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Subject[PATCH v2 4/4] gnss: add driver for mediatek receivers
Date
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>
---

v2:
Renamed from gtop/Globaltop to mtk/Mediatek.
Added "mediatek,mt3339" compatible.

drivers/gnss/Kconfig | 13 +++++
drivers/gnss/Makefile | 3 +
drivers/gnss/core.c | 1 +
drivers/gnss/mtk.c | 153 ++++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 170 insertions(+)
create mode 100644 drivers/gnss/mtk.c

diff --git a/drivers/gnss/Kconfig b/drivers/gnss/Kconfig
index 6abc88514512..51e6282d092a 100644
--- a/drivers/gnss/Kconfig
+++ b/drivers/gnss/Kconfig
@@ -40,4 +40,17 @@ config GNSS_UBX_SERIAL

If unsure, say N.

+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.
+
endif # GNSS
diff --git a/drivers/gnss/Makefile b/drivers/gnss/Makefile
index 5cf0ebe0330a..43318375aa51 100644
--- a/drivers/gnss/Makefile
+++ b/drivers/gnss/Makefile
@@ -14,3 +14,6 @@ gnss-sirf-y := sirf.o

obj-$(CONFIG_GNSS_UBX_SERIAL) += gnss-ubx.o
gnss-ubx-y := ubx.o
+
+obj-$(CONFIG_GNSS_MTK_SERIAL) += gnss-mtk.o
+gnss-mtk-y := mtk.o
diff --git a/drivers/gnss/core.c b/drivers/gnss/core.c
index 4291a0dd22aa..320cfca80d5f 100644
--- a/drivers/gnss/core.c
+++ b/drivers/gnss/core.c
@@ -334,6 +334,7 @@ static const char * const gnss_type_names[GNSS_TYPE_COUNT] = {
[GNSS_TYPE_NMEA] = "NMEA",
[GNSS_TYPE_SIRF] = "SiRF",
[GNSS_TYPE_UBX] = "UBX",
+ [GNSS_TYPE_MTK] = "MTK",
};

static const char *gnss_type_name(struct gnss_device *gdev)
diff --git a/drivers/gnss/mtk.c b/drivers/gnss/mtk.c
new file mode 100644
index 000000000000..c91d4d251098
--- /dev/null
+++ b/drivers/gnss/mtk.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Mediatek GNSS receiver driver
+ *
+ * Copyright (C) 2018 Loys Ollivier <lollivier@baylibre.com>
+ */
+
+#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 *v_bckp;
+ 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->v_bckp = devm_regulator_get_optional(&serdev->dev, "v-bckp");
+ if (IS_ERR(data->v_bckp)) {
+ ret = PTR_ERR(data->v_bckp);
+ if (ret == -ENODEV)
+ data->v_bckp = NULL;
+ else
+ goto err_free_gserial;
+ }
+
+ if (data->v_bckp) {
+ ret = regulator_enable(data->v_bckp);
+ if (ret)
+ goto err_free_gserial;
+ }
+
+ ret = gnss_serial_register(gserial);
+ if (ret)
+ goto err_disable_v_bckp;
+
+ return 0;
+
+err_disable_v_bckp:
+ if (data->v_bckp)
+ regulator_disable(data->v_bckp);
+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->v_bckp)
+ regulator_disable(data->v_bckp);
+ gnss_serial_free(gserial);
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id mtk_of_match[] = {
+ { .compatible = "globaltop,pa6h" },
+ { .compatible = "mediatek,mt3339" },
+ {},
+};
+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");
--
2.7.4
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