Date:   Fri, 9 Apr 2021 15:17:44 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Vincent Knecht <vincent.knecht@...loo.org>
Cc:     phone-devel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht,
        Stephan Gerhold <stephan@...hold.net>,
        Rob Herring <robh+dt@...nel.org>,
        Henrik Rydberg <rydberg@...math.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Michael Srba <Michael.Srba@...nam.cz>,
        linux-input@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/2] Input: add MStar MSG2638 touchscreen driver

Hi Vincent,

On Fri, Mar 05, 2021 at 04:38:05PM +0100, Vincent Knecht wrote:
> Add support for the msg2638 touchscreen IC from MStar.
> Firmware handling, wakeup gestures and other specialties are not supported.
> This driver reuses zinitix.c structure, while the checksum and irq handler
> functions are based on out-of-tree driver for Alcatel Idol 3 (4.7").
> 
> Signed-off-by: Vincent Knecht <vincent.knecht@...loo.org>
> ---
> Changed in v6:
> - minor formatting changes
> - mention wakeup gestures not being supported (yet?) in commit message
> - do not scale coordinates in the driver (Dmitry)
> - multiple suggestions from Linus W.
>   - include linux/gpio/consumer.h instead of linux/gpio.h
>   - rename delay defines to include time unit like _MS and _US
>   - rename `error` variable to `ret`
>   - move enable_irq() call from msg2638_power_on() to msg2638_start()
>   - remove CONFIG_OF #ifdef around of_device_id struct
> Changed in v5:
> - use gpiod_set_value_cansleep() (Stephan G)
> - use msleep/usleep_range() rathen than mdelay() (Stephan G)
> Changed in v4:
> - rename from msg26xx to msg2638, following compatible string change
> - rename mstar_* functions to msg2638_* for consistency
> - add RESET_DELAY define and use it in msg2638_power_on()
> - change a few dev_err() calls to be on one line only
> - add missing \n in a few dev_err() strings
> Changed in v3:
> - no change
> Changed in v2:
> - don't use bitfields in packet struct, to prevent endian-ness related problems (Dmitry)
> - fix reset gpiod calls order in mstar_power_on() (Dmitry)
> ---
>  drivers/input/touchscreen/Kconfig   |  12 +
>  drivers/input/touchscreen/Makefile  |   1 +
>  drivers/input/touchscreen/msg2638.c | 354 ++++++++++++++++++++++++++++
>  3 files changed, 367 insertions(+)
>  create mode 100644 drivers/input/touchscreen/msg2638.c
> 
> diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
> index f012fe746df0..fefbe1c1bb10 100644
> --- a/drivers/input/touchscreen/Kconfig
> +++ b/drivers/input/touchscreen/Kconfig
> @@ -1334,4 +1334,16 @@ config TOUCHSCREEN_ZINITIX
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called zinitix.
>  
> +config TOUCHSCREEN_MSG2638
> +	tristate "MStar msg2638 touchscreen support"
> +	depends on I2C
> +	depends on GPIOLIB || COMPILE_TEST
> +	help
> +	  Say Y here if you have an I2C touchscreen using MStar msg2638.
> +
> +	  If unsure, say N.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called msg2638.
> +
>  endif
> diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
> index 6233541e9173..83e516cb3d33 100644
> --- a/drivers/input/touchscreen/Makefile
> +++ b/drivers/input/touchscreen/Makefile
> @@ -112,3 +112,4 @@ obj-$(CONFIG_TOUCHSCREEN_ROHM_BU21023)	+= rohm_bu21023.o
>  obj-$(CONFIG_TOUCHSCREEN_RASPBERRYPI_FW)	+= raspberrypi-ts.o
>  obj-$(CONFIG_TOUCHSCREEN_IQS5XX)	+= iqs5xx.o
>  obj-$(CONFIG_TOUCHSCREEN_ZINITIX)	+= zinitix.o
> +obj-$(CONFIG_TOUCHSCREEN_MSG2638)	+= msg2638.o
> diff --git a/drivers/input/touchscreen/msg2638.c b/drivers/input/touchscreen/msg2638.c
> new file mode 100644
> index 000000000000..8eb3f195d743
> --- /dev/null
> +++ b/drivers/input/touchscreen/msg2638.c
> @@ -0,0 +1,354 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Driver for MStar msg2638 touchscreens
> + *
> + * Copyright (c) 2021 Vincent Knecht <vincent.knecht@...loo.org>
> + *
> + * Checksum and IRQ handler based on mstar_drv_common.c and mstar_drv_mutual_fw_control.c
> + * Copyright (c) 2006-2012 MStar Semiconductor, Inc.
> + *
> + * Driver structure based on zinitix.c by Michael Srba <Michael.Srba@...nam.cz>
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/i2c.h>
> +#include <linux/input.h>
> +#include <linux/input/mt.h>
> +#include <linux/input/touchscreen.h>
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/slab.h>
> +
> +#define MODE_DATA_RAW			0x5A
> +
> +#define MAX_SUPPORTED_FINGER_NUM	5
> +
> +#define CHIP_ON_DELAY_MS		15
> +#define FIRMWARE_ON_DELAY_MS		50
> +#define RESET_DELAY_MIN_US		10000
> +#define RESET_DELAY_MAX_US		11000
> +
> +struct point_coord {
> +	u16	x;
> +	u16	y;
> +};
> +
> +struct packet {
> +	u8	xy_hi; /* higher bits of x and y coordinates */
> +	u8	x_low;
> +	u8	y_low;
> +	u8	pressure;
> +};
> +
> +struct touch_event {
> +	u8	mode;
> +	struct	packet pkt[MAX_SUPPORTED_FINGER_NUM];
> +	u8	proximity;
> +	u8	checksum;
> +};
> +
> +struct msg2638_ts_data {
> +	struct i2c_client *client;
> +	struct input_dev *input_dev;
> +	struct touchscreen_properties prop;
> +	struct regulator_bulk_data supplies[2];
> +	struct gpio_desc *reset_gpiod;
> +};
> +
> +static int msg2638_init_regulators(struct msg2638_ts_data *msg2638)
> +{
> +	struct i2c_client *client = msg2638->client;
> +	int ret;
> +
> +	msg2638->supplies[0].supply = "vdd";
> +	msg2638->supplies[1].supply = "vddio";
> +	ret = devm_regulator_bulk_get(&client->dev,
> +				      ARRAY_SIZE(msg2638->supplies),
> +				      msg2638->supplies);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Failed to get regulators: %d\n", ret);
> +		return ret;
> +	}
> +
> +	return 0;

