[PATCH v2 0/5] misc: new serdev based drivers for Wi2Wi w2sg00x4 GPS module

[PATCH v2 0/5] misc: new serdev based drivers for Wi2Wi w2sg00x4 GPS module

[H. Nikolaus Schaller]

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: w2sg0004: add bindings documentation (GPS module with serdev
    UART)
  misc: Add w2sg0004 (gps receiver) power control driver
  DTS: gta04: add serdev node for w2sg00x4
  misc: 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 v2 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@goldelico.com>
---
 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

Re: [PATCH v2 1/5] DT: vendor prefix for Wi2Wi, Inc.

[Rob Herring]

On Sun, Nov 12, 2017 at 09:59:54PM +0100, H. Nikolaus Schaller wrote:
> 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(+)

"dt-bindings: ..." is the preferred subject prefix. Otherwise,

Acked-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
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Re: [PATCH v2 1/5] DT: vendor prefix for Wi2Wi, Inc.

[H. Nikolaus Schaller]

> Am 15.11.2017 um 21:04 schrieb Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>:
> 
> On Sun, Nov 12, 2017 at 09:59:54PM +0100, H. Nikolaus Schaller wrote:
>> 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(+)
> 
> "dt-bindings: ..." is the preferred subject prefix. Otherwise,
> 
> Acked-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

Ok,
changed for v4.

BR and thanks,
Nikolaus Schaller
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[PATCH v2 2/5] DT: misc: 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

Re: [PATCH v2 2/5] DT: misc: w2sg0004: add bindings documentation (GPS module with serdev UART)

[Rob Herring]

On Sun, Nov 12, 2017 at 09:59:55PM +0100, H. Nikolaus Schaller wrote:
> add bindings documentation for Wi2Wi W2SG00x4 GPS module

Add ... module.

> 
> Signed-off-by: H. Nikolaus Schaller <hns-xXXSsgcRVICgSpxsJD1C4w@public.gmane.org>
> ---
>  .../devicetree/bindings/misc/wi2wi,w2sg0004.txt    | 24 ++++++++++++++++++++++

The path doesn't have to match the kernel. Use bindings/gps/...

>  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).

Could be connected to any kind of UART and serdev is a Linuxism.

With those fixed,

Acked-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
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Re: [PATCH v2 2/5] DT: misc: w2sg0004: add bindings documentation (GPS module with serdev UART)

[H. Nikolaus Schaller]

Hi Rob,

> Am 15.11.2017 um 21:08 schrieb Rob Herring <robh@kernel.org>:
> 
> On Sun, Nov 12, 2017 at 09:59:55PM +0100, H. Nikolaus Schaller wrote:
>> add bindings documentation for Wi2Wi W2SG00x4 GPS module
> 
> Add ... module.

Ok.

> 
>> 
>> Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
>> ---
>> .../devicetree/bindings/misc/wi2wi,w2sg0004.txt    | 24 ++++++++++++++++++++++
> 
> The path doesn't have to match the kernel. Use bindings/gps/...

Ok.

> 
>> 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).
> 
> Could be connected to any kind of UART and serdev is a Linuxism.
> 
> With those fixed,
> 
> Acked-by: Rob Herring <robh@kernel.org>


Fine and thanks,
Nikolaus Schaller

PS: there is already a [PATCH v3] (no changes for 1/5 and 2/5)

[PATCH v2 3/5] misc: 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..55101aa6beeb
--- /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 %d 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 %d 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 v2 3/5] misc: Add w2sg0004 (gps receiver) power control driver

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 7687 bytes --]

