdev framework?

Maybe. We rewrote the driver in parallel to v4.11-rc where this
was observed. Then we only rebased it to now v4.14 but didn't
verify this detail.

I did now test the driver with debugging enabled (after removing
the pdata stuff) on top of v4.14.

But I could not find a trace of this issue (there was a
double w2sg_probe() right after tty_port_register_device):

dmesg|fgrep w2sg
[    8.039184] w2sg_probe()
[    8.039184] w2sg serdev_device_set_drvdata
[    8.039398] w2sg_probe() lna_regulator = dc944c80
[    8.039398] w2sg devm_gpio_request
[    8.039703] w2sg rfkill_alloc
[    8.039733] w2sg register rfkill
[    8.039886] w2sg alloc_tty_driver
[    8.039916] w2sg tty_register_driver
[    8.039916] w2sg call tty_port_init
[    8.039916] w2sg call tty_port_register_device
[    8.040130] w2sg_rfkill_set_block: blocked: 0
[    8.040161] w2sg_set_lna_power: off
[    8.040222] w2sg tty_port_register_device -> ddeda800
[    8.040222] w2sg port.tty =   (null)
[    8.040222] w2sg probed
[    8.040222] w2sg DEBUGGING MODE enabled
[    8.040222] w2sg power gpio ON
[    8.252227] w2sg power gpio OFF
[    8.876617] w2sg_set_power to state=0 (requested=0)
[    9.127410] w2sg00x4 has sent 124 characters data although it should be off!
[    9.127471] w2sg_set_lna_power: off
[    9.127471] w2sg: power gpio ON
[    9.142700] w2sg: power gpio OFF
[    9.162689] w2sg: idle
[  239.280212] w2sg_tty_install() tty = ddfa3a00
[  239.284759] w2sg_tty_install() data = dc858810
[  239.290344] w2sg_tty_open() data = dc858810 open_count = ++0
[  239.296264] w2sg_set_power to state=1 (requested=0)
[  239.301940] w2sg00x4 scheduled for 1
[  239.305725] w2sg_set_lna_power: on
[  239.310913] w2sg: power gpio ON
[  239.327362] w2sg: power gpio OFF
[  239.347351] w2sg: idle
[  239.385162] w2sg00x4: push 1 chars to tty port
[  239.390228] w2sg00x4: push 4 chars to tty port
[  239.395141] w2sg00x4: push 5 chars to tty port
[  239.401184] w2sg00x4: push 5 chars to tty port
[  239.406097] w2sg00x4: push 4 chars to tty port
[  239.412994] w2sg00x4: push 6 chars to tty port
[  239.418731] w2sg00x4: push 5 chars to tty port
[  240.241821] w2sg_tty_close()
[  240.244873] w2sg_set_power to state=0 (requested=1)
[  240.251281] w2sg00x4 scheduled for 0
[  240.255065] w2sg_set_lna_power: off
[  240.261322] w2sg: power gpio ON
[  240.277435] w2sg: power gpio OFF
[  240.297424] w2sg: idle

So it is probed only once. Maybe we did note a bug in early
serdev that already has been fixed?

Hence we are discussing a problem that already has disappeared.

> 
> It seems like something that should be fixed, so maybe
> put a WARN_ON() at the beginning of the probe
> function to see where we come from.

Well, I'd say this notice can be removed as well.

So I'll post a v4 asap.

BR,
Nikolaus

Re: [PATCH v3 3/5] misc serdev: Add w2sg0004 (gps receiver) power control driver

[Arnd Bergmann]

