[PATCH 2/3] Input: Add driver for ESWIN EPH8621 touchscreen IC

[Luca Weiss <luca.weiss@fairphone.com>]

Add a driver for the ESWIN EPH8621 touchscreens, connected via SPI.

The driver this is based on - EPH861X - also supports I2C but this is
not added the Fairphone (Gen. 6) has the touchscreen connected via SPI.

Assisted-by: Gemini:gemini-3.1-pro
Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
---
 drivers/input/touchscreen/Kconfig         |  12 ++
 drivers/input/touchscreen/Makefile        |   1 +
 drivers/input/touchscreen/eswin_eph8621.c | 310 ++++++++++++++++++++++++++++++
 3 files changed, 323 insertions(+)

diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
index 9b9ae8ac3f7f..007b589cef8e 100644
--- a/drivers/input/touchscreen/Kconfig
+++ b/drivers/input/touchscreen/Kconfig
@@ -360,6 +360,18 @@ config TOUCHSCREEN_EGALAX_SERIAL
 	  To compile this driver as a module, choose M here: the
 	  module will be called egalax_ts_serial.
 
+config TOUCHSCREEN_ESWIN_EPH8621
+	tristate "ESWIN EPH8621 touchscreen"
+	depends on SPI_MASTER
+	help
+	  Say Y here if you have a ESWIN EPH8621 connected to
+	  your system via SPI.
+
+	  If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called eswin_eph8621.
+
 config TOUCHSCREEN_EXC3000
 	tristate "EETI EXC3000 multi-touch panel support"
 	depends on I2C
diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
index bfd9de83389d..4540169d9b54 100644
--- a/drivers/input/touchscreen/Makefile
+++ b/drivers/input/touchscreen/Makefile
@@ -42,6 +42,7 @@ obj-$(CONFIG_TOUCHSCREEN_ELAN)		+= elants_i2c.o
 obj-$(CONFIG_TOUCHSCREEN_ELO)		+= elo.o
 obj-$(CONFIG_TOUCHSCREEN_EGALAX)	+= egalax_ts.o
 obj-$(CONFIG_TOUCHSCREEN_EGALAX_SERIAL)	+= egalax_ts_serial.o
+obj-$(CONFIG_TOUCHSCREEN_ESWIN_EPH8621)	+= eswin_eph8621.o
 obj-$(CONFIG_TOUCHSCREEN_EXC3000)	+= exc3000.o
 obj-$(CONFIG_TOUCHSCREEN_FUJITSU)	+= fujitsu_ts.o
 obj-$(CONFIG_TOUCHSCREEN_GOODIX)	+= goodix_ts.o
diff --git a/drivers/input/touchscreen/eswin_eph8621.c b/drivers/input/touchscreen/eswin_eph8621.c
new file mode 100644
index 000000000000..12b90cc89052
--- /dev/null
+++ b/drivers/input/touchscreen/eswin_eph8621.c
@@ -0,0 +1,310 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ESWIN EPH8621 series touchscreen driver
+ *
+ * Copyright (C) 2026 Luca Weiss <luca.weiss@fairphone.com>
+ *
+ * Based on original EPH861X driver by chris.ollerenshaw@eswin.com
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/input.h>
+#include <linux/input/mt.h>
+#include <linux/input/touchscreen.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <linux/sizes.h>
+#include <linux/spi/spi.h>
+
+#define ESWIN_MAX_TOUCHES		10
+#define ESWIN_COMMS_BUF_SIZE		3072
+
+/* TLV Protocol Definitions */
+#define TLV_HEADER_SIZE			3 /* 1 byte Type + 2 bytes Length */
+#define TLV_TYPE_FIELD			0
+#define TLV_LENGTH_FIELD		1
+
+#define TLV_REPORT_DATA			0x23
+#define EVENT_REPORT_TYPE_OFFSET	4
+#define EVENT_REPORT_TYPE_MASK		0xF0
+#define EVENT_REPORT_LENGTH_MASK	0x0F
+
+/* Event Types */
+#define CONTACT_TYPE			1
+#define RELEASE_TYPE			2
+
+struct eswin_touch {
+	struct device *dev;
+	struct input_dev *input;
+
+	struct gpio_desc *reset_gpio;
+	struct regulator_bulk_data supplies[2];
+
+	struct touchscreen_properties prop;
+
+	u8 *rx_buf;
+	u8 *tx_buf;
+};
+
