Re: [PATCH 3/3] input/touchscreen: Add Hynitron cstxxx touchscreen

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

Hi Chris,

On Wed, Sep 28, 2022 at 04:48:06PM -0500, Chris Morgan wrote:
> From: Chris Morgan <macromorgan@hotmail.com>
> 
> Add support for the Hynitron cst3xx controller found on devices such
> as the Anbernic RG353P and RG353V (the Hynitron CST348). This driver
> was built from sources provided by Hynitron to Anbernic (possibly
> via Rockchip as an intermediary) and marked as GPLv2 in the code.
> This driver was written strictly for the cst3xx series, but in
> most places was left somewhat generic so support could be easily
> added to other devices in the future.

Thank you for the patches. This looks generally good, just a few
suggestions below.

> 
> Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
> ---
>  drivers/input/touchscreen/Kconfig           |  12 +
>  drivers/input/touchscreen/Makefile          |   1 +
>  drivers/input/touchscreen/hynitron_cstxxx.c | 483 ++++++++++++++++++++
>  3 files changed, 496 insertions(+)
>  create mode 100644 drivers/input/touchscreen/hynitron_cstxxx.c
> 
> diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
> index 2d70c945b20a..9a9528e59c36 100644
> --- a/drivers/input/touchscreen/Kconfig
> +++ b/drivers/input/touchscreen/Kconfig
> @@ -422,6 +422,18 @@ config TOUCHSCREEN_HYCON_HY46XX
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called hycon-hy46xx.
>  
> +config TOUCHSCREEN_HYNITRON_CSTXXX
> +	tristate "Hynitron touchscreen support"
> +	depends on I2C
> +	help
> +	  Say Y here if you have a touchscreen using a Hynitron
> +	  touchscreen controller.
> +
> +	  If unsure, say N.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called hynitron-cstxxx.
> +
>  config TOUCHSCREEN_ILI210X
>  	tristate "Ilitek ILI210X based touchscreen"
>  	depends on I2C
> diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
> index 557f84fd2075..43860ca19b98 100644
> --- a/drivers/input/touchscreen/Makefile
> +++ b/drivers/input/touchscreen/Makefile
> @@ -47,6 +47,7 @@ obj-$(CONFIG_TOUCHSCREEN_EXC3000)	+= exc3000.o
>  obj-$(CONFIG_TOUCHSCREEN_FUJITSU)	+= fujitsu_ts.o
>  obj-$(CONFIG_TOUCHSCREEN_GOODIX)	+= goodix_ts.o
>  obj-$(CONFIG_TOUCHSCREEN_HIDEEP)	+= hideep.o
> +obj-$(CONFIG_TOUCHSCREEN_HYNITRON_CSTXXX)	+= hynitron_cstxxx.o
>  obj-$(CONFIG_TOUCHSCREEN_ILI210X)	+= ili210x.o
>  obj-$(CONFIG_TOUCHSCREEN_ILITEK)	+= ilitek_ts_i2c.o
>  obj-$(CONFIG_TOUCHSCREEN_IMAGIS)	+= imagis.o
> diff --git a/drivers/input/touchscreen/hynitron_cstxxx.c b/drivers/input/touchscreen/hynitron_cstxxx.c
> new file mode 100644
> index 000000000000..e963968593c3
> --- /dev/null
> +++ b/drivers/input/touchscreen/hynitron_cstxxx.c
> @@ -0,0 +1,483 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + *  Driver for Hynitron cstxxx Touchscreen
> + *
> + *  Copyright (c) 2022 Chris Morgan <macromorgan@hotmail.com>
> + *
> + *  This code is based on hynitron_core.c authored by Hynitron.
> + *  Note that no datasheet was available, so much of these registers
> + *  are undocumented. This is essentially a cleaned-up version of the
> + *  vendor driver with support removed for hardware I cannot test and
> + *  device-specific functions replated with generic functions wherever
> + *  possible.
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/gpio.h>
> +#include <linux/i2c.h>
> +#include <linux/input.h>
> +#include <linux/input/mt.h>
> +#include <linux/input/touchscreen.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +
> +/* Per device data */
> +struct hynitron_ts_platform_data {

This better be called hynitron_ts_chip as we call "platform data"
something that differs per-board, not per-chip version.

