Input: add Atmel Captouch Button driver

Add I2C driver for Atmel Capacitive Touch Button device.

Signed-off-by: Hung-yu Wu <hywu@google.com>
Signed-off-by: Grant Grundler <grundler@chromium.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

3 files changed, 304 insertions, 0 deletions

diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
index 1f2337abcf2f..9c3dfe79d4d4 100644
--- a/drivers/input/misc/Kconfig
+++ b/drivers/input/misc/Kconfig
@@ -82,6 +82,19 @@ config INPUT_ARIZONA_HAPTICS
           To compile this driver as a module, choose M here: the
           module will be called arizona-haptics.
 
+config INPUT_ATMEL_CAPTOUCH
+        tristate "Atmel Capacitive Touch Button Driver"
+        depends on OF || COMPILE_TEST
+        help
+          Say Y here if an Atmel Capacitive Touch Button device which
+          implements "captouch" protocol is connected to I2C bus. Typically
+          this device consists of Atmel Touch sensor controlled by AtMegaXX
+          MCU running firmware based on Qtouch library.
+          One should find "atmel,captouch" node in the board specific DTS.
+
+          To compile this driver as a module, choose M here: the
+          module will be called atmel_captouch.
+
 config INPUT_BMA150
         tristate "BMA150/SMB380 acceleration sensor support"
         depends on I2C
diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
index 0357a088c6a9..5373f493f370 100644
--- a/drivers/input/misc/Makefile
+++ b/drivers/input/misc/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_INPUT_APANEL)		+= apanel.o
 obj-$(CONFIG_INPUT_ARIZONA_HAPTICS)     += arizona-haptics.o
 obj-$(CONFIG_INPUT_ATI_REMOTE2)         += ati_remote2.o
 obj-$(CONFIG_INPUT_ATLAS_BTNS)          += atlas_btns.o
+obj-$(CONFIG_INPUT_ATMEL_CAPTOUCH)      += atmel_captouch.o
 obj-$(CONFIG_INPUT_BFIN_ROTARY)         += bfin_rotary.o
 obj-$(CONFIG_INPUT_BMA150)              += bma150.o
 obj-$(CONFIG_INPUT_CM109)               += cm109.o
diff --git a/drivers/input/misc/atmel_captouch.c b/drivers/input/misc/atmel_captouch.c
new file mode 100644
index 000000000000..941265415a89
--- /dev/null
+++ b/drivers/input/misc/atmel_captouch.c
@@ -0,0 +1,290 @@
+/*
+ * Atmel Atmegaxx Capacitive Touch Button Driver
+ *
+ * Copyright (C) 2016 Google, inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+/*
+ * It's irrelevant that the HW used to develop captouch driver is based
+ * on Atmega88PA part and uses QtouchADC parts for sensing touch.
+ * Calling this driver "captouch" is an arbitrary way to distinguish
+ * the protocol this driver supported by other atmel/qtouch drivers.
+ *
+ * Captouch driver supports a newer/different version of the I2C
+ * registers/commands than the qt1070.c driver.
+ * Don't let the similarity of the general driver structure fool you.
+ *
+ * For raw i2c access from userspace, use i2cset/i2cget
+ * to poke at /dev/i2c-N devices.
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+
+/* Maximum number of buttons supported */
+#define MAX_NUM_OF_BUTTONS              8
+
+/* Registers */
+#define REG_KEY1_THRESHOLD              0x02
+#define REG_KEY2_THRESHOLD              0x03
+#define REG_KEY3_THRESHOLD              0x04
+#define REG_KEY4_THRESHOLD              0x05
+
+#define REG_KEY1_REF_H                  0x20
+#define REG_KEY1_REF_L                  0x21
+#define REG_KEY2_REF_H                  0x22
+#define REG_KEY2_REF_L                  0x23
+#define REG_KEY3_REF_H                  0x24
+#define REG_KEY3_REF_L                  0x25
+#define REG_KEY4_REF_H                  0x26
+#define REG_KEY4_REF_L                  0x27
+
+#define REG_KEY1_DLT_H                  0x30
+#define REG_KEY1_DLT_L                  0x31
+#define REG_KEY2_DLT_H                  0x32
+#define REG_KEY2_DLT_L                  0x33
