[RFC PATCH 0/4] Input: mpr121-polled: Add polled driver for MPR121

[RFC PATCH 0/4] Input: mpr121-polled: Add polled driver for MPR121

[Michal Vokáč]

Hi,

I have to deal with a situation where we have a custom i.MX6 based
platform in production that uses the MPR121 touchkey controller.
Unfortunately the chip is connected using only the I2C interface.
The interrupt line is not used. Back in 2015 (Linux v3.14), my
colleague modded the existing mpr121_touchkey.c driver to use polling
instead of interrupt.

For quite some time yet I am in a process of updating the product from
the ancient Freescale v3.14 kernel to the latest mainline and pushing
any needed changes upstream. The DT files for our imx6dl-yapp4 platform
already made it into v5.1-rc.

I rebased and updated our mpr121 patch to the latest mainline.
It is created as a separate driver, similarly to gpio_keys_polled.

The I2C device is quite susceptible to ESD. An ESD test quite often
causes reset of the chip or some register randomly changes its value.
The [PATCH 3/4] adds a write-through register cache. With the cache
this state can be detected and the device can be re-initialied.

The main question is: Is there any chance that such a polled driver
could be accepted? Is it correct to implement it as a separate driver
or should it be done as an option in the existing driver? I can not
really imagine how I would do that though..

There are also certain worries that the MPR121 chip may no longer be
available in nonspecifically distant future. In case of EOL I will need
to add a polled driver for an other touchkey chip. May it be already
in mainline or a completely new one.

I am also little bit confused from the dt-binding documentation.
The MPR121 is mentioned in the trivial-devices.yaml but it also has
its own binding documentation in input/mpr121_touchkey.txt.
I thought that a certain device/compatible should be documented in just
one place. The MPR121 device certainly needs more properties than
just compatible, reg and interrupt so trivial-devices.yaml does not
seem appropriate.

I will appreciate any comments. Thank you in advance,
Michal


Michal Vokáč (4):
  dt-bindings: input: Add support for the MPR121 without interrupt line
  Input: mpr121-polled: Add polling variant of the MPR121 touchkey
    driver
  Input: mpr121-polled: Add write-through cache to detect corrupted
    registers
  ARM: dts: imx6dl-yapp4: Enable MPR121 touch keypad on Hydra

 .../bindings/input/mpr121-touchkey-polled.txt      |  26 ++
 arch/arm/boot/dts/imx6dl-yapp4-common.dtsi         |  12 +
 arch/arm/boot/dts/imx6dl-yapp4-hydra.dts           |   4 +
 drivers/input/keyboard/Kconfig                     |  13 +
 drivers/input/keyboard/Makefile                    |   1 +
 drivers/input/keyboard/mpr121_touchkey_polled.c    | 493 +++++++++++++++++++++
 6 files changed, 549 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/input/mpr121-touchkey-polled.txt
 create mode 100644 drivers/input/keyboard/mpr121_touchkey_polled.c

-- 
2.1.4

[RFC PATCH 1/4] dt-bindings: input: Add support for the MPR121 without interrupt line

[Michal Vokáč]

Normally, the MPR121 controller uses separate interrupt line to notify
the I2C host that a key was touched/released. To support platforms that
can not use the interrupt line, polling of the MPR121 registers can be
used.

Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
---
 .../bindings/input/mpr121-touchkey-polled.txt      | 26 ++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/input/mpr121-touchkey-polled.txt

diff --git a/Documentation/devicetree/bindings/input/mpr121-touchkey-polled.txt b/Documentation/devicetree/bindings/input/mpr121-touchkey-polled.txt
new file mode 100644
index 000000000000..6bb1d312614c
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/mpr121-touchkey-polled.txt
@@ -0,0 +1,26 @@
+* Freescale MPR121 Controller without interrupt line
+
+Required Properties:
+- compatible:		Should be "fsl,mpr121-touchkey-polled"
+- reg:			The I2C slave address of the device.
+- vdd-supply:		Phandle to the Vdd power supply.
+- linux,keycodes:	Specifies an array of numeric keycode values to
+			be used for reporting button presses. The array can
+			contain up to 12 entries.
+
+Optional Properties:
+- autorepeat:		Enable autorepeat feature.
+
+Example:
+
+#include "dt-bindings/input/input.h"
+
+	touchkeys: keys@5a {
+		compatible = "fsl,mpr121-touchkey-polled";
+		reg = <0x5a>;
+		autorepeat;
+		vdd-supply = <&ldo4_reg>;
+		linux,keycodes = <KEY_0>, <KEY_1>, <KEY_2>, <KEY_3>,
+				<KEY_4> <KEY_5>, <KEY_6>, <KEY_7>,
+				<KEY_8>, <KEY_9>, <KEY_A>, <KEY_B>;
+	};
-- 
2.1.4

[RFC PATCH 2/4] Input: mpr121-polled: Add polling variant of the MPR121 touchkey driver

[Michal Vokáč]

This driver is based on the original driver with interrupts. Polling
driver may be used in cases where the MPR121 chip is connected using
only the I2C interface and the interrupt line is not available.

Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
---
 drivers/input/keyboard/Kconfig                  |  13 +
 drivers/input/keyboard/Makefile                 |   1 +
 drivers/input/keyboard/mpr121_touchkey_polled.c | 417 ++++++++++++++++++++++++
 3 files changed, 431 insertions(+)
 create mode 100644 drivers/input/keyboard/mpr121_touchkey_polled.c

diff --git a/drivers/input/keyboard/Kconfig b/drivers/input/keyboard/Kconfig
index a878351f1643..a674e72cdeef 100644
--- a/drivers/input/keyboard/Kconfig
+++ b/drivers/input/keyboard/Kconfig
@@ -418,6 +418,19 @@ config KEYBOARD_MPR121
 	  To compile this driver as a module, choose M here: the
 	  module will be called mpr121_touchkey.
 
+config KEYBOARD_MPR121_POLLED
+	tristate "Polled Freescale MPR121 Touchkey"
+	depends on I2C
+	help
+	  Say Y here if you have Freescale MPR121 touchkey controller
+	  chip in your system connected only using the I2C line without
+	  the interrupt line.
+
+	  If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called mpr121_touchkey_polled.
+
 config KEYBOARD_SNVS_PWRKEY
 	tristate "IMX SNVS Power Key Driver"
 	depends on SOC_IMX6SX || SOC_IMX7D
diff --git a/drivers/input/keyboard/Makefile b/drivers/input/keyboard/Makefile
index 182e92985dbf..903f50842844 100644
--- a/drivers/input/keyboard/Makefile
+++ b/drivers/input/keyboard/Makefile
@@ -40,6 +40,7 @@ obj-$(CONFIG_KEYBOARD_MATRIX)		+= matrix_keypad.o
 obj-$(CONFIG_KEYBOARD_MAX7359)		+= max7359_keypad.o
 obj-$(CONFIG_KEYBOARD_MCS)		+= mcs_touchkey.o
 obj-$(CONFIG_KEYBOARD_MPR121)		+= mpr121_touchkey.o
+obj-$(CONFIG_KEYBOARD_MPR121_POLLED)	+= mpr121_touchkey_polled.o
 obj-$(CONFIG_KEYBOARD_MTK_PMIC) 	+= mtk-pmic-keys.o
 obj-$(CONFIG_KEYBOARD_NEWTON)		+= newtonkbd.o
 obj-$(CONFIG_KEYBOARD_NOMADIK)		+= nomadik-ske-keypad.o
diff --git a/drivers/input/keyboard/mpr121_touchkey_polled.c b/drivers/input/keyboard/mpr121_touchkey_polled.c
new file mode 100644
index 000000000000..e5e80530c9d8
--- /dev/null
+++ b/drivers/input/keyboard/mpr121_touchkey_polled.c
@@ -0,0 +1,417 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Touchkey driver for Freescale MPR121 Controllor
+//
+// Copyright (C) 2011 Freescale Semiconductor, Inc.
+// Author: Zhang Jiejing <jiejing.zhang@freescale.com>
+//
+// Based on mcs_touchkey.c
+//
+// Copyright (C) 2019 Y Soft Corporation, a.s.
+// Author: Pavel Staněk <pavel.stanek@ysoft.com>
+// Author: Michal Vokáč <michal.vokac@ysoft.com>
+//
+// Reworked into polled driver based on mpr121_touchkey.c
+
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/input-polldev.h>
+#include <linux/input/matrix_keypad.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/property.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+/* Register definitions */
+#define ELE_TOUCH_STATUS_0_ADDR	0x0
+#define ELE_TOUCH_STATUS_1_ADDR	0X1
+#define MHD_RISING_ADDR		0x2b
+#define NHD_RISING_ADDR		0x2c
+#define NCL_RISING_ADDR		0x2d
+#define FDL_RISING_ADDR		0x2e
+#define MHD_FALLING_ADDR	0x2f
+#define NHD_FALLING_ADDR	0x30
+#define NCL_FALLING_ADDR	0x31
+#define FDL_FALLING_ADDR	0x32
+#define ELE0_TOUCH_THRESHOLD_ADDR	0x41
+#define ELE0_RELEASE_THRESHOLD_ADDR	0x42
+#define AFE_CONF_ADDR			0x5c
+#define FILTER_CONF_ADDR		0x5d
+
+/*
+ * ELECTRODE_CONF_ADDR: This register configures the number of
+ * enabled capacitance sensing inputs and its run/suspend mode.
+ */
+#define ELECTRODE_CONF_ADDR		0x5e
+#define ELECTRODE_CONF_QUICK_CHARGE	0x80
+#define AUTO_CONFIG_CTRL_ADDR		0x7b
+#define AUTO_CONFIG_USL_ADDR		0x7d
+#define AUTO_CONFIG_LSL_ADDR		0x7e
+#define AUTO_CONFIG_TL_ADDR		0x7f
+
+/* Threshold of touch/release trigger */
+#define TOUCH_THRESHOLD			0x08
+#define RELEASE_THRESHOLD		0x05
+/* Masks for touch and release triggers */
+#define TOUCH_STATUS_MASK		0xfff
+/* MPR121 has 12 keys */
+#define MPR121_MAX_KEY_COUNT		12
+
+#define MPR121_POLL_INTERVAL		50
+#define MPR121_POLL_INTERVAL_MIN	10
+#define MPR121_POLL_INTERVAL_MAX	200
+#define MPR121_POLL_INTERVAL_REINIT	500
+#define MPR121_POLL_RETRY_MAX		4
+
+struct mpr121_polled {
+	struct i2c_client *client;
+	struct input_dev *input_dev;
+	struct input_polled_dev	*poll_dev;
+	unsigned int statusbits;
+	unsigned int keycount;
+	u32 keycodes[MPR121_MAX_KEY_COUNT];
+	u8 read_errors;
+	int vdd_uv;
+};
+
+struct mpr121_polled_init_register {
+	int addr;
+	u8 val;
+};
+
+static const struct mpr121_polled_init_register init_reg_table[] = {
+	{ MHD_RISING_ADDR,	0x1 },
+	{ NHD_RISING_ADDR,	0x1 },
+	{ MHD_FALLING_ADDR,	0x1 },