I do not see benefit of factoring out into separate function so I moved
it directly into probe(), similarly how we acquire reset GPIO.

> +}
> +
> +static void msg2638_power_on(struct msg2638_ts_data *msg2638)

Renamed to msg2638_reset().

> +{
> +	gpiod_set_value_cansleep(msg2638->reset_gpiod, 1);
> +	usleep_range(RESET_DELAY_MIN_US, RESET_DELAY_MAX_US);
> +	gpiod_set_value_cansleep(msg2638->reset_gpiod, 0);
> +	msleep(FIRMWARE_ON_DELAY_MS);
> +}
> +
> +static void msg2638_report_finger(struct msg2638_ts_data *msg2638, int slot,
> +				const struct point_coord *pc)
> +{
> +	input_mt_slot(msg2638->input_dev, slot);
> +	input_mt_report_slot_state(msg2638->input_dev, MT_TOOL_FINGER, true);
> +	touchscreen_report_pos(msg2638->input_dev, &msg2638->prop, pc->x, pc->y, true);
> +	input_report_abs(msg2638->input_dev, ABS_MT_TOUCH_MAJOR, 1);

The device does not really report "touch major", this is synthetic data,
and therefore I removed it.

All in all this is quite simple function, I pushed it down into
msg2638_ts_irq_handler().