+#define REG_KEY3_DLT_H                  0x34
+#define REG_KEY3_DLT_L                  0x35
+#define REG_KEY4_DLT_H                  0x36
+#define REG_KEY4_DLT_L                  0x37
+
+#define REG_KEY_STATE                   0x3C
+
+/*
+ * @i2c_client: I2C slave device client pointer
+ * @input: Input device pointer
+ * @num_btn: Number of buttons
+ * @keycodes: map of button# to KeyCode
+ * @prev_btn: Previous key state to detect button "press" or "release"
+ * @xfer_buf: I2C transfer buffer
+ */
+struct atmel_captouch_device {
+        struct i2c_client *client;
+        struct input_dev *input;
+        u32 num_btn;
+        u32 keycodes[MAX_NUM_OF_BUTTONS];
+        u8 prev_btn;
+        u8 xfer_buf[8] ____cacheline_aligned;
+};
+
+/*
+ * Read from I2C slave device
+ * The protocol is that the client has to provide both the register address
+ * and the length, and while reading back the device would prepend the data
+ * with address and length for verification.
+ */
+static int atmel_read(struct atmel_captouch_device *capdev,
+                         u8 reg, u8 *data, size_t len)
+{
+        struct i2c_client *client = capdev->client;
+        struct device *dev = &client->dev;
+        struct i2c_msg msg[2];
+        int err;
+
+        if (len > sizeof(capdev->xfer_buf) - 2)
+                return -EINVAL;
+
+        capdev->xfer_buf[0] = reg;
+        capdev->xfer_buf[1] = len;
+
+        msg[0].addr = client->addr;
+        msg[0].flags = 0;
+        msg[0].buf = capdev->xfer_buf;
+        msg[0].len = 2;
+
+        msg[1].addr = client->addr;
+        msg[1].flags = I2C_M_RD;
+        msg[1].buf = capdev->xfer_buf;
+        msg[1].len = len + 2;
+
+        err = i2c_transfer(client->adapter, msg, ARRAY_SIZE(msg));
+        if (err != ARRAY_SIZE(msg))
+                return err < 0 ? err : -EIO;
+
+        if (capdev->xfer_buf[0] != reg) {
+                dev_err(dev,
+                        "I2C read error: register address does not match (%#02x vs %02x)\n",
+                        capdev->xfer_buf[0], reg);
+                return -ECOMM;
+        }
+
+        memcpy(data, &capdev->xfer_buf[2], len);
+
+        return 0;
+}
+
+/*
+ * Handle interrupt and report the key changes to the input system.
+ * Multi-touch can be supported; however, it really depends on whether
+ * the device can multi-touch.
+ */
+static irqreturn_t atmel_captouch_isr(int irq, void *data)
+{
+        struct atmel_captouch_device *capdev = data;
+        struct device *dev = &capdev->client->dev;
+        int error;
+        int i;
+        u8 new_btn;
+        u8 changed_btn;
+
+        error = atmel_read(capdev, REG_KEY_STATE, &new_btn, 1);
+        if (error) {
+                dev_err(dev, "failed to read button state: %d\n", error);
+                goto out;
+        }
+
+        dev_dbg(dev, "%s: button state %#02x\n", __func__, new_btn);
+
+        changed_btn = new_btn ^ capdev->prev_btn;
+        capdev->prev_btn = new_btn;
+
+        for (i = 0; i < capdev->num_btn; i++) {
+                if (changed_btn & BIT(i))
+                        input_report_key(capdev->input,
+                                         capdev->keycodes[i],
+                                         new_btn & BIT(i));
+        }
+
+        input_sync(capdev->input);
+
+out:
+        return IRQ_HANDLED;
+}
+
+/*
+ * Probe function to setup the device, input system and interrupt
+ */
+static int atmel_captouch_probe(struct i2c_client *client,
+                const struct i2c_device_id *id)
+{
+        struct atmel_captouch_device *capdev;
+        struct device *dev = &client->dev;
+        struct device_node *node;
+        int i;
+        int err;
+
+        if (!i2c_check_functionality(client->adapter,
+                                     I2C_FUNC_SMBUS_BYTE_DATA |
