Message-ID: <20210128183459.GA14341@duo.ucw.cz>
Date:   Thu, 28 Jan 2021 19:34:59 +0100
From:   Pavel Machek <pavel@....cz>
To:     johan@...nel.org, kernel list <linux-kernel@...r.kernel.org>,
        phone-devel@...r.kernel.org, tony@...mide.com,
        Greg KH <greg@...ah.com>
Subject: Re: [PATCH] gnss: motmdm: Add support for Motorola Mapphone MDM6600
 modem

Hi!

> Motorola is using a custom TS 27.010 based serial port line discipline
> for various devices on the modem. These devices can be accessed on
> dedicated channels using Linux kernel serdev-ngsm driver.
> 
> For the GNSS on these devices, we need to kick the GNSS device at a
> desired rate. Otherwise the GNSS device stops sending data after a
> few minutes. The rate we poll data defaults to 1000 ms, and can be
> specified with a module option rate_ms between 1 to 16 seconds.
> 
> [Tony Lindgren did most of the work here, I just converted it to be
> normal serdev.]
> 
> Signed-off-by: Pavel Machek <pavel@....cz>

20 days... ping...?
								Pavel

> diff --git a/drivers/gnss/Kconfig b/drivers/gnss/Kconfig
> index bd12e3d57baa..a7c449d8428c 100644
> --- a/drivers/gnss/Kconfig
> +++ b/drivers/gnss/Kconfig
> @@ -13,6 +13,14 @@ menuconfig GNSS
>  
>  if GNSS
>  
> +config GNSS_MOTMDM
> +	tristate "Motorola Modem TS 27.010 serdev GNSS receiver support"
> +	depends on SERIAL_DEV_N_GSM
> +	help
> +	  Say Y here if you have a Motorola modem using TS 27.010 line
> +	  discipline for GNSS such as a Motorola Mapphone series device
> +	  like Droid 4.
> +
>  config GNSS_SERIAL
>  	tristate
>  
> diff --git a/drivers/gnss/Makefile b/drivers/gnss/Makefile
> index 451f11401ecc..f5afc2c22a3b 100644
> --- a/drivers/gnss/Makefile
> +++ b/drivers/gnss/Makefile
> @@ -6,6 +6,9 @@
>  obj-$(CONFIG_GNSS)			+= gnss.o
>  gnss-y := core.o
>  
> +obj-$(CONFIG_GNSS_MOTMDM)		+= gnss-motmdm.o
> +gnss-motmdm-y := motmdm.o
> +
>  obj-$(CONFIG_GNSS_SERIAL)		+= gnss-serial.o
>  gnss-serial-y := serial.o
>  
> diff --git a/drivers/gnss/motmdm.c b/drivers/gnss/motmdm.c
> new file mode 100644
> index 000000000000..bfd50e130631
> --- /dev/null
> +++ b/drivers/gnss/motmdm.c
> @@ -0,0 +1,409 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Motorola Modem TS 27.010 serdev GNSS driver
> + *
> + * Copyright (C) 2018 - 2020 Tony Lindgren <tony@...mide.com>
> + * Copyright (C) 2020 - 2021 Pavel Machek <pavel@....cz>
> + *
> + * Based on drivers/gnss/sirf.c driver example:
> + * Copyright (C) 2018 Johan Hovold <johan@...nel.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/platform_device.h>
> +#include <linux/serdev-gsm.h>
> +#include <linux/slab.h>
> +
> +#define MOTMDM_GNSS_TIMEOUT	1000
> +#define MOTMDM_GNSS_RATE	1000
> +
> +/*
> + * Motorola MDM GNSS device communicates over a dedicated TS 27.010 channel
> + * using custom data packets. The packets look like AT commands embedded into
> + * a Motorola invented packet using format like "U1234AT+MPDSTART=0,1,100,0".
> + * But it's not an AT compatible serial interface, it's a packet interface
> + * using AT like commands.