On Wed, Nov 15, 2017 at 8:55 PM, H. Nikolaus Schaller <hns-xXXSsgcRVICgSpxsJD1C4w@public.gmane.org> wrote:
>> Am 15.11.2017 um 18:03 schrieb Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>:
>> On Wed, Nov 15, 2017 at 5:27 PM, H. Nikolaus Schaller <hns-xXXSsgcRVICgSpxsJD1C4w@public.gmane.org> wrote:
>>>> Am 15.11.2017 um 16:54 schrieb Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>:
>>>> On Wed, Nov 15, 2017 at 4:19 PM, H. Nikolaus Schaller <hns-xXXSsgcRVICgSpxsJD1C4w@public.gmane.org> wrote:
>>>>> Add driver for Wi2Wi W2SG0004/84 GPS module connected through uart.
>>>
>>> There is one more goal. Some people are dreaming about a generic GPS interface.
>>> Then, the driver wouldn't have to register a /dev/GPS tty any more but a
>>> gps_interface and mangle serial data as requested by that API. This will become
>>> a simple upgrade.
>>>
>>> So you can consider creating a new tty as sort of temporary solution. Like we
>>> had for years for UART HCI based bluetooth devices using a user-space daemon.
>>
>> It shouldn't be hard to split out the tty_driver portion of your file from the
>> part that registers the port, basically getting two files that each handle
>> half of the work, and the second one would be generic from the start.
>
> Hm. Sounds like a big hack to me instead of using existing API (serdev and tty_port)
> and making the best out of it.
>
> But I may have misunderstood what you mean by splitting out parts of
> a tty (which one?) and why I need two files?
>
> The structure of the driver is:
>
> UART --> serdev magic ---> this device driver ---> register something to present data to user space ---> user space read()
>
> Data should flow following this arrows.
> And power control happens this way:
>
> UART --> serdev magic ---> this device driver <--- register something to present data to user space <--- user space open()
> GPIO <----------------------------+
>
> So we need one serdev port to communicate with the device and something to present serial data to user-space (where gpsd runs).

My suggestion was directed at replacing the big hack (adding one
driver per port, and a different driver for each type of GPS hardware)
with a smaller hack, using one driver to manage the ttyGPS name
space for any implementation. That same driver could later even be
expanded to offer additional ioctl interfaces, e.g. for reading the
current position or time.

Let's ignore that point for the moment though and finish the
discussion below, I think it will become clearer what I meant here
when the split between init() and probe() function is resolved.

>>>>> +       /* initialize the tty driver */
>>>>> +       data->tty_drv->owner = THIS_MODULE;
>>>>> +       data->tty_drv->driver_name = "w2sg0004";
>>>>> +       data->tty_drv->name = "ttyGPS";
>>>>> +       data->tty_drv->major = 0;
>>>>> +       data->tty_drv->minor_start = 0;
>>>>> +       data->tty_drv->type = TTY_DRIVER_TYPE_SERIAL;
>>>>> +       data->tty_drv->subtype = SERIAL_TYPE_NORMAL;
>>>>> +       data->tty_drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
>>>>> +       data->tty_drv->init_termios = tty_std_termios;
>>>>> +       data->tty_drv->init_termios.c_cflag = B9600 | CS8 | CREAD |
>>>>> +                                             HUPCL | CLOCAL;
>>>>> +       /*
>>>>> +        * optional:
>>>>> +        * tty_termios_encode_baud_rate(&data->tty_drv->init_termios,
>>>>> +                                       115200, 115200);
>>>>> +        * w2sg_tty_termios(&data->tty_drv->init_termios);
>>>>> +        */
>>>>> +       tty_set_operations(data->tty_drv, &w2sg_serial_ops);
>>>>
>>>> While I'm still not sure about why we want nested tty port, it
>>>> seems that we should have only one tty_driver that gets initialized
>>>> at module load time, rather than one driver structure per port.
>>>
>>> If we have several such chips connected to different serdev UARTs
>>> we need different /dev/GPS to separate them in user-space.
>>
>> I understand that you need multiple devices, but I don't see
>> what having multiple drivers that all share the same name
>> "w2sg0004" helps. I would have expected that to fail in
>> tty_register_driver() when you get to the second driver,
>> but looking at the code, it doesn't actually try to make the name
>> unique
>
> Yes, that is missing because I copied that from other drivers
> and have no full understanding what is needed to make it really
> work with multiple /dev/ttyGPS0 tty ports.
>
> Therefore each probe (for each device connected to a different uart
> of the SoC) should create a different /dev/ttyGPSn. Like you can have
> multiple and independent i2c clients of the same type and driver.

