[PATCH v4 6/6] auxdisplay: TM16xx: Add support for SPI-based controllers

["Jean-François Lessard" <jefflessard3@gmail.com>]

Add support for TM16xx-compatible auxiliary display controllers connected
via the SPI bus.

The implementation includes:
- SPI driver registration and initialization
- Probe/remove logic for SPI devices
- Controller-specific handling and communication sequences
- Integration with the TM16xx core driver for common functionality

This allows platforms using TM16xx or compatible controllers over SPI to be
managed by the TM16xx driver infrastructure.

Signed-off-by: Jean-François Lessard <jefflessard3@gmail.com>
---

Notes:
    include <linux/of.h> is required for of_match_ptr

 MAINTAINERS                     |   1 +
 drivers/auxdisplay/Kconfig      |   7 +
 drivers/auxdisplay/Makefile     |   1 +
 drivers/auxdisplay/tm16xx_spi.c | 398 ++++++++++++++++++++++++++++++++
 4 files changed, 407 insertions(+)
 create mode 100644 drivers/auxdisplay/tm16xx_spi.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 51cc910e2..1ee45be14 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -25411,6 +25411,7 @@ F:	drivers/auxdisplay/tm16xx.h
 F:	drivers/auxdisplay/tm16xx_core.c
 F:	drivers/auxdisplay/tm16xx_i2c.c
 F:	drivers/auxdisplay/tm16xx_keypad.c
+F:	drivers/auxdisplay/tm16xx_spi.c
 
 TMIO/SDHI MMC DRIVER
 M:	Wolfram Sang <wsa+renesas@sang-engineering.com>
diff --git a/drivers/auxdisplay/Kconfig b/drivers/auxdisplay/Kconfig
index 6238e753d..868625596 100644
--- a/drivers/auxdisplay/Kconfig
+++ b/drivers/auxdisplay/Kconfig
@@ -536,6 +536,7 @@ config TM16XX
 	select INPUT_MATRIXKMAP
 	select TM16XX_KEYPAD if (INPUT)
 	select TM16XX_I2C if (I2C)
+	select TM16XX_SPI if (SPI)
 	help
 	  This driver supports the following TM16XX compatible
 	  I2C and SPI 7-segment led display chips:
@@ -560,6 +561,12 @@ config TM16XX_I2C
 	help
 	  Enable I2C support for TM16XX driver.
 