+static int eswin_spi_read(struct eswin_touch *ts, u16 len, u8 *buf)
+{
+	struct spi_device *spi = to_spi_device(ts->dev);
+	struct spi_transfer xfer = {
+		.tx_buf = ts->tx_buf,
+		.rx_buf = ts->rx_buf,
+		.len = len,
+	};
+	int error;
+
+	if (len > ESWIN_COMMS_BUF_SIZE)
+		return -EINVAL;
+
+	/* ESWIN requires 0xFF dummy bytes clocked out to read data */
+	memset(ts->tx_buf, 0xFF, len);
+	error = spi_sync_transfer(spi, &xfer, 1);
+	if (error)
+		return error;
+
+	memcpy(buf, ts->rx_buf, len);
+	return 0;
+}
+
+/*
+ * Core Touch Handling
+ */
+static int eswin_comms_two_stage_read(struct eswin_touch *ts, u8 *buf)
+{
+	u16 payload_len;
+	int error;
+
+	/* Stage 1: Read 3-byte header */
+	error = eswin_spi_read(ts, TLV_HEADER_SIZE, buf);
+	if (error)
+		return error;
+
+	payload_len = buf[TLV_LENGTH_FIELD] | (buf[TLV_LENGTH_FIELD + 1] << 8);
+	if (payload_len == 0 || payload_len > ESWIN_COMMS_BUF_SIZE - TLV_HEADER_SIZE)
+		return -EINVAL;
+
+	udelay(50);
+
+	/* Stage 2: Read full packet (Header + Payload) */
+	return eswin_spi_read(ts, payload_len + TLV_HEADER_SIZE, buf);
+}
+
+static void eswin_report_contact(struct eswin_touch *ts, u8 *payload)
+{
+	u8 touch_type = (payload[0] & EVENT_REPORT_TYPE_MASK) >> EVENT_REPORT_TYPE_OFFSET;
+	u8 slot = payload[1];
+	u16 x = payload[2] | (payload[3] << 8);
+	u16 y = payload[4] | (payload[5] << 8);
+	u8 width = payload[6];
+	u8 height = payload[7];
+	bool active = false;
+
+	switch (touch_type) {
+	case CONTACT_TYPE:
+		active = true;
+		break;
+	case RELEASE_TYPE:
+		active = false;
+		break;
+	default:
+		dev_warn_ratelimited(ts->dev, "Unhandled touch type: %d\n", touch_type);
+		return;
+	}
+
+	input_mt_slot(ts->input, slot);
+	input_mt_report_slot_state(ts->input, MT_TOOL_FINGER, active);
+
+	if (active) {
+		touchscreen_report_pos(ts->input, &ts->prop, x, y, true);
+		input_report_abs(ts->input, ABS_MT_TOUCH_MAJOR, height);
+		input_report_abs(ts->input, ABS_MT_TOUCH_MINOR, width);
+	}
+}
+
+static void eswin_process_report(struct eswin_touch *ts, u8 *buf)
+{
+	u16 total_len = buf[TLV_LENGTH_FIELD] | (buf[TLV_LENGTH_FIELD + 1] << 8);
+	u16 offset = TLV_HEADER_SIZE;
+
+	if (buf[TLV_TYPE_FIELD] != TLV_REPORT_DATA)
+		return;
+
+	while (offset < total_len + TLV_HEADER_SIZE) {
+		u8 ev_len = buf[offset] & EVENT_REPORT_LENGTH_MASK;
+
+		eswin_report_contact(ts, &buf[offset]);
+		offset += (ev_len + 1);
+	}
+
+	input_mt_sync_frame(ts->input);
+	input_sync(ts->input);
+}
+
+static irqreturn_t eswin_interrupt(int irq, void *dev_id)
+{
+	struct eswin_touch *ts = dev_id;
+	int error;
+
+	error = eswin_comms_two_stage_read(ts, ts->rx_buf);
+	if (!error)
+		eswin_process_report(ts, ts->rx_buf);
+
+	return IRQ_HANDLED;
+}
+
+static int eswin_power_on(struct eswin_touch *ts)
+{
+	int error;
+
+	error = regulator_bulk_enable(ARRAY_SIZE(ts->supplies), ts->supplies);
+	if (error)
+		return error;
+
+	msleep(150);
+	gpiod_set_value_cansleep(ts->reset_gpio, 0);
+	msleep(100);
+
+	return 0;
+}
+
+static void eswin_power_off(struct eswin_touch *ts)
+{
+	gpiod_set_value_cansleep(ts->reset_gpio, 1);
+	regulator_bulk_disable(ARRAY_SIZE(ts->supplies), ts->supplies);
+}
+
+static void eswin_power_off_act(void *data)
+{
+	struct eswin_touch *ts = data;
+
+	eswin_power_off(ts);
+}
+
+static int eswin_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct eswin_touch *ts;