+	{ NHD_FALLING_ADDR,	0x1 },
+	{ NCL_FALLING_ADDR,	0xff },
+	{ FDL_FALLING_ADDR,	0x02 },
+	{ FILTER_CONF_ADDR,	0x04 },
+	{ AFE_CONF_ADDR,	0x0b },
+	{ AUTO_CONFIG_CTRL_ADDR, 0x0b },
+};
+
+static void mpr121_polled_vdd_supply_disable(void *data)
+{
+	struct regulator *vdd_supply = data;
+
+	regulator_disable(vdd_supply);
+}
+
+static struct regulator *mpr121_polled_vdd_supply_init(struct device *dev)
+{
+	struct regulator *vdd_supply;
+	int err;
+
+	vdd_supply = devm_regulator_get(dev, "vdd");
+	if (IS_ERR(vdd_supply)) {
+		dev_err(dev, "failed to get vdd regulator: %ld\n",
+			PTR_ERR(vdd_supply));
+		return vdd_supply;
+	}
+
+	err = regulator_enable(vdd_supply);
+	if (err) {
+		dev_err(dev, "failed to enable vdd regulator: %d\n", err);
+		return ERR_PTR(err);
+	}
+
+	err = devm_add_action(dev, mpr121_polled_vdd_supply_disable,
+			      vdd_supply);
+	if (err) {
+		regulator_disable(vdd_supply);
+		dev_err(dev, "failed to add disable regulator action: %d\n",
+			err);
+		return ERR_PTR(err);
+	}
+
+	return vdd_supply;
+}
+
+static int mpr121_polled_phys_init(struct mpr121_polled *mpr121,
+				   struct i2c_client *client)
+{
+	const struct mpr121_polled_init_register *reg;
+	unsigned char usl, lsl, tl, eleconf;
+	int i, t, vdd, ret;
+
+	/* Set stop mode prior to writing any register */
+	ret = i2c_smbus_write_byte_data(client, ELECTRODE_CONF_ADDR, 0x00);
+	if (ret < 0)
+		goto err_i2c_write;
+
+	/* Set up touch/release threshold for ele0-ele11 */
+	for (i = 0; i <= MPR121_MAX_KEY_COUNT; i++) {
+		t = ELE0_TOUCH_THRESHOLD_ADDR + (i * 2);
+		ret = i2c_smbus_write_byte_data(client, t, TOUCH_THRESHOLD);
+		if (ret < 0)
+			goto err_i2c_write;
+		ret = i2c_smbus_write_byte_data(client, t + 1,
+						RELEASE_THRESHOLD);
+		if (ret < 0)
+			goto err_i2c_write;
+	}
+
+	/* Set up init register */
+	for (i = 0; i < ARRAY_SIZE(init_reg_table); i++) {
+		reg = &init_reg_table[i];
+		ret = i2c_smbus_write_byte_data(client, reg->addr, reg->val);
+		if (ret < 0)
+			goto err_i2c_write;
+	}
+
+	/*
+	 * Capacitance on sensing input varies and needs to be compensated.
+	 * The internal MPR121-auto-configuration can do this if it's
+	 * registers are set properly (based on vdd_uv).
+	 */
+	vdd = mpr121->vdd_uv / 1000;
+	usl = ((vdd - 700) * 256) / vdd;
+	lsl = (usl * 65) / 100;
+	tl = (usl * 90) / 100;
+	ret = i2c_smbus_write_byte_data(client, AUTO_CONFIG_USL_ADDR, usl);
+	ret |= i2c_smbus_write_byte_data(client, AUTO_CONFIG_LSL_ADDR, lsl);
+	ret |= i2c_smbus_write_byte_data(client, AUTO_CONFIG_TL_ADDR, tl);
+
+	/*
+	 * Quick charge bit will let the capacitive charge to ready
+	 * state quickly, or the buttons may not function after system
+	 * boot.
+	 */
+	eleconf = mpr121->keycount | ELECTRODE_CONF_QUICK_CHARGE;
+	ret |= i2c_smbus_write_byte_data(client, ELECTRODE_CONF_ADDR,
+					 eleconf);
+	if (ret != 0)
+		goto err_i2c_write;
+
+	dev_dbg(&client->dev, "set up with %x keys.\n", mpr121->keycount);
+
+	return 0;
+
+err_i2c_write:
+	dev_err(&client->dev, "i2c write error: %d\n", ret);
+	return ret;
+}
+
+static void mpr121_polled_release_keys(struct mpr121_polled *mpr121)
+{
+	struct input_dev *input = mpr121->input_dev;
+	struct i2c_client *client = mpr121->client;
+	unsigned long statusbits;
+	unsigned int key_num;
+
+	if (!mpr121->statusbits)
+		return;
+
+	statusbits = mpr121->statusbits;
+	mpr121->statusbits = 0;
+	for_each_set_bit(key_num, &statusbits, mpr121->keycount) {
+		unsigned int key_val;
+
+		key_val = mpr121->keycodes[key_num];
+
+		input_event(input, EV_MSC, MSC_SCAN, key_num);
+		input_report_key(input, key_val, 0);
+
+		dev_dbg(&client->dev, "key %d %d %s\n", key_num, key_val,
+			"released");
+	}
+	input_sync(input);
+}
+
+static int mpr121_polled_process_keys(struct mpr121_polled *mpr121)
+{
+	struct input_dev *input = mpr121->input_dev;
+	struct i2c_client *client = mpr121->client;
+	unsigned long bit_changed;
+	unsigned int key_num;
+	int reg;
+
+	reg = i2c_smbus_read_word_data(client, ELE_TOUCH_STATUS_0_ADDR);
+	if (reg < 0) {
+		dev_err(&client->dev, "i2c read error: %d\n", reg);
+		return reg;
+	}
+
+	reg &= TOUCH_STATUS_MASK;
+	bit_changed = reg ^ mpr121->statusbits;
+	mpr121->statusbits = reg;
+	for_each_set_bit(key_num, &bit_changed, mpr121->keycount) {
+		unsigned int key_val, pressed;
+
+		pressed = reg & BIT(key_num);
+		key_val = mpr121->keycodes[key_num];
+
+		input_event(input, EV_MSC, MSC_SCAN, key_num);
+		input_report_key(input, key_val, pressed);
+