Hi Nikolaus,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on v4.14]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/H-Nikolaus-Schaller/misc-new-serdev-based-drivers-for-Wi2Wi-w2sg00x4-GPS-module/20171115-115158
config: x86_64-allmodconfig (attached as .config)
compiler: gcc-6 (Debian 6.4.0-9) 6.4.0 20171026
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   In file included from include/linux/kernel.h:13:0,
                    from include/linux/delay.h:21,
                    from drivers/misc/w2sg0004.c:25:
   drivers/misc/w2sg0004.c: In function 'w2sg_uart_receive_buf':
>> drivers/misc/w2sg0004.c:156:12: warning: format '%d' expects argument of type 'int', but argument 3 has type 'size_t {aka long unsigned int}' [-Wformat=]
      pr_debug("w2sg00x4: push %d chars to tty port\n", count);
               ^
   include/linux/printk.h:285:21: note: in definition of macro 'pr_fmt'
    #define pr_fmt(fmt) fmt
                        ^~~
   include/linux/printk.h:333:2: note: in expansion of macro 'dynamic_pr_debug'
     dynamic_pr_debug(fmt, ##__VA_ARGS__)
     ^~~~~~~~~~~~~~~~
>> drivers/misc/w2sg0004.c:156:3: note: in expansion of macro 'pr_debug'
      pr_debug("w2sg00x4: push %d chars to tty port\n", count);
      ^~~~~~~~
   In file included from include/linux/printk.h:6:0,
                    from include/linux/kernel.h:13,
                    from include/linux/delay.h:21,
                    from drivers/misc/w2sg0004.c:25:
   include/linux/kern_levels.h:4:18: warning: format '%d' expects argument of type 'int', but argument 2 has type 'size_t {aka long unsigned int}' [-Wformat=]
    #define KERN_SOH "\001"  /* ASCII Start Of Header */
                     ^
   include/linux/kern_levels.h:10:18: note: in expansion of macro 'KERN_SOH'
    #define KERN_ERR KERN_SOH "3" /* error conditions */
                     ^~~~~~~~
   include/linux/printk.h:301:9: note: in expansion of macro 'KERN_ERR'
     printk(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__)
            ^~~~~~~~
>> drivers/misc/w2sg0004.c:161:4: note: in expansion of macro 'pr_err'
       pr_err("w2sg00x4: did loose %d characters\n", count - n);
       ^~~~~~

