Commit d4584bbf authored by Loys Ollivier's avatar Loys Ollivier Committed by Johan Hovold
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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: default avatarLoys Ollivier <lollivier@baylibre.com>
[ johan: rename backup supply ]
Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
parent 625239d4

drivers/gnss/Kconfig

+13 −0
Original line number Diff line number Diff line
@@ -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

drivers/gnss/Makefile

+3 −0
Original line number Diff line number Diff line
@@ -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

drivers/gnss/mtk.c

0 → 100644
+152 −0
Original line number Diff line number Diff line 
// 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");

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