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From:   Kamel Bouhara <kamel.bouhara@bootlin.com>
To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Henrik Rydberg <rydberg@bitmath.org>
Cc:     linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org, Marco Felsch <m.felsch@pengutronix.de>,
        mark.satterthwaite@touchnetix.com, bartp@baasheep.co.uk,
        hannah.rossiter@touchnetix.com,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        Gregory Clement <gregory.clement@bootlin.com>,
        bsp-development.geo@leica-geosystems.com,
        Kamel Bouhara <kamel.bouhara@bootlin.com>
Subject: [PATCH v3 3/3] Input: Add TouchNetix axiom i2c touchscreen driver
Date:   Thu, 12 Oct 2023 09:40:34 +0200
Message-Id: <20231012074034.1090436-4-kamel.bouhara@bootlin.com>
In-Reply-To: <20231012074034.1090436-1-kamel.bouhara@bootlin.com>
References: <20231012074034.1090436-1-kamel.bouhara@bootlin.com>
MIME-Version: 1.0
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Precedence: bulk

Add a new driver for the TouchNetix's axiom family of
touchscreen controllers. This driver only supports i2c
and can be later adapted for SPI and USB support.

Signed-off-by: Kamel Bouhara <kamel.bouhara@bootlin.com>
---
 MAINTAINERS                                   |   1 +
 drivers/input/touchscreen/Kconfig             |  13 +
 drivers/input/touchscreen/Makefile            |   1 +
 .../input/touchscreen/touchnetix_axiom_i2c.c  | 740 ++++++++++++++++++
 4 files changed, 755 insertions(+)
 create mode 100644 drivers/input/touchscreen/touchnetix_axiom_i2c.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 12ae8bc6b8cf..2d1e0b025e89 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -21415,6 +21415,7 @@ M:	Kamel Bouhara <kamel.bouhara@bootlin.com>
 L:	linux-input@vger.kernel.org
 S:	Maintained
 F:	Documentation/devicetree/bindings/input/touchscreen/touchnetix,axiom-ax54a.yaml
+F:	drivers/input/touchscreen/touchnetix_axiom_i2c.c
 
 THUNDERBOLT DMA TRAFFIC TEST DRIVER
 M:	Isaac Hazan <isaac.hazan@intel.com>
diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
index e3e2324547b9..58665ccbe077 100644
--- a/drivers/input/touchscreen/Kconfig
+++ b/drivers/input/touchscreen/Kconfig
@@ -803,6 +803,19 @@ config TOUCHSCREEN_MIGOR
 	  To compile this driver as a module, choose M here: the
 	  module will be called migor_ts.
 
+config TOUCHSCREEN_TOUCHNETIX_AXIOM_I2C
+	tristate "TouchNetix AXIOM based touchscreen controllers"
+	depends on I2C
+	depends on GPIOLIB || COMPILE_TEST
+	help
+	  Say Y here if you have a axiom touchscreen connected to
+	  your system.
+
+	  If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called axiom_i2c.
+
 config TOUCHSCREEN_TOUCHRIGHT
 	tristate "Touchright serial touchscreen"
 	select SERIO
diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
index 62bd24f3ac8e..23b6fb8864b0 100644
--- a/drivers/input/touchscreen/Makefile
+++ b/drivers/input/touchscreen/Makefile
@@ -88,6 +88,7 @@ obj-$(CONFIG_TOUCHSCREEN_SUR40)		+= sur40.o
 obj-$(CONFIG_TOUCHSCREEN_SURFACE3_SPI)	+= surface3_spi.o
 obj-$(CONFIG_TOUCHSCREEN_TI_AM335X_TSC)	+= ti_am335x_tsc.o
 obj-$(CONFIG_TOUCHSCREEN_TOUCHIT213)	+= touchit213.o
+obj-$(CONFIG_TOUCHSCREEN_TOUCHNETIX_AXIOM_I2C)	+= touchnetix_axiom_i2c.o
 obj-$(CONFIG_TOUCHSCREEN_TOUCHRIGHT)	+= touchright.o
 obj-$(CONFIG_TOUCHSCREEN_TOUCHWIN)	+= touchwin.o
 obj-$(CONFIG_TOUCHSCREEN_TS4800)	+= ts4800-ts.o
diff --git a/drivers/input/touchscreen/touchnetix_axiom_i2c.c b/drivers/input/touchscreen/touchnetix_axiom_i2c.c
new file mode 100644
index 000000000000..fb6239a87341
--- /dev/null
+++ b/drivers/input/touchscreen/touchnetix_axiom_i2c.c
@@ -0,0 +1,740 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * TouchNetix aXiom Touchscreen Driver
+ *
+ * Copyright (C) 2020-2023 TouchNetix Ltd.
