[RFC 3/3] misc: Add w2cbw003 (wifi/bluetooth) power control driver

[H. Nikolaus Schaller]

Add driver for Wi2Wi W2CBW003 WiFi and Bluetooth module
where the Bluetooth interface is connected through uart.

Uses the new serdev API to glue with tty and turn on/off the
module if the tty port (/dev/ttyBTn) is opened.

Note that this is only for the Bluetooth side. The WLAN
(libertas) sdio driver should be abe to enable the same vdd
regulator. So that the device is powered on if either WiFi or
Bluetooth is activated (or both) and powered down if neither
is in use.

Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
---
 drivers/misc/Kconfig              |   7 +
 drivers/misc/Makefile             |   1 +
 drivers/misc/w2cbw003-bluetooth.c | 390 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 398 insertions(+)
 create mode 100644 drivers/misc/w2cbw003-bluetooth.c

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 7f97ef8fb6cd..90ce23bef77b 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -525,4 +525,11 @@ config W2SG0004_DEBUG
 	help
 	  Enable driver debugging mode of W2SG0004 GPS.
 
+config W2CBW003
+	tristate "W2CBW003 power on/off control"
+	depends on GPIOLIB
+	help
+	  Enable on/off power control of W2CBW003 if the /dev/tty$n for
+	  Bluetooth is opened.
+
 endmenu
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 0e88e06e5ee0..f6d3f096c5e0 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -51,6 +51,7 @@ obj-y				+= mic/
 obj-$(CONFIG_GENWQE)		+= genwqe/
 obj-$(CONFIG_ECHO)		+= echo/
 obj-$(CONFIG_W2SG0004)		+= w2sg0004.o
+obj-$(CONFIG_W2CBW003)		+= w2cbw003-bluetooth.o
 obj-$(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/w2cbw003-bluetooth.c b/drivers/misc/w2cbw003-bluetooth.c
new file mode 100644
index 000000000000..3bcfd51bbf09
--- /dev/null
+++ b/drivers/misc/w2cbw003-bluetooth.c
@@ -0,0 +1,390 @@
+/*
+ * w2scbw003.c
+ * Driver for power controlling the w2cbw003 WiFi/Bluetooth chip.
+ *
+ * powers on the chip if the tty port associated/connected
+ * to the bluetooth subsystem is opened (e.g. hciattach /dev/ttyBT0)
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/regulator/consumer.h>
+#include <linux/serdev.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+
+#undef pr_debug
+#define pr_debug printk
+
+struct w2cbw_data {
+	struct		regulator *vdd_regulator;
+	struct		serdev_device *uart;	/* the uart connected to the chip */
+	struct		tty_driver *tty_drv;	/* this is the user space tty */
+	struct		device *dev;	/* returned by tty_port_register_device() */
+	struct		tty_port port;
+	int		open_count;	/* how often we were opened */
+};
+
+static struct w2cbw_data *w2cbw_by_minor[1];
+
+static void w2cbw_set_power(void *pdata, int val)
+{
+	struct w2cbw_data *data = (struct w2cbw_data *) pdata;
+
+	pr_debug("%s(...,%x)\n", __func__, val);
+
+	if (val != 0)
+		WARN_ON(regulator_enable(data->vdd_regulator));
+	else
+		regulator_disable(data->vdd_regulator);
+}
+
+/* called each time data is received by the UART (i.e. sent by the w2cbw003) */
+
+static int w2cbw_uart_receive_buf(struct serdev_device *serdev, const unsigned char *rxdata,
+				size_t count)
+{
+	struct w2cbw_data *data = (struct w2cbw_data *) serdev_device_get_drvdata(serdev);
+
+//	pr_debug("%s() characters\n", __func__, count);
+
