Date:   Sun, 12 Mar 2023 22:40:54 +0200
From:   Markuss Broks <markuss.broks@...il.com>
To:     Joel Selvaraj <joelselvaraj.oss@...il.com>,
        Caleb Connolly <caleb@...nolly.tech>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Henrik Rydberg <rydberg@...math.org>,
        Arnd Bergmann <arnd@...db.de>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        Jeff LaBundy <jeff@...undy.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Jean Delvare <jdelvare@...e.de>,
        Max Krummenacher <max.krummenacher@...adex.com>,
        Job Noorman <job@...rman.info>,
        Alistair Francis <alistair@...stair23.me>,
        Chris Morgan <macromorgan@...mail.com>
Cc:     linux-input@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org
Subject: Re: [PATCH 2/5] Input: add driver for Focaltech FTS touchscreen

Hi Joel,

Some comments about the driver below,

On 3/12/23 11:32, Joel Selvaraj wrote:
> The Focaltech FTS driver supports several variants of focaltech
> touchscreens found in ~2018 era smartphones including variants found on
> the PocoPhone F1 and the SHIFT6mq which are already present in mainline.
> This driver is loosely based on the original driver from Focaltech
> but has been simplified and largely reworked.
>
> Co-developed-by: Caleb Connolly <caleb@...nolly.tech>
> Signed-off-by: Caleb Connolly <caleb@...nolly.tech>
> Signed-off-by: Joel Selvaraj <joelselvaraj.oss@...il.com>
> ---
>   MAINTAINERS                               |   8 +
>   drivers/input/touchscreen/Kconfig         |  12 +
>   drivers/input/touchscreen/Makefile        |   1 +
>   drivers/input/touchscreen/focaltech_fts.c | 448 ++++++++++++++++++++++
>   4 files changed, 469 insertions(+)
>   create mode 100644 drivers/input/touchscreen/focaltech_fts.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 2892858cb040..deb561c356f2 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -7993,6 +7993,14 @@ L:	linux-input@...r.kernel.org
>   S:	Maintained
>   F:	drivers/input/joystick/fsia6b.c
>   
> +FOCALTECH FTS TOUCHSCREEN DRIVER
> +M:	Joel Selvaraj <joelselvaraj.oss@...il.com>
> +M:	Caleb Connolly <caleb@...nolly.tech>
> +L:	linux-input@...r.kernel.org
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/input/touchscreen/focaltech,fts.yaml
> +F:	drivers/input/touchscreen/focaltech_fts.c
> +
>   FOCUSRITE SCARLETT GEN 2/3 MIXER DRIVER
>   M:	Geoffrey D. Bennett <g@...vu>
>   L:	alsa-devel@...a-project.org (moderated for non-subscribers)
> diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
> index 1a2049b336a6..320925bac3a1 100644
> --- a/drivers/input/touchscreen/Kconfig
> +++ b/drivers/input/touchscreen/Kconfig
> @@ -388,6 +388,18 @@ config TOUCHSCREEN_EXC3000
>   	  To compile this driver as a module, choose M here: the
>   	  module will be called exc3000.
>   
> +config TOUCHSCREEN_FOCALTECH_FTS
> +	tristate "Focaltech FTS Touchscreen"
> +	depends on I2C
> +	help
> +	  Say Y here to enable support for I2C connected Focaltech FTS
> +	  based touch panels, including the 5452 and 8917 panels.
> +
> +	  If unsure, say N.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called focaltech_fts.
