* [PATCH v2 2/3] Input: Add driver for ESWIN EPH8621 touchscreen IC
2026-09-17 8:25 [PATCH v2 0/3] ESWIN EPH8621 touchscreen support for Fairphone (Gen. 6) Luca Weiss
2026-09-17 8:25 ` [PATCH v2 1/3] dt-bindings: input: touchscreen: document ESWIN EPH8621 Luca Weiss
@ 2026-09-17 8:25 ` Luca Weiss
2026-09-17 8:35 ` sashiko-bot
2026-09-17 8:25 ` [PATCH v2 3/3] arm64: dts: qcom: milos-fairphone-fp6: Add touchscreen Luca Weiss
2 siblings, 1 reply; 5+ messages in thread
From: Luca Weiss @ 2026-09-17 8:25 UTC (permalink / raw)
To: Dmitry Torokhov, Rob Herring, Krzysztof Kozlowski, Conor Dooley,
Henrik Rydberg, Bjorn Andersson, Konrad Dybcio
Cc: ~postmarketos/upstreaming, phone-devel, linux-input, devicetree,
linux-kernel, linux-arm-msm, Luca Weiss
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 | 333 ++++++++++++++++++++++++++++++
3 files changed, 346 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..866cdc7e9334
--- /dev/null
+++ b/drivers/input/touchscreen/eswin_eph8621.c
@@ -0,0 +1,333 @@
+// 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;
+
+ if (buf != ts->rx_buf)
+ 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) */
+ error = eswin_spi_read(ts, payload_len + TLV_HEADER_SIZE, buf);
+ if (error)
+ return error;
+
+ return payload_len;
+}
+
+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;
+
+ if (slot >= ESWIN_MAX_TOUCHES) {
+ dev_warn_ratelimited(ts->dev, "Invalid slot ID: %d\n", slot);
+ return;
+ }
+
+ 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, unsigned int payload_len)
+{
+ u16 total_len = payload_len + TLV_HEADER_SIZE;
+ u16 offset = TLV_HEADER_SIZE;
+
+ if (buf[TLV_TYPE_FIELD] != TLV_REPORT_DATA)
+ return;
+
+ while (offset < total_len) {
+ u8 ev_len = buf[offset] & EVENT_REPORT_LENGTH_MASK;
+
+ /* Event length must cover the 8-byte payload (ev_len is exclusive of the 1-byte header) */
+ if (ev_len < 7) {
+ dev_warn_ratelimited(ts->dev, "Malformed event length: %d\n", ev_len);
+ break;
+ }
+
+ /* Ensure at least 8 bytes remain for a full contact payload */
+ if (total_len - offset < 8) {
+ dev_warn_ratelimited(ts->dev, "Truncated touch payload\n");
+ break;
+ }
+
+ 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 payload_len;
+
+ payload_len = eswin_comms_two_stage_read(ts, ts->rx_buf);
+ if (payload_len > 0)
+ eswin_process_report(ts, ts->rx_buf, payload_len);
+
+ 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
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