+		dev_dbg(&client->dev, "key %d %d %s\n", key_num, key_val,
+			pressed ? "pressed" : "released");
+	}
+	input_sync(input);
+
+	return 0;
+}
+static void mpr121_poll(struct input_polled_dev *dev)
+{
+	struct mpr121_polled *mpr121 = dev->private;
+	struct i2c_client *client = mpr121->client;
+	int ret;
+
+	if (mpr121->read_errors > MPR121_POLL_RETRY_MAX) {
+		dev_warn(&client->dev,
+			 "device does not respond, re-initializing\n");
+		mpr121_polled_release_keys(mpr121);
+		ret = mpr121_polled_phys_init(mpr121, client);
+		if (ret >= 0) {
+			mpr121->read_errors = 0;
+			dev->poll_interval = MPR121_POLL_INTERVAL;
+		} else {
+			dev->poll_interval = MPR121_POLL_INTERVAL_REINIT;
+		}
+	}
+
+	ret = mpr121_polled_process_keys(mpr121);
+	if (ret < 0) {
+		mpr121->read_errors++;
+		return;
+	}
+
+	mpr121->read_errors = 0;
+}
+
+static int mpr121_polled_probe(struct i2c_client *client,
+			       const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct regulator *vdd_supply;
+	struct mpr121_polled *mpr121;
+	struct input_dev *input_dev;
+	struct input_polled_dev *poll_dev;
+	int error;
+	int i;
+
+	vdd_supply = mpr121_polled_vdd_supply_init(dev);
+	if (IS_ERR(vdd_supply))
+		return PTR_ERR(vdd_supply);
+
+	mpr121 = devm_kzalloc(dev, sizeof(*mpr121), GFP_KERNEL);
+	if (!mpr121)
+		return -ENOMEM;
+
+	poll_dev = devm_input_allocate_polled_device(dev);
+	if (!poll_dev)
+		return -ENOMEM;
+
+	mpr121->vdd_uv = regulator_get_voltage(vdd_supply);
+	mpr121->client = client;
+	mpr121->input_dev = poll_dev->input;
+	mpr121->poll_dev = poll_dev;
+	mpr121->keycount = device_property_read_u32_array(dev, "linux,keycodes",
+							  NULL, 0);
+	if (mpr121->keycount > MPR121_MAX_KEY_COUNT) {
+		dev_err(dev, "too many keys defined (%d)\n", mpr121->keycount);
+		return -EINVAL;
+	}
+
+	error = device_property_read_u32_array(dev, "linux,keycodes",
+					       mpr121->keycodes,
+					       mpr121->keycount);
+	if (error) {
+		dev_err(dev,
+			"failed to read linux,keycode property: %d\n", error);
+		return error;
+	}
+
+	poll_dev->private = mpr121;
+	poll_dev->poll = mpr121_poll;
+	poll_dev->poll_interval = MPR121_POLL_INTERVAL;
+	poll_dev->poll_interval_max = MPR121_POLL_INTERVAL_MAX;
+	poll_dev->poll_interval_min = MPR121_POLL_INTERVAL_MIN;
+
+	input_dev = poll_dev->input;
+	input_dev->name = "Freescale MPR121 Polled Touchkey";
+	input_dev->id.bustype = BUS_I2C;
+	input_dev->dev.parent = dev;
+	if (device_property_read_bool(dev, "autorepeat"))
+		__set_bit(EV_REP, input_dev->evbit);
+	input_set_capability(input_dev, EV_MSC, MSC_SCAN);
+
+	input_dev->keycode = mpr121->keycodes;
+	input_dev->keycodesize = sizeof(mpr121->keycodes[0]);
+	input_dev->keycodemax = mpr121->keycount;
+
+	for (i = 0; i < mpr121->keycount; i++)
+		input_set_capability(input_dev, EV_KEY, mpr121->keycodes[i]);
+
+	error = mpr121_polled_phys_init(mpr121, client);
+	if (error) {
+		dev_err(dev, "Failed to init register\n");
+		return error;
+	}
+
+	error = input_register_polled_device(poll_dev);
+	if (error)
+		return error;
+
+	i2c_set_clientdata(client, mpr121);
+
+	return 0;
+}
+
+static int __maybe_unused mpr121_polled_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+
+	i2c_smbus_write_byte_data(client, ELECTRODE_CONF_ADDR, 0x00);
+
+	return 0;
+}
+
+static int __maybe_unused mpr121_polled_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct mpr121_polled *mpr121 = i2c_get_clientdata(client);
+
+	i2c_smbus_write_byte_data(client, ELECTRODE_CONF_ADDR,
+				  mpr121->keycount);
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(mpr121_polled_pm_ops, mpr121_polled_suspend,
+			 mpr121_polled_resume);
+
+static const struct i2c_device_id mpr121_polled_id[] = {
+	{ "mpr121_polled", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, mpr121_polled_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id mpr121_polled_dt_match_table[] = {
+	{ .compatible = "fsl,mpr121-touchkey-polled" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, mpr121_polled_dt_match_table);
+#endif
+
+static struct i2c_driver mpr121_polled_driver = {
+	.driver = {
+		.name	= "mpr121-polled",
+		.pm	= &mpr121_polled_pm_ops,
+		.of_match_table = of_match_ptr(mpr121_polled_dt_match_table),
+	},
+	.id_table	= mpr121_polled_id,
+	.probe		= mpr121_polled_probe,
+};
+
+module_i2c_driver(mpr121_polled_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Michal Vokáč <michal.vokac@ysoft.com>");
+MODULE_DESCRIPTION("Polled driver for Freescale MPR121 chip");
-- 
2.1.4