Right, that's what I mean. But each of those devices should
use the same driver, just like each omap tty port uses the same
'serial_omap_reg' (which includes a tty driver).

>> proc_tty_register_driver() will fail to create the second
>> procfs file, but we ignore that failure.
>>
>> Why not call tty_register_driver() in the init function rather than probe()?
>
> We have no dedicated init function. Should we have one?
>
> And if I understand correctly it would prohibit to fix the driver for the
> multiple gps-devices situation. Or makes more work if the device is to be
> registered as a future GPS interface.
>
> So if the ->driver_name or ->name should have a dynamic sequence number,
> please help me to get it correct.

There should only be one driver structure, as in any other tty driver
implementation. You have an init function inside of the
module_serdev_device_driver() macro. When you open-code that,
you can register the tty driver there before registering the serdev driver,
see serial_omap_init() for a similar example using uart_driver and
platform_driver.

>>> The UART tty would be e.g. /dev/ttyO2 (on OMAP3) if no driver is
>>> installed. And the new one that is registered is /dev/GPS0. So the
>>> tty subsystem doesn't (or shouldn't) know they are related. They
>>> are only related/connected inside this driver. So I assume that
>>> some locking or reentrancy happens in tty_port_register_device().
>>
>> I meant the serdev->dev pointer that you pass into
>> tty_port_register_device() seems to be the same one that
>> got passed into the first tty_port_register_device() in the
>> parent uart_port.
>
> Ah, interesting!
>
> Well, I copied that from other drivers registering a tty without
> understanding all side-effects of everything.
>
> Documentations of tty_port_register_device() says:
> @device: parent if exists, otherwise NULL
>
> Do we really need a "parent" here? Could we safely pass NULL?

There should be a parent, to make it show up in the right place in sysfs.

Ideally the parent should point to a device representing the original
uart port. It probably is that right now, so I'd leave it like that if it
works without getting you into a double probe.

       Arnd
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[PATCH v3 1/5] DT: vendor prefix for Wi2Wi, Inc.

[H. Nikolaus Schaller]

Introduce vendor prefix for Wi2Wi, Inc. for W2SG00x4 GPS modules
and W2CBW003 Bluetooth/WiFi combo (CSR/Marvell).

Signed-off-by: H. Nikolaus Schaller <hns-xXXSsgcRVICgSpxsJD1C4w@public.gmane.org>
---
 Documentation/devicetree/bindings/vendor-prefixes.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/devicetree/bindings/vendor-prefixes.txt b/Documentation/devicetree/bindings/vendor-prefixes.txt
index 1afd298eddd7..ad4381738954 100644
--- a/Documentation/devicetree/bindings/vendor-prefixes.txt
+++ b/Documentation/devicetree/bindings/vendor-prefixes.txt
@@ -366,6 +366,7 @@ voipac	Voipac Technologies s.r.o.
 wd	Western Digital Corp.
 wetek	WeTek Electronics, limited.
 wexler	Wexler
+wi2wi	Wi2Wi, Inc.
 winbond Winbond Electronics corp.
 winstar	Winstar Display Corp.
 wlf	Wolfson Microelectronics
-- 
2.12.2

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[PATCH v3 4/5] DTS: gta04: add serdev node for w2sg00x4

[H. Nikolaus Schaller]

GTA04 has a W2SG0004/84 connected to UART2 of the OMAP3
processor. A GPIO can pulse the on/off toggle switch.

The VSIM regulator is used to power on/off the LNA of an external
active GPS antenna so that a driver can turn the LNA off if GPS is
not needed to save battery energy.