+	if (data->open_count > 0) {
+		int n;
+
+		pr_debug("w2cbw003: uart->tty %d chars\n", count);
+		n = tty_insert_flip_string(&data->port, rxdata, count);	/* pass to user-space */
+		if (n != count)
+			pr_debug("w2cbw003: did loose %d characters\n", count - n);
+		tty_flip_buffer_push(&data->port);
+		return n;
+	}
+
+	/* nobody is listenig - ignore incoming data */
+	return count;
+}
+
+static struct serdev_device_ops serdev_ops = {
+	.receive_buf = w2cbw_uart_receive_buf,
+#if 0
+	.write_wakeup = w2cbw_uart_wakeup,
+#endif
+};
+
+static struct w2cbw_data *w2cbw_get_by_minor(unsigned int minor)
+{
+	return w2cbw_by_minor[minor];
+}
+
+static int w2cbw_tty_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+	struct w2cbw_data *data;
+	int retval;
+
+	pr_debug("%s() tty = %p\n", __func__, tty);
+
+	data = w2cbw_get_by_minor(tty->index);
+	pr_debug("%s() data = %p\n", __func__, data);
+
+	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 w2cbw_tty_open(struct tty_struct *tty, struct file *file)
+{
+	struct w2cbw_data *data = tty->driver_data;
+
+	pr_debug("%s() data = %p open_count = ++%d\n", __func__, data, data->open_count);
+//	val = (val & TIOCM_DTR) != 0;	/* DTR controls power on/off */
+
+	w2cbw_set_power(data, ++data->open_count > 0);
+
+// we could/should return -Esomething if already open...
+
+	return tty_port_open(&data->port, tty, file);
+}
+
+static void w2cbw_tty_close(struct tty_struct *tty, struct file *file)
+{
+	struct w2cbw_data *data = tty->driver_data;
+
+	pr_debug("%s()\n", __func__);
+//	val = (val & TIOCM_DTR) != 0;	/* DTR controls power on/off */
+	w2cbw_set_power(data, --data->open_count > 0);
+
+	tty_port_close(&data->port, tty, file);
+}
+
+static int w2cbw_tty_write(struct tty_struct *tty,
+		const unsigned char *buffer, int count)
+{
+	struct w2cbw_data *data = tty->driver_data;
+
+	pr_debug("w2cbw003: tty->uart %d chars\n", count);
+
+	return serdev_device_write_buf(data->uart, buffer, count);	/* simply pass down to UART */
+}
+
+static void w2cbw_tty_set_termios(struct tty_struct *tty,
+		struct ktermios *old)
+{ /* copy from tty settings */
+	struct w2cbw_data *data = tty->driver_data;
+
+pr_debug("%s() flow = %d\n", __func__, tty_port_cts_enabled(tty->port));
+pr_debug("%s() baud rate = %d\n", __func__, tty_termios_baud_rate(&tty->termios));
+
+	serdev_device_set_flow_control(data->uart, tty_port_cts_enabled(tty->port));
+	serdev_device_set_baudrate(data->uart, tty_termios_baud_rate(&tty->termios));
+/* this may trigger
+[  295.607781]
+[  295.609349] =============================================
+[  295.615024] [ INFO: possible recursive locking detected ]
+[  295.620707] 4.11.0-rc8-letux+ #1026 Tainted: G        W
+[  295.626745] ---------------------------------------------
+[  295.632421] hciattach/2633 is trying to acquire lock:
+[  295.637737]  (&tty->termios_rwsem){++++.+}, at: [<c04bb400>] tty_set_termios+0x40/0x1b0
+[  295.646190]
+[  295.646190] but task is already holding lock:
+[  295.652329]  (&tty->termios_rwsem){++++.+}, at: [<c04bb400>] tty_set_termios+0x40/0x1b0
+[  295.660780]
+[  295.660780] other info that might help us debug this:
+[  295.667646]  Possible unsafe locking scenario:
+[  295.667646]
+[  295.673873]        CPU0
+[  295.676444]        ----
+[  295.679017]   lock(&tty->termios_rwsem);
