[PATCH v2 4/4] input: touchscreen: add SPI support for Goodix Berlin Touchscreen IC

[Neil Armstrong]

Add initial support for the new Goodix "Berlin" touchscreen ICs
over the SPI interface.

The driver doesn't use the regmap_spi code since the SPI messages
needs to be prefixed, thus this custom regmap code.

This initial driver is derived from the Goodix goodix_ts_berlin
available at [1] and [2] and only supports the GT9916 IC
present on the Qualcomm SM8550 MTP & QRD touch panel.

The current implementation only supports BerlinD, aka GT9916.

[1] https://github.com/goodix/goodix_ts_berlin
[2] https://git.codelinaro.org/clo/la/platform/vendor/opensource/touch-drivers

Signed-off-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
---
 drivers/input/touchscreen/Kconfig             |  13 ++
 drivers/input/touchscreen/Makefile            |   1 +
 drivers/input/touchscreen/goodix_berlin_spi.c | 172 ++++++++++++++++++++++++++
 3 files changed, 186 insertions(+)

diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
index 5e21cca6025d..2d86615e5090 100644
--- a/drivers/input/touchscreen/Kconfig
+++ b/drivers/input/touchscreen/Kconfig
@@ -435,6 +435,19 @@ config TOUCHSCREEN_GOODIX_BERLIN_I2C
 	  To compile this driver as a module, choose M here: the
 	  module will be called goodix_berlin_i2c.
 