> +
>   config TOUCHSCREEN_FUJITSU
>   	tristate "Fujitsu serial touchscreen"
>   	select SERIO
> diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
> index f2fd28cc34a6..83ea2e3ce754 100644
> --- a/drivers/input/touchscreen/Makefile
> +++ b/drivers/input/touchscreen/Makefile
> @@ -45,6 +45,7 @@ obj-$(CONFIG_TOUCHSCREEN_ELO)		+= elo.o
>   obj-$(CONFIG_TOUCHSCREEN_EGALAX)	+= egalax_ts.o
>   obj-$(CONFIG_TOUCHSCREEN_EGALAX_SERIAL)	+= egalax_ts_serial.o
>   obj-$(CONFIG_TOUCHSCREEN_EXC3000)	+= exc3000.o
> +obj-$(CONFIG_TOUCHSCREEN_FOCALTECH_FTS)	+= focaltech_fts.o
>   obj-$(CONFIG_TOUCHSCREEN_FUJITSU)	+= fujitsu_ts.o
>   obj-$(CONFIG_TOUCHSCREEN_GOODIX)	+= goodix_ts.o
>   obj-$(CONFIG_TOUCHSCREEN_HIDEEP)	+= hideep.o
> diff --git a/drivers/input/touchscreen/focaltech_fts.c b/drivers/input/touchscreen/focaltech_fts.c
> new file mode 100644
> index 000000000000..d389c8b88944
> --- /dev/null
> +++ b/drivers/input/touchscreen/focaltech_fts.c
> @@ -0,0 +1,448 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + *
> + * FocalTech touchscreen driver.
> + *
> + * Copyright (c) 2010-2017, FocalTech Systems, Ltd., all rights reserved.
> + * Copyright (C) 2018 XiaoMi, Inc.
> + * Copyright (c) 2021 Caleb Connolly <caleb@...nolly.tech>
> + * Copyright (c) 2023 Joel Selvaraj <joelselvaraj.oss@...il.com>
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/input.h>
> +#include <linux/input/mt.h>
> +#include <linux/input/touchscreen.h>
> +#include <linux/slab.h>
> +#include <linux/interrupt.h>
> +#include <linux/i2c.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/delay.h>
> +#include <linux/regmap.h>
> +#include <linux/mutex.h>
Includes must be sorted alphabetically.
> +
> +#define FTS_REG_CHIP_ID_H 0xA3
> +#define FTS_REG_CHIP_ID_L 0x9F
> +
> +#define FTS_MAX_POINTS_SUPPORT 10
> +#define FTS_ONE_TOUCH_LEN 6
> +
> +#define FTS_TOUCH_X_H_OFFSET 3
> +#define FTS_TOUCH_X_L_OFFSET 4
> +#define FTS_TOUCH_Y_H_OFFSET 5
> +#define FTS_TOUCH_Y_L_OFFSET 6
> +#define FTS_TOUCH_PRESSURE_OFFSET 7
> +#define FTS_TOUCH_AREA_OFFSET 8
> +#define FTS_TOUCH_TYPE_OFFSET 3
> +#define FTS_TOUCH_ID_OFFSET 5
> +
> +#define FTS_TOUCH_DOWN 0
> +#define FTS_TOUCH_UP 1
> +#define FTS_TOUCH_CONTACT 2
> +
> +#define FTS_DRIVER_NAME "fts-i2c"
> +#define INTERVAL_READ_REG 100 /* unit:ms */
> +#define TIMEOUT_READ_REG 2000 /* unit:ms */
Instead of using those comments, it's better to use the _MS suffix.
> +
> +#define CHIP_TYPE_5452 0x5452
> +#define CHIP_TYPE_8719 0x8719
> +
> +struct fts_ts_data {
> +	struct i2c_client *client;
> +	struct input_dev *input_dev;
> +	struct touchscreen_properties prop;
> +
> +	struct regmap *regmap;
> +	int irq;
> +
> +	struct regulator_bulk_data regulators[2];
> +
> +	/* Touch data */
> +	u8 max_touch_number;
> +	u8 *point_buf;
> +	int point_buf_size;
> +
> +	/* DT data */
> +	struct gpio_desc *reset_gpio;
> +};
> +
> +static const struct regmap_config fts_ts_i2c_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +};
> +
> +static bool fts_chip_is_valid(struct fts_ts_data *data, u16 id)
> +{
> +	if (id != CHIP_TYPE_5452 && id != CHIP_TYPE_8719)
> +		return false;
> +
> +	return true;
> +}
> +
> +int fts_check_status(struct fts_ts_data *data)
> +{
> +	int count = 0;
> +	unsigned int val, id;
> +
> +	do {
> +		regmap_read(data->regmap, FTS_REG_CHIP_ID_H, &val);
> +		id = val << 8;
> +		regmap_read(data->regmap, FTS_REG_CHIP_ID_L, &val);
> +		id |= val;
That register layout is surely... weird. Anyway, I'd probably do
```
         regmap_read(data->regmap, FTS_REG_CHIP_ID_L, &id);
         regmap_read(data->regmap, FTS_REG_CHIP_ID_H, &val);
         id |= val << 8;
```
to make it less actions. Also, this lacks error checking for the regmap 
calls.