> + */
> +#define MOTMDM_GNSS_HEADER_LEN	5				/* U1234 */
> +#define MOTMDM_GNSS_RESP_LEN	(MOTMDM_GNSS_HEADER_LEN + 4)	/* U1234+MPD */
> +#define MOTMDM_GNSS_DATA_LEN	(MOTMDM_GNSS_RESP_LEN + 1)	/* U1234~+MPD */
> +#define MOTMDM_GNSS_STATUS_LEN	(MOTMDM_GNSS_DATA_LEN + 7)	/* STATUS= */
> +#define MOTMDM_GNSS_NMEA_LEN	(MOTMDM_GNSS_DATA_LEN + 8)	/* NMEA=NN, */
> +
> +enum motmdm_gnss_status {
> +	MOTMDM_GNSS_UNKNOWN,
> +	MOTMDM_GNSS_INITIALIZED,
> +	MOTMDM_GNSS_DATA_OR_TIMEOUT,
> +	MOTMDM_GNSS_STARTED,
> +	MOTMDM_GNSS_STOPPED,
> +};
> +
> +struct motmdm_gnss_data {
> +	struct gnss_device *gdev;
> +	struct device *modem;
> +	struct serdev_device *serdev;
> +	struct delayed_work restart_work;
> +	struct mutex mutex;	/* For modem commands */
> +	ktime_t last_update;
> +	int status;
> +	unsigned char *buf;
> +	size_t len;
> +	wait_queue_head_t read_queue;
> +	unsigned int parsed:1;
> +};
> +
> +static unsigned int rate_ms = MOTMDM_GNSS_RATE;
> +module_param(rate_ms, uint, 0644);
> +MODULE_PARM_DESC(rate_ms, "GNSS refresh rate between 1000 and 16000 ms (default 1000 ms)");
> +
> +/*
> + * Note that multiple commands can be sent in series with responses coming
> + * out-of-order. For GNSS, we don't need to care about the out-of-order
> + * responses, and can assume we have at most one command active at a time.
> + * For the commands, can use just a jiffies base packet ID and let the modem
> + * sort out the ID conflicts with the modem's unsolicited message ID
> + * numbering.
> + */
> +int motmdm_gnss_send_command(struct motmdm_gnss_data *ddata,
> +			     const u8 *buf, int len)
> +{
> +	struct gnss_device *gdev = ddata->gdev;
> +	const int timeout_ms = 1000;
> +	unsigned char cmd[128];
> +	int ret, cmdlen;
> +
> +	cmdlen = len + MOTMDM_GNSS_HEADER_LEN + 1;
> +	if (cmdlen > 128)
> +		return -EINVAL;
> +
> +	mutex_lock(&ddata->mutex);
> +	memset(ddata->buf, 0, ddata->len);
> +	ddata->parsed = false;
> +	snprintf(cmd, cmdlen, "U%04li%s", jiffies % 10000, buf);
> +
> +	ret = serdev_device_write(ddata->serdev, cmd, cmdlen, MAX_SCHEDULE_TIMEOUT);
> +	if (ret < 0)
> +		goto out_unlock;
> +
> +	serdev_device_wait_until_sent(ddata->serdev, 0);
> +
> +	ret = wait_event_timeout(ddata->read_queue, ddata->parsed,
> +				 msecs_to_jiffies(timeout_ms));
> +	if (ret == 0) {
> +		ret = -ETIMEDOUT;
> +		goto out_unlock;
> +	} else if (ret < 0) {
> +		goto out_unlock;
> +	}
> +
> +	if (!strstr(ddata->buf, ":OK")) {
> +		dev_err(&gdev->dev, "command %s error %s\n",
> +			cmd, ddata->buf);
> +		ret = -EPIPE;
> +	}
> +
> +	ret = len;
> +
> +out_unlock:
> +	mutex_unlock(&ddata->mutex);
> +
> +	return ret;
> +}
> +
> +/*
> + * Android uses AT+MPDSTART=0,1,100,0 which starts GNSS for a while,
> + * and then GNSS needs to be kicked with an AT command based on a
> + * status message.
> + */
> +static void motmdm_gnss_restart(struct work_struct *work)
> +{
> +	struct motmdm_gnss_data *ddata =
> +		container_of(work, struct motmdm_gnss_data,
> +			     restart_work.work);
> +	struct gnss_device *gdev = ddata->gdev;
> +	const unsigned char *cmd = "AT+MPDSTART=0,1,100,0";
> +	int error;
> +
> +	ddata->last_update = ktime_get();
> +
> +	error = motmdm_gnss_send_command(ddata, cmd, strlen(cmd));
> +	if (error < 0) {
> +		/* Timeouts can happen, don't warn and try again */
> +		if (error != -ETIMEDOUT)
> +			dev_warn(&gdev->dev, "%s: could not start: %i\n",
> +				 __func__, error);
> +
> +		schedule_delayed_work(&ddata->restart_work,
> +				      msecs_to_jiffies(MOTMDM_GNSS_RATE));
> +	}
> +}
> +
> +static void motmdm_gnss_start(struct gnss_device *gdev, int delay_ms)