> +	unsigned int max_touch_num;
> +	u32 ic_chkcode;
> +	int (*firmware_info)(struct i2c_client *client);
> +	int (*bootloader_enter)(struct i2c_client *client);
> +	int (*init_input)(struct i2c_client *client);
> +	void (*report_touch)(struct i2c_client *client);
> +};
> +
> +/* Data generic to all (supported and non-supported) controllers. */
> +struct hynitron_ts_data {
> +	const struct hynitron_ts_platform_data *pdata;
> +	struct i2c_client *client;
> +	struct device *dev;

Not sure if this really needed as I think everywhere you use it you also
have "client->dev" available.

> +	struct input_dev *input_dev;
> +	struct touchscreen_properties prop;
> +	struct gpio_desc *reset_gpio;
> +	struct gpio_desc *irq_gpio;

I do not believe this field is being used.

> +	u32 fw_version;
> +};
> +
> +/*
> + * Hard coded reset delay value of 20ms not IC dependent in
> + * vendor driver.
> + */
> +void hyn_reset_proc(struct i2c_client *client, int delay)
> +{
> +	struct hynitron_ts_data *ts_data = i2c_get_clientdata(client);
> +
> +	gpiod_set_value(ts_data->reset_gpio, 1);
> +	mdelay(20);
> +	gpiod_set_value(ts_data->reset_gpio, 0);

I think you can use gpiod_set_value_cansleep() in both places.

> +	if (delay)
> +		mdelay(delay);
> +}
> +
> +static irqreturn_t hyn_interrupt_handler(int irq, void *dev_id)
> +{
> +	struct i2c_client *client = dev_id;
> +	struct hynitron_ts_data *ts_data = i2c_get_clientdata(client);
> +
> +	ts_data->pdata->report_touch(client);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +/*
> + * The vendor driver would retry twice before failing to read or write
> + * to the i2c device.
> + */
> +int cst3xx_i2c_read(struct i2c_client *client,
> +		    unsigned char *buf, int len)
> +{
> +	int ret;
> +	int retries = 0;
> +
> +	while (retries < 2) {
> +		ret = i2c_master_recv(client, buf, len);
> +		if (ret <= 0)
> +			retries++;
> +		else
> +			break;
> +	}
> +
> +	return ret;

I like when functions return 0 or negative, not positive (when
possible). So I wonder if we should do something like:

	if (ret == len)
		return 0;

	return ret < 0 ? ret : -EIO;

and then in callers we can do:

	error = cst3xx_i2c_read(...)
	if (error)
		...

> +}
> +
> +int cst3xx_i2c_write(struct i2c_client *client,
> +		     unsigned char *buf, int len)
> +{
> +	int ret;
> +	int retries = 0;
> +
> +	while (retries < 2) {
> +		ret = i2c_master_send(client, buf, len);
> +		if (ret <= 0)
> +			retries++;
> +		else
> +			break;
> +	}
> +
> +	return ret;
> +}
> +
> +int cst3xx_i2c_read_register(struct i2c_client *client,
> +			     unsigned char *buf, int len)

Why don't you have register as a separate u16 argument and then use
cpu_to_le16[p] to convert to on-wire format.

> +{
> +	int ret;
> +
> +	ret = cst3xx_i2c_write(client, buf, 2);
> +	ret = cst3xx_i2c_read(client, buf, len);

This clobbers errors from writing register. I also wonder if you can
use i2c_transfer with 2 messages, one for writing register, and another
for reading data.

> +
> +	return ret;
> +}
> +
> +int cst3xx_firmware_info(struct i2c_client *client)
> +{
> +	struct hynitron_ts_data *ts_data = i2c_get_clientdata(client);
> +	int ret;
> +	u32 tmp;
> +	unsigned char buf[4];
> +
> +	/*
> +	 * Testing suggests command is required to allow reading of
> +	 * firmware registers.
> +	 */
> +	buf[0] = 0xd1;
> +	buf[1] = 0x01;

I wonder if we can define some symbolic names for these.

> +	ret = cst3xx_i2c_write(client, buf, 2);

This looks like a candidate for

	error = cst3xx_i2c_send_command(client, 0x01d1);

helper that would wrap cst3xx_i2c_write.