+ *
+ * Author(s): Bart Prescott <bartp@baasheep.co.uk>
+ *            Pedro Torruella <pedro.torruella@touchnetix.com>
+ *            Mark Satterthwaite <mark.satterthwaite@touchnetix.com>
+ *            Hannah Rossiter <hannah.rossiter@touchnetix.com>
+ *            Kamel Bouhara <kamel.bouhara@bootlin.com>
+ *
+ */
+
+#include <linux/crc16.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/input/mt.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/pm.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+/*
+ * Runtime TCP mode: device is executing normal code and is
+ * accessible via the Touch Controller Mode
+ */
+#define BOOT_TCP			0
+/*
+ * Bootloader BLP mode: device is executing bootloader and is
+ * accessible via the Boot Loader Protocol.
+ */
+#define BOOT_BLP			1
+#define AXIOM_PROX_LEVEL		-128
+/*
+ * Register group u31 has 2 pages for usage table entries.
+ * (2 * AXIOM_COMMS_PAGE_SIZE) / AXIOM_U31_BYTES_PER_USAGE = 85
+ */
+#define AXIOM_U31_MAX_USAGES		85
+#define AXIOM_U31_BYTES_PER_USAGE	6
+#define AXIOM_U31_PAGE0_LENGTH		0x0C
+#define AXIOM_U31_BOOTMODE_MASK		BIT(7)
+#define AXIOM_U31_FW_INFO_VARIANT_MASK	GENMASK(6, 0)
+#define AXIOM_U31_FW_INFO_STATUS_MASK	BIT(7)
+
+#define AXIOM_U41_MAX_TARGETS		10
+
+#define AXIOM_U46_AUX_CHANNELS		4
+#define AXIOM_U46_AUX_MASK		GENMASK(11, 0)
+
+#define AXIOM_COMMS_MAX_USAGE_PAGES	3
+#define AXIOM_COMMS_PAGE_SIZE		256
+#define AXIOM_COMMS_OVERFLOW_MASK	BIT(7)
+#define AXIOM_COMMS_REPORT_LEN_MASK	GENMASK(7, 0)
+
+#define AXIOM_REBASELINE_CMD		0x03
+
+#define AXIOM_REPORT_USAGE_ID		0x34
+#define AXIOM_DEVINFO_USAGE_ID		0x31
+#define AXIOM_USAGE_2HB_REPORT_ID	0x01
+#define AXIOM_REBASELINE_USAGE_ID	0x02
+#define AXIOM_USAGE_2AUX_REPORT_ID	0x46
+#define AXIOM_USAGE_2DCTS_REPORT_ID	0x41
+
+#define AXIOM_PAGE_MASK			GENMASK(15, 8)
+#define AXIOM_PAGE_OFFSET_MASK		GENMASK(7, 0)
+
+struct axiom_devinfo {
+	char bootloader_fw_major;
+	char bootloader_fw_minor;
+	char bootmode;
+	u16 device_id;
+	char fw_major;
+	char fw_minor;
+	char fw_info_extra;
+	char tcp_revision;
+	u16 jedec_id;
+	char num_usages;
+	char silicon_revision;
+};
+
+/*
+ * Describes parameters of a specific usage, essenstially a single element of
+ * the "Usage Table"
+ */
+struct usage_entry {
+	char id;
+	char is_report;
+	char start_page;
+	char num_pages;
+};
+
+/*
+ * Holds state of a touch or target when detected prior a touch (eg.
+ * hover or proximity events).
