ice: use GNSS subsystem instead of TTY

Previously support for GNSS was implemented as a TTY driver, it allowed
to access GNSS receiver on /dev/ttyGNSS_<bus><func>.

Use generic GNSS subsystem API instead of implementing own TTY driver.
The receiver is accessible on /dev/gnss<id>. In case of multiple receivers
in the OS, correct device can be found by enumerating either:
- /sys/class/net/<eth port>/device/gnss/
- /sys/class/gnss/gnss<id>/device/

Using GNSS subsystem is superior to implementing own TTY driver, as the
GNSS subsystem was designed solely for this purpose. It also implements
TTY driver but in a common and defined way.

From user perspective, there is no difference in communicating with a
device, except new path to the device shall be used. The device will
provide same information to the userspace as the old one, and can be used
in the same way, i.e.:
old # gpsmon /dev/ttyGNSS_2100_0
new # gpsmon /dev/gnss0
There is no other impact on userspace tools.

User expecting onboard GNSS receiver support is required to enable
CONFIG_GNSS=y/m in kernel config.

Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Signed-off-by: Karol Kolacinski <karol.kolacinski@intel.com>
Signed-off-by: Michal Michalik <michal.michalik@intel.com>
Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 140 insertions, 237 deletions

diff --git a/drivers/net/ethernet/intel/ice/ice_gnss.c b/drivers/net/ethernet/intel/ice/ice_gnss.c
index 43e199b5b513..8dec748bb53a 100644
--- a/drivers/net/ethernet/intel/ice/ice_gnss.c
+++ b/drivers/net/ethernet/intel/ice/ice_gnss.c
@@ -3,15 +3,18 @@
 
 #include "ice.h"
 #include "ice_lib.h"
-#include <linux/tty_driver.h>
 
 /**
- * ice_gnss_do_write - Write data to internal GNSS
+ * ice_gnss_do_write - Write data to internal GNSS receiver
  * @pf: board private structure
  * @buf: command buffer
  * @size: command buffer size
  *
  * Write UBX command data to the GNSS receiver
+ *
+ * Return:
+ * * number of bytes written - success
+ * * negative - error code
  */
 static unsigned int
 ice_gnss_do_write(struct ice_pf *pf, unsigned char *buf, unsigned int size)
@@ -82,6 +85,12 @@ static void ice_gnss_write_pending(struct kthread_work *work)
 						write_work);
 	struct ice_pf *pf = gnss->back;
 
+	if (!pf)
+		return;
+
+	if (!test_bit(ICE_FLAG_GNSS, pf->flags))
+		return;
+
 	if (!list_empty(&gnss->queue)) {
 		struct gnss_write_buf *write_buf = NULL;
 		unsigned int bytes;
@@ -102,16 +111,14 @@ static void ice_gnss_write_pending(struct kthread_work *work)
  * ice_gnss_read - Read data from internal GNSS module
  * @work: GNSS read work structure
  *
- * Read the data from internal GNSS receiver, number of bytes read will be
- * returned in *read_data parameter.
+ * Read the data from internal GNSS receiver, write it to gnss_dev.
  */
 static void ice_gnss_read(struct kthread_work *work)
 {
 	struct gnss_serial *gnss = container_of(work, struct gnss_serial,
 						read_work.work);
+	unsigned int i, bytes_read, data_len, count;
 	struct ice_aqc_link_topo_addr link_topo;
-	unsigned int i, bytes_read, data_len;
-	struct tty_port *port;
 	struct ice_pf *pf;
 	struct ice_hw *hw;
 	__be16 data_len_b;
@@ -120,14 +127,15 @@ static void ice_gnss_read(struct kthread_work *work)
 	int err = 0;
 
 	pf = gnss->back;
-	if (!pf || !gnss->tty || !gnss->tty->port) {
+	if (!pf) {
 		err = -EFAULT;
 		goto exit;
 	}
 