> +	if (ret < 0)
> +		return -EIO;
> +
> +	mdelay(10);
> +
> +	/*
> +	 * Read register for check-code to determine if device detected
> +	 * correctly.
> +	 */
> +	buf[0] = 0xd1;
> +	buf[1] = 0xfc;
> +	ret = cst3xx_i2c_read_register(client, buf, 4);
> +	if (ret < 0)
> +		return -EIO;
> +
> +	memcpy(&tmp, buf, 4);
> +	if ((le32_to_cpu(tmp) & 0xffff0000) != ts_data->pdata->ic_chkcode) {
> +		dev_err(&client->dev, "%s ic mismatch\n", __func__);
> +		return -ENODEV;
> +	}
> +
> +	mdelay(10);
> +
> +	/* Read firmware version and test if firmware missing. */
> +	buf[0] = 0xd2;
> +	buf[1] = 0x08;
> +	ret = cst3xx_i2c_read_register(client, buf, 4);
> +	if (ret < 0)
> +		return -EIO;
> +
> +	memcpy(&tmp, buf, 4);
> +
> +	ts_data->fw_version = le32_to_cpu(tmp);
> +	if (ts_data->fw_version == 0xa5a5a5a5) {
> +		dev_err(&client->dev, "Device firmware missing\n");
> +		return -ENODEV;
> +	}
> +
> +	/*
> +	 * Testing suggests command required to exit register reading mode
> +	 * and allow device to function as touchscreen.
> +	 */
> +	buf[0] = 0xd1;
> +	buf[1] = 0x09;
> +	ret = cst3xx_i2c_write(client, buf, 2);
> +	if (ret < 0)
> +		return -EIO;
> +
> +	mdelay(5);
> +
> +	return 0;
> +}
> +
> +int cst3xx_bootloader_enter(struct i2c_client *client)
> +{
> +	int ret;
> +	u8 retry;
> +	unsigned char buf[4];
> +
> +	for (retry = 0; retry < 5; retry++) {
> +		hyn_reset_proc(client, (7 + retry));
> +		/* set cmd to enter program mode */
> +		buf[0] = 0xa0;
> +		buf[1] = 0x01;
> +		buf[2] = 0xaa;
> +		ret = cst3xx_i2c_write(client, buf, 3);
> +		if (ret < 0)
> +			continue;
> +		mdelay(2);
> +
> +		/* check whether in program mode */
> +		buf[0] = 0xa0;
> +		buf[1] = 0x02;
> +		ret = cst3xx_i2c_read_register(client, buf, 1);
> +
> +		if (ret < 0)
> +			continue;
> +
> +		if (buf[0] == 0xac)
> +			break;
> +	}
> +
> +	if (buf[0] != 0xac) {
> +		dev_err(&client->dev, "%s unable to enter bootloader mode\n",
> +			__func__);
> +		return -ENODEV;
> +	}
> +
> +	hyn_reset_proc(client, 40);
> +
> +	return 0;
> +}
> +
> +static void cst3xx_touch_update(struct hynitron_ts_data *ts_data, s32 id,
> +				s32 x, s32 y, s32 w)
> +{
> +	input_mt_slot(ts_data->input_dev, id);
> +	input_mt_report_slot_state(ts_data->input_dev, MT_TOOL_FINGER, 1);
> +	touchscreen_report_pos(ts_data->input_dev, &ts_data->prop, x, y, true);
> +	input_report_abs(ts_data->input_dev, ABS_MT_TOUCH_MAJOR, w);
> +}
> +
> +int cst3xx_finish_touch_read(struct i2c_client *client)
> +{
> +	struct hynitron_ts_data *ts_data = i2c_get_clientdata(client);
> +	unsigned char buf[3];
> +	int ret;
> +
> +	buf[0] = 0xd0;
> +	buf[1] = 0x00;
> +	buf[2] = 0xab;
> +	ret = cst3xx_i2c_write(ts_data->client, buf, 3);
> +	if (ret < 0) {
> +		dev_err(ts_data->dev, "send read touch info ending failed.\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +/*
> + * Handle events from IRQ. Note that for cst3xx it appears that IRQ
> + * fires continuously while touched, otherwise once every 1500ms
> + * when not touched (assume touchscreen waking up periodically).
> + */
> +static void cst3xx_touch_report(struct i2c_client *client)
> +{
> +	struct hynitron_ts_data *ts_data = i2c_get_clientdata(client);
> +	unsigned char buf[30];
> +	unsigned char finger_id, sw;
> +	unsigned int input_x = 0;
> +	unsigned int input_y = 0;
> +	unsigned int input_w = 0;
> +	int idx = 0;
> +	int i, ret;
> +	int touch_cnt, i2c_len;
> +
> +	buf[0] = 0xd0;
> +	buf[1] = 0x00;
> +
> +	/* Read and validate the first bits of input data. */
> +	ret = cst3xx_i2c_read_register(ts_data->client, buf, 7);
> +	if ((ret < 0) || (buf[6] != 0xab) || (buf[0] == 0xab))
> +		goto end;
> +
> +	touch_cnt = buf[5] & 0x7f;
> +
> +	/* If no touches registered, clear the input slots. */
> +	if (touch_cnt == 0) {
> +		input_mt_sync_frame(ts_data->input_dev);
> +		input_sync(ts_data->input_dev);
> +		return;
> +	}
> +
> +	/*
> +	 * If we have only one touch, we have enough data to process
> +	 * the event. If we have more than one touch we need to read
> +	 * the rest of the data. Note these functions are not combined
> +	 * because this is how it was done in the vendor driver and I
> +	 * lack the datasheet to modify the necessary values for
> +	 * reading from all the registers at once.
> +	 */
> +	if (touch_cnt > 1) {
> +		buf[5] = 0xd0;
> +		buf[6] = 0x07;
> +		i2c_len = (touch_cnt - 1) * 5 + 1;
> +		ret = cst3xx_i2c_read_register(ts_data->client,
> +					       &buf[5], i2c_len);
> +		if (ret < 0)
> +			goto end;
> +		i2c_len += 5;
> +
> +		if (buf[i2c_len - 1] != 0xab)
> +			goto end;
> +	}
> +
> +	ret = cst3xx_finish_touch_read(client);