+ */
+enum axiom_target_state {
+	TARGET_STATE_NOT_PRESENT = 0,
+	TARGET_STATE_PROX = 1,
+	TARGET_STATE_HOVER = 2,
+	TARGET_STATE_TOUCHING = 3,
+	TARGET_STATE_MIN = TARGET_STATE_NOT_PRESENT,
+	TARGET_STATE_MAX = TARGET_STATE_TOUCHING,
+};
+
+struct u41_target {
+	enum axiom_target_state state;
+	u16 x;
+	u16 y;
+	s8 z;
+	bool insert;
+	bool touch;
+};
+
+struct axiom_target_report {
+	u8 index;
+	u8 present;
+	u16 x;
+	u16 y;
+	s8 z;
+};
+
+struct axiom_cmd_header {
+	u16 target_address;
+	u16 length:15;
+	u16 read:1;
+} __packed;
+
+struct axiom_data {
+	struct axiom_devinfo devinfo;
+	struct device *dev;
+	struct gpio_desc *reset_gpio;
+	struct gpio_desc *irq_gpio;
+	struct i2c_client *client;
+	struct input_dev *input_dev;
+	u32 max_report_len;
+	u32 report_overflow_counter;
+	u32 report_counter;
+	char rx_buf[AXIOM_COMMS_MAX_USAGE_PAGES * AXIOM_COMMS_PAGE_SIZE];
+	struct u41_target targets[AXIOM_U41_MAX_TARGETS];
+	struct usage_entry usage_table[AXIOM_U31_MAX_USAGES];
+	bool usage_table_populated;
+};
+
+/*
+ * aXiom devices are typically configured to report
+ * touches at a rate of 100Hz (10ms). For systems
+ * that require polling for reports, 100ms seems like
+ * an acceptable polling rate.
+ * When reports are polled, it will be expected to
+ * occasionally observe the overflow bit being set
+ * in the reports. This indicates that reports are not
+ * being read fast enough.
+ */
+#define POLL_INTERVAL_DEFAULT_MS 100
+
+/* Translate usage/page/offset triplet into physical address. */
+static u16
+usage_to_target_address(struct axiom_data *ts, char usage, char page,
+			char offset)
+{
+	struct axiom_devinfo *device_info;
+	struct usage_entry *usage_table;
+	u32 i;
+
+	device_info = &ts->devinfo;
+	usage_table = ts->usage_table;
+
+	/* At the moment the convention is that u31 is always at physical address 0x0 */
+	if (!ts->usage_table_populated) {
+		if (usage == AXIOM_DEVINFO_USAGE_ID)
+			return ((page << 8) + offset);
+		else
+			return 0xffff;
+	}
+
+	for (i = 0; i < device_info->num_usages; i++) {
+		if (usage_table[i].id != usage)
+			continue;
+
+		if (page >= usage_table[i].num_pages) {
+			dev_err(ts->dev, "Invalid usage table! usage: %u, page: %u, offset: %u\n",
+				usage, page, offset);
+			return 0xffff;
+		}
+	}
+
+	return ((usage_table[i].start_page + page) << 8) + offset;
+}
+
+static int
+axiom_i2c_read(struct i2c_client *client, u8 usage, u8 page, u8 *buf, u16 len)
+{
+	struct axiom_data *ts = i2c_get_clientdata(client);
+	struct axiom_cmd_header cmd_header;
+	struct i2c_msg msg[2];
+	int ret;
+
+	cmd_header.target_address = cpu_to_le16(usage_to_target_address(ts, usage, page, 0));
+	cmd_header.length = cpu_to_le16(len);
+	cmd_header.read = 1;
+
+	msg[0].addr = client->addr;
+	msg[0].flags = 0;
+	msg[0].len = sizeof(cmd_header);
+	msg[0].buf = (u8 *)&cmd_header;
+
+	msg[1].addr = client->addr;
+	msg[1].flags = I2C_M_RD;
+	msg[1].len = len;
+	msg[1].buf = (char *)buf;
+
+	ret = i2c_transfer(client->adapter, msg, 2);
+	if (ret != ARRAY_SIZE(msg)) {
+		dev_err(&client->dev,
+			"Failed reading usage %#x page %#x, error=%d\n",
+			usage, page, ret);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int
+axiom_i2c_write(struct i2c_client *client, u8 usage, u8 page, u8 *buf, u16 len)
+{
+	struct axiom_data *ts = i2c_get_clientdata(client);
+	struct axiom_cmd_header cmd_header;
+	struct i2c_msg msg[2];
+	int ret;
+
+	cmd_header.target_address = cpu_to_le16(usage_to_target_address(ts, usage, page, 0));
+	cmd_header.length = cpu_to_le16(len);
+	cmd_header.read = 0;
+
+	msg[0].addr = client->addr;
+	msg[0].flags = 0;
+	msg[0].len = sizeof(cmd_header);
+	msg[0].buf = (u8 *)&cmd_header;
+
+	msg[1].addr = client->addr;
+	msg[1].flags = 0;
+	msg[1].len = len;
+	msg[1].buf = (char *)buf;
+
+	ret = i2c_transfer(client->adapter, msg, 2);
+	if (ret < 0) {
+		dev_err(&client->dev,
+			"Failed to write usage %#x page %#x, error=%d\n", usage,
+			page, ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+/*
+ * Decodes and populates the local Usage Table.