vim +156 drivers/misc/w2sg0004.c

  > 25	#include <linux/delay.h>
    26	#include <linux/err.h>
    27	#include <linux/interrupt.h>
    28	#include <linux/irq.h>
    29	#include <linux/module.h>
    30	#include <linux/of.h>
    31	#include <linux/of_irq.h>
    32	#include <linux/of_gpio.h>
    33	#include <linux/platform_device.h>
    34	#include <linux/rfkill.h>
    35	#include <linux/serdev.h>
    36	#include <linux/sched.h>
    37	#include <linux/slab.h>
    38	#include <linux/tty.h>
    39	#include <linux/tty_flip.h>
    40	#include <linux/w2sg0004.h>
    41	#include <linux/workqueue.h>
    42	
    43	/*
    44	 * There seems to be restrictions on how quickly we can toggle the
    45	 * on/off line.  data sheets says "two rtc ticks", whatever that means.
    46	 * If we do it too soon it doesn't work.
    47	 * So we have a state machine which uses the common work queue to ensure
    48	 * clean transitions.
    49	 * When a change is requested we record that request and only act on it
    50	 * once the previous change has completed.
    51	 * A change involves a 10ms low pulse, and a 990ms raised level, so only
    52	 * one change per second.
    53	 */
    54	
    55	enum w2sg_state {
    56		W2SG_IDLE,	/* is not changing state */
    57		W2SG_PULSE,	/* activate on/off impulse */
    58		W2SG_NOPULSE	/* deactivate on/off impulse */
    59	};
    60	
    61	struct w2sg_data {
    62		struct		rfkill *rf_kill;
    63		struct		regulator *lna_regulator;
    64		int		lna_blocked;	/* rfkill block gps active */
    65		int		lna_is_off;	/* LNA is currently off */
    66		int		is_on;		/* current state (0/1) */
    67		unsigned long	last_toggle;
    68		unsigned long	backoff;	/* time to wait since last_toggle */
    69		int		on_off_gpio;	/* the on-off gpio number */
    70		struct		serdev_device *uart;	/* uart connected to the chip */
    71		struct		tty_driver *tty_drv;	/* this is the user space tty */
    72		struct		device *dev;	/* from tty_port_register_device() */
    73		struct		tty_port port;
    74		int		open_count;	/* how often we were opened */
    75		enum		w2sg_state state;
    76		int		requested;	/* requested state (0/1) */
    77		int		suspended;
    78		struct delayed_work work;
    79		int		discard_count;
    80	};
    81	
    82	static struct w2sg_data *w2sg_by_minor[1];
    83	
    84	static int w2sg_set_lna_power(struct w2sg_data *data)
    85	{
    86		int ret = 0;
    87		int off = data->suspended || !data->requested || data->lna_blocked;
    88	
    89		pr_debug("%s: %s\n", __func__, off ? "off" : "on");
    90	
    91		if (off != data->lna_is_off) {
    92			data->lna_is_off = off;
    93			if (!IS_ERR_OR_NULL(data->lna_regulator)) {
    94				if (off)
    95					regulator_disable(data->lna_regulator);
    96				else
    97					ret = regulator_enable(data->lna_regulator);
    98			}
    99		}
   100	
   101		return ret;
   102	}
   103	
   104	static void w2sg_set_power(void *pdata, int val)
   105	{
   106		struct w2sg_data *data = (struct w2sg_data *) pdata;
   107	
   108		pr_debug("%s to state=%d (requested=%d)\n", __func__, val, data->requested);
   109	
   110		if (val && !data->requested) {
   111			data->requested = true;
   112		} else if (!val && data->requested) {
   113			data->backoff = HZ;
   114			data->requested = false;
   115		} else
   116			return;
   117	
   118		pr_debug("w2sg00x4 scheduled for %d\n", data->requested);
   119	
   120		if (!data->suspended)
   121			schedule_delayed_work(&data->work, 0);
   122	}
   123	
   124	/* called each time data is received by the UART (i.e. sent by the w2sg0004) */
   125	
   126	static int w2sg_uart_receive_buf(struct serdev_device *serdev,
   127					const unsigned char *rxdata,
   128					size_t count)
   129	{
   130		struct w2sg_data *data =
   131			(struct w2sg_data *) serdev_device_get_drvdata(serdev);
   132	
   133		if (!data->requested && !data->is_on) {
   134			/*
   135			 * we have received characters while the w2sg
   136			 * should have been be turned off
   137			 */
   138			data->discard_count += count;
   139			if ((data->state == W2SG_IDLE) &&
   140			    time_after(jiffies,
   141			    data->last_toggle + data->backoff)) {
   142				/* Should be off by now, time to toggle again */
   143				pr_debug("w2sg00x4 has sent %d characters data although it should be off!\n",
   144					data->discard_count);
   145	
   146				data->discard_count = 0;
   147	
   148				data->is_on = true;
   149				data->backoff *= 2;
   150				if (!data->suspended)
   151					schedule_delayed_work(&data->work, 0);
   152			}
   153		} else if (data->open_count > 0) {
   154			int n;
   155	
 > 156			pr_debug("w2sg00x4: push %d chars to tty port\n", count);
   157	
   158			/* pass to user-space */
   159			n = tty_insert_flip_string(&data->port, rxdata, count);
   160			if (n != count)
 > 161				pr_err("w2sg00x4: did loose %d characters\n", count - n);
   162			tty_flip_buffer_push(&data->port);
   163			return n;
   164		}
   165	
   166		/* assume we have processed everything */
   167		return count;
   168	}
   169	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 61726 bytes --]

Re: [PATCH v2 3/5] misc: Add w2sg0004 (gps receiver) power control driver

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 3034 bytes --]

Hi Nikolaus,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on v4.14 next-20171115]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/H-Nikolaus-Schaller/misc-new-serdev-based-drivers-for-Wi2Wi-w2sg00x4-GPS-module/20171115-115158
config: tile-allmodconfig (attached as .config)
compiler: tilegx-linux-gcc (GCC) 4.6.2
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=tile 

All warnings (new ones prefixed by >>):

   drivers/misc/w2sg0004.c: In function 'w2sg_uart_receive_buf':
>> drivers/misc/w2sg0004.c:156:3: warning: format '%d' expects argument of type 'int', but argument 3 has type 'size_t' [-Wformat]
   drivers/misc/w2sg0004.c:161:4: warning: format '%d' expects argument of type 'int', but argument 2 has type 'size_t' [-Wformat]
   drivers/misc/w2sg0004.c: At top level:
   drivers/misc/w2sg0004.c:487:12: warning: 'w2sg_suspend' defined but not used [-Wunused-function]
   drivers/misc/w2sg0004.c:523:12: warning: 'w2sg_resume' defined but not used [-Wunused-function]