Do we have to do this here? Can we jump to "end" label? The function
looks a bit messy.

> +	if (ret < 0) {
> +		dev_err(ts_data->dev, "cst3xx touch read failure\n");
> +		return;
> +	}
> +
> +	for (i = 0; i < touch_cnt; i++) {
> +		input_x = ((buf[idx + 1] << 4) | ((buf[idx + 3] >> 4) & 0x0f));
> +		input_y = ((buf[idx + 2] << 4) | (buf[idx + 3] & 0x0f));
> +		input_w = (buf[idx + 4] >> 3);
> +		sw = (buf[idx] & 0x0f) >> 1;
> +		finger_id = (buf[idx] >> 4) & 0x0f;
> +
> +		/* Sanity check we don't have more fingers than we expect */
> +		if (ts_data->pdata->max_touch_num < finger_id) {
> +			dev_err(ts_data->dev, "cst3xx touch read failure\n");
> +			break;
> +		}
> +
> +		/* sw value of 0 means no touch, 0x03 means touch */
> +		if (sw == 0x03)
> +			cst3xx_touch_update(ts_data, finger_id,
> +					    input_x, input_y, input_w);
> +
> +		idx += 5;
> +	}
> +
> +	input_mt_sync_frame(ts_data->input_dev);
> +	input_sync(ts_data->input_dev);
> +	return;
> +end:
> +	cst3xx_finish_touch_read(client);
> +	dev_err(ts_data->dev, "cst3xx touch read failure\n");
> +}
> +
> +int cst3xx_input_dev_int(struct i2c_client *client)
> +{
> +	struct hynitron_ts_data *ts_data = i2c_get_clientdata(client);
> +	int ret = 0;

Call this variable "error" and not initialize to 0.

> +
> +	ts_data->input_dev = devm_input_allocate_device(&ts_data->client->dev);
> +	if (!ts_data->input_dev) {
> +		dev_err(&ts_data->client->dev,
> +			"Failed to allocate input device.\n");
> +		return -ENOMEM;
> +	}
> +
> +	ts_data->input_dev->name = "Hynitron cst3xx Touchscreen";
> +	ts_data->input_dev->phys = "input/ts";
> +	ts_data->input_dev->id.bustype = BUS_I2C;
> +	ts_data->input_dev->dev.parent = ts_data->dev;

No need to set parent because devm_input_allocate_device() does this for
us.

