Re: [PATCH v4 3/3] touchscreen: colibri-vf50-ts: Add touchscreen support for Colibri VF50

[maitysanchayan]

Hello Dmitry,

On 15-08-21 18:30:57, Dmitry Torokhov wrote:
> Hi Sanchayan,
> 
> On Fri, Aug 21, 2015 at 06:56:32PM +0530, Sanchayan Maity wrote:
> > The Colibri Vybrid VF50 module supports 4-wire touchscreens using
> > FETs and ADC inputs. This driver uses the IIO consumer interface
> > and relies on the vf610_adc driver based on the IIO framework.
> > 
> 
> Thank you for making changes. I have a few comments still.

It has really improved with your comments. Thanks for your feedback.

> 
> > Signed-off-by: Sanchayan Maity <maitysanchayan@xxxxxxxxx>
> > ---
> >  drivers/input/touchscreen/Kconfig           |  12 +
> >  drivers/input/touchscreen/Makefile          |   1 +
> >  drivers/input/touchscreen/colibri-vf50-ts.c | 370 ++++++++++++++++++++++++++++
> >  3 files changed, 383 insertions(+)
> >  create mode 100644 drivers/input/touchscreen/colibri-vf50-ts.c
> > 
> > diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
> > index 80f6386..28948ca 100644
> > --- a/drivers/input/touchscreen/Kconfig
> > +++ b/drivers/input/touchscreen/Kconfig
> > @@ -1027,4 +1027,16 @@ config TOUCHSCREEN_ZFORCE
> >  	  To compile this driver as a module, choose M here: the
> >  	  module will be called zforce_ts.
> >  
> > +config TOUCHSCREEN_COLIBRI_VF50
> > +	tristate "Toradex Colibri on board touchscreen driver"
> > +	depends on GPIOLIB && IIO && VF610_ADC
> 
> Can we possibly add "|| COMPILE_TEST" dependency? Will it compile
> without IIO or VF610_ADC enabled?

I will add and do the checks. It should compile without VF610_ADC
atleast, I don't see how it will without the others. I will check
once at my end also with other configs.

> 
> 
> > +	help
> > +	  Say Y here if you have a Colibri VF50 and plan to use
> > +	  the on-board provided 4-wire touchscreen driver.
> > +
> > +	  If unsure, say N.
> > +
> > +	  To compile this driver as a module, choose M here: the
> > +	  module will be called colibri_vf50_ts.
> > +
> >  endif
> > diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
> > index 44deea7..93746a0 100644
> > --- a/drivers/input/touchscreen/Makefile
> > +++ b/drivers/input/touchscreen/Makefile
> > @@ -84,3 +84,4 @@ obj-$(CONFIG_TOUCHSCREEN_W90X900)	+= w90p910_ts.o
> >  obj-$(CONFIG_TOUCHSCREEN_SX8654)	+= sx8654.o
> >  obj-$(CONFIG_TOUCHSCREEN_TPS6507X)	+= tps6507x-ts.o
> >  obj-$(CONFIG_TOUCHSCREEN_ZFORCE)	+= zforce_ts.o
> > +obj-$(CONFIG_TOUCHSCREEN_COLIBRI_VF50)	+= colibri-vf50-ts.o
> > diff --git a/drivers/input/touchscreen/colibri-vf50-ts.c b/drivers/input/touchscreen/colibri-vf50-ts.c
> > new file mode 100644
> > index 0000000..0793fdc
> > --- /dev/null
> > +++ b/drivers/input/touchscreen/colibri-vf50-ts.c
> > @@ -0,0 +1,370 @@
> > +/* Copyright 2015 Toradex AG
> > + *
> > + * Toradex Colibri VF50 Touchscreen driver
> > + *
> > + * Originally authored by Stefan Agner for 3.0 kernel
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License as published by
> > + * the Free Software Foundation; either version 2 of the License, or
> > + * (at your option) any later version.
> > + */
> > +
> > +#include <linux/delay.h>
> > +#include <linux/err.h>
> > +#include <linux/gpio.h>
> > +#include <linux/iio/consumer.h>
> > +#include <linux/iio/types.h>
> > +#include <linux/input.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/pinctrl/consumer.h>
> 
> Don't you need gpio/consumer.h?

Yes.

