Re: [PATCH] Input: add bu21029 touch driver

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

Hi Mark,

On Wed, Mar 21, 2018 at 06:04:34PM +0100, Mark Jonas wrote:
> From: Zhu Yi <yi.zhu5@cn.bosch.com>
> 
> Add the ROHM BU21029 resistive touch panel controller
> support with i2c interface.
> 
> Signed-off-by: Zhu Yi <yi.zhu5@cn.bosch.com>
> Signed-off-by: Mark Jonas <mark.jonas@de.bosch.com>
> Reviewed-by: Heiko Schocher <hs@denx.de>
> ---
>  .../bindings/input/touchscreen/bu21029.txt         |  30 ++
>  drivers/input/touchscreen/Kconfig                  |  12 +
>  drivers/input/touchscreen/Makefile                 |   1 +
>  drivers/input/touchscreen/bu21029_ts.c             | 456 +++++++++++++++++++++
>  4 files changed, 499 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/input/touchscreen/bu21029.txt
>  create mode 100644 drivers/input/touchscreen/bu21029_ts.c
> 
> diff --git a/Documentation/devicetree/bindings/input/touchscreen/bu21029.txt b/Documentation/devicetree/bindings/input/touchscreen/bu21029.txt
> new file mode 100644
> index 0000000..7b61602
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/input/touchscreen/bu21029.txt
> @@ -0,0 +1,30 @@
> +* Rohm BU21029 Touch Screen Controller
> +
> +Required properties:
> + - compatible              : must be "rohm,bu21029"
> + - reg                     : i2c device address of the chip
> + - interrupt-parent        : the phandle for the gpio controller
> + - interrupts              : (gpio) interrupt to which the chip is connected
> + - reset-gpios             : gpio pin to reset the chip
> + - rohm,x-plate-ohms       : x-plate resistance in ohms
> +
> +Optional properties:
> + - touchscreen-max-pressure: maximum pressure value
> +
> +Example:
> +
> +	&i2c1 {
> +		/* ... */
> +
> +		bu21029: bu21029@40 {
> +			compatible = "rohm,bu21029";
> +			reg = <0x40>;
> +			interrupt-parent = <&gpio1>;
> +			interrupts = <4 IRQ_TYPE_EDGE_FALLING>;
> +			reset-gpios = <&gpio6 16 GPIO_ACTIVE_LOW>;
> +			rohm,x-plate-ohms = <600>;
> +			touchscreen-max-pressure = <4095>;
> +		};
> +
> +		/* ... */
> +	};
> diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
> index 4f15496..e09fe8f 100644
> --- a/drivers/input/touchscreen/Kconfig
> +++ b/drivers/input/touchscreen/Kconfig
> @@ -151,6 +151,18 @@ config TOUCHSCREEN_BU21013
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called bu21013_ts.
>  
> +config TOUCHSCREEN_BU21029
> +	tristate "Rohm BU21029 based touch panel controllers"
> +	depends on I2C
> +	help
> +	  Say Y here if you have a Rohm BU21029 touchscreen controller
> +	  connected to your system.
> +
> +	  If unsure, say N.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called bu21029_ts.
> +
>  config TOUCHSCREEN_CHIPONE_ICN8318
>  	tristate "chipone icn8318 touchscreen controller"
>  	depends on GPIOLIB || COMPILE_TEST
> diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
> index dddae79..f50624c 100644
> --- a/drivers/input/touchscreen/Makefile
> +++ b/drivers/input/touchscreen/Makefile
> @@ -18,6 +18,7 @@ obj-$(CONFIG_TOUCHSCREEN_AR1021_I2C)	+= ar1021_i2c.o
>  obj-$(CONFIG_TOUCHSCREEN_ATMEL_MXT)	+= atmel_mxt_ts.o
>  obj-$(CONFIG_TOUCHSCREEN_AUO_PIXCIR)	+= auo-pixcir-ts.o
>  obj-$(CONFIG_TOUCHSCREEN_BU21013)	+= bu21013_ts.o
> +obj-$(CONFIG_TOUCHSCREEN_BU21029)	+= bu21029_ts.o
>  obj-$(CONFIG_TOUCHSCREEN_CHIPONE_ICN8318)	+= chipone_icn8318.o
>  obj-$(CONFIG_TOUCHSCREEN_CY8CTMG110)	+= cy8ctmg110_ts.o
>  obj-$(CONFIG_TOUCHSCREEN_CYTTSP_CORE)	+= cyttsp_core.o
> diff --git a/drivers/input/touchscreen/bu21029_ts.c b/drivers/input/touchscreen/bu21029_ts.c
> new file mode 100644
> index 0000000..d5cbf11
> --- /dev/null
> +++ b/drivers/input/touchscreen/bu21029_ts.c
> @@ -0,0 +1,456 @@