+ * Given a buffer of data read from page 1 onwards of u31 from an aXiom
+ * device.
+ */
+static u32 axiom_populate_usage_table(struct axiom_data *ts, char *rx_data)
+{
+	u32 usage_id = 0;
+	u32 max_report_len = 0;
+	struct axiom_devinfo *device_info;
+	struct usage_entry *usage_table;
+
+	device_info = &ts->devinfo;
+	usage_table = ts->usage_table;
+
+	for (usage_id = 0; usage_id < device_info->num_usages; usage_id++) {
+		u16 offset = (usage_id * AXIOM_U31_BYTES_PER_USAGE);
+		char id = rx_data[offset + 0];
+		char start_page = rx_data[offset + 1];
+		char num_pages = rx_data[offset + 2];
+		u32 max_offset = ((rx_data[offset + 3] & AXIOM_PAGE_OFFSET_MASK) + 1) * 2;
+
+		if (!num_pages)
+			usage_table[usage_id].is_report = true;
+
+		/* Store the entry into the usage table */
+		usage_table[usage_id].id = id;
+		usage_table[usage_id].start_page = start_page;
+		usage_table[usage_id].num_pages = num_pages;
+
+		dev_dbg(ts->dev, "Usage %2u Info: %*ph\n", usage_id,
+			AXIOM_U31_BYTES_PER_USAGE,
+			&rx_data[offset]);
+
+		/* Identify the max report length the module will receive */
+		if (usage_table[usage_id].is_report && max_offset > max_report_len)
+			max_report_len = max_offset;
+	}
+	ts->usage_table_populated = true;
+
+	return max_report_len;
+}
+
+/* Retrieve, store and print the axiom device information */
+static int axiom_discover(struct axiom_data *ts)
+{
+	struct axiom_devinfo *devinfo = &ts->devinfo;
+	struct device *dev = ts->dev;
+	char *rx_data = ts->rx_buf;
+	int ret;
+
+	/*
+	 * Fetch the first page of usage u31 to get the
+	 * device information and the number of usages
+	 */
+	ret = axiom_i2c_read(ts->client, AXIOM_DEVINFO_USAGE_ID, 0, rx_data,
+			     AXIOM_U31_PAGE0_LENGTH);
+	if (ret)
+		return ret;
+
+	devinfo->bootmode = (rx_data[0] & AXIOM_U31_BOOTMODE_MASK);
+	devinfo->device_id = ((rx_data[1] & AXIOM_PAGE_OFFSET_MASK) << 8) | rx_data[0];
+	devinfo->fw_minor = rx_data[2];
+	devinfo->fw_major = rx_data[3];
+	devinfo->fw_info_extra = rx_data[4];
+	devinfo->bootloader_fw_minor = rx_data[6];
+	devinfo->bootloader_fw_major = rx_data[7];
+	devinfo->jedec_id = (rx_data[8]) | (rx_data[9] << 8);
+	devinfo->num_usages = rx_data[10];
+	devinfo->silicon_revision = rx_data[11];
+
+	dev_dbg(dev, "  Boot Mode: %s\n", ts->devinfo.bootmode ? "BLP" : "TCP");
+	dev_dbg(dev, "  Device ID      : %04x\n", ts->devinfo.device_id);
+	dev_dbg(dev, "  Firmware Rev   : %02x.%02x\n", ts->devinfo.fw_major,
+		ts->devinfo.fw_minor);
+	dev_dbg(dev, "  Bootloader Rev : %02x.%02x\n",
+		ts->devinfo.bootloader_fw_major,
+		ts->devinfo.bootloader_fw_minor);
+	dev_dbg(dev, "  FW Extra Info  : %04x\n", ts->devinfo.fw_info_extra);
+	dev_dbg(dev, "  Silicon        : %02x\n", ts->devinfo.jedec_id);
+	dev_dbg(dev, "  Num Usages     : %04x\n", ts->devinfo.num_usages);
+
+	/* Read the second page of usage u31 to get the usage table */