+config TM16XX_SPI
+	tristate
+	depends on TM16XX
+	help
+	  Enable SPI support for TM16XX driver.
+
 #
 # Character LCD with non-conforming interface section
 #
diff --git a/drivers/auxdisplay/Makefile b/drivers/auxdisplay/Makefile
index ba7b310f5..2485a3a67 100644
--- a/drivers/auxdisplay/Makefile
+++ b/drivers/auxdisplay/Makefile
@@ -20,3 +20,4 @@ obj-$(CONFIG_TM16XX)		+= tm16xx.o
 tm16xx-y			+= tm16xx_core.o
 tm16xx-$(CONFIG_TM16XX_KEYPAD)	+= tm16xx_keypad.o
 obj-$(CONFIG_TM16XX_I2C)	+= tm16xx_i2c.o
+obj-$(CONFIG_TM16XX_SPI)	+= tm16xx_spi.o
diff --git a/drivers/auxdisplay/tm16xx_spi.c b/drivers/auxdisplay/tm16xx_spi.c
new file mode 100644
index 000000000..fcc69c5f6
--- /dev/null
+++ b/drivers/auxdisplay/tm16xx_spi.c
@@ -0,0 +1,398 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * TM16xx and compatible LED display/keypad controller driver
+ * Supports TM16xx, FD6xx, PT6964, HBS658, AIP16xx and related chips.
+ *
+ * Copyright (C) 2024 Jean-François Lessard
+ */
+
+#include <linux/mod_devicetable.h>
+#include <linux/of.h>
+#include <linux/spi/spi.h>
+
+#include "tm16xx.h"
+
+#define TM16XX_SPI_BUFFER_SIZE	8
+#define TM16XX_SPI_TWAIT_US	2
+
+static int tm16xx_spi_probe(struct spi_device *spi)
+{
+	const struct tm16xx_controller *controller;
+	struct tm16xx_display *display;
+	int ret;
+
+	controller = spi_get_device_match_data(spi);
+	if (!controller)
+		return -EINVAL;
+
+	display = devm_kzalloc(&spi->dev, sizeof(*display), GFP_KERNEL);
+	if (!display)
+		return -ENOMEM;
+
+	/* Allocate DMA-safe buffer */
+	display->spi_buffer = devm_kzalloc(&spi->dev, TM16XX_SPI_BUFFER_SIZE,
+					   GFP_KERNEL);
+	if (!display->spi_buffer)
+		return -ENOMEM;
+
+	display->client.spi = spi;
+	display->dev = &spi->dev;
+	display->controller = controller;
+
+	spi_set_drvdata(spi, display);
+
+	ret = tm16xx_probe(display);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static void tm16xx_spi_remove(struct spi_device *spi)
+{
+	struct tm16xx_display *display = spi_get_drvdata(spi);
+
+	tm16xx_remove(display);
+}
+
+/**
+ * tm16xx_spi_read() - SPI read helper for controller
+ * @display: pointer to tm16xx_display
+ * @cmd: command to send
+ * @cmd_len: length of command
+ * @data: buffer for received data
+ * @data_len: length of data to read
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+static int tm16xx_spi_read(struct tm16xx_display *display, u8 *cmd,
+			   size_t cmd_len, u8 *data, size_t data_len)
+{
+	struct spi_device *spi = display->client.spi;
+	struct spi_message msg;
+	int ret;
+
+	dev_dbg(display->dev, "spi_write %*ph", (char)cmd_len, cmd);
+
+	/* If STB is high during transmission, command is invalid.
+	 * Reading requires a minimum 2 microseconds wait (Twait)
+	 * after the 8th CLK rising edge before reading on falling edge.
+	 */
+	struct spi_transfer xfers[2] = {
+		{
+			.tx_buf = cmd,
+			.len = cmd_len,
+			.cs_change = 0, /* NO CS toggle */
+			.delay.value = TM16XX_SPI_TWAIT_US,
+			.delay.unit = SPI_DELAY_UNIT_USECS,
+		}, {
+			.rx_buf = data,
+			.len = data_len,
+		}
+	};
+
+	spi_message_init_with_transfers(&msg, xfers, ARRAY_SIZE(xfers));
+
+	ret = spi_sync(spi, &msg);
+
+	dev_dbg(display->dev, "spi_read %*ph", (char)data_len, data);
+
+	return ret;
+}
+
+/**
+ * tm16xx_spi_write() - SPI write helper for controller
+ * @display: pointer to tm16xx_display
+ * @data: data to write
+ * @len: number of bytes to write
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+static int tm16xx_spi_write(struct tm16xx_display *display, u8 *data, size_t len)
+{
+	dev_dbg(display->dev, "spi_write %*ph", (char)len, data);
+
+	struct spi_device *spi = display->client.spi;
+
+	return spi_write(spi, data, len);
+}
+