> +
> +		if (fts_chip_is_valid(data, id)) {
> +			dev_dbg(&data->client->dev, "TS Ready: Chip ID = 0x%x", id);
> +			return 0;
> +		}
> +
> +		count++;
> +		msleep(INTERVAL_READ_REG);
> +	} while ((count * INTERVAL_READ_REG) < TIMEOUT_READ_REG);
> +
> +	return -EIO;
> +}
> +
> +static void fts_report_touch(struct fts_ts_data *data)
> +{
> +	struct input_dev *input_dev = data->input_dev;
> +	int base;
> +	unsigned int x, y, z, maj;
> +	u8 slot, type;
> +	int error, i = 0;
> +
> +	u8 *buf = data->point_buf;
> +
> +	memset(buf, 0, data->point_buf_size);
> +
> +	error = regmap_bulk_read(data->regmap, 0, buf, data->point_buf_size);
> +	if (error) {
> +		dev_err_ratelimited(&data->client->dev, "I2C read failed: %d\n",
> +				    error);
Why is the _ratelimited variant necessary?
> +		return;
> +	}
> +
> +	for (i = 0; i < data->max_touch_number; i++) {
> +		base = FTS_ONE_TOUCH_LEN * i;
> +
> +		slot = (buf[base + FTS_TOUCH_ID_OFFSET]) >> 4;
I believe parentheses aren't needed?
> +		if (slot >= data->max_touch_number)
> +			break;
> +
> +		x = ((buf[base + FTS_TOUCH_X_H_OFFSET] & 0x0F) << 8) +
> +			 (buf[base + FTS_TOUCH_X_L_OFFSET] & 0xFF);
> +		y = ((buf[base + FTS_TOUCH_Y_H_OFFSET] & 0x0F) << 8) +
> +			 (buf[base + FTS_TOUCH_Y_L_OFFSET] & 0xFF);
> +
> +		z = buf[base + FTS_TOUCH_PRESSURE_OFFSET];
> +		if (z <= 0)
> +			z = 0x3f;
> +
> +		maj = buf[base + FTS_TOUCH_AREA_OFFSET] >> 4;
> +		if (maj <= 0)
> +			maj = 0x09;
> +
> +		type = buf[base + FTS_TOUCH_TYPE_OFFSET] >> 6;
> +
> +		input_mt_slot(input_dev, slot);
> +		if (type == FTS_TOUCH_DOWN || type == FTS_TOUCH_CONTACT) {
> +			input_mt_report_slot_state(input_dev, MT_TOOL_FINGER, true);
> +			touchscreen_report_pos(data->input_dev, &data->prop, x, y, true);
> +			input_report_abs(input_dev, ABS_MT_PRESSURE, z);
> +			input_report_abs(input_dev, ABS_MT_TOUCH_MAJOR, maj);
> +			input_report_key(data->input_dev, BTN_TOUCH, 1);
> +		} else {
> +			input_report_key(data->input_dev, BTN_TOUCH, 0);
> +			input_mt_report_slot_inactive(input_dev);
> +		}
> +	}
Overall, I think it's better to cast the data type to a struct, which 
would make this seem with less random.