+	ret = axiom_i2c_read(ts->client, AXIOM_DEVINFO_USAGE_ID, 1, rx_data,
+			     (AXIOM_U31_BYTES_PER_USAGE * ts->devinfo.num_usages));
+	if (ret)
+		return ret;
+
+	ts->max_report_len = axiom_populate_usage_table(ts, rx_data);
+	dev_dbg(dev, "Max Report Length: %u\n", ts->max_report_len);
+
+	return 0;
+}
+
+/*
+ * Support function to axiom_process_u41_report.
+ * Generates input-subsystem events for every target.
+ * After calling this function the caller shall issue
+ * a Sync to the input sub-system.
+ */
+static bool
+axiom_process_u41_report_target(struct axiom_data *ts,
+				struct axiom_target_report *target)
+{
+	struct input_dev *input_dev = ts->input_dev;
+	enum axiom_target_state current_state;
+	struct u41_target *target_prev_state;
+	struct device *dev = ts->dev;
+	bool update = false;
+	int slot;
+
+	/* Verify the target index */
+	if (target->index >= AXIOM_U41_MAX_TARGETS) {
+		dev_dbg(dev, "Invalid target index! %u\n", target->index);
+		return false;
+	}
+
+	target_prev_state = &ts->targets[target->index];
+
+	current_state = TARGET_STATE_NOT_PRESENT;
+
+	if (target->present) {
+		if (target->z >= 0)
+			current_state = TARGET_STATE_TOUCHING;
+		else if (target->z > AXIOM_PROX_LEVEL && target->z < 0)
+			current_state = TARGET_STATE_HOVER;
+		else if (target->z AXIOM_PROX_LEVEL)
+			current_state = TARGET_STATE_PROX;
+	}
+
+	if (target_prev_state->state == current_state &&
+	    target_prev_state->x == target->x &&
+	    target_prev_state->y == target->y &&
+	    target_prev_state->z == target->z) {
+		return false;
+	}
+
+	slot = target->index;
+
+	dev_dbg(dev, "U41 Target T%u, slot:%u present:%u, x:%u, y:%u, z:%d\n",
+		target->index, slot, target->present,
+		target->x, target->y, target->z);
+
+	switch (current_state) {
+	case TARGET_STATE_NOT_PRESENT:
+	case TARGET_STATE_PROX:
+		if (target_prev_state->insert)
+			break;
+		update = true;
+		target_prev_state->insert = false;
+		input_mt_slot(input_dev, slot);
+
+		if (!slot)
+			input_report_key(input_dev, BTN_LEFT, 0);
+
+		input_mt_report_slot_inactive(input_dev);
+		/*
+		 * make sure the previous coordinates are
+		 * all off screen when the finger comes back
+		 */
+		target->x = 65535;
+		target->y = 65535;
+		target->z = AXIOM_PROX_LEVEL;
+		break;
+	case TARGET_STATE_HOVER:
+	case TARGET_STATE_TOUCHING:
+		target_prev_state->insert = true;
+		update = true;
+		input_mt_slot(input_dev, slot);
+		input_report_abs(input_dev, ABS_MT_TRACKING_ID, slot);
+		input_report_abs(input_dev, ABS_MT_POSITION_X, target->x);
+		input_report_abs(input_dev, ABS_X, target->x);
+		input_report_abs(input_dev, ABS_MT_POSITION_Y, target->y);
+		input_report_abs(input_dev, ABS_Y, target->y);
+
+		if (current_state == TARGET_STATE_TOUCHING) {
+			input_report_abs(input_dev, ABS_MT_DISTANCE, 0);
+			input_report_abs(input_dev, ABS_DISTANCE, 0);
