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

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. 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@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.

• 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