+[  295.683151]   lock(&tty->termios_rwsem);
+[  295.687288]
+[  295.687288]  *** DEADLOCK ***
+[  295.687288]
+[  295.693517]  May be due to missing lock nesting notation
+[  295.693517]
+[  295.700666] 2 locks held by hciattach/2633:
+[  295.705063]  #0:  (&tty->ldisc_sem){++++++}, at: [<c04bc790>] tty_ldisc_ref_wait+0x18/0x34
+[  295.713789]  #1:  (&tty->termios_rwsem){++++.+}, at: [<c04bb400>] tty_set_termios+0x40/0x1b0
+[  295.722691]
+[  295.722691] stack backtrace:
+[  295.727285] CPU: 1 PID: 2633 Comm: hciattach Tainted: G        W       4.11.0-rc8-letux+ #1026
+[  295.736342] Hardware name: Generic OMAP5 (Flattened Device Tree)
+[  295.742679] [<c010f378>] (unwind_backtrace) from [<c010b8fc>] (show_stack+0x10/0x14)
+[  295.750841] [<c010b8fc>] (show_stack) from [<c043e4a0>] (dump_stack+0x98/0xd0)
+[  295.758450] [<c043e4a0>] (dump_stack) from [<c0186ff0>] (validate_chain+0x760/0x1010)
+[  295.766694] [<c0186ff0>] (validate_chain) from [<c0188e58>] (__lock_acquire+0x690/0x760)
+[  295.775214] [<c0188e58>] (__lock_acquire) from [<c0189428>] (lock_acquire+0x1d0/0x29c)
+[  295.783558] [<c0189428>] (lock_acquire) from [<c0754a88>] (down_write+0x28/0x78)
+[  295.791354] [<c0754a88>] (down_write) from [<c04bb400>] (tty_set_termios+0x40/0x1b0)
+[  295.799508] [<c04bb400>] (tty_set_termios) from [<c04d50dc>] (ttyport_set_flow_control+0x58/0x60)
+[  295.808856] [<c04d50dc>] (ttyport_set_flow_control) from [<bf0a4080>] (w2cbw_tty_set_termios+0x58/0x80 [w2cbw003_bluetooth])
+[  295.820675] [<bf0a4080>] (w2cbw_tty_set_termios [w2cbw003_bluetooth]) from [<c04bb514>] (tty_set_termios+0x154/0x1b0)
+[  295.831859] [<c04bb514>] (tty_set_termios) from [<c04bbd18>] (set_termios.part.1+0x3b4/0x42c)
+[  295.840841] [<c04bbd18>] (set_termios.part.1) from [<c04bbff4>] (tty_mode_ioctl+0x1e8/0x598)
+[  295.849721] [<c04bbff4>] (tty_mode_ioctl) from [<c04b7080>] (tty_ioctl+0xe84/0xedc)
+[  295.857784] [<c04b7080>] (tty_ioctl) from [<c0282e80>] (vfs_ioctl+0x20/0x34)
+[  295.865215] [<c0282e80>] (vfs_ioctl) from [<c0283844>] (do_vfs_ioctl+0x82c/0x93c)
+[  295.873098] [<c0283844>] (do_vfs_ioctl) from [<c02839a0>] (SyS_ioctl+0x4c/0x74)
+[  295.880801] [<c02839a0>] (SyS_ioctl) from [<c0107040>] (ret_fast_syscall+0x0/0x1c)
+*/
+}
+
+static const struct tty_operations w2cbw_serial_ops = {
+	.install = w2cbw_tty_install,
+	.open = w2cbw_tty_open,
+	.close = w2cbw_tty_close,
+	.write = w2cbw_tty_write,
+	.set_termios = w2cbw_tty_set_termios,
+#if 0
+	/* sometimes: [  300.314968] ttyBT ttyBT0: missing write_room method */
+	.write_room = w2cbw_tty_write_room,
+	.cleanup = w2cbw_tty_cleanup,
+	.ioctl = w2cbw_tty_ioctl,
+	.chars_in_buffer = w2cbw_tty_chars_in_buffer,
+	.tiocmget = w2cbw_tty_tiocmget,
+	.tiocmset = w2cbw_tty_tiocmset,
+	.get_icount = w2cbw_tty_get_count,
+	.unthrottle = w2cbw_tty_unthrottle
+#endif
+};
+
+static const struct tty_port_operations w2cbw_port_ops = {
+};
+
+static int w2cbw_probe(struct serdev_device *serdev)
+{
+	struct device *dev = &serdev->dev;
+	struct w2cbw_data *data;
+	int err;
+	int minor;
+
+	pr_debug("%s()\n", __func__);
+
+	minor = 0;
+	if (w2cbw_by_minor[minor]) {
+		pr_err("w2cbw minor is already in use!\n");
+		return -ENODEV;
+	}
+
+	if (!serdev->dev.of_node) {
+		dev_err(&serdev->dev, "No device tree data\n");