vim +156 drivers/misc/w2sg0004.c

   125	
   126	static int w2sg_uart_receive_buf(struct serdev_device *serdev,
   127					const unsigned char *rxdata,
   128					size_t count)
   129	{
   130		struct w2sg_data *data =
   131			(struct w2sg_data *) serdev_device_get_drvdata(serdev);
   132	
   133		if (!data->requested && !data->is_on) {
   134			/*
   135			 * we have received characters while the w2sg
   136			 * should have been be turned off
   137			 */
   138			data->discard_count += count;
   139			if ((data->state == W2SG_IDLE) &&
   140			    time_after(jiffies,
   141			    data->last_toggle + data->backoff)) {
   142				/* Should be off by now, time to toggle again */
   143				pr_debug("w2sg00x4 has sent %d characters data although it should be off!\n",
   144					data->discard_count);
   145	
   146				data->discard_count = 0;
   147	
   148				data->is_on = true;
   149				data->backoff *= 2;
   150				if (!data->suspended)
   151					schedule_delayed_work(&data->work, 0);
   152			}
   153		} else if (data->open_count > 0) {
   154			int n;
   155	
 > 156			pr_debug("w2sg00x4: push %d chars to tty port\n", count);
   157	
   158			/* pass to user-space */
   159			n = tty_insert_flip_string(&data->port, rxdata, count);
   160			if (n != count)
   161				pr_err("w2sg00x4: did loose %d characters\n", count - n);
   162			tty_flip_buffer_push(&data->port);
   163			return n;
   164		}
   165	
   166		/* assume we have processed everything */
   167		return count;
   168	}
   169	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 50385 bytes --]

Re: [PATCH v2 3/5] misc: Add w2sg0004 (gps receiver) power control driver

[Rob Herring]

On Sun, Nov 12, 2017 at 09:59:56PM +0100, H. Nikolaus Schaller 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>
> ---
>  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..55101aa6beeb
> --- /dev/null
> +++ b/drivers/misc/w2sg0004.c
> @@ -0,0 +1,565 @@
> +/*
> + * w2sg0004.c

Listing the filename is pointless IMO. You need a license too. Use SPDX 
tag (on first line with C++ style comment).

> + * 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 %d 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 %d 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;

NULL ptr dereference if you have no of_node.

> +	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);

Is there an advantage or reason to make this a tty driver rather than 
just a char driver?

Perhaps this should be under drivers/tty if it is a tty driver.

> +	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-l3A5Bk7waGM@public.gmane.org>");
> +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-+NVA1uvv1dVBDLzU/O5InQ@public.gmane.org>
> + *
> + * 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 {

You don't really support platform_data, so you can move this into the 
driver.

> +	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
> 
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Re: [PATCH v2 3/5] misc: Add w2sg0004 (gps receiver) power control driver

[H. Nikolaus Schaller]

Hi Rob,

> Am 15.11.2017 um 21:17 schrieb Rob Herring <robh@kernel.org>:
> 
> On Sun, Nov 12, 2017 at 09:59:56PM +0100, H. Nikolaus Schaller 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@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..55101aa6beeb
>> --- /dev/null
>> +++ b/drivers/misc/w2sg0004.c
>> @@ -0,0 +1,565 @@
>> +/*
>> + * w2sg0004.c
> 
> Listing the filename is pointless IMO.

Ok.

> You need a license too. Use SPDX 
> tag (on first line with C++ style comment).

Well, this is too new to be aware of...
Isn't the MODULE_LICENSE enough any more?

> 
>> + * 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 %d 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 %d 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;
> 
> NULL ptr dereference if you have no of_node.

has more or less already commented by Arnd and will be fixed in PATCH v4.

> 
>> +	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);
> 
> Is there an advantage or reason to make this a tty driver rather than 
> just a char driver?

Well, gpsd and other daemons might assume they can tcsetattr or a line discipline etc.

> 
> Perhaps this should be under drivers/tty if it is a tty driver.

Well, primarily it is a gps driver... And in some bright future there
should be specific gps interfaces (like networking or bluetooth).

But there is no drivers/gps and I am not sure if this one should be the
first. If you prefer it, it is a simple rename...

> 
>> +	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 {
> 
> You don't really support platform_data, so you can move this into the 
> driver.

Yes, I am working on that as recommended by Arnd.

> 
>> +	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
>> 


BR and thanks,
Nikolaus

[PATCH v2 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@goldelico.com>
---
 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

[PATCH v2 5/5] misc: 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 55101aa6beeb..b6e2253a580f 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