Date:   Thu, 3 Mar 2022 23:11:27 -0600
From:   Jeff LaBundy <jeff@...undy.com>
To:     Markuss Broks <markuss.broks@...il.com>
Cc:     linux-kernel@...r.kernel.org, phone-devel@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht, dmitry.torokhov@...il.com,
        robh+dt@...nel.org, krzysztof.kozlowski@...onical.com,
        rydberg@...math.com, sfr@...b.auug.org.au,
        linux-input@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v9 2/2] Input: add Imagis touchscreen driver

Hi Markuss,

Great work driving this one to the finish line. I caught four remaining
minor items; once they are fixed for v10, please feel free to add my:

Reviewed-by: Jeff LaBundy <jeff@...undy.com>

On Thu, Mar 03, 2022 at 06:31:33PM +0200, Markuss Broks wrote:
> Add support for the IST3038C touchscreen IC from Imagis, based on
> downstream driver. The driver supports multi-touch (10 touch points)
> The IST3038C IC supports touch keys, but the support isn't added
> because the touch screen used for testing doesn't utilize touch keys.
> Looking at the downstream driver, it is possible to add support
> for other Imagis ICs of IST30**C series.
> 
> Signed-off-by: Markuss Broks <markuss.broks@...il.com>
> ---
>  MAINTAINERS                        |   6 +
>  drivers/input/touchscreen/Kconfig  |  10 +
>  drivers/input/touchscreen/Makefile |   1 +
>  drivers/input/touchscreen/imagis.c | 331 +++++++++++++++++++++++++++++
>  4 files changed, 348 insertions(+)
>  create mode 100644 drivers/input/touchscreen/imagis.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d7ea92ce1b1d..feab0c765d4b 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -9509,6 +9509,12 @@ M:	Stanislaw Gruszka <stf_xl@...pl>
>  S:	Maintained
>  F:	drivers/usb/atm/ueagle-atm.c
>  
> +IMAGIS TOUCHSCREEN DRIVER
> +M:	Markuss Broks <markuss.broks@...il.com>
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/input/touchscreen/imagis,ist3038c.yaml
> +F:	drivers/input/touchscreen/imagis.c
> +
>  IMGTEC ASCII LCD DRIVER
>  M:	Paul Burton <paulburton@...nel.org>
>  S:	Maintained
> diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
> index 2f6adfb7b938..f1414f0ad7af 100644
> --- a/drivers/input/touchscreen/Kconfig
> +++ b/drivers/input/touchscreen/Kconfig
> @@ -638,6 +638,16 @@ config TOUCHSCREEN_MTOUCH
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called mtouch.
>  
> +config TOUCHSCREEN_IMAGIS
> +	tristate "Imagis touchscreen support"
> +	depends on I2C
> +	help
> +	  Say Y here if you have an Imagis IST30xxC touchscreen.
> +	  If unsure, say N.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called imagis.
> +
>  config TOUCHSCREEN_IMX6UL_TSC
>  	tristate "Freescale i.MX6UL touchscreen controller"
>  	depends on ((OF && GPIOLIB) || COMPILE_TEST) && HAS_IOMEM
> diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
> index 39a8127cf6a5..557f84fd2075 100644
> --- a/drivers/input/touchscreen/Makefile
> +++ b/drivers/input/touchscreen/Makefile
> @@ -49,6 +49,7 @@ obj-$(CONFIG_TOUCHSCREEN_GOODIX)	+= goodix_ts.o
>  obj-$(CONFIG_TOUCHSCREEN_HIDEEP)	+= hideep.o
>  obj-$(CONFIG_TOUCHSCREEN_ILI210X)	+= ili210x.o
>  obj-$(CONFIG_TOUCHSCREEN_ILITEK)	+= ilitek_ts_i2c.o
> +obj-$(CONFIG_TOUCHSCREEN_IMAGIS)	+= imagis.o
>  obj-$(CONFIG_TOUCHSCREEN_IMX6UL_TSC)	+= imx6ul_tsc.o
>  obj-$(CONFIG_TOUCHSCREEN_INEXIO)	+= inexio.o
>  obj-$(CONFIG_TOUCHSCREEN_IPROC)		+= bcm_iproc_tsc.o
> diff --git a/drivers/input/touchscreen/imagis.c b/drivers/input/touchscreen/imagis.c
> new file mode 100644
> index 000000000000..5776bd5c0422
> --- /dev/null
> +++ b/drivers/input/touchscreen/imagis.c
> @@ -0,0 +1,331 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include <linux/bits.h>
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/input.h>
> +#include <linux/input/mt.h>
> +#include <linux/input/touchscreen.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/property.h>
> +#include <linux/regulator/consumer.h>
> +
> +#define IST3038C_HIB_ACCESS		(0x800B << 16)