[RFC PATCH 3/4] Input: mpr121-polled: Add write-through cache to detect corrupted registers

[Michal Vokáč]

The MPR121 chip (and I2C bus in general) is quite sensitive to ESD.
An electrostatic discharge can easily cause a reset of the MPR121 chip.
Even though the chip then recovers and respond to read/write commands,
it is not properly initialized.

This state can be detected using a write-through cache of the internal
registers. Each time a register is written to, its value is stored in
the cache and marked as valid. Once per MPR121_REG_CACHE_CHECK_LIMIT
polls one valid cache value is compared with its corresponding register
value. In case of difference an error counter is increased. If the error
counter limit is exceeded, the chip is re-initialized.

Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
---
 drivers/input/keyboard/mpr121_touchkey_polled.c | 100 +++++++++++++++++++++---
 1 file changed, 88 insertions(+), 12 deletions(-)

diff --git a/drivers/input/keyboard/mpr121_touchkey_polled.c b/drivers/input/keyboard/mpr121_touchkey_polled.c
index e5e80530c9d8..6536d9b2eeb8 100644
--- a/drivers/input/keyboard/mpr121_touchkey_polled.c
+++ b/drivers/input/keyboard/mpr121_touchkey_polled.c
@@ -67,6 +67,19 @@
 #define MPR121_POLL_INTERVAL_REINIT	500
 #define MPR121_POLL_RETRY_MAX		4
 