> +}
> +
> +static u8 msg2638_checksum(u8 *data, u32 length)
> +{
> +	s32 sum = 0;
> +	u32 i;
> +
> +	for (i = 0; i < length; i++)
> +		sum += data[i];
> +
> +	return (u8)((-sum) & 0xFF);
> +}
> +
> +static irqreturn_t msg2638_ts_irq_handler(int irq, void *msg2638_handler)
> +{
> +	struct msg2638_ts_data *msg2638 = msg2638_handler;
> +	struct i2c_client *client = msg2638->client;
> +	struct touch_event touch_event;
> +	struct point_coord coord;
> +	struct i2c_msg msg[1];
> +	struct packet *p;
> +	u32 len;
> +	int ret;
> +	int i;
> +
> +	len = sizeof(struct touch_event);
> +	memset(&touch_event, 0, len);
> +
> +	msg[0].addr = client->addr;
> +	msg[0].flags = I2C_M_RD;
> +	msg[0].len = len;
> +	msg[0].buf = (u8 *)&touch_event;
> +
> +	ret = i2c_transfer(client->adapter, msg, 1);
> +	if (ret != 1) {
> +		dev_err(&client->dev, "Failed I2C transfer in irq handler!\n");
> +		goto out;
> +	}
> +
> +	if (touch_event.mode != MODE_DATA_RAW)
> +		goto out;
> +
> +	if (msg2638_checksum((u8 *)&touch_event, len - 1) != touch_event.checksum) {
> +		dev_err(&client->dev, "Failed checksum!\n");
> +		goto out;
> +	}
> +
> +	for (i = 0; i < MAX_SUPPORTED_FINGER_NUM; i++) {
> +		p = &touch_event.pkt[i];
> +		/* Ignore non-pressed finger data */
> +		if (p->xy_hi == 0xFF && p->x_low == 0xFF && p->y_low == 0xFF)
> +			continue;
> +
> +		coord.x = (((p->xy_hi & 0xF0) << 4) | p->x_low);
> +		coord.y = (((p->xy_hi & 0x0F) << 8) | p->y_low);
> +		msg2638_report_finger(msg2638, i, &coord);
> +	}
> +
> +	input_mt_sync_frame(msg2638->input_dev);
> +	input_sync(msg2638->input_dev);
> +
> +out:
> +	return IRQ_HANDLED;
> +}
> +
> +static int msg2638_start(struct msg2638_ts_data *msg2638)
> +{
> +	int ret;
> +
> +	ret = regulator_bulk_enable(ARRAY_SIZE(msg2638->supplies), msg2638->supplies);
> +	if (ret) {
> +		dev_err(&msg2638->client->dev, "Failed to enable regulators: %d\n", ret);
> +		return ret;
> +	}
> +
> +	msleep(CHIP_ON_DELAY_MS);
> +	msg2638_power_on(msg2638);
> +	enable_irq(msg2638->client->irq);
> +
> +	return 0;
> +}
> +
> +static int msg2638_stop(struct msg2638_ts_data *msg2638)
> +{
> +	int ret;
> +
> +	disable_irq(msg2638->client->irq);
> +
> +	ret = regulator_bulk_disable(ARRAY_SIZE(msg2638->supplies), msg2638->supplies);
> +	if (ret) {
> +		dev_err(&msg2638->client->dev, "Failed to disable regulators: %d\n", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int msg2638_input_open(struct input_dev *dev)
> +{
> +	struct msg2638_ts_data *msg2638 = input_get_drvdata(dev);
> +
> +	return msg2638_start(msg2638);
> +}
> +
> +static void msg2638_input_close(struct input_dev *dev)
> +{
> +	struct msg2638_ts_data *msg2638 = input_get_drvdata(dev);
> +
> +	msg2638_stop(msg2638);
> +}
> +
> +static int msg2638_init_input_dev(struct msg2638_ts_data *msg2638)
> +{
> +	struct input_dev *input_dev;
> +	int ret;
> +
> +	input_dev = devm_input_allocate_device(&msg2638->client->dev);
> +	if (!input_dev) {
> +		dev_err(&msg2638->client->dev, "Failed to allocate input device.\n");
> +		return -ENOMEM;
> +	}
> +
> +	input_set_drvdata(input_dev, msg2638);
> +	msg2638->input_dev = input_dev;
> +
> +	input_dev->name = "MStar TouchScreen";
> +	input_dev->phys = "input/ts";
> +	input_dev->id.bustype = BUS_I2C;
> +	input_dev->open = msg2638_input_open;
> +	input_dev->close = msg2638_input_close;
> +
> +	input_set_capability(input_dev, EV_ABS, ABS_MT_POSITION_X);
> +	input_set_capability(input_dev, EV_ABS, ABS_MT_POSITION_Y);
> +	input_set_abs_params(input_dev, ABS_MT_WIDTH_MAJOR, 0, 15, 0, 0);
> +	input_set_abs_params(input_dev, ABS_MT_TOUCH_MAJOR, 0, 255, 0, 0);

The last 2 events are not reported and should not be advertised in the
capabilities.