+/* SPI controller-specific functions */
+static int tm1628_init(struct tm16xx_display *display)
+{
+	const enum led_brightness brightness = display->main_led.brightness;
+	const u8 num_grids = display->num_grids;
+	u8 *cmd = display->spi_buffer;
+	int ret;
+
+	/* Set mode command based on grid count */
+	cmd[0] = TM16XX_CMD_MODE;
+	if (num_grids <= 4)
+		cmd[0] |= TM16XX_MODE_4GRIDS;
+	else if (num_grids == 5)
+		cmd[0] |= TM16XX_MODE_5GRIDS;
+	else if (num_grids == 6)
+		cmd[0] |= TM16XX_MODE_6GRIDS;
+	else
+		cmd[0] |= TM16XX_MODE_7GRIDS;
+
+	ret = tm16xx_spi_write(display, cmd, 1);
+	if (ret < 0)
+		return ret;
+
+	/* Set data command */
+	cmd[0] = TM16XX_CMD_WRITE | TM16XX_DATA_ADDR_AUTO;
+	ret = tm16xx_spi_write(display, cmd, 1);
+	if (ret < 0)
+		return ret;
+
+	/* Set control command with brightness */
+	cmd[0] = TM16XX_CMD_CTRL |
+		 TM16XX_CTRL_BRIGHTNESS(brightness, brightness - 1, TM16XX);
+	ret = tm16xx_spi_write(display, cmd, 1);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static int tm1618_data(struct tm16xx_display *display, u8 index,
+		       unsigned int grid)
+{
+	u8 *cmd = display->spi_buffer;
+
+	cmd[0] = TM16XX_CMD_ADDR + index * 2;
+	cmd[1] = FIELD_GET(TM1618_BYTE1_MASK, grid);
+	cmd[2] = FIELD_GET(TM1618_BYTE2_MASK, grid) << TM1618_BYTE2_SHIFT;
+
+	return tm16xx_spi_write(display, cmd, 3);
+}
+
+static int tm1628_data(struct tm16xx_display *display, u8 index,
+		       unsigned int grid)
+{
+	u8 *cmd = display->spi_buffer;
+
+	cmd[0] = TM16XX_CMD_ADDR + index * 2;
+	cmd[1] = FIELD_GET(TM1628_BYTE1_MASK, grid);
+	cmd[2] = FIELD_GET(TM1628_BYTE2_MASK, grid);
+
+	return tm16xx_spi_write(display, cmd, 3);
+}
+
+static int tm1628_keys(struct tm16xx_display *display)
+{
+	u8 *cmd = display->spi_buffer;
+	u8 *codes = display->spi_buffer;
+	int ret, i;
+
+	cmd[0] = TM16XX_CMD_READ;
+	ret = tm16xx_spi_read(display, cmd, 1, codes, TM1628_KEY_READ_LEN);
+	if (ret)
+		return ret;
+
+	/* prevent false readings */
+	for (i = 0; i < TM1628_KEY_READ_LEN; i++) {
+		if (codes[i] & ~TM1628_KEY_MASK)
+			return -EINVAL;
+	}
+
+	tm16xx_for_each_key(display, row, col) {
+		int byte = col >> 1;
+		int bit = row + ((col & 1) * 3);
+		bool value = !!(codes[byte] & BIT(bit));
+
+		tm16xx_set_key(display, row, col, value);
+	}
+
+	return 0;
+}
+
+static int tm1638_keys(struct tm16xx_display *display)
+{
+	u8 *cmd = display->spi_buffer;
+	u8 *codes = display->spi_buffer;
+	int ret, i;
+
+	cmd[0] = TM16XX_CMD_READ;
+	ret = tm16xx_spi_read(display, cmd, 1, codes, TM1638_KEY_READ_LEN);
+	if (ret)
+		return ret;
+
+	/* prevent false readings */
+	for (i = 0; i < TM1638_KEY_READ_LEN; i++) {
+		if (codes[i] & ~TM1638_KEY_MASK)
+			return -EINVAL;
+	}
+
+	tm16xx_for_each_key(display, row, col) {
+		int byte = col >> 1;
+		int bit = (2 - row) + ((col & 1) << 2);
+		bool value = !!(codes[byte] & BIT(bit));
+
+		tm16xx_set_key(display, row, col, value);
+	}
+
+	return 0;
+}
+
+static int tm1618_keys(struct tm16xx_display *display)
+{
+	u8 *cmd = display->spi_buffer;
+	u8 *codes = display->spi_buffer;
+	int ret, i;
+
+	cmd[0] = TM16XX_CMD_READ;
+	ret = tm16xx_spi_read(display, cmd, 1, codes, TM1618_KEY_READ_LEN);
+	if (ret)
+		return ret;
+
+	/* prevent false readings */
+	for (i = 0; i < TM1618_KEY_READ_LEN; i++) {
+		if (codes[i] & ~TM1618_KEY_MASK)
+			return -EINVAL;
+	}
+
+	tm16xx_set_key(display, 0, 0, !!(codes[0] & BIT(1)));
+	tm16xx_set_key(display, 0, 1, !!(codes[0] & BIT(4)));
+	tm16xx_set_key(display, 0, 2, !!(codes[1] & BIT(1)));
+	tm16xx_set_key(display, 0, 3, !!(codes[1] & BIT(4)));
+	tm16xx_set_key(display, 0, 4, !!(codes[2] & BIT(1)));
+
+	return 0;
+}
+
+static int fd620_data(struct tm16xx_display *display, u8 index,