+#define MPR121_REG_CACHE_MIN_ADDR	0x2b
+#define MPR121_REG_CACHE_MAX_ADDR	0x7f
+#define MPR121_REG_CACHE_SIZE		\
+		(MPR121_REG_CACHE_MAX_ADDR - MPR121_REG_CACHE_MIN_ADDR + 1)
+#define MPR121_REG_CACHE_CHECK_LIMIT	8
+#define mpr121_addr_to_cache_idx(addr)	(addr - MPR121_REG_CACHE_MIN_ADDR)
+#define mpr121_cache_idx_to_addr(idx)	(idx + MPR121_REG_CACHE_MIN_ADDR)
+
+struct mpr121_polled_reg_cache {
+	bool valid;
+	u8 value;
+};
+
 struct mpr121_polled {
 	struct i2c_client *client;
 	struct input_dev *input_dev;
@@ -76,6 +89,9 @@ struct mpr121_polled {
 	u32 keycodes[MPR121_MAX_KEY_COUNT];
 	u8 read_errors;
 	int vdd_uv;
+	struct mpr121_polled_reg_cache reg_cache[MPR121_REG_CACHE_SIZE];
+	u8 reg_cache_check_count;
+	u8 reg_cache_next_check_item;
 };
 
 struct mpr121_polled_init_register {
@@ -95,6 +111,29 @@ static const struct mpr121_polled_init_register init_reg_table[] = {
 	{ AUTO_CONFIG_CTRL_ADDR, 0x0b },
 };
 
+static int mpr121_polled_write_reg(struct mpr121_polled *mpr121, u8 addr,
+				   u8 value)
+{
+	struct i2c_client *client = mpr121->client;
+	int ret;
+
+	ret = i2c_smbus_write_byte_data(client, addr, value);
+	if (ret < 0) {
+		dev_err(&client->dev, "i2c write error: %d\n", ret);
+		return ret;
+	}
+
+	if (addr >= MPR121_REG_CACHE_MIN_ADDR &&
+	    addr <= MPR121_REG_CACHE_MAX_ADDR) {
+		u8 i = mpr121_addr_to_cache_idx(addr);
+
+		mpr121->reg_cache[i].valid = 1;
+		mpr121->reg_cache[i].value = value;
+	}
+
+	return 0;
+}
+
 static void mpr121_polled_vdd_supply_disable(void *data)
 {
 	struct regulator *vdd_supply = data;
@@ -140,18 +179,18 @@ static int mpr121_polled_phys_init(struct mpr121_polled *mpr121,
 	int i, t, vdd, ret;
 
 	/* Set stop mode prior to writing any register */
-	ret = i2c_smbus_write_byte_data(client, ELECTRODE_CONF_ADDR, 0x00);
+	ret = mpr121_polled_write_reg(mpr121, ELECTRODE_CONF_ADDR, 0x00);
 	if (ret < 0)
 		goto err_i2c_write;
 
 	/* Set up touch/release threshold for ele0-ele11 */
 	for (i = 0; i <= MPR121_MAX_KEY_COUNT; i++) {
 		t = ELE0_TOUCH_THRESHOLD_ADDR + (i * 2);
-		ret = i2c_smbus_write_byte_data(client, t, TOUCH_THRESHOLD);
+		ret = mpr121_polled_write_reg(mpr121, t, TOUCH_THRESHOLD);
 		if (ret < 0)
 			goto err_i2c_write;
-		ret = i2c_smbus_write_byte_data(client, t + 1,
-						RELEASE_THRESHOLD);
+		ret = mpr121_polled_write_reg(mpr121, t + 1,
+					      RELEASE_THRESHOLD);
 		if (ret < 0)
 			goto err_i2c_write;
 	}
@@ -159,7 +198,7 @@ static int mpr121_polled_phys_init(struct mpr121_polled *mpr121,
 	/* Set up init register */
 	for (i = 0; i < ARRAY_SIZE(init_reg_table); i++) {
 		reg = &init_reg_table[i];
-		ret = i2c_smbus_write_byte_data(client, reg->addr, reg->val);
+		ret = mpr121_polled_write_reg(mpr121, reg->addr, reg->val);
 		if (ret < 0)
 			goto err_i2c_write;
 	}
@@ -173,9 +212,9 @@ static int mpr121_polled_phys_init(struct mpr121_polled *mpr121,
 	usl = ((vdd - 700) * 256) / vdd;
 	lsl = (usl * 65) / 100;
 	tl = (usl * 90) / 100;
-	ret = i2c_smbus_write_byte_data(client, AUTO_CONFIG_USL_ADDR, usl);
-	ret |= i2c_smbus_write_byte_data(client, AUTO_CONFIG_LSL_ADDR, lsl);
-	ret |= i2c_smbus_write_byte_data(client, AUTO_CONFIG_TL_ADDR, tl);
+	ret = mpr121_polled_write_reg(mpr121, AUTO_CONFIG_USL_ADDR, usl);
+	ret |= mpr121_polled_write_reg(mpr121, AUTO_CONFIG_LSL_ADDR, lsl);
+	ret |= mpr121_polled_write_reg(mpr121, AUTO_CONFIG_TL_ADDR, tl);
 