-	hw = &pf->hw;
-	port = gnss->tty->port;
+	if (!test_bit(ICE_FLAG_GNSS, pf->flags))
+		return;
 
+	hw = &pf->hw;
 	buf = (char *)get_zeroed_page(GFP_KERNEL);
 	if (!buf) {
 		err = -ENOMEM;
@@ -159,7 +167,6 @@ static void ice_gnss_read(struct kthread_work *work)
 	}
 
 	data_len = min_t(typeof(data_len), data_len, PAGE_SIZE);
-	data_len = tty_buffer_request_room(port, data_len);
 	if (!data_len) {
 		err = -ENOMEM;
 		goto exit_buf;
@@ -179,12 +186,11 @@ static void ice_gnss_read(struct kthread_work *work)
 			goto exit_buf;
 	}
 
-	/* Send the data to the tty layer for users to read. This doesn't
-	 * actually push the data through unless tty->low_latency is set.
-	 */
-	tty_insert_flip_string(port, buf, i);
-	tty_flip_buffer_push(port);
-
+	count = gnss_insert_raw(pf->gnss_dev, buf, i);
+	if (count != i)
+		dev_warn(ice_pf_to_dev(pf),
+			 "gnss_insert_raw ret=%d size=%d\n",
+			 count, i);
 exit_buf:
 	free_page((unsigned long)buf);
 	kthread_queue_delayed_work(gnss->kworker, &gnss->read_work,
@@ -195,11 +201,16 @@ exit:
 }
 
 /**
- * ice_gnss_struct_init - Initialize GNSS structure for the TTY
+ * ice_gnss_struct_init - Initialize GNSS receiver
  * @pf: Board private structure
- * @index: TTY device index
+ *
+ * Initialize GNSS structures and workers.
+ *
+ * Return:
+ * * pointer to initialized gnss_serial struct - success
+ * * NULL - error
  */
-static struct gnss_serial *ice_gnss_struct_init(struct ice_pf *pf, int index)
+static struct gnss_serial *ice_gnss_struct_init(struct ice_pf *pf)
 {
 	struct device *dev = ice_pf_to_dev(pf);
 	struct kthread_worker *kworker;
@@ -209,17 +220,12 @@ static struct gnss_serial *ice_gnss_struct_init(struct ice_pf *pf, int index)
 	if (!gnss)
 		return NULL;
 
-	mutex_init(&gnss->gnss_mutex);
-	gnss->open_count = 0;
 	gnss->back = pf;
-	pf->gnss_serial[index] = gnss;
+	pf->gnss_serial = gnss;
 
 	kthread_init_delayed_work(&gnss->read_work, ice_gnss_read);
 	INIT_LIST_HEAD(&gnss->queue);
 	kthread_init_work(&gnss->write_work, ice_gnss_write_pending);
-	/* Allocate a kworker for handling work required for the GNSS TTY
-	 * writes.
-	 */
 	kworker = kthread_create_worker(0, "ice-gnss-%s", dev_name(dev));
 	if (IS_ERR(kworker)) {
 		kfree(gnss);
@@ -232,140 +238,100 @@ static struct gnss_serial *ice_gnss_struct_init(struct ice_pf *pf, int index)
 }
 
 /**
- * ice_gnss_tty_open - Initialize GNSS structures on TTY device open
- * @tty: pointer to the tty_struct
- * @filp: pointer to the file
+ * ice_gnss_open - Open GNSS device
+ * @gdev: pointer to the gnss device struct
+ *
+ * Open GNSS device and start filling the read buffer for consumer.
  *
- * This routine is mandatory. If this routine is not filled in, the attempted
- * open will fail with ENODEV.
+ * Return:
+ * * 0 - success
+ * * negative - error code
  */
-static int ice_gnss_tty_open(struct tty_struct *tty, struct file *filp)
+static int ice_gnss_open(struct gnss_device *gdev)
 {
+	struct ice_pf *pf = gnss_get_drvdata(gdev);
 	struct gnss_serial *gnss;
-	struct ice_pf *pf;
 