Please add SPDX tag for the driver.

> +/*
> + * Rohm BU21029 touchscreen controller driver
> + *
> + * Copyright (C) 2015 Bosch Sicherheitssysteme GmbH
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/gpio.h>
> +#include <linux/i2c.h>
> +#include <linux/input.h>
> +#include <linux/interrupt.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_gpio.h>


Please use GPIOD API (and include linux/gpio/consumer.h instead of
of_gpio.h).

> +#include <linux/timer.h>
> +
> +/* HW_ID1 Register (PAGE=0, ADDR=0x0E, Reset value=0x02, Read only)

Multi-line comments start with empty comment line:

/*
 * Multi
 * line.
 */

> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |   D7   |   D6   |   D5   |   D4   |   D3   |   D2   |   D1   |   D0   |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |                                 HW_IDH                                |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * HW_ID2 Register (PAGE=0, ADDR=0x0F, Reset value=0x29, Read only)
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |   D7   |   D6   |   D5   |   D4   |   D3   |   D2   |   D1   |   D0   |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |                                 HW_IDL                                |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * HW_IDH: high 8bits of IC's ID
> + * HW_IDL: low  8bits of IC's ID
> + */
> +#define BU21029_HWID_REG (0x0E << 3)
> +#define SUPPORTED_HWID    0x0229
> +
> +/* CFR0 Register (PAGE=0, ADDR=0x00, Reset value=0x20)
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |   D7   |   D6   |   D5   |   D4   |   D3   |   D2   |   D1   |   D0   |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |   0    |   0    |  CALIB |  INTRM |   0    |   0    |   0    |   0    |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * CALIB: 0 = not to use calibration result (*)
> + *        1 = use calibration result
> + * INTRM: 0 = INT output depend on "pen down" (*)
> + *        1 = INT output always "0"
> + */
> +#define BU21029_CFR0_REG (0x00 << 3)
> +#define CFR0_VALUE        0x00
> +
> +/* CFR1 Register (PAGE=0, ADDR=0x01, Reset value=0xA6)
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |   D7   |   D6   |   D5   |   D4   |   D3   |   D2   |   D1   |   D0   |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |  MAV   |         AVE[2:0]         |   0    |         SMPL[2:0]        |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * MAV:  0 = median average filter off
> + *       1 = median average filter on (*)
> + * AVE:  AVE+1 = number of average samples for MAV,
> + *               if AVE>SMPL, then AVE=SMPL (=3)
> + * SMPL: SMPL+1 = number of conversion samples for MAV (=7)
> + */
> +#define BU21029_CFR1_REG (0x01 << 3)
> +#define CFR1_VALUE        0xA6
> +
> +/* CFR2 Register (PAGE=0, ADDR=0x02, Reset value=0x04)
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |   D7   |   D6   |   D5   |   D4   |   D3   |   D2   |   D1   |   D0   |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |          INTVL_TIME[3:0]          |          TIME_ST_ADC[3:0]         |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * INTVL_TIME: waiting time between completion of conversion
> + *             and start of next conversion, only usable in
> + *             autoscan mode (=20.480ms)
> + * TIME_ST_ADC: waiting time between application of voltage
> + *              to panel and start of A/D conversion (=100us)
> + */
> +#define BU21029_CFR2_REG (0x02 << 3)
> +#define CFR2_VALUE        0xC9
> +
> +/* CFR3 Register (PAGE=0, ADDR=0x0B, Reset value=0x72)
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |   D7   |   D6   |   D5   |   D4   |   D3   |   D2   |   D1   |   D0   |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |  RM8   | STRETCH|  PU90K |  DUAL  |           PIDAC_OFS[3:0]          |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * RM8: 0 = coordinate resolution is 12bit (*)
> + *      1 = coordinate resolution is 8bit
> + * STRETCH: 0 = SCL_STRETCH function off
> + *          1 = SCL_STRETCH function on (*)
> + * PU90K: 0 = internal pull-up resistance for touch detection is ~50kohms (*)
> + *        1 = internal pull-up resistance for touch detection is ~90kohms