 	/*
 	 * Quick charge bit will let the capacitive charge to ready
@@ -183,7 +222,7 @@ static int mpr121_polled_phys_init(struct mpr121_polled *mpr121,
 	 * boot.
 	 */
 	eleconf = mpr121->keycount | ELECTRODE_CONF_QUICK_CHARGE;
-	ret |= i2c_smbus_write_byte_data(client, ELECTRODE_CONF_ADDR,
+	ret |= mpr121_polled_write_reg(mpr121, ELECTRODE_CONF_ADDR,
 					 eleconf);
 	if (ret != 0)
 		goto err_i2c_write;
@@ -256,6 +295,36 @@ static int mpr121_polled_process_keys(struct mpr121_polled *mpr121)
 
 	return 0;
 }
+
+static int mpr121_polled_check_regs(struct mpr121_polled *mpr121)
+{
+	struct i2c_client *client = mpr121->client;
+	int i, reg;
+
+	/* Skip registers that were never written to (have invalid cache) */
+	i = mpr121->reg_cache_next_check_item;
+	for (; i < MPR121_REG_CACHE_SIZE; i++)
+		if (mpr121->reg_cache[i].valid)
+			break;
+
+	if (i == MPR121_REG_CACHE_SIZE) {
+		mpr121->reg_cache_next_check_item = 0;
+		return 0;
+	}
+
+	reg = i2c_smbus_read_byte_data(client, mpr121_cache_idx_to_addr(i));
+	if (reg < 0) {
+		dev_err(&client->dev, "i2c read error: %d\n", reg);
+		return -1;
+	}
+
+	if (reg != mpr121->reg_cache[i].value)
+		return -1;
+
+	mpr121->reg_cache_next_check_item = i + 1;
+	return 0;
+}
+
 static void mpr121_poll(struct input_polled_dev *dev)
 {
 	struct mpr121_polled *mpr121 = dev->private;
@@ -282,6 +351,13 @@ static void mpr121_poll(struct input_polled_dev *dev)
 	}
 
 	mpr121->read_errors = 0;
+	mpr121->reg_cache_check_count++;
+	if (mpr121->reg_cache_check_count > MPR121_REG_CACHE_CHECK_LIMIT) {
+		mpr121->reg_cache_check_count = 0;
+		ret = mpr121_polled_check_regs(mpr121);
+		if (ret < 0)
+			mpr121->read_errors++;
+	}
 }
 
 static int mpr121_polled_probe(struct i2c_client *client,
@@ -366,8 +442,9 @@ static int mpr121_polled_probe(struct i2c_client *client,
 static int __maybe_unused mpr121_polled_suspend(struct device *dev)
 {
 	struct i2c_client *client = to_i2c_client(dev);
+	struct mpr121_polled *mpr121 = i2c_get_clientdata(client);
 
-	i2c_smbus_write_byte_data(client, ELECTRODE_CONF_ADDR, 0x00);
+	mpr121_polled_write_reg(mpr121, ELECTRODE_CONF_ADDR, 0x00);
 
 	return 0;
 }
@@ -377,8 +454,7 @@ static int __maybe_unused mpr121_polled_resume(struct device *dev)
 	struct i2c_client *client = to_i2c_client(dev);
 	struct mpr121_polled *mpr121 = i2c_get_clientdata(client);
 
-	i2c_smbus_write_byte_data(client, ELECTRODE_CONF_ADDR,
-				  mpr121->keycount);
+	mpr121_polled_write_reg(mpr121, ELECTRODE_CONF_ADDR, mpr121->keycount);
 
 	return 0;
 }
-- 
2.1.4

[RFC PATCH 4/4] ARM: dts: imx6dl-yapp4: Enable MPR121 touch keypad on Hydra

[Michal Vokáč]

Enable the I2C connected touch keypad on Hydra board.
Use the polled binding as the interrupt line is not available.

Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
---
 arch/arm/boot/dts/imx6dl-yapp4-common.dtsi | 12 ++++++++++++
 arch/arm/boot/dts/imx6dl-yapp4-hydra.dts   |  4 ++++
 2 files changed, 16 insertions(+)

diff --git a/arch/arm/boot/dts/imx6dl-yapp4-common.dtsi b/arch/arm/boot/dts/imx6dl-yapp4-common.dtsi
index e8d800fec637..65a670e5bd4f 100644
--- a/arch/arm/boot/dts/imx6dl-yapp4-common.dtsi
+++ b/arch/arm/boot/dts/imx6dl-yapp4-common.dtsi
@@ -4,6 +4,7 @@
 
 #include <dt-bindings/gpio/gpio.h>
 #include <dt-bindings/interrupt-controller/irq.h>
+#include <dt-bindings/input/input.h>
 #include <dt-bindings/pwm/pwm.h>
 
 / {
@@ -330,6 +331,17 @@
 		vcc-supply = <&sw2_reg>;
 		status = "disabled";
 	};
+
+	touchkeys: keys@5a {
+		compatible = "fsl,mpr121-touchkey-polled";
+		reg = <0x5a>;
+		vdd-supply = <&sw2_reg>;
+		autorepeat;
+		linux,keycodes = <KEY_1>, <KEY_2>, <KEY_3>, <KEY_4>, <KEY_5>,
+				<KEY_6>, <KEY_7>, <KEY_8>, <KEY_9>,
+				<KEY_BACKSPACE>, <KEY_0>, <KEY_ENTER>;
+		status = "disabled";
+	};
 };
 
 &iomuxc {
diff --git a/arch/arm/boot/dts/imx6dl-yapp4-hydra.dts b/arch/arm/boot/dts/imx6dl-yapp4-hydra.dts
index f97927064750..84c275bfdd38 100644
--- a/arch/arm/boot/dts/imx6dl-yapp4-hydra.dts
+++ b/arch/arm/boot/dts/imx6dl-yapp4-hydra.dts
@@ -45,6 +45,10 @@
 	status = "okay";
 };
 