-	pf = (struct ice_pf *)tty->driver->driver_state;
 	if (!pf)
 		return -EFAULT;
 
-	/* Clear the pointer in case something fails */
-	tty->driver_data = NULL;
-
-	/* Get the serial object associated with this tty pointer */
-	gnss = pf->gnss_serial[tty->index];
-	if (!gnss) {
-		/* Initialize GNSS struct on the first device open */
-		gnss = ice_gnss_struct_init(pf, tty->index);
-		if (!gnss)
-			return -ENOMEM;
-	}
+	if (!test_bit(ICE_FLAG_GNSS, pf->flags))
+		return -EFAULT;
 
-	mutex_lock(&gnss->gnss_mutex);
+	gnss = pf->gnss_serial;
+	if (!gnss)
+		return -ENODEV;
 
-	/* Save our structure within the tty structure */
-	tty->driver_data = gnss;
-	gnss->tty = tty;
-	gnss->open_count++;
 	kthread_queue_delayed_work(gnss->kworker, &gnss->read_work, 0);
 
-	mutex_unlock(&gnss->gnss_mutex);
-
 	return 0;
 }
 
 /**
- * ice_gnss_tty_close - Cleanup GNSS structures on tty device close
- * @tty: pointer to the tty_struct
- * @filp: pointer to the file
+ * ice_gnss_close - Close GNSS device
+ * @gdev: pointer to the gnss device struct
+ *
+ * Close GNSS device, cancel worker, stop filling the read buffer.
  */
-static void ice_gnss_tty_close(struct tty_struct *tty, struct file *filp)
+static void ice_gnss_close(struct gnss_device *gdev)
 {
-	struct gnss_serial *gnss = tty->driver_data;
-	struct ice_pf *pf;
-
-	if (!gnss)
-		return;
+	struct ice_pf *pf = gnss_get_drvdata(gdev);
+	struct gnss_serial *gnss;
 
-	pf = (struct ice_pf *)tty->driver->driver_state;
 	if (!pf)
 		return;
 
-	mutex_lock(&gnss->gnss_mutex);
-
-	if (!gnss->open_count) {
-		/* Port was never opened */
-		dev_err(ice_pf_to_dev(pf), "GNSS port not opened\n");
-		goto exit;
-	}
+	gnss = pf->gnss_serial;
+	if (!gnss)
+		return;
 
-	gnss->open_count--;
-	if (gnss->open_count <= 0) {
-		/* Port is in shutdown state */
-		kthread_cancel_delayed_work_sync(&gnss->read_work);
-	}
-exit:
-	mutex_unlock(&gnss->gnss_mutex);
+	kthread_cancel_work_sync(&gnss->write_work);
+	kthread_cancel_delayed_work_sync(&gnss->read_work);
 }
 
 /**
- * ice_gnss_tty_write - Write GNSS data
- * @tty: pointer to the tty_struct
+ * ice_gnss_write - Write to GNSS device
+ * @gdev: pointer to the gnss device struct
  * @buf: pointer to the user data
- * @count: the number of characters queued to be sent to the HW
+ * @count: size of the buffer to be sent to the GNSS device
  *
- * The write function call is called by the user when there is data to be sent
- * to the hardware. First the tty core receives the call, and then it passes the
- * data on to the tty driver's write function. The tty core also tells the tty
- * driver the size of the data being sent.
- * If any errors happen during the write call, a negative error value should be
- * returned instead of the number of characters queued to be written.
+ * Return:
+ * * number of written bytes - success
+ * * negative - error code
  */
 static int
-ice_gnss_tty_write(struct tty_struct *tty, const unsigned char *buf, int count)
+ice_gnss_write(struct gnss_device *gdev, const unsigned char *buf,
+	       size_t count)
 {
+	struct ice_pf *pf = gnss_get_drvdata(gdev);
 	struct gnss_write_buf *write_buf;
 	struct gnss_serial *gnss;
 	unsigned char *cmd_buf;
-	struct ice_pf *pf;
 	int err = count;
 