> +{
> +	struct motmdm_gnss_data *ddata = gnss_get_drvdata(gdev);
> +	ktime_t now, next, delta;
> +	int next_ms;
> +
> +	now = ktime_get();
> +	next = ktime_add_ms(ddata->last_update, delay_ms);
> +	delta = ktime_sub(next, now);
> +	next_ms = ktime_to_ms(delta);
> +
> +	if (next_ms < 0)
> +		next_ms = 0;
> +	if (next_ms > delay_ms)
> +		next_ms = delay_ms;
> +
> +	schedule_delayed_work(&ddata->restart_work, msecs_to_jiffies(next_ms));
> +}
> +
> +static int motmdm_gnss_stop(struct gnss_device *gdev)
> +{
> +	struct motmdm_gnss_data *ddata = gnss_get_drvdata(gdev);
> +	const unsigned char *cmd = "AT+MPDSTOP";
> +
> +	cancel_delayed_work_sync(&ddata->restart_work);
> +
> +	return motmdm_gnss_send_command(ddata, cmd, strlen(cmd));
> +}
> +
> +static int motmdm_gnss_init(struct gnss_device *gdev)
> +{
> +	struct motmdm_gnss_data *ddata = gnss_get_drvdata(gdev);
> +	const unsigned char *cmd = "AT+MPDINIT=1";
> +	int error;
> +
> +	error = motmdm_gnss_send_command(ddata, cmd, strlen(cmd));
> +	if (error < 0)
> +		return error;
> +
> +	motmdm_gnss_start(gdev, 0);
> +
> +	return 0;
> +}
> +
> +static int motmdm_gnss_finish(struct gnss_device *gdev)
> +{
> +	struct motmdm_gnss_data *ddata = gnss_get_drvdata(gdev);
> +	const unsigned char *cmd = "AT+MPDINIT=0";
> +	int error;
> +
> +	error = motmdm_gnss_stop(gdev);
> +	if (error < 0)
> +		return error;
> +
> +	return motmdm_gnss_send_command(ddata, cmd, strlen(cmd));
> +}
> +
> +static int motmdm_gnss_receive_data(struct serdev_device *serdev,
> +					const unsigned char *buf, size_t len)
> +{
> +	struct motmdm_gnss_data *ddata = serdev_device_get_drvdata(serdev);
> +	struct gnss_device *gdev = ddata->gdev;
> +	const unsigned char *msg;
> +	size_t msglen;
> +	int error = 0;
> +
> +	if (len <= MOTMDM_GNSS_RESP_LEN)
> +		return 0;
> +
> +	/* Handle U1234+MPD style command response */
> +	if (buf[MOTMDM_GNSS_HEADER_LEN] != '~') {
> +		msg = buf + MOTMDM_GNSS_RESP_LEN;
> +		strncpy(ddata->buf, msg, len - MOTMDM_GNSS_RESP_LEN);
> +		ddata->parsed = true;
> +		wake_up(&ddata->read_queue);
> +
> +		return len;
> +	}
> +
> +	if (len <= MOTMDM_GNSS_DATA_LEN)
> +		return 0;
> +
> +	/* Handle U1234~+MPD style unsolicted message */
> +	switch (buf[MOTMDM_GNSS_DATA_LEN]) {
> +	case 'N':	/* UNNNN~+MPDNMEA=NN, */
> +		msg = buf + MOTMDM_GNSS_NMEA_LEN;
> +		msglen = len - MOTMDM_GNSS_NMEA_LEN;
> +
> +		/*
> +		 * Firmware bug: Strip out extra duplicate line break always
> +		 * in the data
> +		 */
> +		msglen--;
> +
> +		/*
> +		 * Firmware bug: Strip out extra data based on an
> +		 * earlier line break in the data
> +		 */
> +		if (msg[msglen - 5 - 1] == 0x0a)
> +			msglen -= 5;
> +
> +		error = gnss_insert_raw(gdev, msg, msglen);
> +		WARN_ON(error);
> +		break;
> +	case 'S':	/* UNNNN~+MPDSTATUS=N,NN */
> +		msg = buf + MOTMDM_GNSS_STATUS_LEN;
> +		msglen = len - MOTMDM_GNSS_STATUS_LEN;
> +
> +		switch (msg[0]) {
> +		case '1':
> +			ddata->status = MOTMDM_GNSS_INITIALIZED;
> +			break;
> +		case '2':
> +			ddata->status = MOTMDM_GNSS_DATA_OR_TIMEOUT;
> +			if (rate_ms < MOTMDM_GNSS_RATE)
> +				rate_ms = MOTMDM_GNSS_RATE;
> +			if (rate_ms > 16 * MOTMDM_GNSS_RATE)
> +				rate_ms = 16 * MOTMDM_GNSS_RATE;
> +			motmdm_gnss_start(gdev, rate_ms);
> +			break;
> +		case '3':
> +			ddata->status = MOTMDM_GNSS_STARTED;
> +			break;
> +		case '4':
> +			ddata->status = MOTMDM_GNSS_STOPPED;
> +			break;
> +		default:
> +			ddata->status = MOTMDM_GNSS_UNKNOWN;
> +			break;
> +		}
> +		break;
> +	case 'X':	/* UNNNN~+MPDXREQ=N for updated xtra2.bin needed */