> +#define IST3038C_DIRECT_ACCESS		BIT(31)
> +#define IST3038C_REG_CHIPID		0x40001000
> +#define IST3038C_REG_HIB_BASE		0x30000100
> +#define IST3038C_REG_TOUCH_STATUS		(IST3038C_REG_HIB_BASE | IST3038C_HIB_ACCESS)
> +#define IST3038C_REG_TOUCH_COORD		(IST3038C_REG_HIB_BASE | IST3038C_HIB_ACCESS | 0x8)
> +#define IST3038C_REG_INTR_MESSAGE		(IST3038C_REG_HIB_BASE | IST3038C_HIB_ACCESS | 0x4)
> +#define IST3038C_WHOAMI			0x38c
> +#define IST3038C_CHIP_ON_DELAY_MS		60
> +#define IST3038C_I2C_RETRY_COUNT		3
> +#define IST3038C_MAX_SUPPORTED_FINGER_NUM		10
> +#define IST3038C_X_MASK		GENMASK(23, 12)
> +#define IST3038C_X_SHIFT		12
> +#define IST3038C_Y_MASK		GENMASK(11, 0)
> +#define IST3038C_AREA_MASK		GENMASK(27, 24)
> +#define IST3038C_AREA_SHIFT		24
> +#define IST3038C_FINGER_COUNT_MASK		GENMASK(15, 12)
> +#define IST3038C_FINGER_COUNT_SHIFT		12
> +#define IST3038C_FINGER_STATUS_MASK		GENMASK(9, 0)
> +
> +struct imagis_ts {
> +	struct i2c_client *client;
> +	struct input_dev *input_dev;
> +	struct touchscreen_properties prop;
> +	struct regulator_bulk_data supplies[2];
> +};
> +
> +static int imagis_i2c_read_reg(struct imagis_ts *ts,
> +			       unsigned int reg, unsigned int *buffer)
> +{
> +	__be32 ret_be;
> +	__be32 reg_be = cpu_to_be32(reg);
> +	struct i2c_msg msg[] = {
> +		{
> +			.addr = ts->client->addr,
> +			.flags = 0,
> +			.buf = (unsigned char *)&reg_be,
> +			.len = sizeof(reg_be),
> +		}, {
> +			.addr = ts->client->addr,
> +			.flags = I2C_M_RD,
> +			.buf = (unsigned char *)&ret_be,
> +			.len = sizeof(ret_be),
> +		},
> +	};
> +	int ret, error;
> +	int retry = IST3038C_I2C_RETRY_COUNT;
> +
> +	/* Retry in case the controller fails to respond */
> +	do {
> +		ret = i2c_transfer(ts->client->adapter, msg, ARRAY_SIZE(msg));
> +		if (ret == ARRAY_SIZE(msg)) {
> +			*buffer = be32_to_cpu(ret_be);
> +			return 0;
> +		}
> +
> +		error = ret < 0 ? ret : -EIO;
> +		dev_err(&ts->client->dev,
> +			"%s - i2c_transfer failed: %d (%d)\n",
> +			__func__, error, ret);
> +	} while (--retry);
> +
> +	return error;
> +}
> +
> +static irqreturn_t imagis_interrupt(int irq, void *dev_id)
> +{
> +	struct imagis_ts *ts = dev_id;
> +	unsigned int finger_status, intr_message;
> +	int error, i, finger_count, finger_pressed;
> +
> +	error = imagis_i2c_read_reg(ts, IST3038C_REG_INTR_MESSAGE, &intr_message);
> +	if (error) {
> +		dev_err(&ts->client->dev, "failed to read the interrupt message\n");
> +		return IRQ_HANDLED;
> +	}
> +
> +	finger_count = (intr_message & IST3038C_FINGER_COUNT_MASK) >> IST3038C_FINGER_COUNT_SHIFT;
> +	finger_pressed = intr_message & IST3038C_FINGER_STATUS_MASK;
> +	if (finger_count > IST3038C_MAX_SUPPORTED_FINGER_NUM) {
> +		dev_err(&ts->client->dev, "finger count is more than maximum supported\n");
> +		return IRQ_HANDLED;
> +	}
> +
> +	for (i = 0; i < finger_count; i++) {
> +		error = imagis_i2c_read_reg(ts, IST3038C_REG_TOUCH_COORD + (i * 4), &finger_status);
> +		if (error) {
> +			dev_err(&ts->client->dev, "failed to read coordinates for finger %d\n", i);
> +			return IRQ_HANDLED;
> +		}
> +		input_mt_slot(ts->input_dev, i);
> +		input_mt_report_slot_state(ts->input_dev, MT_TOOL_FINGER,
> +					   finger_pressed & BIT(i));
> +		touchscreen_report_pos(ts->input_dev, &ts->prop,
> +				       (finger_status & IST3038C_X_MASK) >> IST3038C_X_SHIFT,
> +				       finger_status & IST3038C_Y_MASK, 1);
> +		input_report_abs(ts->input_dev, ABS_MT_TOUCH_MAJOR,
> +				 (finger_status & IST3038C_AREA_MASK) >> IST3038C_AREA_SHIFT);
> +	}
> +	input_mt_sync_frame(ts->input_dev);
> +	input_sync(ts->input_dev);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static void imagis_power_off(void *_ts)
> +{
> +	struct imagis_ts *ts = _ts;
> +
> +	regulator_bulk_disable(ARRAY_SIZE(ts->supplies), ts->supplies);
> +}
> +
> +static int imagis_power_on(struct imagis_ts *ts)
> +{
> +	int error;
> +
> +	error = regulator_bulk_enable(ARRAY_SIZE(ts->supplies), ts->supplies);