> + * DUAL: 0 = dual touch detection off (*)
> + *       1 = dual touch detection on
> + * PIDAC_OFS: dual touch detection circuit adjustment, it is not necessary
> + *            to change this from initial value
> + */
> +#define BU21029_CFR3_REG (0x0B << 3)
> +#define CFR3_VALUE        0x42
> +
> +/* LDO Register (PAGE=0, ADDR=0x0C, Reset value=0x00)
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |   D7   |   D6   |   D5   |   D4   |   D3   |   D2   |   D1   |   D0   |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |   0    |         PVDD[2:0]        |   0    |         AVDD[2:0]        |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * PVDD: output voltage of panel output regulator (=2.000V)
> + * AVDD: output voltage of analog circuit regulator (=2.000V)
> + */
> +#define BU21029_LDO_REG  (0x0C << 3)
> +#define LDO_VALUE         0x77
> +
> +/* Serial Interface Command Byte 1 (CID=1)
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |   D7   |   D6   |   D5   |   D4   |   D3   |   D2   |   D1   |   D0   |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * |   1    |                 CF                |  CMSK  |  PDM   |  STP   |
> + * +--------+--------+--------+--------+--------+--------+--------+--------+
> + * CF: conversion function, see table 3 in datasheet p6 (=0000, automatic scan)
> + * CMSK: 0 = executes convert function (*)
> + *       1 = reads the convert result
> + * PDM: 0 = power down after convert function stops (*)
> + *      1 = keep power on after convert function stops
> + * STP: 1 = abort current conversion and power down, set to "0" automatically
> + */
> +#define BU21029_AUTOSCAN  0x80
> +
> +/* The timeout value needs to be larger than INTVL_TIME + tConv4 (sample and
> + * conversion time), where tConv4 is calculated by formula:
> + * tPON + tDLY1 + (tTIME_ST_ADC + (tADC * tSMPL) * 2 + tDLY2) * 3
> + * see figure 8 in datasheet p15 for details of each field.
> + */
> +#define PEN_UP_TIMEOUT msecs_to_jiffies(50)
> +
> +#define STOP_DELAY_US  50L
> +#define START_DELAY_MS 2L
> +#define BUF_LEN        8L
> +#define SCALE_12BIT    (1 << 12)
> +#define MAX_12BIT      ((1 << 12) - 1)
> +#define DRIVER_NAME    "bu21029"
> +
> +struct bu21029_ts_data {
> +	struct i2c_client *client;
> +	struct input_dev  *in_dev;
> +	struct timer_list  timer;
> +	u32                reset_gpios;
> +	u32                reset_gpios_assert;
> +	u32                x_plate_ohms;
> +	u32                max_pressure;
> +};
> +
> +static int bu21029_touch_report(struct bu21029_ts_data *bu21029)
> +{
> +	struct i2c_client *i2c = bu21029->client;
> +	u8 buf[BUF_LEN];
> +	u16 x, y, z1, z2;
> +	u32 rz;
> +
> +	/* read touch data and deassert INT (by restarting the autoscan mode) */
> +	int error = i2c_smbus_read_i2c_block_data(i2c,
> +						  BU21029_AUTOSCAN,
> +						  BUF_LEN,
> +						  buf);
> +	if (error < 0)
> +		return error;
> +
> +	/* compose upper 8 and lower 4 bits into a 12bit value:
> +	 * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
> +	 * |            ByteH              |            ByteL              |
> +	 * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
> +	 * |b07|b06|b05|b04|b03|b02|b01|b00|b07|b06|b05|b04|b03|b02|b01|b00|
> +	 * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
> +	 * |v11|v10|v09|v08|v07|v06|v05|v04|v03|v02|v01|v00| 0 | 0 | 0 | 0 |
> +	 * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
> +	 */
> +	x  = (buf[0] << 4) | (buf[1] >> 4);
> +	y  = (buf[2] << 4) | (buf[3] >> 4);
> +	z1 = (buf[4] << 4) | (buf[5] >> 4);
> +	z2 = (buf[6] << 4) | (buf[7] >> 4);
> +
> +	if (z1 == 0 || z2 == 0)
> +		return 0;
> +
> +	/* calculate Rz (pressure resistance value) by equation:
> +	 * Rz = Rx * (x/Q) * ((z2/z1) - 1), where
> +	 * Rx is x-plate resistance,
> +	 * Q  is the touch screen resolution (8bit = 256, 12bit = 4096)
> +	 * x, z1, z2 are the measured positions.
> +	 */
> +	rz  = z2 - z1;
> +	rz *= x;
> +	rz *= bu21029->x_plate_ohms;
> +	rz /= z1;
> +	rz  = DIV_ROUND_CLOSEST(rz, SCALE_12BIT);
> +	if (rz <= bu21029->max_pressure) {
> +		input_report_abs(bu21029->in_dev, ABS_X, x);
> +		input_report_abs(bu21029->in_dev, ABS_Y, y);
> +		input_report_abs(bu21029->in_dev, ABS_PRESSURE, rz);

