gnss: add driver for mediatek receivers

Add driver for serial-connected Mediatek-based GNSS receivers.

These devices typically boot transmitting vendor specific NMEA output
sequences. The serial port bit rate is read from the device tree
"current-speed".

Note that the driver uses the generic GNSS serial implementation and
therefore essentially only manages power abstracted into three power
states: ACTIVE, STANDBY, and OFF.

For mediatek receivers with a main supply and no enable-gpios, this simply
means that the main supply is disabled in STANDBY and OFF (the optional
backup supply is kept enabled while the driver is bound).

Note that the timepulse-support is left unimplemented.

Signed-off-by: Loys Ollivier <lollivier@baylibre.com>
[ johan: rename backup supply ]
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/gnss/Kconfig b/drivers/gnss/Kconfig
index 6abc885..6d8c802 100644 (file)
--- a/drivers/gnss/Kconfig
+++ b/drivers/gnss/Kconfig
@@ -15,6 +15,19 @@ if GNSS
 config GNSS_SERIAL
        tristate
 
+config GNSS_MTK_SERIAL
+       tristate "Mediatek GNSS receiver support"
+       depends on SERIAL_DEV_BUS
+       select GNSS_SERIAL
+       help
+         Say Y here if you have a Mediatek-based GNSS receiver which uses a
+         serial interface.
+
+         To compile this driver as a module, choose M here: the module will
+         be called gnss-mtk.
+
+         If unsure, say N.
+
 config GNSS_SIRF_SERIAL
        tristate "SiRFstar GNSS receiver support"
        depends on SERIAL_DEV_BUS

diff --git a/drivers/gnss/Makefile b/drivers/gnss/Makefile
index 5cf0ebe..451f114 100644 (file)
--- a/drivers/gnss/Makefile
+++ b/drivers/gnss/Makefile
@@ -9,6 +9,9 @@ gnss-y := core.o
 obj-$(CONFIG_GNSS_SERIAL)              += gnss-serial.o
 gnss-serial-y := serial.o
 
+obj-$(CONFIG_GNSS_MTK_SERIAL)          += gnss-mtk.o
+gnss-mtk-y := mtk.o
+
 obj-$(CONFIG_GNSS_SIRF_SERIAL)         += gnss-sirf.o
 gnss-sirf-y := sirf.o
 

diff --git a/drivers/gnss/mtk.c b/drivers/gnss/mtk.c
new file mode 100644 (file)
index 0000000..d1fc555
--- /dev/null
+++ b/drivers/gnss/mtk.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Mediatek GNSS receiver driver
+ *
+ * Copyright (C) 2018 Johan Hovold <johan@kernel.org>
+ */
+
+#include <linux/errno.h>
+#include <linux/gnss.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regulator/consumer.h>
+#include <linux/serdev.h>
+
+#include "serial.h"
+
+struct mtk_data {
+       struct regulator *vbackup;
+       struct regulator *vcc;
+};
+
+static int mtk_set_active(struct gnss_serial *gserial)
+{
+       struct mtk_data *data = gnss_serial_get_drvdata(gserial);
+       int ret;
+
+       ret = regulator_enable(data->vcc);
+       if (ret)
+               return ret;
+
+       return 0;
+}
+
+static int mtk_set_standby(struct gnss_serial *gserial)
+{
+       struct mtk_data *data = gnss_serial_get_drvdata(gserial);
+       int ret;
+
+       ret = regulator_disable(data->vcc);
+       if (ret)
+               return ret;
+
+       return 0;
+}
+
+static int mtk_set_power(struct gnss_serial *gserial,
+                        enum gnss_serial_pm_state state)
+{
+       switch (state) {
+       case GNSS_SERIAL_ACTIVE:
+               return mtk_set_active(gserial);
+       case GNSS_SERIAL_OFF:
+       case GNSS_SERIAL_STANDBY:
+               return mtk_set_standby(gserial);
+       }
+
+       return -EINVAL;
+}
+
+static const struct gnss_serial_ops mtk_gserial_ops = {
+       .set_power = mtk_set_power,
+};
+
+static int mtk_probe(struct serdev_device *serdev)
+{
+       struct gnss_serial *gserial;
+       struct mtk_data *data;
+       int ret;
+
+       gserial = gnss_serial_allocate(serdev, sizeof(*data));
+       if (IS_ERR(gserial)) {
+               ret = PTR_ERR(gserial);
+               return ret;
+       }
+
+       gserial->ops = &mtk_gserial_ops;
+
+       gserial->gdev->type = GNSS_TYPE_MTK;
+
+       data = gnss_serial_get_drvdata(gserial);
+
+       data->vcc = devm_regulator_get(&serdev->dev, "vcc");
+       if (IS_ERR(data->vcc)) {
+               ret = PTR_ERR(data->vcc);
+               goto err_free_gserial;
+       }
+
+       data->vbackup = devm_regulator_get_optional(&serdev->dev, "vbackup");
+       if (IS_ERR(data->vbackup)) {
+               ret = PTR_ERR(data->vbackup);
+               if (ret == -ENODEV)
+                       data->vbackup = NULL;
+               else
+                       goto err_free_gserial;
+       }
+
+       if (data->vbackup) {
+               ret = regulator_enable(data->vbackup);
+               if (ret)
+                       goto err_free_gserial;
+       }
+
+       ret = gnss_serial_register(gserial);
+       if (ret)
+               goto err_disable_vbackup;
+
+       return 0;
+
+err_disable_vbackup:
+       if (data->vbackup)
+               regulator_disable(data->vbackup);
+err_free_gserial:
+       gnss_serial_free(gserial);
+
+       return ret;
+}
+
+static void mtk_remove(struct serdev_device *serdev)
+{
+       struct gnss_serial *gserial = serdev_device_get_drvdata(serdev);
+       struct mtk_data *data = gnss_serial_get_drvdata(gserial);
+
+       gnss_serial_deregister(gserial);
+       if (data->vbackup)
+               regulator_disable(data->vbackup);
+       gnss_serial_free(gserial);
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id mtk_of_match[] = {
+       { .compatible = "globaltop,pa6h" },
+       {},
+};
+MODULE_DEVICE_TABLE(of, mtk_of_match);
+#endif
+
+static struct serdev_device_driver mtk_driver = {
+       .driver = {
+               .name           = "gnss-mtk",
+               .of_match_table = of_match_ptr(mtk_of_match),
+               .pm             = &gnss_serial_pm_ops,
+       },
+       .probe  = mtk_probe,
+       .remove = mtk_remove,
+};
+module_serdev_device_driver(mtk_driver);
+
+MODULE_AUTHOR("Loys Ollivier <lollivier@baylibre.com>");
+MODULE_DESCRIPTION("Mediatek GNSS receiver driver");
+MODULE_LICENSE("GPL v2");