+                                        I2C_FUNC_SMBUS_WORD_DATA |
+                                        I2C_FUNC_SMBUS_I2C_BLOCK)) {
+                dev_err(dev, "needed i2c functionality is not supported\n");
+                return -EINVAL;
+        }
+
+        capdev = devm_kzalloc(dev, sizeof(*capdev), GFP_KERNEL);
+        if (!capdev)
+                return -ENOMEM;
+
+        capdev->client = client;
+        i2c_set_clientdata(client, capdev);
+
+        err = atmel_read(capdev, REG_KEY_STATE,
+                            &capdev->prev_btn, sizeof(capdev->prev_btn));
+        if (err) {
+                dev_err(dev, "failed to read initial button state: %d\n", err);
+                return err;
+        }
+
+        capdev->input = devm_input_allocate_device(dev);
+        if (!capdev->input) {
+                dev_err(dev, "failed to allocate input device\n");
+                return -ENOMEM;
+        }
+
+        capdev->input->id.bustype = BUS_I2C;
+        capdev->input->id.product = 0x880A;
+        capdev->input->id.version = 0;
+        capdev->input->name = "ATMegaXX Capacitive Button Controller";
+        __set_bit(EV_KEY, capdev->input->evbit);
+
+        node = dev->of_node;
+        if (!node) {
+                dev_err(dev, "failed to find matching node in device tree\n");
+                return -EINVAL;
+        }
+
+        if (of_property_read_bool(node, "autorepeat"))
+                __set_bit(EV_REP, capdev->input->evbit);
+
+        capdev->num_btn = of_property_count_u32_elems(node, "linux,keymap");
+        if (capdev->num_btn > MAX_NUM_OF_BUTTONS)
+                capdev->num_btn = MAX_NUM_OF_BUTTONS;
+
+        err = of_property_read_u32_array(node, "linux,keycodes",
+                                         capdev->keycodes,
+                                         capdev->num_btn);
+        if (err) {
+                dev_err(dev,
+                        "failed to read linux,keycode property: %d\n", err);
+                return err;
+        }
+
+        for (i = 0; i < capdev->num_btn; i++)
+                __set_bit(capdev->keycodes[i], capdev->input->keybit);
+
+        capdev->input->keycode = capdev->keycodes;
+        capdev->input->keycodesize = sizeof(capdev->keycodes[0]);
+        capdev->input->keycodemax = capdev->num_btn;
+
+        err = input_register_device(capdev->input);
+        if (err)
+                return err;
+
+        err = devm_request_threaded_irq(dev, client->irq,
+                                        NULL, atmel_captouch_isr,
+                                        IRQF_ONESHOT,
+                                        "atmel_captouch", capdev);
+        if (err) {
+                dev_err(dev, "failed to request irq %d: %d\n",
+                        client->irq, err);
+                return err;
+        }
+
+        return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id atmel_captouch_of_id[] = {
+        {
+                .compatible = "atmel,captouch",
+        },
+        { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, atmel_captouch_of_id);
+#endif
+
+static const struct i2c_device_id atmel_captouch_id[] = {
+        { "atmel_captouch", 0 },
+        { }
+};
+MODULE_DEVICE_TABLE(i2c, atmel_captouch_id);
+
+static struct i2c_driver atmel_captouch_driver = {
+        .probe          = atmel_captouch_probe,
+        .id_table       = atmel_captouch_id,
+        .driver         = {
+                .name   = "atmel_captouch",
+                .of_match_table = of_match_ptr(atmel_captouch_of_id),
+        },
+};
+module_i2c_driver(atmel_captouch_driver);
+
+/* Module information */
+MODULE_AUTHOR("Hung-yu Wu <hywu@google.com>");
+MODULE_DESCRIPTION("Atmel ATmegaXX Capacitance Touch Sensor I2C Driver");
+MODULE_LICENSE("GPL v2");