+config TOUCHSCREEN_GOODIX_BERLIN_SPI
+	tristate "Goodix Berlin SPI touchscreen"
+	depends on SPI_MASTER
+	select TOUCHSCREEN_GOODIX_BERLIN_CORE
+	help
+	  Say Y here if you have a Goodix Berlin IC 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 goodix_berlin_spi.
+
 config TOUCHSCREEN_HIDEEP
 	tristate "HiDeep Touch IC"
 	depends on I2C
diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
index 921a2da0c2be..29524e8a83db 100644
--- a/drivers/input/touchscreen/Makefile
+++ b/drivers/input/touchscreen/Makefile
@@ -49,6 +49,7 @@ obj-$(CONFIG_TOUCHSCREEN_FUJITSU)	+= fujitsu_ts.o
 obj-$(CONFIG_TOUCHSCREEN_GOODIX)	+= goodix_ts.o
 obj-$(CONFIG_TOUCHSCREEN_GOODIX_BERLIN_CORE)	+= goodix_berlin_core.o
 obj-$(CONFIG_TOUCHSCREEN_GOODIX_BERLIN_I2C)	+= goodix_berlin_i2c.o
+obj-$(CONFIG_TOUCHSCREEN_GOODIX_BERLIN_SPI)	+= goodix_berlin_spi.o
 obj-$(CONFIG_TOUCHSCREEN_HIDEEP)	+= hideep.o
 obj-$(CONFIG_TOUCHSCREEN_HYNITRON_CSTXXX)	+= hynitron_cstxxx.o
 obj-$(CONFIG_TOUCHSCREEN_ILI210X)	+= ili210x.o
diff --git a/drivers/input/touchscreen/goodix_berlin_spi.c b/drivers/input/touchscreen/goodix_berlin_spi.c
new file mode 100644
index 000000000000..3a1bc251b32d
--- /dev/null
+++ b/drivers/input/touchscreen/goodix_berlin_spi.c
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Goodix Berlin Touchscreen Driver
+ *
+ * Copyright (C) 2020 - 2021 Goodix, Inc.
+ * Copyright (C) 2023 Linaro Ltd.
+ *
+ * Based on goodix_ts_berlin driver.
+ */
+#include <asm/unaligned.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/spi/spi.h>
+
+#include "goodix_berlin.h"
+
+#define SPI_TRANS_PREFIX_LEN	1
+#define REGISTER_WIDTH		4
+#define SPI_READ_DUMMY_LEN	3
+#define SPI_READ_PREFIX_LEN	(SPI_TRANS_PREFIX_LEN + REGISTER_WIDTH + SPI_READ_DUMMY_LEN)
+#define SPI_WRITE_PREFIX_LEN	(SPI_TRANS_PREFIX_LEN + REGISTER_WIDTH)
+
+#define SPI_WRITE_FLAG		0xF0
+#define SPI_READ_FLAG		0xF1
+
+static int goodix_berlin_spi_read(void *context, const void *reg_buf,
+				  size_t reg_size, void *val_buf,
+				  size_t val_size)
+{
+	struct spi_device *spi = context;
+	struct spi_transfer xfers;
+	struct spi_message spi_msg;
+	const u32 *reg = reg_buf; /* reg is stored as native u32 at start of buffer */
+	u8 *buf;
+	int ret;
+
+	if (reg_size != REGISTER_WIDTH)
+		return -EINVAL;
+
+	buf = kzalloc(SPI_READ_PREFIX_LEN + val_size, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	spi_message_init(&spi_msg);
+	memset(&xfers, 0, sizeof(xfers));
+
+	/* buffer format: 0xF1 + addr(4bytes) + dummy(3bytes) + data */
+	buf[0] = SPI_READ_FLAG;
+	put_unaligned_be32(*reg, buf + SPI_TRANS_PREFIX_LEN);
+	memset(buf + SPI_TRANS_PREFIX_LEN + REGISTER_WIDTH, 0xff,
+	       SPI_READ_DUMMY_LEN);
+
+	xfers.tx_buf = buf;
+	xfers.rx_buf = buf;
+	xfers.len = SPI_READ_PREFIX_LEN + val_size;
+	xfers.cs_change = 0;
+	spi_message_add_tail(&xfers, &spi_msg);
+
+	ret = spi_sync(spi, &spi_msg);
+	if (ret < 0)
+		dev_err(&spi->dev, "transfer error:%d", ret);
+	else
+		memcpy(val_buf, buf + SPI_READ_PREFIX_LEN, val_size);
+
+	kfree(buf);
+	return ret;
+}
+
+static int goodix_berlin_spi_write(void *context, const void *data,
+				   size_t count)
+{
+	unsigned int len = count - REGISTER_WIDTH;
+	struct spi_device *spi = context;
+	struct spi_transfer xfers;
+	struct spi_message spi_msg;
+	const u32 *reg = data; /* reg is stored as native u32 at start of buffer */
+	u8 *buf;
+	int ret;
+
+	buf = kzalloc(SPI_WRITE_PREFIX_LEN + len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	spi_message_init(&spi_msg);
+	memset(&xfers, 0, sizeof(xfers));
+
+	buf[0] = SPI_WRITE_FLAG;
+	put_unaligned_be32(*reg, buf + SPI_TRANS_PREFIX_LEN);
+	memcpy(buf + SPI_WRITE_PREFIX_LEN, data + REGISTER_WIDTH, len);
+
+	xfers.tx_buf = buf;
+	xfers.len = SPI_WRITE_PREFIX_LEN + len;
+	xfers.cs_change = 0;
+	spi_message_add_tail(&xfers, &spi_msg);
+
+	ret = spi_sync(spi, &spi_msg);
+	if (ret < 0)
+		dev_err(&spi->dev, "transfer error:%d", ret);
+
+	kfree(buf);
+	return ret;
+}
+
+static const struct regmap_config goodix_berlin_spi_regmap_conf = {
+	.reg_bits = 32,
+	.val_bits = 8,
+	.read = goodix_berlin_spi_read,
+	.write = goodix_berlin_spi_write,
+};
+
+/* vendor & product left unassigned here, should probably be updated from fw info */
+static const struct input_id goodix_berlin_spi_input_id = {
+	.bustype = BUS_SPI,
+};
+
+static int goodix_berlin_spi_probe(struct spi_device *spi)
+{
+	struct regmap_config *regmap_config;
+	struct regmap *regmap;
+	size_t max_size;
+	int error = 0;
+
+	regmap_config = devm_kmemdup(&spi->dev, &goodix_berlin_spi_regmap_conf,
+				     sizeof(*regmap_config), GFP_KERNEL);
+	if (!regmap_config)
+		return -ENOMEM;
+
+	spi->mode = SPI_MODE_0;
+	spi->bits_per_word = 8;
+	error = spi_setup(spi);
+	if (error)
+		return error;
+
+	max_size = spi_max_transfer_size(spi);
+	regmap_config->max_raw_read = max_size - SPI_READ_PREFIX_LEN;
+	regmap_config->max_raw_write = max_size - SPI_WRITE_PREFIX_LEN;
+
+	regmap = devm_regmap_init(&spi->dev, NULL, spi, regmap_config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	return goodix_berlin_probe(&spi->dev, spi->irq,
+				   &goodix_berlin_spi_input_id, regmap);
+}
+
+static const struct spi_device_id goodix_berlin_spi_ids[] = {
+	{ "gt9916" },
+	{ },
+};
+MODULE_DEVICE_TABLE(spi, goodix_berlin_spi_ids);
+
+static const struct of_device_id goodix_berlin_spi_of_match[] = {
+	{ .compatible = "goodix,gt9916", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, goodix_berlin_spi_of_match);
+
+static struct spi_driver goodix_berlin_spi_driver = {
+	.driver = {
+		.name = "goodix-berlin-spi",
+		.of_match_table = goodix_berlin_spi_of_match,
+		.pm = pm_sleep_ptr(&goodix_berlin_pm_ops),
+	},
+	.probe = goodix_berlin_spi_probe,
+	.id_table = goodix_berlin_spi_ids,
+};
+module_spi_driver(goodix_berlin_spi_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Goodix Berlin SPI Touchscreen driver");
+MODULE_AUTHOR("Neil Armstrong <neil.armstrong@xxxxxxxxxx>");

-- 
2.34.1