[RFC PATCH v1 2/2] platform: toradex: add preliminary support for Embedded Controller

[Francesco Dolcini <francesco@dolcini.it>]

From: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>

Add new platform driver for the Embedded Controller currently used
in Toradex SMARC iMX8MP and SMARC iMX95.
It currently provides power-off and restart (reset) handlers.

Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
---
 MAINTAINERS                           |   1 +
 drivers/platform/Kconfig              |   2 +
 drivers/platform/Makefile             |   1 +
 drivers/platform/toradex/Kconfig      |  18 +++
 drivers/platform/toradex/Makefile     |   1 +
 drivers/platform/toradex/toradex-ec.c | 155 ++++++++++++++++++++++++++
 6 files changed, 178 insertions(+)
 create mode 100644 drivers/platform/toradex/Kconfig
 create mode 100644 drivers/platform/toradex/Makefile
 create mode 100644 drivers/platform/toradex/toradex-ec.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 19d7c17c0115..fa1630f0f725 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -23977,6 +23977,7 @@ M:	Emanuele Ghidoli <ghidoliemanuele@gmail.com>
 M:	Francesco Dolcini <francesco@dolcini.it>
 S:	Maintained
 F:	Documentation/devicetree/bindings/firmware/toradex,embedded-controller.yaml
+F:	drivers/platform/toradex/toradex-ec.c
 
 TORTURE-TEST MODULES
 M:	Davidlohr Bueso <dave@stgolabs.net>
diff --git a/drivers/platform/Kconfig b/drivers/platform/Kconfig
index 960fd6a82450..84aabb88fb4a 100644
--- a/drivers/platform/Kconfig
+++ b/drivers/platform/Kconfig
@@ -15,6 +15,8 @@ source "drivers/platform/olpc/Kconfig"
 
 source "drivers/platform/surface/Kconfig"
 
+source "drivers/platform/toradex/Kconfig"
+
 source "drivers/platform/x86/Kconfig"
 