 	/* We cannot write a single byte using our I2C implementation. */
 	if (count <= 1 || count > ICE_GNSS_TTY_WRITE_BUF)
 		return -EINVAL;
 
-	gnss = tty->driver_data;
-	if (!gnss)
-		return -EFAULT;
-
-	pf = (struct ice_pf *)tty->driver->driver_state;
 	if (!pf)
 		return -EFAULT;
 
-	/* Only allow to write on TTY 0 */
-	if (gnss != pf->gnss_serial[0])
-		return -EIO;
-
-	mutex_lock(&gnss->gnss_mutex);
+	if (!test_bit(ICE_FLAG_GNSS, pf->flags))
+		return -EFAULT;
 
-	if (!gnss->open_count) {
-		err = -EINVAL;
-		goto exit;
-	}
+	gnss = pf->gnss_serial;
+	if (!gnss)
+		return -ENODEV;
 
 	cmd_buf = kcalloc(count, sizeof(*buf), GFP_KERNEL);
-	if (!cmd_buf) {
-		err = -ENOMEM;
-		goto exit;
-	}
+	if (!cmd_buf)
+		return -ENOMEM;
 
 	memcpy(cmd_buf, buf, count);
-
-	/* Send the data out to a hardware port */
 	write_buf = kzalloc(sizeof(*write_buf), GFP_KERNEL);
 	if (!write_buf) {
 		kfree(cmd_buf);
-		err = -ENOMEM;
-		goto exit;
+		return -ENOMEM;
 	}
 
 	write_buf->buf = cmd_buf;
@@ -373,141 +339,89 @@ ice_gnss_tty_write(struct tty_struct *tty, const unsigned char *buf, int count)
 	INIT_LIST_HEAD(&write_buf->queue);
 	list_add_tail(&write_buf->queue, &gnss->queue);
 	kthread_queue_work(gnss->kworker, &gnss->write_work);
-exit:
-	mutex_unlock(&gnss->gnss_mutex);
+
 	return err;
 }
 
+static const struct gnss_operations ice_gnss_ops = {
+	.open = ice_gnss_open,
+	.close = ice_gnss_close,
+	.write_raw = ice_gnss_write,
+};
+
 /**
- * ice_gnss_tty_write_room - Returns the numbers of characters to be written.
- * @tty: pointer to the tty_struct
+ * ice_gnss_register - Register GNSS receiver
+ * @pf: Board private structure
+ *
+ * Allocate and register GNSS receiver in the Linux GNSS subsystem.
  *
- * This routine returns the numbers of characters the tty driver will accept
- * for queuing to be written or 0 if either the TTY is not open or user
- * tries to write to the TTY other than the first.
+ * Return:
+ * * 0 - success
+ * * negative - error code
  */
-static unsigned int ice_gnss_tty_write_room(struct tty_struct *tty)
+static int ice_gnss_register(struct ice_pf *pf)
 {
-	struct gnss_serial *gnss = tty->driver_data;
-
-	/* Only allow to write on TTY 0 */
-	if (!gnss || gnss != gnss->back->gnss_serial[0])
-		return 0;
-
-	mutex_lock(&gnss->gnss_mutex);
+	struct gnss_device *gdev;
+	int ret;
+
+	gdev = gnss_allocate_device(ice_pf_to_dev(pf));
+	if (!gdev) {
+		dev_err(ice_pf_to_dev(pf),
+			"gnss_allocate_device returns NULL\n");
+		return -ENOMEM;
+	}
 