> +
> +	touchscreen_parse_properties(input_dev, true, &msg2638->prop);
> +	if (!msg2638->prop.max_x || !msg2638->prop.max_y) {
> +		dev_err(&msg2638->client->dev,
> +			"touchscreen-size-x and/or touchscreen-size-y not set in dts\n");
> +		return -EINVAL;
> +	}
> +
> +	ret = input_mt_init_slots(input_dev, MAX_SUPPORTED_FINGER_NUM,
> +				  INPUT_MT_DIRECT | INPUT_MT_DROP_UNUSED);
> +	if (ret) {
> +		dev_err(&msg2638->client->dev, "Failed to initialize MT slots: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = input_register_device(input_dev);
> +	if (ret) {
> +		dev_err(&msg2638->client->dev, "Failed to register input device: %d\n", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int msg2638_ts_probe(struct i2c_client *client)
> +{
> +	struct msg2638_ts_data *msg2638;
> +	int ret;
> +
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
> +		dev_err(&client->dev, "Failed to assert adapter's support for plain I2C.\n");
> +		return -ENXIO;
> +	}
> +
> +	msg2638 = devm_kzalloc(&client->dev, sizeof(*msg2638), GFP_KERNEL);
> +	if (!msg2638)
> +		return -ENOMEM;
> +
> +	msg2638->client = client;
> +	i2c_set_clientdata(client, msg2638);
> +
> +	ret = msg2638_init_regulators(msg2638);
> +	if (ret) {
> +		dev_err(&client->dev, "Failed to initialize regulators: %d\n", ret);
> +		return ret;
> +	}
> +
> +	msg2638->reset_gpiod = devm_gpiod_get(&client->dev, "reset", GPIOD_OUT_LOW);
> +	if (IS_ERR(msg2638->reset_gpiod)) {
> +		ret = PTR_ERR(msg2638->reset_gpiod);
> +		dev_err(&client->dev, "Failed to request reset GPIO: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = msg2638_init_input_dev(msg2638);
> +	if (ret) {
> +		dev_err(&client->dev, "Failed to initialize input device: %d\n", ret);
> +		return ret;
> +	}
> +
> +	irq_set_status_flags(client->irq, IRQ_NOAUTOEN);

We now have IRQF_NO_AUTOEN as a flag for request_irq() and friends so I
used it instead of irq_set_status_flags().

> +	ret = devm_request_threaded_irq(&client->dev, client->irq,
> +					NULL, msg2638_ts_irq_handler,
> +					IRQF_ONESHOT, client->name, msg2638);
> +	if (ret) {
> +		dev_err(&client->dev, "Failed to request IRQ: %d\n", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int __maybe_unused msg2638_suspend(struct device *dev)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct msg2638_ts_data *msg2638 = i2c_get_clientdata(client);
> +
> +	mutex_lock(&msg2638->input_dev->mutex);
> +
> +	if (input_device_enabled(msg2638->input_dev))
> +		msg2638_stop(msg2638);
> +
> +	mutex_unlock(&msg2638->input_dev->mutex);
> +
> +	return 0;
> +}
> +
> +static int __maybe_unused msg2638_resume(struct device *dev)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct msg2638_ts_data *msg2638 = i2c_get_clientdata(client);
> +	int ret = 0;
> +
> +	mutex_lock(&msg2638->input_dev->mutex);
> +
> +	if (input_device_enabled(msg2638->input_dev))
> +		ret = msg2638_start(msg2638);
> +
> +	mutex_unlock(&msg2638->input_dev->mutex);
> +
> +	return ret;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(msg2638_pm_ops, msg2638_suspend, msg2638_resume);
> +
> +static const struct of_device_id msg2638_of_match[] = {
> +	{ .compatible = "mstar,msg2638" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, msg2638_of_match);
> +
> +static struct i2c_driver msg2638_ts_driver = {
> +	.probe_new = msg2638_ts_probe,
> +	.driver = {
> +		.name = "MStar-TS",
> +		.pm = &msg2638_pm_ops,
> +		.of_match_table = of_match_ptr(msg2638_of_match),

Given that the driver is not depending on OF, when !CONFIG_OF this will
cause unused variable msg2638_of_match. Given that we can use OF
matchinv with ACPI I dropped of_match_ptr().

> +	},
> +};
> +module_i2c_driver(msg2638_ts_driver);
> +
> +MODULE_AUTHOR("Vincent Knecht <vincent.knecht@...loo.org>");
> +MODULE_DESCRIPTION("MStar MSG2638 touchscreen driver");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.29.2
> 
> 
> 

Thanks.

-- 
Dmitry

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