+		      unsigned int grid)
+{
+	u8 *cmd = display->spi_buffer;
+
+	cmd[0] = TM16XX_CMD_ADDR + index * 2;
+	cmd[1] = FIELD_GET(FD620_BYTE1_MASK, grid);
+	cmd[2] = FIELD_GET(FD620_BYTE2_MASK, grid) << FD620_BYTE2_SHIFT;
+
+	return tm16xx_spi_write(display, cmd, 3);
+}
+
+static int fd620_keys(struct tm16xx_display *display)
+{
+	u8 *cmd = display->spi_buffer;
+	u8 *codes = display->spi_buffer;
+	int ret, i;
+
+	cmd[0] = TM16XX_CMD_READ;
+	ret = tm16xx_spi_read(display, cmd, 1, codes, FD620_KEY_READ_LEN);
+	if (ret)
+		return ret;
+
+	/* prevent false readings */
+	for (i = 0; i < FD620_KEY_READ_LEN; i++) {
+		if (codes[i] & ~FD620_KEY_MASK)
+			return -EINVAL;
+	}
+
+	tm16xx_set_key(display, 0, 0, codes[0] & BIT(0));
+	tm16xx_set_key(display, 0, 1, codes[0] & BIT(3));
+	tm16xx_set_key(display, 0, 2, codes[1] & BIT(0));
+	tm16xx_set_key(display, 0, 3, codes[1] & BIT(3));
+	tm16xx_set_key(display, 0, 4, codes[2] & BIT(0));
+	tm16xx_set_key(display, 0, 5, codes[2] & BIT(3));
+	tm16xx_set_key(display, 0, 6, codes[3] & BIT(0));
+
+	return 0;
+}
+
+/* SPI controller definitions */
+static const struct tm16xx_controller tm1618_controller = {
+	.max_grids = 7,
+	.max_segments = 8,
+	.max_brightness = 8,
+	.max_key_rows = 1,
+	.max_key_cols = 5,
+	.init = tm1628_init,
+	.data = tm1618_data,
+	.keys = tm1618_keys,
+};
+
+static const struct tm16xx_controller tm1620_controller = {
+	.max_grids = 6,
+	.max_segments = 10,
+	.max_brightness = 8,
+	.max_key_rows = 0,
+	.max_key_cols = 0,
+	.init = tm1628_init,
+	.data = tm1628_data,
+	.keys = NULL,
+};
+
+static const struct tm16xx_controller tm1628_controller = {
+	.max_grids = 7,
+	.max_segments = 14, /* seg 11 unused */
+	.max_brightness = 8,
+	.max_key_rows = 2,
+	.max_key_cols = 10,
+	.init = tm1628_init,
+	.data = tm1628_data,
+	.keys = tm1628_keys,
+};
+
+static const struct tm16xx_controller tm1638_controller = {
+	.max_grids = 8,
+	.max_segments = 10,
+	.max_brightness = 8,
+	.max_key_rows = 3,
+	.max_key_cols = 8,
+	.init = tm1628_init,
+	.data = tm1628_data,
+	.keys = tm1638_keys,
+};
+
+static const struct tm16xx_controller fd620_controller = {
+	.max_grids = 5,
+	.max_segments = 8,
+	.max_brightness = 8,
+	.max_key_rows = 1,
+	.max_key_cols = 7,
+	.init = tm1628_init,
+	.data = fd620_data,
+	.keys = fd620_keys,
+};
+
+#if IS_ENABLED(CONFIG_OF)
+static const struct of_device_id tm16xx_spi_of_match[] = {
+	{ .compatible = "titanmec,tm1618",  .data = &tm1618_controller },
+	{ .compatible = "titanmec,tm1620",  .data = &tm1620_controller },
+	{ .compatible = "titanmec,tm1628",  .data = &tm1628_controller },
+	{ .compatible = "titanmec,tm1638",  .data = &tm1638_controller },
+	{ .compatible = "fdhisi,fd620",     .data = &fd620_controller  },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, tm16xx_spi_of_match);
+#endif
+
+static const struct spi_device_id tm16xx_spi_id[] = {
+	{ "tm1618",  (kernel_ulong_t)&tm1618_controller },
+	{ "tm1620",  (kernel_ulong_t)&tm1620_controller },
+	{ "tm1628",  (kernel_ulong_t)&tm1628_controller },
+	{ "tm1638",  (kernel_ulong_t)&tm1638_controller },
+	{ "fd620",   (kernel_ulong_t)&fd620_controller  },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(spi, tm16xx_spi_id);
+
+static struct spi_driver tm16xx_spi_driver = {
+	.driver = {
+		.name = "tm16xx-spi",
+		.of_match_table = of_match_ptr(tm16xx_spi_of_match),
+	},
+	.probe = tm16xx_spi_probe,
+	.remove = tm16xx_spi_remove,
+	.shutdown = tm16xx_spi_remove,
+	.id_table = tm16xx_spi_id,
+};
+module_spi_driver(tm16xx_spi_driver);
+
+MODULE_AUTHOR("Jean-François Lessard");
+MODULE_DESCRIPTION("TM16xx-spi LED Display Controllers");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("TM16XX");
-- 
2.43.0