-	if (!gnss->open_count) {
-		mutex_unlock(&gnss->gnss_mutex);
-		return 0;
+	gdev->ops = &ice_gnss_ops;
+	gdev->type = GNSS_TYPE_UBX;
+	gnss_set_drvdata(gdev, pf);
+	ret = gnss_register_device(gdev);
+	if (ret) {
+		dev_err(ice_pf_to_dev(pf), "gnss_register_device err=%d\n",
+			ret);
+		gnss_put_device(gdev);
+	} else {
+		pf->gnss_dev = gdev;
 	}
 
-	mutex_unlock(&gnss->gnss_mutex);
-	return ICE_GNSS_TTY_WRITE_BUF;
+	return ret;
 }
 
-static const struct tty_operations tty_gps_ops = {
-	.open =		ice_gnss_tty_open,
-	.close =	ice_gnss_tty_close,
-	.write =	ice_gnss_tty_write,
-	.write_room =	ice_gnss_tty_write_room,
-};
-
 /**
- * ice_gnss_create_tty_driver - Create a TTY driver for GNSS
+ * ice_gnss_deregister - Deregister GNSS receiver
  * @pf: Board private structure
+ *
+ * Deregister GNSS receiver from the Linux GNSS subsystem,
+ * release its resources.
  */
-static struct tty_driver *ice_gnss_create_tty_driver(struct ice_pf *pf)
+static void ice_gnss_deregister(struct ice_pf *pf)
 {
-	struct device *dev = ice_pf_to_dev(pf);
-	const int ICE_TTYDRV_NAME_MAX = 14;
-	struct tty_driver *tty_driver;
-	char *ttydrv_name;
-	unsigned int i;
-	int err;
-
-	tty_driver = tty_alloc_driver(ICE_GNSS_TTY_MINOR_DEVICES,
-				      TTY_DRIVER_REAL_RAW);
-	if (IS_ERR(tty_driver)) {
-		dev_err(dev, "Failed to allocate memory for GNSS TTY\n");
-		return NULL;
-	}
-
-	ttydrv_name = kzalloc(ICE_TTYDRV_NAME_MAX, GFP_KERNEL);
-	if (!ttydrv_name) {
-		tty_driver_kref_put(tty_driver);
-		return NULL;
+	if (pf->gnss_dev) {
+		gnss_deregister_device(pf->gnss_dev);
+		gnss_put_device(pf->gnss_dev);
+		pf->gnss_dev = NULL;
 	}
-
-	snprintf(ttydrv_name, ICE_TTYDRV_NAME_MAX, "ttyGNSS_%02x%02x_",
-		 (u8)pf->pdev->bus->number, (u8)PCI_SLOT(pf->pdev->devfn));
-
-	/* Initialize the tty driver*/
-	tty_driver->owner = THIS_MODULE;
-	tty_driver->driver_name = dev_driver_string(dev);
-	tty_driver->name = (const char *)ttydrv_name;
-	tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
-	tty_driver->subtype = SERIAL_TYPE_NORMAL;
-	tty_driver->init_termios = tty_std_termios;
-	tty_driver->init_termios.c_iflag &= ~INLCR;
-	tty_driver->init_termios.c_iflag |= IGNCR;
-	tty_driver->init_termios.c_oflag &= ~OPOST;
-	tty_driver->init_termios.c_lflag &= ~ICANON;
-	tty_driver->init_termios.c_cflag &= ~(CSIZE | CBAUD | CBAUDEX);
-	/* baud rate 9600 */
-	tty_termios_encode_baud_rate(&tty_driver->init_termios, 9600, 9600);
-	tty_driver->driver_state = pf;
-	tty_set_operations(tty_driver, &tty_gps_ops);
-
-	for (i = 0; i < ICE_GNSS_TTY_MINOR_DEVICES; i++) {
-		pf->gnss_tty_port[i] = kzalloc(sizeof(*pf->gnss_tty_port[i]),
-					       GFP_KERNEL);
-		if (!pf->gnss_tty_port[i])
-			goto err_out;
-
-		pf->gnss_serial[i] = NULL;
-
-		tty_port_init(pf->gnss_tty_port[i]);
-		tty_port_link_device(pf->gnss_tty_port[i], tty_driver, i);
-	}
-
-	err = tty_register_driver(tty_driver);
-	if (err) {
-		dev_err(dev, "Failed to register TTY driver err=%d\n", err);
-		goto err_out;
-	}
-
-	for (i = 0; i < ICE_GNSS_TTY_MINOR_DEVICES; i++)
-		dev_info(dev, "%s%d registered\n", ttydrv_name, i);
-
-	return tty_driver;
-
-err_out:
-	while (i--) {
-		tty_port_destroy(pf->gnss_tty_port[i]);
-		kfree(pf->gnss_tty_port[i]);
-	}
-	kfree(ttydrv_name);
-	tty_driver_kref_put(pf->ice_gnss_tty_driver);
-
-	return NULL;
 }
 