 source "drivers/platform/arm64/Kconfig"
diff --git a/drivers/platform/Makefile b/drivers/platform/Makefile
index 19ac54648586..2d849a8f3ccf 100644
--- a/drivers/platform/Makefile
+++ b/drivers/platform/Makefile
@@ -13,3 +13,4 @@ obj-$(CONFIG_CHROME_PLATFORMS)	+= chrome/
 obj-$(CONFIG_CZNIC_PLATFORMS)	+= cznic/
 obj-$(CONFIG_SURFACE_PLATFORMS)	+= surface/
 obj-$(CONFIG_ARM64_PLATFORM_DEVICES)	+= arm64/
+obj-$(CONFIG_TORADEX_PLATFORMS)	+= toradex/
diff --git a/drivers/platform/toradex/Kconfig b/drivers/platform/toradex/Kconfig
new file mode 100644
index 000000000000..635d955df79d
--- /dev/null
+++ b/drivers/platform/toradex/Kconfig
@@ -0,0 +1,18 @@
+menuconfig TORADEX_PLATFORMS
+	bool "Platform support for Toradex hardware"
+	help
+	  Say Y here to be able to choose driver support for Toradex
+	  devices. This option alone does not add any kernel code.
+
+if TORADEX_PLATFORMS
+config TORADEX_EC
+	tristate "Toradex Embedded Controller driver"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  Say Y here to add support for the features implemented by the
+	  Embedded Controller on the Toradex Modules.
+	  To compile this driver as a module, choose M here; the module will be
+	  called toradex-ec.
+
+endif # TORADEX_PLATFORMS
diff --git a/drivers/platform/toradex/Makefile b/drivers/platform/toradex/Makefile
new file mode 100644
index 000000000000..eb918819ad35
--- /dev/null
+++ b/drivers/platform/toradex/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_TORADEX_EC)			+= toradex-ec.o
diff --git a/drivers/platform/toradex/toradex-ec.c b/drivers/platform/toradex/toradex-ec.c
new file mode 100644
index 000000000000..f01addf2a0a6
--- /dev/null
+++ b/drivers/platform/toradex/toradex-ec.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Toradex Embedded Controller driver
+ *
+ * Copyright (C) 2025 Toradex
+ *
+ * Author: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>
+ */
+
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/reboot.h>
+#include <linux/regmap.h>
+
+#define EC_CHIP_ID_REG                  0x00
+#define EC_VERSION_REG_MAJOR            0x01
+#define EC_VERSION_REG_MINOR            0x02
+#define EC_CMD_REG                      0xD0
+#define EC_REG_MAX                      0xD0
+
+#define EC_CHIP_ID_SMARC_IMX95          0x11
+#define EC_CHIP_ID_SMARC_IMX8MP         0x12
+
+#define EC_POWEROFF_CMD                 0x01
+#define EC_RESET_CMD                    0x02
+
+#define EC_ID_VERSION_LEN               3
+
+struct tdx_ec {
+	struct i2c_client *client;
+	struct regmap *regmap;
+};
+
+static const struct regmap_range volatile_ranges[] = {
+	regmap_reg_range(EC_CMD_REG, EC_CMD_REG),
+};
+
+static const struct regmap_access_table volatile_table = {
+	.yes_ranges	= volatile_ranges,
+	.n_yes_ranges	= ARRAY_SIZE(volatile_ranges),
+};
+
+static const struct regmap_range read_ranges[] = {
+	regmap_reg_range(EC_CHIP_ID_REG, EC_VERSION_REG_MINOR),
+};
+
+static const struct regmap_access_table read_table = {
+	.yes_ranges	= read_ranges,
+	.n_yes_ranges	= ARRAY_SIZE(read_ranges),
+};
+
+static const struct regmap_config regmap_config = {
+	.reg_bits	= 8,
+	.val_bits	= 8,
+	.max_register	= EC_REG_MAX,
+	.cache_type	= REGCACHE_RBTREE,
+	.rd_table	= &read_table,
+	.volatile_table = &volatile_table,
+};
+
+static int tdx_ec_cmd(struct tdx_ec *ec, u8 cmd)
+{
+	int err = regmap_write(ec->regmap, EC_CMD_REG, cmd);
+
+	if (err)
+		dev_err(&ec->client->dev, "Failed to send command 0x%02X: %d\n", cmd, err);
+	return err;
+}
+
+static int tdx_ec_power_off(struct sys_off_data *data)
+{
+	struct tdx_ec *ec = data->cb_data;
+	int err;
+
+	err = tdx_ec_cmd(ec, EC_POWEROFF_CMD);
+	return err ? NOTIFY_BAD : NOTIFY_DONE;
+}
+
+static int tdx_ec_restart(struct sys_off_data *data)
+{
+	struct tdx_ec *ec = data->cb_data;
+	int err;
+
+	err = tdx_ec_cmd(ec, EC_RESET_CMD);
+	return err ? NOTIFY_BAD : NOTIFY_DONE;
+}
+
+static int tdx_ec_register_power_off_restart(struct device *dev, struct tdx_ec *ec)
+{
+	int err;
+
+	err = devm_register_sys_off_handler(dev, SYS_OFF_MODE_RESTART,
+					    SYS_OFF_PRIO_FIRMWARE,
+					    tdx_ec_restart, ec);
+	if (err)
+		return err;
+
+	err = devm_register_sys_off_handler(dev, SYS_OFF_MODE_POWER_OFF,
+					    SYS_OFF_PRIO_FIRMWARE,
+					    tdx_ec_power_off, ec);
+	return err;
+}
+
+static int tdx_ec_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	u8 reg_val[EC_ID_VERSION_LEN];
+	struct tdx_ec *ec;
+	int err;
+
+	ec = devm_kzalloc(dev, sizeof(*ec), GFP_KERNEL);
+	if (!ec)
+		return -ENOMEM;
+
+	ec->client = client;
+	i2c_set_clientdata(client, ec);
+
+	ec->regmap = devm_regmap_init_i2c(client, &regmap_config);
+	if (IS_ERR(ec->regmap))
+		return PTR_ERR(ec->regmap);
+
+	err = regmap_bulk_read(ec->regmap, EC_CHIP_ID_REG, &reg_val, EC_ID_VERSION_LEN);
+	if (err)
+		return dev_err_probe(dev, err,
+				     "Cannot read id and version registers\n");
+
+	dev_info(dev, "Toradex Embedded Controller id %x - Firmware %d.%d\n",
+		 reg_val[0], reg_val[1], reg_val[2]);
+
+	err = tdx_ec_register_power_off_restart(dev, ec);
+	if (err)
+		return dev_err_probe(dev, err,
+				     "Cannot register system restart handler\n");
+
+	return 0;
+}
+
+static const struct of_device_id __maybe_unused of_tdx_ec_match[] = {
+	{ .compatible = "toradex,embedded-controller" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, of_tdx_ec_match);
+
+static struct i2c_driver toradex_ec_driver = {
+	.probe			= tdx_ec_probe,
+	.driver			= {
+		.name		= "toradex-ec",
+		.of_match_table = of_tdx_ec_match,
+	},
+};
+module_i2c_driver(toradex_ec_driver);
+
+MODULE_AUTHOR("Emanuele Ghidoli <emanuele.ghidoli@toradex.com>");
+MODULE_DESCRIPTION("Toradex Embedded Controller driver");
+MODULE_LICENSE("GPL");
-- 
2.39.5