+	int error;
+
+	ts = devm_kzalloc(dev, sizeof(*ts), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+
+	ts->dev = dev;
+	spi_set_drvdata(spi, ts);
+
+	spi->mode = SPI_MODE_3;
+	spi->bits_per_word = 8;
+	error = spi_setup(spi);
+	if (error)
+		return dev_err_probe(dev, error, "Failed to setup SPI\n");
+
+	ts->rx_buf = devm_kzalloc(dev, ESWIN_COMMS_BUF_SIZE, GFP_KERNEL);
+	ts->tx_buf = devm_kzalloc(dev, ESWIN_COMMS_BUF_SIZE, GFP_KERNEL);
+	if (!ts->rx_buf || !ts->tx_buf)
+		return -ENOMEM;
+
+	ts->supplies[0].supply = "vddio";
+	ts->supplies[1].supply = "avdd";
+	error = devm_regulator_bulk_get(dev, ARRAY_SIZE(ts->supplies), ts->supplies);
+	if (error)
+		return dev_err_probe(dev, error, "Failed to get regulators\n");
+
+	ts->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(ts->reset_gpio))
+		return dev_err_probe(dev, PTR_ERR(ts->reset_gpio),
+				     "Failed to request reset GPIO\n");
+
+	error = eswin_power_on(ts);
+	if (error)
+		return dev_err_probe(dev, error, "Failed to power on\n");
+
+	error = devm_add_action_or_reset(dev, eswin_power_off_act, ts);
+	if (error)
+		return error;
+
+	ts->input = devm_input_allocate_device(dev);
+	if (!ts->input)
+		return -ENOMEM;
+
+	ts->input->name = "ESWIN Touchscreen";
+	ts->input->id.bustype = BUS_SPI;
+
+	input_set_abs_params(ts->input, ABS_MT_POSITION_X, 0, SZ_64K - 1, 0, 0);
+	input_set_abs_params(ts->input, ABS_MT_POSITION_Y, 0, SZ_64K - 1, 0, 0);
+	input_set_abs_params(ts->input, ABS_MT_TOUCH_MAJOR, 0, 255, 0, 0);
+	input_set_abs_params(ts->input, ABS_MT_TOUCH_MINOR, 0, 255, 0, 0);
+
+	touchscreen_parse_properties(ts->input, true, &ts->prop);
+
+	error = input_mt_init_slots(ts->input, ESWIN_MAX_TOUCHES, INPUT_MT_DIRECT);
+	if (error)
+		return dev_err_probe(dev, error, "Failed to initialize MT slots\n");
+
+	error = devm_request_threaded_irq(dev, spi->irq, NULL, eswin_interrupt,
+					  IRQF_ONESHOT, dev_name(dev), ts);
+	if (error)
+		return dev_err_probe(dev, error, "Failed to request IRQ\n");
+
+	return input_register_device(ts->input);
+}
+
+static int eswin_suspend(struct device *dev)
+{
+	struct spi_device *spi = to_spi_device(dev);
+	struct eswin_touch *ts = spi_get_drvdata(spi);
+
+	disable_irq(spi->irq);
+	eswin_power_off(ts);
+
+	return 0;
+}
+
+static int eswin_resume(struct device *dev)
+{
+	struct spi_device *spi = to_spi_device(dev);
+	struct eswin_touch *ts = spi_get_drvdata(spi);
+	int error;
+
+	error = eswin_power_on(ts);
+	if (error)
+		return error;
+
+	enable_irq(spi->irq);
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(eswin_pm_ops, eswin_suspend, eswin_resume);
+
+static const struct of_device_id eswin_of_match[] = {
+	{ .compatible = "eswin,eph8621" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, eswin_of_match);
+
+static const struct spi_device_id eswin_spi_id[] = {
+	{ .name = "eph8621" },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, eswin_spi_id);
+
+static struct spi_driver eswin_spi_driver = {
+	.driver = {
+		.name = "eswin_eph8621",
+		.of_match_table = eswin_of_match,
+		.pm = pm_sleep_ptr(&eswin_pm_ops),
+	},
+	.probe = eswin_probe,
+	.id_table = eswin_spi_id,
+};
+module_spi_driver(eswin_spi_driver);
+
+MODULE_AUTHOR("Luca Weiss <luca.weiss@fairphone.com>");
+MODULE_DESCRIPTION("ESWIN EPH8621 SPI touchscreen driver");
+MODULE_LICENSE("GPL");

-- 
2.55.0