Please update as follows:

        error = regulator_bulk_enable(...);
        if (error)
                return error;

        msleep(...);

        return 0;

If the regulators failed to be enabled and the driver needs to bail, there
is no reason to sleep before doing so.

> +	msleep(IST3038C_CHIP_ON_DELAY_MS);
> +
> +	return error;
> +}
> +
> +static int imagis_start(struct imagis_ts *ts)
> +{
> +	int error;
> +
> +	error = imagis_power_on(ts);
> +	if (error)
> +		return error;
> +
> +	msleep(IST3038C_CHIP_ON_DELAY_MS);

This same delay is already administered from imagis_power_on(); I assume it
is a duplicate?

> +
> +	enable_irq(ts->client->irq);
> +	return error;

Nit: error would only ever be zero by this point, so consider simply returning
zero as you have done in imagis_stop() below.

> +}
> +
> +static int imagis_stop(struct imagis_ts *ts)
> +{
> +	disable_irq(ts->client->irq);
> +
> +	imagis_power_off(ts);
> +
> +	return 0;
> +}
> +
> +static int imagis_input_open(struct input_dev *dev)
> +{
> +	struct imagis_ts *ts = input_get_drvdata(dev);
> +
> +	return imagis_start(ts);
> +}
> +
> +static void imagis_input_close(struct input_dev *dev)
> +{
> +	struct imagis_ts *ts = input_get_drvdata(dev);
> +
> +	imagis_stop(ts);
> +}
> +
> +static int imagis_init_input_dev(struct imagis_ts *ts)
> +{
> +	struct input_dev *input_dev;
> +	int error;
> +
> +	input_dev = devm_input_allocate_device(&ts->client->dev);
> +	if (!input_dev)
> +		return -ENOMEM;
> +
> +	ts->input_dev = input_dev;
> +
> +	input_dev->name = "Imagis capacitive touchscreen";
> +	input_dev->phys = "input/ts";
> +	input_dev->id.bustype = BUS_I2C;
> +	input_dev->open = imagis_input_open;
> +	input_dev->close = imagis_input_close;
> +
> +	input_set_drvdata(input_dev, ts);
> +
> +	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);
> +
> +	touchscreen_parse_properties(input_dev, true, &ts->prop);
> +	if (!ts->prop.max_x || !ts->prop.max_y) {
> +		dev_err(&ts->client->dev,
> +			"Touchscreen-size-x and/or touchscreen-size-y not set in dts\n");
> +		return -EINVAL;
> +	}
> +
> +	error = input_mt_init_slots(input_dev, IST3038C_MAX_SUPPORTED_FINGER_NUM,
> +				    INPUT_MT_DIRECT | INPUT_MT_DROP_UNUSED);
> +	if (error) {
> +		dev_err(&ts->client->dev,
> +			"Failed to initialize MT slots: %d", error);
> +		return error;
> +	}
> +
> +	error = input_register_device(input_dev);
> +	if (error)
> +		dev_err(&ts->client->dev,
> +			"Failed to register input device: %d", error);
> +
> +	return error;
> +}
> +
> +static int imagis_init_regulators(struct imagis_ts *ts)
> +{
> +	struct i2c_client *client = ts->client;
> +
> +	ts->supplies[0].supply = "vdd";
> +	ts->supplies[1].supply = "vddio";
> +	return devm_regulator_bulk_get(&client->dev,
> +				       ARRAY_SIZE(ts->supplies),
> +				       ts->supplies);
> +
> +}
> +
> +static int imagis_probe(struct i2c_client *i2c)
> +{
> +	struct device *dev = &i2c->dev;
> +	struct imagis_ts *ts;
> +	int chip_id, error;
> +
> +	ts = devm_kzalloc(dev, sizeof(*ts), GFP_KERNEL);
> +	if (!ts)
> +		return -ENOMEM;
> +
> +	ts->client = i2c;
> +
> +	error = imagis_init_regulators(ts);
> +	if (error)
> +		return dev_err_probe(dev, error, "regulator init error: %d\n", error);
> +
> +	error = devm_add_action_or_reset(dev, imagis_power_off, ts);
> +	if (error)
> +		return dev_err_probe(dev, error, "failed to install poweroff action: %d\n", error);