> +
> +	input_set_drvdata(ts_data->input_dev, ts_data);
> +
> +	input_set_capability(ts_data->input_dev, EV_ABS, ABS_MT_POSITION_X);
> +	input_set_capability(ts_data->input_dev, EV_ABS, ABS_MT_POSITION_Y);
> +	input_set_abs_params(ts_data->input_dev, ABS_MT_TOUCH_MAJOR,
> +			     0, 255, 0, 0);
> +
> +	touchscreen_parse_properties(ts_data->input_dev, true, &ts_data->prop);
> +
> +	if (!ts_data->prop.max_x || !ts_data->prop.max_y) {
> +		dev_err(&ts_data->client->dev,
> +			"Invalid x/y (%d, %d), using defaults\n",
> +			ts_data->prop.max_x, ts_data->prop.max_y);
> +		ts_data->prop.max_x = 1152;
> +		ts_data->prop.max_y = 1920;
> +		input_abs_set_max(ts_data->input_dev,
> +				  ABS_MT_POSITION_X, ts_data->prop.max_x);
> +		input_abs_set_max(ts_data->input_dev,
> +				  ABS_MT_POSITION_Y, ts_data->prop.max_y);
> +	}
> +
> +	input_mt_init_slots(ts_data->input_dev, ts_data->pdata->max_touch_num,
> +			    INPUT_MT_DIRECT | INPUT_MT_DROP_UNUSED);

This mat fail so please handle errors here too.

> +
> +	ret = input_register_device(ts_data->input_dev);
> +	if (ret < 0) {
> +		dev_err(&ts_data->client->dev,
> +			"Input device registration failed\n");
> +		return ret;
> +	}
> +
> +	return ret;

	return 0;

> +}
> +
> +static int hyn_probe(struct i2c_client *client)
> +{
> +	struct hynitron_ts_data *ts_data;
> +	int ret;

Call this variable "error" please.

> +
> +	ts_data = devm_kzalloc(&client->dev, sizeof(*ts_data), GFP_KERNEL);
> +	if (!ts_data)
> +		return -ENOMEM;
> +
> +	ts_data->client = client;
> +	ts_data->dev = &client->dev;
> +	i2c_set_clientdata(client, ts_data);
> +
> +	ts_data->reset_gpio = devm_gpiod_get(&client->dev,
> +					     "reset", GPIOD_OUT_LOW);

I've become fond of:

	error = PTR_ERR_OR_ZERO(ts_data->reset_gpio);

> +	if (IS_ERR(ts_data->reset_gpio)) {
> +		ret = PTR_ERR(ts_data->reset_gpio);
> +		dev_err(&client->dev, "request reset gpio failed: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ts_data->pdata = of_device_get_match_data(&client->dev);
> +	if (!ts_data->pdata)
> +		return -EINVAL;
> +
> +	hyn_reset_proc(client, 60);
> +
> +	ret = ts_data->pdata->bootloader_enter(client);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = ts_data->pdata->init_input(client);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = ts_data->pdata->firmware_info(client);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = devm_request_threaded_irq(&client->dev, client->irq, NULL,
> +					hyn_interrupt_handler,
> +					IRQF_ONESHOT,
> +					"Hynitron Touch Int", client);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "failed to request IRQ\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct hynitron_ts_platform_data cst3xx_data = {
> +	.max_touch_num		= 5,
> +	.ic_chkcode		= 0xcaca0000,
> +	.firmware_info		= &cst3xx_firmware_info,
> +	.bootloader_enter	= &cst3xx_bootloader_enter,
> +	.init_input		= &cst3xx_input_dev_int,
> +	.report_touch		= &cst3xx_touch_report,
> +};
> +
> +static const struct i2c_device_id hyn_tpd_id[] = {
> +	{ .name = "hynitron_ts", 0 },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(i2c, hyn_tpd_id);
> +
> +static const struct of_device_id hyn_dt_match[] = {
> +	{ .compatible = "hynitron,cst3xx", .data = &cst3xx_data },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, hyn_dt_match);
> +
> +static struct i2c_driver hynitron_i2c_driver = {
> +	.driver = {
> +		.name = "Hynitron-TS",
> +		.of_match_table = of_match_ptr(hyn_dt_match),
> +		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
> +	},
> +	.id_table = hyn_tpd_id,
> +	.probe_new = hyn_probe,
> +};
> +
> +module_i2c_driver(hynitron_i2c_driver);
> +
> +MODULE_AUTHOR("Chris Morgan");
> +MODULE_DESCRIPTION("Hynitron Touchscreen Driver");
> +MODULE_LICENSE("GPL");
> -- 
> 2.25.1
> 

Thanks.

-- 
Dmitry