What is the values of pressure reported when finger is touching the
surface? IOW is 'rz' pressure or resistance?

> +		input_report_key(bu21029->in_dev, BTN_TOUCH, 1);
> +		input_sync(bu21029->in_dev);
> +	}
> +
> +	return 0;
> +}
> +
> +static void bu21029_touch_release(struct timer_list *t)
> +{
> +	struct bu21029_ts_data *bu21029 = from_timer(bu21029, t, timer);
> +
> +	input_report_abs(bu21029->in_dev, ABS_PRESSURE, 0);
> +	input_report_key(bu21029->in_dev, BTN_TOUCH, 0);
> +	input_sync(bu21029->in_dev);
> +}
> +
> +static irqreturn_t bu21029_touch_soft_irq(int irq, void *data)
> +{
> +	struct bu21029_ts_data *bu21029 = data;
> +	struct i2c_client *i2c = bu21029->client;
> +
> +	/* report touch and deassert interrupt (will assert again after
> +	 * INTVL_TIME + tConv4 for continuous touch)
> +	 */
> +	int error = bu21029_touch_report(bu21029);
> +
> +	if (error) {
> +		dev_err(&i2c->dev, "failed to report (error: %d)\n", error);
> +		return IRQ_NONE;
> +	}
> +
> +	/* reset timer for pen up detection */
> +	mod_timer(&bu21029->timer, jiffies + PEN_UP_TIMEOUT);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static void bu21029_reset_chip(struct bu21029_ts_data *bu21029)
> +{
> +	gpio_set_value(bu21029->reset_gpios,
> +		       bu21029->reset_gpios_assert);
> +	udelay(STOP_DELAY_US);
> +	gpio_set_value(bu21029->reset_gpios,
> +		       !bu21029->reset_gpios_assert);
> +	mdelay(START_DELAY_MS);
> +}
> +
> +static int bu21029_init_chip(struct bu21029_ts_data *bu21029)
> +{
> +	struct i2c_client *i2c = bu21029->client;
> +	struct {
> +		u8 reg;
> +		u8 value;
> +	} init_table[] = {
> +		{BU21029_CFR0_REG, CFR0_VALUE},
> +		{BU21029_CFR1_REG, CFR1_VALUE},
> +		{BU21029_CFR2_REG, CFR2_VALUE},
> +		{BU21029_CFR3_REG, CFR3_VALUE},
> +		{BU21029_LDO_REG,  LDO_VALUE}
> +	};
> +	int error, i;
> +	u16 hwid;
> +
> +	bu21029_reset_chip(bu21029);
> +
> +	error = i2c_smbus_read_i2c_block_data(i2c,