+			input_report_abs(input_dev, ABS_MT_PRESSURE, target->z);
+			input_report_abs(input_dev, ABS_PRESSURE, target->z);
+		} else {
+			input_report_abs(input_dev, ABS_MT_DISTANCE, -target->z);
+			input_report_abs(input_dev, ABS_DISTANCE, -target->z);
+			input_report_abs(input_dev, ABS_MT_PRESSURE, 0);
+			input_report_abs(input_dev, ABS_PRESSURE, 0);
+		}
+
+		if (!slot)
+			input_report_key(input_dev, BTN_LEFT, (current_state ==
+					 TARGET_STATE_TOUCHING));
+		break;
+	}
+
+	target_prev_state->state = current_state;
+	target_prev_state->x = target->x;
+	target_prev_state->y = target->y;
+	target_prev_state->z = target->z;
+
+	if (update)
+		input_mt_sync_frame(input_dev);
+
+	return update;
+}
+
+/*
+ * Take a raw buffer with u41 report data and decode it.
+ * Also generate input events if needed.
+ * rx_buf: ptr to a byte array [0]: Usage number [1]: Status LSB [2]: Status MSB
+ */
+static void axiom_process_u41_report(struct axiom_data *ts, char *rx_buf)
+{
+	struct input_dev *input_dev = ts->input_dev;
+	struct axiom_target_report target;
+	bool update_done = false;
+	u16 target_status;
+	u32 i;
+
+	target_status = ((rx_buf[1]) | (rx_buf[2] << 8));
+
+	for (i = 0; i < AXIOM_U41_MAX_TARGETS; i++) {
+		char target_step = rx_buf[(i * 4)];
+
+		target.index = i;
+		target.present = ((target_status & (1 << i)) != 0) ? 1 : 0;
+		target.x = ((target_step + 3) | ((target_step + 4) << 8));
+		target.y = ((target_step + 5) | ((target_step + 6) << 8));
+		target.z = (s8)(rx_buf[i + 43]);
+		update_done |= axiom_process_u41_report_target(ts, &target);
+	}
+
+	if (update_done)
+		input_sync(input_dev);
+}
+
+static void axiom_process_u46_report(struct axiom_data *ts, char *rx_buf)
+{
+	struct input_dev *input_dev = ts->input_dev;
+	u32 event_value;
+	u16 aux_value;
+	u32 i = 0;
+
+	for (i = 0; i < AXIOM_U46_AUX_CHANNELS; i++) {
+		char target_step = rx_buf[(i * 2)];
+
+		aux_value = (((target_step + 2) << 8) | (target_step + 1)) & AXIOM_U46_AUX_MASK;
+		event_value = (i << 16) | (aux_value);
+		input_event(input_dev, EV_MSC, MSC_RAW, event_value);
+	}
+
+	input_mt_sync(input_dev);
+	input_sync(input_dev);
+}
+
+/*
+ * Validates the crc and demultiplexes the axiom reports to the appropriate
+ * report handler
+ */
+static void axiom_handle_events(struct axiom_data *ts)
+{
+	char *report_data = ts->rx_buf;
+	struct device *dev = ts->dev;
+	char usage = report_data[1];
+	u16 crc_report;
+	u16 crc_calc;
+	char len;
+
+	axiom_i2c_read(ts->client, AXIOM_REPORT_USAGE_ID, 0, report_data, ts->max_report_len);
+
+	if ((report_data[0] & AXIOM_COMMS_OVERFLOW_MASK) != 0)
+		ts->report_overflow_counter++;
+
+	len = (report_data[0] & AXIOM_COMMS_REPORT_LEN_MASK) * 2;
+	if (!len) {
+		dev_err(dev, "Zero length report discarded.\n");
+		return;
+	}
+
+	dev_dbg(dev, "Payload Data %*ph\n", len, report_data);
+
+	/* Validate the report CRC */