Signed-off-by: H. Nikolaus Schaller <hns-xXXSsgcRVICgSpxsJD1C4w@public.gmane.org>
---
 arch/arm/boot/dts/omap3-gta04.dtsi | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm/boot/dts/omap3-gta04.dtsi b/arch/arm/boot/dts/omap3-gta04.dtsi
index 4504908c23fe..e967d738aaaf 100644
--- a/arch/arm/boot/dts/omap3-gta04.dtsi
+++ b/arch/arm/boot/dts/omap3-gta04.dtsi
@@ -477,6 +477,12 @@
 &uart2 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&uart2_pins>;
+
+	gps: gps {
+		compatible = "wi2wi,w2sg0004";
+		lna-supply = <&vsim>;   /* LNA regulator */
+		enable-gpios = <&gpio5 17 GPIO_ACTIVE_HIGH>;    /* GPIO_145: trigger for turning on/off w2sg0004 */
+	};
 };
 
 &uart3 {
-- 
2.12.2

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[PATCH v3 5/5] misc serdev: w2sg0004: add debugging code and Kconfig

[H. Nikolaus Schaller]

This allows to set CONFIG_W2SG0004_DEBUG which will
make the driver report more activities and it will turn on the
GPS module during boot while the driver assumes that it
is off. This can be used to debug the correct functioning of
the hardware. Therefore we add it as an option to the driver
because we think it is of general use (and a little tricky to
add by system testers).

Normally it should be off.
---
 drivers/misc/Kconfig    |  8 ++++++++
 drivers/misc/w2sg0004.c | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 09d171d68408..f15ff5a97e42 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -528,4 +528,12 @@ config W2SG0004
 	  is opened/closed.
 	  It also provides a rfkill gps name to control the LNA power.
 
+config W2SG0004_DEBUG
+	bool "W2SG0004 on/off debugging"
+	depends on W2SG0004
+	help
+	  Enable driver debugging mode of W2SG0004 GPS. If you say y here
+	  this will turn on the module and you can check if it is turned
+	  off by the driver.
+
 endmenu
diff --git a/drivers/misc/w2sg0004.c b/drivers/misc/w2sg0004.c
index 385d35c99791..612e129aa639 100644
--- a/drivers/misc/w2sg0004.c
+++ b/drivers/misc/w2sg0004.c
@@ -22,6 +22,10 @@
  *
  */
 
+#ifdef CONFIG_W2SG0004_DEBUG
+#define DEBUG 1
+#endif
+
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/interrupt.h>
@@ -251,6 +255,7 @@ static int w2sg_tty_install(struct tty_driver *driver, struct tty_struct *tty)
 	pr_debug("%s() tty = %p\n", __func__, tty);
 
 	data = w2sg_get_by_minor(tty->index);
+	pr_debug("%s() data = %p\n", __func__, data);
 
 	if (!data)
 		return -ENODEV;
@@ -363,6 +368,8 @@ static int w2sg_probe(struct serdev_device *serdev)
 
 	w2sg_by_minor[minor] = data;
 
+	pr_debug("w2sg serdev_device_set_drvdata\n");
+
 	serdev_device_set_drvdata(serdev, data);
 
 	data->lna_regulator = pdata->lna_regulator;
@@ -381,6 +388,8 @@ static int w2sg_probe(struct serdev_device *serdev)
 
 	INIT_DELAYED_WORK(&data->work, toggle_work);
 
+	pr_debug("w2sg devm_gpio_request\n");
+
 	err = devm_gpio_request(&serdev->dev, data->on_off_gpio,
 				"w2sg0004-on-off");
 	if (err < 0)
@@ -394,6 +403,8 @@ static int w2sg_probe(struct serdev_device *serdev)
 	serdev_device_set_baudrate(data->uart, 9600);
 	serdev_device_set_flow_control(data->uart, false);
 
+	pr_debug("w2sg rfkill_alloc\n");
+
 	rf_kill = rfkill_alloc("GPS", &serdev->dev, RFKILL_TYPE_GPS,
 				&w2sg0004_rfkill_ops, data);
 	if (rf_kill == NULL) {
@@ -401,6 +412,8 @@ static int w2sg_probe(struct serdev_device *serdev)
 		goto err_rfkill;
 	}
 