+		return -EINVAL;
+	}
+
+	data = devm_kzalloc(&serdev->dev, sizeof(*data), GFP_KERNEL);
+	if (data == NULL)
+		return -ENOMEM;
+
+	data->vdd_regulator = devm_regulator_get_optional(dev, "vdd");
+
+	if (IS_ERR(data->vdd_regulator)) {
+		if (PTR_ERR(data->vdd_regulator) == -EPROBE_DEFER)
+			return -EPROBE_DEFER;	/* we can't probe yet */
+		data->uart = NULL;	/* no regulator yet */
+	}
+
+	pr_debug("%s() vdd_regulator = %p\n", __func__, data->vdd_regulator);
+
+	w2cbw_by_minor[minor] = data;
+
+	serdev_device_set_drvdata(serdev, data);
+
+	pr_debug("w2cbw003 probed\n");
+
+	data->uart = serdev;
+
+	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);
+#if 1
+	pr_debug("w2cbw alloc_tty_driver\n");
+#endif
+	/* 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 = "w2cbw003";
+	data->tty_drv->name = "ttyBT";
+	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;
+	/*
+	 * tty_termios_encode_baud_rate(&data->tty_drv->init_termios, 115200, 115200);
+	 * w2cbw_tty_termios(&data->tty_drv->init_termios);
+	 */
+	tty_set_operations(data->tty_drv, &w2cbw_serial_ops);
+
+#if 1
+	pr_debug("w2cbw tty_register_driver\n");
+#endif
+	/* 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;
+	}
+
+#if 1
+	pr_debug("w2cbw call tty_port_init\n");
+#endif
+	tty_port_init(&data->port);
+	data->port.ops = &w2cbw_port_ops;
+
+#if 1
+	pr_debug("w2cbw call tty_port_register_device\n");
+#endif
+/*
+ * FIXME: this appears to reenter this probe() function a second time
+ * which only fails because the minor number is already assigned
+ */
+
+	data->dev = tty_port_register_device(&data->port,
+			data->tty_drv, minor, &serdev->dev);
+
+#if 1
+	pr_debug("w2cbw tty_port_register_device -> %p\n", data->dev);
+	pr_debug("w2cbw port.tty = %p\n", data->port.tty);
+#endif
+//	data->port.tty->driver_data = data;	/* make us known in tty_struct */
+
+	/* keep off until user space requests the device */
+	if (regulator_is_enabled(data->vdd_regulator))
+		w2cbw_set_power(data, false);
+
+	pr_debug("w2cbw probed\n");
+
+	return 0;
+
+err:
+	serdev_device_close(data->uart);
+#if 0
+	if (err == -EBUSY)
+		err = -EPROBE_DEFER;
+#endif
+#if 1
+	pr_debug("w2cbw error %d\n", err);
+#endif
+	return err;
+}
+
+static void w2cbw_remove(struct serdev_device *serdev)
+{
+	struct w2cbw_data *data = serdev_device_get_drvdata(serdev);
+	int minor;
+
+	/* what is the right sequence to avoid problems? */
+	serdev_device_close(data->uart);
+
+	// should get minor from searching for data == w2cbw_by_minor[minor]
+	minor = 0;
+	tty_unregister_device(data->tty_drv, minor);
+
+	tty_unregister_driver(data->tty_drv);
+}
+
+// suspend/resume? handle by regulator
+
+static const struct of_device_id w2cbw_of_match[] = {
+	{ .compatible = "wi2wi,w2cbw003-bluetooth" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, w2cbw_of_match);
+
+static struct serdev_device_driver w2cbw_driver = {
+	.probe		= w2cbw_probe,
+	.remove		= w2cbw_remove,
+	.driver = {
+		.name	= "w2cbw003",
+		.owner	= THIS_MODULE,
+		.of_match_table = of_match_ptr(w2cbw_of_match)
+	},
+};
+
+module_serdev_device_driver(w2cbw_driver);
+
+MODULE_ALIAS("w2cbw003-bluetooth");
+
+MODULE_AUTHOR("H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("w2cbw003 power management driver");
+MODULE_LICENSE("GPL v2");
-- 
2.12.2