+	crc_report = (report_data[len - 1] << 8) | (report_data[len - 2]);
+	/* Length is in 16 bit words and remove the size of the CRC16 itself */
+	crc_calc = crc16(0, report_data, (len - 2));
+
+	if (crc_calc != crc_report) {
+		dev_err(dev,
+			"CRC mismatch! Expected: %#x, Calculated CRC: %#x.\n",
+			crc_report, crc_calc);
+		return;
+	}
+
+	switch (usage) {
+	case AXIOM_USAGE_2DCTS_REPORT_ID:
+		axiom_process_u41_report(ts, &report_data[1]);
+		break;
+
+	case AXIOM_USAGE_2AUX_REPORT_ID:
+		/* This is an aux report (force) */
+		axiom_process_u46_report(ts, &report_data[1]);
+		break;
+
+	case AXIOM_USAGE_2HB_REPORT_ID:
+		/* This is a heartbeat report */
+		break;
+	}
+
+	ts->report_counter++;
+}
+
+static void axiom_i2c_poll(struct input_dev *input_dev)
+{
+	struct axiom_data *ts = input_get_drvdata(input_dev);
+
+	axiom_handle_events(ts);
+}
+
+static irqreturn_t axiom_irq(int irq, void *dev_id)
+{
+	struct axiom_data *ts = dev_id;
+
+	axiom_handle_events(ts);
+
+	return IRQ_HANDLED;
+}
+
+static void axiom_reset(struct gpio_desc *reset_gpio)
+{
+	gpiod_set_value_cansleep(reset_gpio, 1);
+	usleep_range(1000, 2000);
+	gpiod_set_value_cansleep(reset_gpio, 0);
+	msleep(100);
+}
+
+/* Rebaseline the touchscreen, effectively zero-ing it */
+static int axiom_rebaseline(struct axiom_data *ts)
+{
+	char buffer[8] = {};
+
+	buffer[0] = AXIOM_REBASELINE_CMD;
+
+	return axiom_i2c_write(ts->client, AXIOM_REPORT_USAGE_ID, 0, buffer, sizeof(buffer));
+}
+
+static int axiom_i2c_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct input_dev *input_dev;
+	struct axiom_data *ts;
+	int ret;
+	int target;
+
+	ts = devm_kzalloc(dev, sizeof(*ts), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+
+	ts->client = client;
+	i2c_set_clientdata(client, ts);
+	ts->dev = dev;
+
+	ts->irq_gpio = devm_gpiod_get_optional(dev, "irq", GPIOD_IN);
+	if (IS_ERR(ts->irq_gpio))
+		return dev_err_probe(dev, PTR_ERR(ts->irq_gpio), "failed to get irq GPIO");
+
+	ts->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(ts->reset_gpio))
+		return dev_err_probe(dev, PTR_ERR(ts->reset_gpio), "failed to get reset GPIO\n");
+
+	axiom_reset(ts->reset_gpio);
+
+	if (ts->irq_gpio) {
+		ret = devm_request_threaded_irq(dev, client->irq, NULL,
+						axiom_irq, 0, dev_name(dev), ts);
+		if (ret < 0)
+			return dev_err_probe(dev, ret, "Failed to request threaded IRQ\n");
+	}
+
+	ret = axiom_discover(ts);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed touchscreen discover\n");
+
+	ret = axiom_rebaseline(ts);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed touchscreen re-baselining\n");
+
+	input_dev = devm_input_allocate_device(ts->dev);
+	if (!input_dev)
+		return -ENOMEM;
+
+	input_dev->name = "TouchNetix aXiom Touchscreen";
+	input_dev->phys = "input/axiom_ts";
+
+	/* Single Touch */
+	input_set_abs_params(input_dev, ABS_X, 0, 65535, 0, 0);