> 
> > +#include <linux/platform_device.h>
> > +#include <linux/slab.h>
> > +#include <linux/types.h>
> > +
> > +#define DRIVER_NAME "colibri-vf50-ts"
> > +#define DRV_VERSION "1.0"
> > +
> > +#define VF_ADC_MAX ((1 << 12) - 1)
> > +
> > +#define COLI_TOUCH_MIN_DELAY_US 1000
> > +#define COLI_TOUCH_MAX_DELAY_US 2000
> > +#define COLI_TOUCH_NO_OF_AVGS	5
> > +
> > +struct vf50_touch_device {
> > +	struct platform_device	*pdev;
> > +	struct input_dev	*ts_input;
> > +	struct iio_channel	*channels;
> > +	struct gpio_desc *gpio_xp;
> > +	struct gpio_desc *gpio_xm;
> > +	struct gpio_desc *gpio_yp;
> > +	struct gpio_desc *gpio_ym;
> > +	struct gpio_desc *gpio_pen_detect;
> 
> I do not see gpio_pen_detect being used anymore.

Sorry. My mistake. It needs to be deleted. Will fix.

> 
> > +	int pen_irq;
> > +	int min_pressure;
> > +	bool stop_touchscreen;
> > +};
> > +
> > +/*
> > + * Enables given plates and measures touch parameters using ADC
> > + */
> > +static int adc_ts_measure(struct iio_channel *channel,
> > +		  struct gpio_desc *plate_p, struct gpio_desc *plate_m)
> > +{
> > +	int i, value = 0, val = 0;
> > +	int ret;
> > +
> > +	gpiod_set_value(plate_p, 1);
> > +	gpiod_set_value(plate_m, 1);
> > +
> > +	usleep_range(COLI_TOUCH_MIN_DELAY_US, COLI_TOUCH_MAX_DELAY_US);
> > +
> > +	for (i = 0; i < COLI_TOUCH_NO_OF_AVGS; i++) {
> > +		ret = iio_read_channel_raw(channel, &val);
> > +		if (ret < 0) {
> > +			value = ret;
> > +			goto error_iio_read;
> > +		}
> > +
> > +		value += val;
> > +	}
> > +
> > +	value /= COLI_TOUCH_NO_OF_AVGS;
> > +
> > +error_iio_read:
> > +	gpiod_set_value(plate_p, 0);
> > +	gpiod_set_value(plate_m, 0);
> > +
> > +	return value;
> > +}
> > +
> > +/*
> > + * Enable touch detection using falling edge detection on XM
> > + */
> > +static void vf50_ts_enable_touch_detection(struct vf50_touch_device *vf50_ts)
> > +{
> > +	/* Enable plate YM (needs to be strong GND, high active) */
> > +	gpiod_set_value(vf50_ts->gpio_ym, 1);
> > +
> > +	/*
> > +	 * Let the platform mux to idle state in order to enable
> > +	 * Pull-Up on GPIO
> > +	 */
> > +	pinctrl_pm_select_idle_state(&vf50_ts->pdev->dev);
> > +}
> > +
> > +/*
> > + * ADC touch screen sampling bottom half irq handler
> > + */
> > +static irqreturn_t vf50_ts_irq_bh(int irq, void *private)
> > +{
> > +	struct vf50_touch_device *vf50_ts = (struct vf50_touch_device *)private;
> 
> No need to cast from void * pointer.

Ok.