+	pr_debug("w2sg register rfkill\n");
+
 	err = rfkill_register(rf_kill);
 	if (err) {
 		dev_err(&serdev->dev, "Cannot register rfkill device\n");
@@ -409,6 +422,8 @@ static int w2sg_probe(struct serdev_device *serdev)
 
 	data->rf_kill = rf_kill;
 
+	pr_debug("w2sg alloc_tty_driver\n");
+
 	/* allocate the tty driver */
 	data->tty_drv = alloc_tty_driver(1);
 	if (!data->tty_drv)
@@ -434,6 +449,8 @@ static int w2sg_probe(struct serdev_device *serdev)
 	 */
 	tty_set_operations(data->tty_drv, &w2sg_serial_ops);
 
+	pr_debug("w2sg tty_register_driver\n");
+
 	/* register the tty driver */
 	err = tty_register_driver(data->tty_drv);
 	if (err) {
@@ -443,6 +460,8 @@ static int w2sg_probe(struct serdev_device *serdev)
 		goto err_rfkill;
 	}
 
+	pr_debug("w2sg call tty_port_init\n");
+
 	tty_port_init(&data->port);
 	data->port.ops = &w2sg_port_ops;
 
@@ -451,11 +470,27 @@ static int w2sg_probe(struct serdev_device *serdev)
  * which only fails because the gpio is already assigned
  */
 
+	pr_debug("w2sg call tty_port_register_device\n");
+
 	data->dev = tty_port_register_device(&data->port,
 			data->tty_drv, minor, &serdev->dev);
 
+	pr_debug("w2sg tty_port_register_device -> %p\n", data->dev);
+	pr_debug("w2sg port.tty = %p\n", data->port.tty);
+
 	pr_debug("w2sg probed\n");
 
+#ifdef CONFIG_W2SG0004_DEBUG
+	pr_debug("w2sg DEBUGGING MODE enabled\n");
+	/* turn on for debugging rx notifications */
+	pr_debug("w2sg power gpio ON\n");
+	gpio_set_value_cansleep(data->on_off_gpio, 1);
+	mdelay(100);
+	pr_debug("w2sg power gpio OFF\n");
+	gpio_set_value_cansleep(data->on_off_gpio, 0);
+	mdelay(300);
+#endif
+
 	/* keep off until user space requests the device */
 	w2sg_set_power(data, false);
 
@@ -465,6 +500,8 @@ static int w2sg_probe(struct serdev_device *serdev)
 	rfkill_destroy(rf_kill);
 	serdev_device_close(data->uart);
 out:
+	pr_debug("w2sg error %d\n", err);
+
 	return err;
 }
 
-- 
2.12.2

Re: [PATCH v3 5/5] misc serdev: w2sg0004: add debugging code and Kconfig

[Andreas Färber]

Hi,

Am 15.11.2017 um 16:19 schrieb H. Nikolaus Schaller:
> This allows to set CONFIG_W2SG0004_DEBUG which will
> make the driver report more activities and it will turn on the
> GPS module during boot while the driver assumes that it
> is off. This can be used to debug the correct functioning of
> the hardware. Therefore we add it as an option to the driver
> because we think it is of general use (and a little tricky to
> add by system testers).
> 
> Normally it should be off.
> ---

If you want to merge this, it is lacking a Sob.

Cheers,
Andreas

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Re: [PATCH v3 5/5] misc serdev: w2sg0004: add debugging code and Kconfig

[H. Nikolaus Schaller]

Hi Andreas,

> Am 15.11.2017 um 16:53 schrieb Andreas Färber <afaerber@suse.de>:
> 
> Hi,
> 
> Am 15.11.2017 um 16:19 schrieb H. Nikolaus Schaller:
>> This allows to set CONFIG_W2SG0004_DEBUG which will
>> make the driver report more activities and it will turn on the
>> GPS module during boot while the driver assumes that it
>> is off. This can be used to debug the correct functioning of
>> the hardware. Therefore we add it as an option to the driver
>> because we think it is of general use (and a little tricky to
>> add by system testers).
>> 
>> Normally it should be off.
>> ---
> 
> If you want to merge this, it is lacking a Sob.