+	input_set_abs_params(input_dev, ABS_Y, 0, 65535, 0, 0);
+
+	/* Multi Touch */
+	/* Min, Max, Fuzz (expected noise in px, try 4?) and Flat */
+	input_set_abs_params(input_dev, ABS_MT_POSITION_X, 0, 65535, 0, 0);
+	/* Min, Max, Fuzz (expected noise in px, try 4?) and Flat */
+	input_set_abs_params(input_dev, ABS_MT_POSITION_Y, 0, 65535, 0, 0);
+	input_set_abs_params(input_dev, ABS_MT_TOOL_TYPE, 0, MT_TOOL_MAX, 0, 0);
+	input_set_abs_params(input_dev, ABS_MT_DISTANCE, 0, 127, 0, 0);
+	input_set_abs_params(input_dev, ABS_MT_PRESSURE, 0, 127, 0, 0);
+
+	/* Registers the axiom device as a touchscreen instead of as a mouse pointer */
+	input_mt_init_slots(input_dev, AXIOM_U41_MAX_TARGETS, INPUT_MT_DIRECT);
+
+	input_set_capability(input_dev, EV_KEY, BTN_LEFT);
+
+	/* Enables the raw data for up to 4 force channels to be sent to the input subsystem */
+	set_bit(EV_REL, input_dev->evbit);
+	set_bit(EV_MSC, input_dev->evbit);
+	/* Declare that we support "RAW" Miscellaneous events */
+	set_bit(MSC_RAW, input_dev->mscbit);
+
+	if (!ts->irq_gpio) {
+		ret = input_setup_polling(input_dev, axiom_i2c_poll);
+		if (ret)
+			return	dev_err_probe(ts->dev, ret, "Unable to set up polling mode\n");
+		input_set_poll_interval(input_dev, POLL_INTERVAL_DEFAULT_MS);
+	}
+
+	ts->input_dev = input_dev;
+	input_set_drvdata(ts->input_dev, ts);
+
+	/* Ensure that all reports are initialised to not be present. */
+	for (target = 0; target < AXIOM_U41_MAX_TARGETS; target++)
+		ts->targets[target].state = TARGET_STATE_NOT_PRESENT;
+
+	ret = input_register_device(input_dev);
+
+	if (ret)
+		return dev_err_probe(ts->dev, ret,
+					"Could not register with Input Sub-system.\n");
+
+	return 0;
+}
+
+static void axiom_i2c_remove(struct i2c_client *client)
+{
+	struct axiom_data *ts = i2c_get_clientdata(client);
+
+	input_unregister_device(ts->input_dev);
+}
+
+static const struct i2c_device_id axiom_i2c_id_table[] = {
+	{ "axiom-ax54a" },
+	{},
+};
+
+MODULE_DEVICE_TABLE(i2c, axiom_i2c_id_table);
+
+static const struct of_device_id axiom_i2c_of_match[] = {
+	{ .compatible = "touchnetix,axiom-ax54a", },
+	{}
+};
+
+MODULE_DEVICE_TABLE(of, axiom_i2c_of_match);
+
+static struct i2c_driver axiom_i2c_driver = {
+	.driver = {
+		   .name = "axiom",
+		   .of_match_table = axiom_i2c_of_match,
+	},
+	.id_table = axiom_i2c_id_table,
+	.probe = axiom_i2c_probe,
+	.remove = axiom_i2c_remove,
+};
+
+module_i2c_driver(axiom_i2c_driver);
+
+MODULE_AUTHOR("Bart Prescott <bartp@baasheep.co.uk>");
+MODULE_AUTHOR("Pedro Torruella <pedro.torruella@touchnetix.com>");
+MODULE_AUTHOR("Mark Satterthwaite <mark.satterthwaite@touchnetix.com>");
+MODULE_AUTHOR("Hannah Rossiter <hannah.rossiter@touchnetix.com>");
+MODULE_AUTHOR("Kamel Bouhara <kamel.bouhara@bootlin.com>");
+MODULE_DESCRIPTION("TouchNetix aXiom touchscreen I2C bus driver");
+MODULE_LICENSE("GPL");
-- 
2.25.1