+&touchkeys {
+	status = "okay";
+};
+
 &usdhc3 {
 	status = "okay";
 };
-- 
2.1.4

Re: [RFC PATCH 1/4] dt-bindings: input: Add support for the MPR121 without interrupt line

[Rob Herring]

On Fri, Apr 26, 2019 at 10:30:17AM +0200, Michal Vokáč wrote:
> Normally, the MPR121 controller uses separate interrupt line to notify
> the I2C host that a key was touched/released. To support platforms that
> can not use the interrupt line, polling of the MPR121 registers can be
> used.

Other than making the 'interrupts' property optional, that's a driver 
change, not a DT change. IOW, we shouldn't need a whole new binding.

> 
> Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
> ---
>  .../bindings/input/mpr121-touchkey-polled.txt      | 26 ++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/input/mpr121-touchkey-polled.txt
> 
> diff --git a/Documentation/devicetree/bindings/input/mpr121-touchkey-polled.txt b/Documentation/devicetree/bindings/input/mpr121-touchkey-polled.txt
> new file mode 100644
> index 000000000000..6bb1d312614c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/input/mpr121-touchkey-polled.txt
> @@ -0,0 +1,26 @@
> +* Freescale MPR121 Controller without interrupt line
> +
> +Required Properties:
> +- compatible:		Should be "fsl,mpr121-touchkey-polled"
> +- reg:			The I2C slave address of the device.
> +- vdd-supply:		Phandle to the Vdd power supply.
> +- linux,keycodes:	Specifies an array of numeric keycode values to
> +			be used for reporting button presses. The array can
> +			contain up to 12 entries.
> +
> +Optional Properties:
> +- autorepeat:		Enable autorepeat feature.
> +
> +Example:
> +
> +#include "dt-bindings/input/input.h"
> +
> +	touchkeys: keys@5a {
> +		compatible = "fsl,mpr121-touchkey-polled";
> +		reg = <0x5a>;
> +		autorepeat;
> +		vdd-supply = <&ldo4_reg>;
> +		linux,keycodes = <KEY_0>, <KEY_1>, <KEY_2>, <KEY_3>,
> +				<KEY_4> <KEY_5>, <KEY_6>, <KEY_7>,
> +				<KEY_8>, <KEY_9>, <KEY_A>, <KEY_B>;
> +	};
> -- 
> 2.1.4
> 

Re: [RFC PATCH 1/4] dt-bindings: input: Add support for the MPR121 without interrupt line

[Michal Vokáč]

On 02. 05. 19 2:48, Rob Herring wrote:
> On Fri, Apr 26, 2019 at 10:30:17AM +0200, Michal Vokáč wrote:
>> Normally, the MPR121 controller uses separate interrupt line to notify
>> the I2C host that a key was touched/released. To support platforms that
>> can not use the interrupt line, polling of the MPR121 registers can be
>> used.
> 
> Other than making the 'interrupts' property optional, that's a driver
> change, not a DT change. IOW, we shouldn't need a whole new binding.
> 

OK, I will update the existing binding instead.

Thank you,
Michal

>>
>> Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
>> ---
>>   .../bindings/input/mpr121-touchkey-polled.txt      | 26 ++++++++++++++++++++++
>>   1 file changed, 26 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/input/mpr121-touchkey-polled.txt
>>
>> diff --git a/Documentation/devicetree/bindings/input/mpr121-touchkey-polled.txt b/Documentation/devicetree/bindings/input/mpr121-touchkey-polled.txt
>> new file mode 100644
>> index 000000000000..6bb1d312614c
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/input/mpr121-touchkey-polled.txt
>> @@ -0,0 +1,26 @@
>> +* Freescale MPR121 Controller without interrupt line
>> +
>> +Required Properties:
>> +- compatible:		Should be "fsl,mpr121-touchkey-polled"
>> +- reg:			The I2C slave address of the device.
>> +- vdd-supply:		Phandle to the Vdd power supply.
>> +- linux,keycodes:	Specifies an array of numeric keycode values to
>> +			be used for reporting button presses. The array can
>> +			contain up to 12 entries.
>> +
>> +Optional Properties:
>> +- autorepeat:		Enable autorepeat feature.
>> +
>> +Example:
>> +
>> +#include "dt-bindings/input/input.h"
>> +
>> +	touchkeys: keys@5a {
>> +		compatible = "fsl,mpr121-touchkey-polled";
>> +		reg = <0x5a>;
>> +		autorepeat;
>> +		vdd-supply = <&ldo4_reg>;
>> +		linux,keycodes = <KEY_0>, <KEY_1>, <KEY_2>, <KEY_3>,
>> +				<KEY_4> <KEY_5>, <KEY_6>, <KEY_7>,
>> +				<KEY_8>, <KEY_9>, <KEY_A>, <KEY_B>;
>> +	};
>> -- 
>> 2.1.4
>>