> +	input_sync(input_dev);
> +}
> +
> +static irqreturn_t fts_ts_interrupt(int irq, void *dev_id)
> +{
> +	struct fts_ts_data *data = dev_id;
> +
> +	fts_report_touch(data);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static void fts_power_off(void *d)
> +{
> +	struct fts_ts_data *data = d;
> +
> +	regulator_bulk_disable(ARRAY_SIZE(data->regulators),
> +			       data->regulators);
> +}
> +
> +static int fts_start(struct fts_ts_data *data)
> +{
> +	int error;
> +
> +	error = regulator_bulk_enable(ARRAY_SIZE(data->regulators),
> +				      data->regulators);
> +	if (error) {
> +		dev_err(&data->client->dev, "failed to enable regulators\n");
> +		return error;
> +	}
> +
> +	gpiod_set_value_cansleep(data->reset_gpio, 0);
> +	msleep(200);
> +
> +	enable_irq(data->irq);
> +
> +	return 0;
> +}
> +
> +static int fts_stop(struct fts_ts_data *data)
> +{
> +	disable_irq(data->irq);
> +	gpiod_set_value_cansleep(data->reset_gpio, 1);
> +	fts_power_off(data);
> +
> +	return 0;
> +}
> +
> +static int fts_input_open(struct input_dev *dev)
> +{
> +	struct fts_ts_data *data = input_get_drvdata(dev);
> +	int error;
> +
> +	error = fts_start(data);
> +	if (error)
> +		return error;
> +
> +	error = fts_check_status(data);
> +	if (error) {
> +		dev_err(&data->client->dev, "Failed to start or unsupported chip");
> +		return error;
> +	}
> +
> +	return 0;
> +}
> +
> +static void fts_input_close(struct input_dev *dev)
> +{
> +	struct fts_ts_data *data = input_get_drvdata(dev);
> +
> +	fts_stop(data);
> +}
> +
> +static int fts_input_init(struct fts_ts_data *data)
> +{
> +	struct device *dev = &data->client->dev;
> +	struct input_dev *input_dev;
> +	int error = 0;
> +
> +	input_dev = devm_input_allocate_device(dev);
> +	if (!input_dev)
> +		return -ENOMEM;
> +
> +	data->input_dev = input_dev;
> +
> +	/* Init and register Input device */
> +	input_dev->name = FTS_DRIVER_NAME;
> +	input_dev->id.bustype = BUS_I2C;
> +	input_dev->dev.parent = dev;
> +	input_dev->open = fts_input_open;
> +	input_dev->close = fts_input_close;
> +
> +	input_set_drvdata(input_dev, data);
> +
> +	__set_bit(EV_SYN, input_dev->evbit);
> +	__set_bit(EV_ABS, input_dev->evbit);
> +	__set_bit(INPUT_PROP_DIRECT, input_dev->propbit);
> +
> +	input_mt_init_slots(input_dev, data->max_touch_number,
> +			    INPUT_MT_DIRECT);
> +	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_TOUCH_MAJOR, 0, 255, 0, 0);
> +	input_set_abs_params(input_dev, ABS_MT_PRESSURE, 0, 255, 0, 0);
> +
> +	touchscreen_parse_properties(input_dev, true, &data->prop);
> +	if (!data->prop.max_x || !data->prop.max_y) {
> +		dev_err(dev,
> +			"touchscreen-size-x and/or touchscreen-size-y not set in dts\n");
> +		return -EINVAL;
> +	}
> +
> +	data->point_buf_size = (data->max_touch_number * FTS_ONE_TOUCH_LEN) + 3;
> +	data->point_buf = devm_kzalloc(dev, data->point_buf_size, GFP_KERNEL);
> +	if (!data->point_buf) {
> +		dev_err(dev, "Failed to alloc memory for point buffer\n");
> +		return -ENOMEM;
> +	}
> +
> +	error = input_register_device(input_dev);
> +	if (error) {
> +		dev_err(dev, "Failed to register input device\n");
> +		return error;
> +	}
> +
> +	return 0;
> +}
> +
> +static int fts_parse_dt(struct fts_ts_data *data)
> +{
> +	int error = 0;
> +	struct device *dev = &data->client->dev;
> +	struct device_node *np = dev->of_node;
> +	u32 val;
> +
> +	error = of_property_read_u32(np, "focaltech,max-touch-number", &val);
> +	if (error) {
> +		dev_err(dev, "Unable to read property 'focaltech,max-touch-number'");
> +		return -EINVAL;
> +	}
> +	if (val < 2 || val > FTS_MAX_POINTS_SUPPORT) {
