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@xxxxxxx>
> but simplified and adapted to use the new serdev API introduced in 4.11.
>
> Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
> ---
> 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@xxxxxxx>");
> +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@xxxxxxxxxx>
> + *
> + * 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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