> 
> > +	struct device *dev = &vf50_ts->pdev->dev;
> > +	int val_x, val_y, val_z1, val_z2, val_p = 0;
> > +	bool discard_val_on_start = true;
> > +
> > +	/* Disable the touch detection plates */
> > +	gpiod_set_value(vf50_ts->gpio_ym, 0);
> > +
> > +	/* Let the platform mux to default state in order to mux as ADC */
> > +	pinctrl_pm_select_default_state(dev);
> > +
> > +	while (!vf50_ts->stop_touchscreen) {
> > +		/* X-Direction */
> > +		val_x = adc_ts_measure(&vf50_ts->channels[0],
> > +				vf50_ts->gpio_xp, vf50_ts->gpio_xm);
> > +		if (val_x < 0)
> > +			break;
> > +
> > +		/* Y-Direction */
> > +		val_y = adc_ts_measure(&vf50_ts->channels[1],
> > +				vf50_ts->gpio_yp, vf50_ts->gpio_ym);
> > +		if (val_y < 0)
> > +			break;
> > +
> > +		/*
> > +		 * Touch pressure
> > +		 * Measure on XP/YM
> > +		 */
> > +		val_z1 = adc_ts_measure(&vf50_ts->channels[2],
> > +				vf50_ts->gpio_yp, vf50_ts->gpio_xm);
> > +		if (val_z1 < 0)
> > +			break;
> > +		val_z2 = adc_ts_measure(&vf50_ts->channels[3],
> > +				vf50_ts->gpio_yp, vf50_ts->gpio_xm);
> > +		if (val_z2 < 0)
> > +			break;
> > +
> > +		/* Validate signal (avoid calculation using noise) */
> > +		if (val_z1 > 64 && val_x > 64) {
> > +			/*
> > +			 * Calculate resistance between the plates
> > +			 * lower resistance means higher pressure
> > +			 */
> > +			int r_x = (1000 * val_x) / VF_ADC_MAX;
> > +
> > +			val_p = (r_x * val_z2) / val_z1 - r_x;
> > +
> > +		} else {
> > +			val_p = 2000;
> > +		}
> > +
> > +		val_p = 2000 - val_p;
> > +		dev_dbg(dev, "Measured values: x: %d, y: %d, z1: %d, z2: %d, "
> > +			"p: %d\n", val_x, val_y, val_z1, val_z2, val_p);
> > +
> > +		/*
> > +		 * If touch pressure is too low, stop measuring and reenable
> > +		 * touch detection
> > +		 */
> > +		if (val_p < vf50_ts->min_pressure || val_p > 2000)
> > +			break;
> > +
> > +		/*
> > +		 * The pressure may not be enough for the first x and the
> > +		 * second y measurement, but, the pressure is ok when the
> > +		 * driver is doing the third and fourth measurement. To
> > +		 * take care of this, we drop the first measurement always.
> > +		 */
> > +		if (discard_val_on_start) {
> > +			discard_val_on_start = false;
> > +		} else {
> > +			/*
> > +			 * Report touch position and sleep for
> > +			 * next measurement
> > +			 */
> > +			input_report_abs(vf50_ts->ts_input,
> > +					ABS_X, VF_ADC_MAX - val_x);
> > +			input_report_abs(vf50_ts->ts_input,
> > +					ABS_Y, VF_ADC_MAX - val_y);
> > +			input_report_abs(vf50_ts->ts_input,
> > +					ABS_PRESSURE, val_p);
> > +			input_report_key(vf50_ts->ts_input, BTN_TOUCH, 1);
> > +			input_sync(vf50_ts->ts_input);
> > +		}
> > +
> > +		msleep(10);
> > +	}
> > +
> > +	/* Report no more touch, reenable touch detection */
> > +	input_report_abs(vf50_ts->ts_input, ABS_PRESSURE, 0);
> > +	input_report_key(vf50_ts->ts_input, BTN_TOUCH, 0);
> > +	input_sync(vf50_ts->ts_input);
> > +
> > +	vf50_ts_enable_touch_detection(vf50_ts);
> > +
> > +	/* Wait for the pull-up to be stable on high */
> > +	msleep(10);
> > +
> > +	return IRQ_HANDLED;
> > +}
> > +
> > +static int vf50_ts_open(struct input_dev *dev_input)
> > +{
> > +	struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
> > +	struct device *dev = &touchdev->pdev->dev;
> > +
> > +	dev_dbg(dev, "Input device %s opened, starting touch detection\n",
> > +			dev_input->name);
> > +
> > +	touchdev->stop_touchscreen = false;
> > +
> > +	/* Mux detection before request IRQ, wait for pull-up to settle */
> > +	vf50_ts_enable_touch_detection(touchdev);
> > +	msleep(10);
> > +
> > +	return 0;
> > +}
> > +
> > +static void vf50_ts_close(struct input_dev *dev_input)
> > +{
> > +	struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
> > +	struct device *dev = &touchdev->pdev->dev;
> > +
> > +	touchdev->stop_touchscreen = true;
> > +
> > +	/* Make sure IRQ is not running past close */
> > +	mb();
> > +	synchronize_irq(touchdev->pen_irq);
> > +
> 
> Should we drive the gpio_ym inactive here? What about pin control?

My understanding is that the last IRQ handler run should leave things in
the pen irq detect and idle pictrl state. And since these lines are not
provided for any other use on the module, that state is left as is since
it is the same state we assume in open. However yes, I should turn off the
ym gpio inactive.

> 
> > +	dev_dbg(dev, "Input device %s closed, disable touch detection\n",
> > +		dev_input->name);
> > +}
> > +
> > +static int vf50_ts_get_gpiod(struct device *dev,
> > +	struct gpio_desc **gpio_d, const char *con_id, enum gpiod_flags flags)
> > +{
> > +	int error;
> > +
> > +	*gpio_d = devm_gpiod_get(dev, con_id, flags);
> > +	if (IS_ERR(*gpio_d)) {
> > +		error = PTR_ERR(*gpio_d);
> > +		dev_err(dev, "Could not get gpio_%s %d\n", con_id, error);
> > +		return error;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static void vf50_ts_channel_release(void *data)
> > +{
> > +	struct vf50_touch_device *touchdev = data;
> > +
> > +	iio_channel_release_all(touchdev->channels);
> > +}
> > +
> > +static int vf50_ts_probe(struct platform_device *pdev)
> > +{
> > +	struct input_dev *input;
> > +	struct iio_channel *channels;
> > +	struct device *dev = &pdev->dev;
> > +	struct vf50_touch_device *touchdev;
> > +	int error;
> > +
> > +	channels = iio_channel_get_all(dev);
> > +	if (IS_ERR(channels))
> > +		return PTR_ERR(channels);
> > +
> > +	touchdev = devm_kzalloc(dev, sizeof(*touchdev), GFP_KERNEL);
> > +	if (!touchdev) {
> > +		error = -ENOMEM;
> > +		return error;
> 
> Why not simply
> 
> 		return -ENOMEM;
> 
> here?