Note that devm_add_action_or_reset() is special in that if it fails, it
will call the callback which is imagis_power_off().

In this case, you would disable regulators before they have even been
enabled which will cause a stack dump. To solve this problem, move the
call to devm_add_action_or_reset() from here, to...

> +
> +	error = imagis_power_on(ts);
> +	if (error)
> +		return dev_err_probe(dev, error, "failed to enable regulators: %d\n", error);

...here.

> +
> +	error = imagis_i2c_read_reg(ts, IST3038C_REG_CHIPID | IST3038C_DIRECT_ACCESS, &chip_id);
> +	if (error)
> +		return dev_err_probe(dev, error, "chip ID read failure: %d\n", error);
> +
> +	if (chip_id != IST3038C_WHOAMI)
> +		return dev_err_probe(dev, -EINVAL, "unknown chip ID: 0x%x\n", chip_id);
> +
> +	error = devm_request_threaded_irq(dev, i2c->irq,
> +					  NULL, imagis_interrupt,
> +					  IRQF_ONESHOT | IRQF_NO_AUTOEN,
> +					  "imagis-touchscreen", ts);
> +	if (error)
> +		return dev_err_probe(dev, error, "IRQ allocation failure: %d\n", error);
> +
> +	error = imagis_init_input_dev(ts);
> +	if (error)
> +		return dev_err_probe(dev, error, "input subsystem init error: %d\n", error);
> +
> +	return 0;
> +}
> +
> +static int __maybe_unused imagis_suspend(struct device *dev)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct imagis_ts *ts = i2c_get_clientdata(client);
> +	int error = 0;
> +
> +	mutex_lock(&ts->input_dev->mutex);
> +
> +	if (input_device_enabled(ts->input_dev))
> +		error = imagis_stop(ts);
> +
> +	mutex_unlock(&ts->input_dev->mutex);
> +
> +	return error;
> +}
> +
> +static int __maybe_unused imagis_resume(struct device *dev)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct imagis_ts *ts = i2c_get_clientdata(client);
> +	int error = 0;
> +
> +	mutex_lock(&ts->input_dev->mutex);
> +
> +	if (input_device_enabled(ts->input_dev))
> +		error = imagis_start(ts);
> +
> +	mutex_unlock(&ts->input_dev->mutex);
> +
> +	return error;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(imagis_pm_ops, imagis_suspend, imagis_resume);
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id imagis_of_match[] = {
> +	{ .compatible = "imagis,ist3038c", },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, imagis_of_match);
> +#endif
> +
> +static struct i2c_driver imagis_ts_driver = {
> +	.driver = {
> +		.name = "imagis-touchscreen",
> +		.pm = &imagis_pm_ops,
> +		.of_match_table = of_match_ptr(imagis_of_match),
> +	},
> +	.probe_new = imagis_probe,
> +};
> +
> +module_i2c_driver(imagis_ts_driver);
> +
> +MODULE_DESCRIPTION("Imagis IST3038C Touchscreen Driver");
> +MODULE_AUTHOR("Markuss Broks <markuss.broks@...il.com>");
> +MODULE_LICENSE("GPL");
> -- 
> 2.20.1
> 

Kind regards,
Jeff LaBundy

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