> +					      BU21029_HWID_REG,
> +					      2,
> +					      (u8 *)&hwid);
> +	if (error < 0) {
> +		dev_err(&i2c->dev, "failed to read HW ID\n");
> +		return error;
> +	}
> +
> +	if (cpu_to_be16(hwid) != SUPPORTED_HWID) {
> +		dev_err(&i2c->dev, "unsupported HW ID 0x%x\n", hwid);
> +		return -ENODEV;
> +	}
> +
> +	for (i = 0; i < ARRAY_SIZE(init_table); ++i) {
> +		error = i2c_smbus_write_byte_data(i2c,
> +						  init_table[i].reg,
> +						  init_table[i].value);
> +		if (error < 0) {
> +			dev_err(&i2c->dev,
> +				"failed to write 0x%x to register 0x%x\n",
> +				init_table[i].value,
> +				init_table[i].reg);
> +			return error;
> +		}
> +	}
> +
> +	error = i2c_smbus_write_byte(i2c, BU21029_AUTOSCAN);
> +	if (error < 0) {
> +		dev_err(&i2c->dev, "failed to start autoscan\n");
> +		return error;
> +	}
> +
> +	return 0;
> +}
> +
> +static int bu21029_parse_dt(struct bu21029_ts_data *bu21029)
> +{
> +	struct device *dev = &bu21029->client->dev;
> +	struct device_node *np = dev->of_node;
> +	enum of_gpio_flags flags;
> +	u32 val32;
> +	int gpio;
> +
> +	if (!np) {
> +		dev_err(dev, "no device tree data\n");
> +		return -EINVAL;
> +	}
> +
> +	gpio = of_get_named_gpio_flags(np, "reset-gpios", 0, &flags);
> +	if (!gpio_is_valid(gpio)) {
> +		dev_err(dev, "invalid 'reset-gpios' supplied\n");
> +		return -EINVAL;
> +	}
> +	bu21029->reset_gpios = gpio;
> +	bu21029->reset_gpios_assert = (flags & OF_GPIO_ACTIVE_LOW) ? 0 : 1;
> +
> +	if (of_property_read_u32(np, "rohm,x-plate-ohms", &val32)) {
> +		dev_err(dev, "invalid 'x-plate-ohms' supplied\n");
> +		return -EINVAL;
> +	}
> +	bu21029->x_plate_ohms = val32;
> +
> +	if (of_property_read_u32(np, "touchscreen-max-pressure", &val32))
> +		bu21029->max_pressure = MAX_12BIT;
> +	else
> +		bu21029->max_pressure = val32;

Please use infrastructure form include/linux/input/touchscreen.h
so that you handle different sizes and orientations.