Whats is a "Sob" in this context (https://acronyms.thefreedictionary.com/SOB)?

BR and thanks,
Nikolaus Schaller


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Re: [PATCH v3 5/5] misc serdev: w2sg0004: add debugging code and Kconfig

[Ladislav Michl]

On Wed, Nov 15, 2017 at 05:29:25PM +0100, H. Nikolaus Schaller wrote:
> Hi Andreas,
> 
> > Am 15.11.2017 um 16:53 schrieb Andreas Färber <afaerber-l3A5Bk7waGM@public.gmane.org>:
> > 
> > Hi,
> > 
> > Am 15.11.2017 um 16:19 schrieb H. Nikolaus Schaller:
> >> This allows to set CONFIG_W2SG0004_DEBUG which will
> >> make the driver report more activities and it will turn on the
> >> GPS module during boot while the driver assumes that it
> >> is off. This can be used to debug the correct functioning of
> >> the hardware. Therefore we add it as an option to the driver
> >> because we think it is of general use (and a little tricky to
> >> add by system testers).
> >> 
> >> Normally it should be off.
> >> ---
> > 
> > If you want to merge this, it is lacking a Sob.
> 
> Whats is a "Sob" in this context (https://acronyms.thefreedictionary.com/SOB)?

https://acronyms.thefreedictionary.com/Signed-Off-By

Also please read Documentation/process/submitting-patches.rst

	ladis

> BR and thanks,
> Nikolaus Schaller
> 
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Re: [PATCH v3 5/5] misc serdev: w2sg0004: add debugging code and Kconfig

[H. Nikolaus Schaller]

Hi Ladislav,

> Am 15.11.2017 um 17:42 schrieb Ladislav Michl <ladis@linux-mips.org>:
> 
> On Wed, Nov 15, 2017 at 05:29:25PM +0100, H. Nikolaus Schaller wrote:
>> Hi Andreas,
>> 
>>> Am 15.11.2017 um 16:53 schrieb Andreas Färber <afaerber@suse.de>:
>>> 
>>> Hi,
>>> 
>>> Am 15.11.2017 um 16:19 schrieb H. Nikolaus Schaller:
>>>> This allows to set CONFIG_W2SG0004_DEBUG which will
>>>> make the driver report more activities and it will turn on the
>>>> GPS module during boot while the driver assumes that it
>>>> is off. This can be used to debug the correct functioning of
>>>> the hardware. Therefore we add it as an option to the driver
>>>> because we think it is of general use (and a little tricky to
>>>> add by system testers).
>>>> 
>>>> Normally it should be off.
>>>> ---
>>> 
>>> If you want to merge this, it is lacking a Sob.
>> 
>> Whats is a "Sob" in this context (https://acronyms.thefreedictionary.com/SOB)?
> 
> https://acronyms.thefreedictionary.com/Signed-Off-By

Ah, ok. Too obvious to associate :) Tnx.

I did never think about that this could be missing. And I don't know why :(

> Also please read Documentation/process/submitting-patches.rst

We have automated things by calling checkpatch but it somwhow failed here.

BR and thanks,
Nikolaus

Re: [PATCH v3 5/5] misc serdev: w2sg0004: add debugging code and Kconfig

[Joe Perches]

On Wed, 2017-11-15 at 18:13 +0100, H. Nikolaus Schaller wrote:
> We have automated things by calling checkpatch but it somwhow failed here.

what failed?

Re: [PATCH v3 5/5] misc serdev: w2sg0004: add debugging code and Kconfig

[H. Nikolaus Schaller]

> Am 15.11.2017 um 18:52 schrieb Joe Perches <joe@perches.com>:
> 
> On Wed, 2017-11-15 at 18:13 +0100, H. Nikolaus Schaller wrote:
>> We have automated things by calling checkpatch but it somwhow failed here.
> 
> what failed?

I don't know. It didn't tell us that the signature was missing. Maybe
a glitch in our post-processing script. I tried again and checkpatch.pl
did clearly report the ERROR this time.

So nothing you can fix.

BR and thanks,
Nikolaus Schaller