 /**
- * ice_gnss_init - Initialize GNSS TTY support
+ * ice_gnss_init - Initialize GNSS support
  * @pf: Board private structure
  */
 void ice_gnss_init(struct ice_pf *pf)
 {
-	struct tty_driver *tty_driver;
+	int ret;
 
-	tty_driver = ice_gnss_create_tty_driver(pf);
-	if (!tty_driver)
+	pf->gnss_serial = ice_gnss_struct_init(pf);
+	if (!pf->gnss_serial)
 		return;
 
-	pf->ice_gnss_tty_driver = tty_driver;
-
-	set_bit(ICE_FLAG_GNSS, pf->flags);
-	dev_info(ice_pf_to_dev(pf), "GNSS TTY init successful\n");
+	ret = ice_gnss_register(pf);
+	if (!ret) {
+		set_bit(ICE_FLAG_GNSS, pf->flags);
+		dev_info(ice_pf_to_dev(pf), "GNSS init successful\n");
+	} else {
+		ice_gnss_exit(pf);
+		dev_err(ice_pf_to_dev(pf), "GNSS init failure\n");
+	}
 }
 
 /**
@@ -516,31 +430,20 @@ void ice_gnss_init(struct ice_pf *pf)
  */
 void ice_gnss_exit(struct ice_pf *pf)
 {
-	unsigned int i;
+	ice_gnss_deregister(pf);
+	clear_bit(ICE_FLAG_GNSS, pf->flags);
 
-	if (!test_bit(ICE_FLAG_GNSS, pf->flags) || !pf->ice_gnss_tty_driver)
-		return;
-
-	for (i = 0; i < ICE_GNSS_TTY_MINOR_DEVICES; i++) {
-		if (pf->gnss_tty_port[i]) {
-			tty_port_destroy(pf->gnss_tty_port[i]);
-			kfree(pf->gnss_tty_port[i]);
-		}
+	if (pf->gnss_serial) {
+		struct gnss_serial *gnss = pf->gnss_serial;
 
-		if (pf->gnss_serial[i]) {
-			struct gnss_serial *gnss = pf->gnss_serial[i];
+		kthread_cancel_work_sync(&gnss->write_work);
+		kthread_cancel_delayed_work_sync(&gnss->read_work);
+		kthread_destroy_worker(gnss->kworker);
+		gnss->kworker = NULL;
 
-			kthread_cancel_work_sync(&gnss->write_work);
-			kthread_cancel_delayed_work_sync(&gnss->read_work);
-			kfree(gnss);
-			pf->gnss_serial[i] = NULL;
-		}
+		kfree(gnss);
+		pf->gnss_serial = NULL;
 	}
-
-	tty_unregister_driver(pf->ice_gnss_tty_driver);
-	kfree(pf->ice_gnss_tty_driver->name);
-	tty_driver_kref_put(pf->ice_gnss_tty_driver);
-	pf->ice_gnss_tty_driver = NULL;
 }
 
 /**