> +		dev_err(dev, "'focaltech,max-touch-number' out of range [2, %d]",
> +			FTS_MAX_POINTS_SUPPORT);
> +		return -EINVAL;
> +	}
> +	data->max_touch_number = val;
> +
> +	data->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
> +	if (IS_ERR(data->reset_gpio)) {
> +		error = PTR_ERR(data->reset_gpio);
> +		dev_err(dev, "Failed to request reset gpio, error %d\n", error);
> +		return error;
> +	}
> +
> +	return 0;
> +}
> +
> +static int fts_ts_probe(struct i2c_client *client)
> +{
> +	int error = 0;
> +	struct fts_ts_data *data;
> +
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
> +		dev_err(&client->dev, "I2C not supported");
> +		return -ENODEV;
> +	}
> +
> +	if (!client->irq) {
> +		dev_err(&client->dev, "No irq specified\n");
> +		return -EINVAL;
> +	}
> +
> +	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	data->client = client;
> +
> +	error = fts_parse_dt(data);
> +	if (error)
> +		return error;
> +
> +	i2c_set_clientdata(client, data);
> +
> +	data->regmap = devm_regmap_init_i2c(client, &fts_ts_i2c_regmap_config);
> +	if (IS_ERR(data->regmap)) {
> +		dev_err(&client->dev, "regmap allocation failed\n");
> +		return PTR_ERR(data->regmap);
> +	}
> +
> +	/*
> +	 * AVDD is the analog voltage supply (2.6V to 3.3V)
> +	 * VDDIO is the digital voltage supply (1.8V)
> +	 */
> +	data->regulators[0].supply = "avdd";
> +	data->regulators[1].supply = "vddio";
> +	error = devm_regulator_bulk_get(&client->dev, ARRAY_SIZE(data->regulators),
> +				      data->regulators);
> +	if (error) {
> +		dev_err(&client->dev, "Failed to get regulators %d\n", error);
> +		return error;
> +	}
> +
> +	error = devm_add_action_or_reset(&client->dev, fts_power_off, data);
> +	if (error) {
> +		dev_err(&client->dev, "failed to install power off handler\n");
> +		return error;
> +	}
> +
> +	error = devm_request_threaded_irq(&client->dev, client->irq, NULL,
> +					fts_ts_interrupt, IRQF_ONESHOT,
> +					client->name, data);
> +	if (error) {
> +		dev_err(&client->dev, "Failed to request IRQ: %d\n", error);
> +		return error;
> +	}
> +
> +	error = fts_input_init(data);
> +	if (error)
> +		return error;
> +
> +	return 0;
> +}
> +
> +static int fts_pm_suspend(struct device *dev)
> +{
> +	struct fts_ts_data *data = dev_get_drvdata(dev);
> +
> +	mutex_lock(&data->input_dev->mutex);
> +
> +	if (input_device_enabled(data->input_dev))
> +		fts_stop(data);
> +
> +	mutex_unlock(&data->input_dev->mutex);
> +
> +	return 0;
> +}
> +
> +static int fts_pm_resume(struct device *dev)
> +{
> +	struct fts_ts_data *data = dev_get_drvdata(dev);
> +	int error = 0;
> +
> +	mutex_lock(&data->input_dev->mutex);
> +
> +	if (input_device_enabled(data->input_dev))
> +		error = fts_start(data);
> +
> +	mutex_unlock(&data->input_dev->mutex);
> +
> +	return error;
> +}
> +
> +static const struct dev_pm_ops fts_dev_pm_ops = {
> +	.suspend = fts_pm_suspend,
> +	.resume = fts_pm_resume,
> +};
> +
> +static const struct of_device_id fts_match_table[] = {
> +	{ .compatible = "focaltech,fts5452", },
> +	{ .compatible = "focaltech,fts8719", },
> +	{ /* sentinel */ },
> +};
> +
> +MODULE_DEVICE_TABLE(of, fts_match_table);
> +
> +static struct i2c_driver fts_ts_driver = {
> +	.probe_new = fts_ts_probe,
> +	.driver = {
> +		.name = FTS_DRIVER_NAME,
> +		.pm = &fts_dev_pm_ops,
> +		.of_match_table = fts_match_table,
> +	},
> +};
> +module_i2c_driver(fts_ts_driver);
> +
> +MODULE_AUTHOR("Joel Selvaraj <joelselvaraj.oss@...il.com>");
> +MODULE_AUTHOR("Caleb Connolly <caleb@...nolly.tech>");
> +MODULE_DESCRIPTION("FocalTech touchscreen Driver");
> +MODULE_LICENSE("GPL");
- Markuss

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