> +
> +	return 0;
> +}
> +
> +static int bu21029_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	struct bu21029_ts_data *bu21029;
> +	struct input_dev *in_dev;
> +	int error;
> +
> +	if (!i2c_check_functionality(client->adapter,
> +				     I2C_FUNC_SMBUS_WRITE_BYTE |
> +				     I2C_FUNC_SMBUS_WRITE_BYTE_DATA |
> +				     I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
> +		dev_err(&client->dev,
> +			"i2c functionality support is not sufficient\n");
> +		return -EIO;
> +	}
> +
> +	bu21029 = devm_kzalloc(&client->dev, sizeof(*bu21029), GFP_KERNEL);
> +	if (!bu21029)
> +		return -ENOMEM;
> +
> +	in_dev = devm_input_allocate_device(&client->dev);
> +	if (!in_dev) {
> +		dev_err(&client->dev, "unable to allocate input device\n");
> +		return -ENOMEM;
> +	}
> +
> +	bu21029->client = client;
> +	bu21029->in_dev	= in_dev;
> +	timer_setup(&bu21029->timer, bu21029_touch_release, 0);
> +
> +	error = bu21029_parse_dt(bu21029);
> +	if (error)
> +		return error;
> +
> +	error = devm_gpio_request_one(&client->dev,
> +				      bu21029->reset_gpios,
> +				      GPIOF_OUT_INIT_HIGH,
> +				      DRIVER_NAME);
> +	if (error) {
> +		dev_err(&client->dev, "unable to request reset-gpios\n");
> +		return error;
> +	}
> +
> +	error = bu21029_init_chip(bu21029);
> +	if (error) {
> +		dev_err(&client->dev, "unable to config bu21029\n");
> +		return error;
> +	}
> +
> +	in_dev->name       = DRIVER_NAME;
> +	in_dev->id.bustype = BUS_I2C;
> +	in_dev->dev.parent = &client->dev;

Not needed with devm_input_allocate_device().

> +
> +	__set_bit(EV_SYN,       in_dev->evbit);
> +	__set_bit(EV_KEY,       in_dev->evbit);
> +	__set_bit(EV_ABS,       in_dev->evbit);
> +	__set_bit(ABS_X,        in_dev->absbit);
> +	__set_bit(ABS_Y,        in_dev->absbit);
> +	__set_bit(ABS_PRESSURE, in_dev->absbit);
> +	__set_bit(BTN_TOUCH,    in_dev->keybit);
> +
> +	input_set_abs_params(in_dev, ABS_X, 0, MAX_12BIT, 0, 0);
> +	input_set_abs_params(in_dev, ABS_Y, 0, MAX_12BIT, 0, 0);
> +	input_set_abs_params(in_dev, ABS_PRESSURE,
> +			     0, bu21029->max_pressure, 0, 0);
> +	input_set_drvdata(in_dev, bu21029);
> +
> +	error = input_register_device(in_dev);
> +	if (error) {
> +		dev_err(&client->dev, "unable to register input device\n");
> +		return error;
> +	}
> +
> +	i2c_set_clientdata(client, bu21029);
> +
> +	error = devm_request_threaded_irq(&client->dev,
> +					  client->irq,
> +					  NULL,
> +					  bu21029_touch_soft_irq,
> +					  IRQF_ONESHOT,
> +					  DRIVER_NAME,
> +					  bu21029);
> +	if (error) {
> +		dev_err(&client->dev, "unable to request touch irq\n");
> +		return error;
> +	}
> +
> +	return 0;
> +}
> +
> +static int bu21029_remove(struct i2c_client *client)
> +{
> +	struct bu21029_ts_data *bu21029 = i2c_get_clientdata(client);
> +
> +	del_timer_sync(&bu21029->timer);

If interrupt comes here kernel will be unhappy. You need to either work
canceling timer into devm unwid stream (devm_add_action_or_reset()) or
somehow make sure that you shut off interrupts before canceling the
timer.

> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id bu21029_ids[] = {
> +	{DRIVER_NAME, 0},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, bu21029_ids);
> +
> +static struct i2c_driver bu21029_driver = {
> +	.driver = {
> +		.name  = DRIVER_NAME,
> +		.owner = THIS_MODULE,

Not needed.

> +	},
> +	.id_table = bu21029_ids,
> +	.probe    = bu21029_probe,
> +	.remove   = bu21029_remove,
> +};
> +module_i2c_driver(bu21029_driver);
> +
> +MODULE_AUTHOR("Zhu Yi <yi.zhu5@cn.bosch.com>");
> +MODULE_DESCRIPTION("Rohm BU21029 touchscreen controller driver");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.7.4
> 

Thanks.

-- 
Dmitry