Ok.

> 
> Also you are leaking your iio channels here. You need to install the
> custom action earlier.

I will reorder this set of four calls here which will be better.

> 
> > +	}
> > +
> > +	error = of_property_read_u32(dev->of_node, "vf50-ts-min-pressure",
> > +				 &touchdev->min_pressure);
> > +	if (error)
> > +		return error;
> > +
> > +	error = devm_add_action(dev, vf50_ts_channel_release, channels);
> > +	if (error) {
> > +		dev_err(dev, "Failed to register iio channel release action");
> 
> You also need
> 
> 		vf50_ts_channel_release(touchdev);
> 
> > +		return error;
> > +	}
> > +
> > +	input = devm_input_allocate_device(dev);
> > +	if (!input) {
> > +		dev_err(dev, "Failed to allocate TS input device\n");
> > +		error = -ENOMEM;
> > +		return error;
> 
> Again simply return error code, no need to assign to the error variable.

Ok.

> 
> > +	}
> > +
> > +	platform_set_drvdata(pdev, touchdev);
> > +
> > +	touchdev->pdev = pdev;
> > +	touchdev->channels = channels;
> > +
> > +	input->name = DRIVER_NAME;
> > +	input->id.bustype = BUS_HOST;
> > +	input->dev.parent = dev;
> > +	input->open = vf50_ts_open;
> > +	input->close = vf50_ts_close;
> > +
> > +	input_set_capability(input, EV_KEY, BTN_TOUCH);
> > +	input_set_abs_params(input, ABS_X, 0, VF_ADC_MAX, 0, 0);
> > +	input_set_abs_params(input, ABS_Y, 0, VF_ADC_MAX, 0, 0);
> > +	input_set_abs_params(input, ABS_PRESSURE, 0, VF_ADC_MAX, 0, 0);
> > +
> > +	touchdev->ts_input = input;
> > +	input_set_drvdata(input, touchdev);
> > +	error = input_register_device(input);
> > +	if (error) {
> > +		dev_err(dev, "Failed to register input device\n");
> > +		return error;
> > +	}
> > +
> > +	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xp,
> > +				"xp", GPIOD_OUT_LOW);
> > +	if (error)
> > +		return error;
> > +
> > +	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xm,
> > +				"xm", GPIOD_OUT_LOW);
> > +	if (error)
> > +		return error;
> > +
> > +	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_yp,
> > +				"yp", GPIOD_OUT_LOW);
> > +	if (error)
> > +		return error;
> > +
> > +	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_ym,
> > +				"ym", GPIOD_OUT_LOW);
> > +	if (error)
> > +		return error;
> > +
> > +	touchdev->pen_irq = platform_get_irq(pdev, 0);
> > +	if (touchdev->pen_irq < 0)
> > +		return touchdev->pen_irq;
> > +
> > +	error = devm_request_threaded_irq(dev, touchdev->pen_irq, NULL,
> > +			vf50_ts_irq_bh, IRQF_ONESHOT,
> > +			"vf50 touch", touchdev);
> > +	if (error < 0)
> > +		return error;
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct of_device_id vf50_touch_of_match[] = {
> > +	{ .compatible = "toradex,vf50-touchscreen", },
> > +	{ }
> > +};
> > +MODULE_DEVICE_TABLE(of, vf50_touch_of_match);
> > +
> > +static struct platform_driver vf50_touch_driver = {
> > +	.driver = {
> > +		.name = "toradex,vf50_touchctrl",
> > +		.of_match_table = vf50_touch_of_match,
> > +	},
> > +	.probe = vf50_ts_probe,
> > +};
> > +
> > +module_platform_driver(vf50_touch_driver);
> > +
> > +MODULE_AUTHOR("Sanchayan Maity");
> > +MODULE_DESCRIPTION("Colibri VF50 Touchscreen driver");
> > +MODULE_LICENSE("GPL v2");
> 
> Please change it to "GPL" which means GPL v2+ to match license notice at
> the top.

Ok.

--  Sanchayan.

> 
> > +MODULE_VERSION(DRV_VERSION);
> > -- 
> > 2.5.0
> > 
> 
> Thank you.
> 
> -- 
> Dmitry
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