> +	default:
> +		break;
> +	}
> +
> +	return len;
> +}
> +
> +static const struct serdev_device_ops gnss_serdev_ops = {
> +	.receive_buf    = motmdm_gnss_receive_data,
> +	.write_wakeup   = serdev_device_write_wakeup,
> +};
> +
> +static int motmdm_gnss_open(struct gnss_device *gdev)
> +{
> +	struct motmdm_gnss_data *ddata = gnss_get_drvdata(gdev);
> +	int error;
> +
> +	serdev_device_set_client_ops(ddata->serdev, &gnss_serdev_ops);
> +
> +	error = serdev_device_open(ddata->serdev);
> +	if (error) {
> +		return error;
> +	}
> +
> +	error = motmdm_gnss_init(gdev);
> +	if (error) {
> +		return error;
> +	}
> +
> +	return 0;
> +}
> +
> +static void motmdm_gnss_close(struct gnss_device *gdev)
> +{
> +	struct motmdm_gnss_data *ddata = gnss_get_drvdata(gdev);
> +	int error;
> +
> +	error = motmdm_gnss_finish(gdev);
> +	if (error < 0)
> +		dev_warn(&gdev->dev, "%s: close failed: %i\n",
> +			 __func__, error);
> +
> +	serdev_device_close(ddata->serdev);
> +}
> +
> +static int motmdm_gnss_write_raw(struct gnss_device *gdev,
> +				 const unsigned char *buf,
> +				 size_t count)
> +{
> +	struct motmdm_gnss_data *ddata = gnss_get_drvdata(gdev);
> +
> +	return serdev_device_write(ddata->serdev, buf, count, MAX_SCHEDULE_TIMEOUT);
> +	serdev_device_wait_until_sent(ddata->serdev, 0);
> +
> +	return count;
> +}
> +
> +static const struct gnss_operations motmdm_gnss_ops = {
> +	.open		= motmdm_gnss_open,
> +	.close		= motmdm_gnss_close,
> +	.write_raw	= motmdm_gnss_write_raw,
> +};
> +
> +static int motmdm_gnss_probe(struct serdev_device *serdev)
> +{
> +	struct device *dev = &serdev->dev;
> +	struct motmdm_gnss_data *ddata;
> +	struct gnss_device *gdev;
> +	int ret;
> +
> +	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
> +	if (!ddata)
> +		return -ENOMEM;
> +
> +	ddata->serdev = serdev;
> +	ddata->modem = dev->parent;
> +	ddata->len = PAGE_SIZE;
> +	mutex_init(&ddata->mutex);
> +	INIT_DELAYED_WORK(&ddata->restart_work, motmdm_gnss_restart);
> +	init_waitqueue_head(&ddata->read_queue);
> +
> +	ddata->buf = devm_kzalloc(dev, ddata->len, GFP_KERNEL);
> +	if (!ddata->buf)
> +		return -ENOMEM;
> +
> +	serdev_device_set_drvdata(serdev, ddata);
> +
> +	gdev = gnss_allocate_device(dev);
> +	if (!gdev)
> +		return -ENOMEM;
> +
> +	gdev->type = GNSS_TYPE_NMEA;
> +	gdev->ops = &motmdm_gnss_ops;
> +	gnss_set_drvdata(gdev, ddata);
> +	ddata->gdev = gdev;
> +
> +	ret = gnss_register_device(gdev);
> +	if (ret)
> +		gnss_put_device(ddata->gdev);
> +
> +	return ret;
> +}
> +
> +static void motmdm_gnss_remove(struct serdev_device *serdev)
> +{
> +	struct motmdm_gnss_data *data = serdev_device_get_drvdata(serdev);
> +
> +	gnss_deregister_device(data->gdev);
> +	gnss_put_device(data->gdev);
> +};
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id motmdm_gnss_of_match[] = {
> +	{ .compatible = "motorola,mapphone-mdm6600-gnss" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, motmdm_gnss_of_match);
> +#endif
> +
> +static struct serdev_device_driver motmdm_gnss_driver = {
> +	.driver	= {
> +		.name		= "gnss-mot-mdm6600",
> +		.of_match_table	= of_match_ptr(motmdm_gnss_of_match),
> +	},
> +	.probe	= motmdm_gnss_probe,
> +	.remove	= motmdm_gnss_remove,
> +};
> +module_serdev_device_driver(motmdm_gnss_driver);
> +
> +MODULE_AUTHOR("Tony Lindgren <tony@...mide.com>");
> +MODULE_DESCRIPTION("Motorola Mapphone MDM6600 GNSS receiver driver");
> +MODULE_LICENSE("GPL v2");
> 
> 
> -- 
> http://www.livejournal.com/~pavelmachek



-- 
http://www.livejournal.com/~pavelmachek

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