--- /dev/null
+// SPDX-License-Identifier: BSD-2-Clause OR GPL-2.0-or-later
+/*
+ * ENE KB3930 Embedded Controller Driver
+ *
+ * Copyright (C) 2020 Lubomir Rintel
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/reboot.h>
+#include <linux/regmap.h>
+
+/* I2C registers that are multiplexing access to the EC RAM. */
+enum {
+ EC_DATA_IN = 0x00,
+ EC_RAM_OUT = 0x80,
+ EC_RAM_IN = 0x81,
+};
+
+/* EC RAM registers. */
+enum {
+ EC_MODEL = 0x30,
+ EC_VERSION_MAJ = 0x31,
+ EC_VERSION_MIN = 0x32,
+};
+
+struct kb3930 {
+ struct i2c_client *client;
+ struct regmap *ram_regmap;
+ struct gpio_descs *off_gpios;
+};
+
+struct kb3930 *kb3930_power_off;
+
+#define EC_GPIO_WAVE 0
+#define EC_GPIO_OFF_MODE 1
+
+#define EC_OFF_MODE_REBOOT 0
+#define EC_OFF_MODE_POWER 1
+
+static void kb3930_off(struct kb3930 *ddata, int off_mode)
+{
+ gpiod_direction_output(ddata->off_gpios->desc[EC_GPIO_OFF_MODE],
+ off_mode);
+
+ /*
+ * This creates a 10 Hz wave on EC_GPIO_WAVE that signals a
+ * shutdown request to the EC. Once the EC detects it, it will
+ * proceed to turn the power off or reset the board depending on
+ * the value of EC_GPIO_OFF_MODE.
+ */
+ while (1) {
+ mdelay(50);
+ gpiod_direction_output(ddata->off_gpios->desc[EC_GPIO_WAVE], 0);
+ mdelay(50);
+ gpiod_direction_output(ddata->off_gpios->desc[EC_GPIO_WAVE], 1);
+ }
+}
+
+static int kb3930_restart(struct notifier_block *this,
+ unsigned long mode, void *cmd)
+{
+ kb3930_off(kb3930_power_off, EC_OFF_MODE_REBOOT);
+ return NOTIFY_DONE;
+}
+
+static void kb3930_pm_power_off(void)
+{
+ kb3930_off(kb3930_power_off, EC_OFF_MODE_POWER);
+}
+
+static struct notifier_block kb3930_restart_nb = {
+ .notifier_call = kb3930_restart,
+};
+
+static const struct mfd_cell ariel_ec_cells[] = {
+ { .name = "dell-wyse-ariel-led", },
+ { .name = "dell-wyse-ariel-power", },
+};
+
+static int kb3930_ec_ram_reg_write(void *context, unsigned int reg,
+ unsigned int val)
+{
+ struct kb3930 *ddata = context;
+
+ return i2c_smbus_write_word_data(ddata->client, EC_RAM_OUT,
+ (val << 8) | reg);
+}
+
+static int kb3930_ec_ram_reg_read(void *context, unsigned int reg,
+ unsigned int *val)
+{
+ struct kb3930 *ddata = context;
+ int ret;
+
+ ret = i2c_smbus_write_word_data(ddata->client, EC_RAM_IN, reg);
+ if (ret < 0)
+ return ret;
+
+ ret = i2c_smbus_read_word_data(ddata->client, EC_DATA_IN);
+ if (ret < 0)
+ return ret;
+
+ *val = ret >> 8;
+ return 0;
+}
+
+static const struct regmap_config kb3930_ram_regmap_config = {
+ .name = "ec_ram",
+ .reg_bits = 8,
+ .val_bits = 8,
+ .reg_stride = 1,
+ .max_register = 0xff,
+ .reg_write = kb3930_ec_ram_reg_write,
+ .reg_read = kb3930_ec_ram_reg_read,
+ .fast_io = false,
+};
+
+static int kb3930_probe(struct i2c_client *client)
+{
+ struct device *dev = &client->dev;
+ struct device_node *np = dev->of_node;
+ struct kb3930 *ddata;
+ unsigned int model;
+ int ret;
+
+ ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
+ if (!ddata)
+ return -ENOMEM;
+
+ kb3930_power_off = ddata;
+ ddata->client = client;
+ i2c_set_clientdata(client, ddata);
+
+ ddata->ram_regmap = devm_regmap_init(dev, NULL, ddata,
+ &kb3930_ram_regmap_config);
+ if (IS_ERR(ddata->ram_regmap))
+ return PTR_ERR(ddata->ram_regmap);
+
+ ret = regmap_read(ddata->ram_regmap, EC_MODEL, &model);
+ if (ret < 0)
+ return ret;
+
+ /* Currently we only support the cells present on Dell Ariel model. */
+ if (model != 'J') {
+ dev_err(dev, "unknown board model: %02x\n", model);
+ return -ENODEV;
+ }
+
+ ret = devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO,
+ ariel_ec_cells,
+ ARRAY_SIZE(ariel_ec_cells),
+ NULL, 0, NULL);
+ if (ret)
+ return ret;
+
+ if (of_property_read_bool(np, "system-power-controller")) {
+ ddata->off_gpios =
+ devm_gpiod_get_array_optional(dev, "off", GPIOD_IN);
+ if (IS_ERR(ddata->off_gpios))
+ return PTR_ERR(ddata->off_gpios);
+ if (ddata->off_gpios->ndescs < 2) {
+ dev_err(dev, "invalid off-gpios property\n");
+ return -EINVAL;
+ }
+ }
+
+ if (ddata->off_gpios) {
+ register_restart_handler(&kb3930_restart_nb);
+ if (!pm_power_off)
+ pm_power_off = kb3930_pm_power_off;
+ }
+
+ return 0;
+}
+
+static int kb3930_remove(struct i2c_client *client)
+{
+ struct kb3930 *ddata = i2c_get_clientdata(client);
+
+ if (ddata->off_gpios) {
+ if (pm_power_off == kb3930_pm_power_off)
+ pm_power_off = NULL;
+ unregister_restart_handler(&kb3930_restart_nb);
+ }
+ kb3930_power_off = NULL;
+
+ return 0;
+}
+
+static const struct of_device_id kb3930_dt_ids[] = {
+ { .compatible = "ene,kb3930" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, kb3930_dt_ids);
+
+static struct i2c_driver kb3930_driver = {
+ .probe_new = kb3930_probe,
+ .remove = kb3930_remove,
+ .driver = {
+ .name = "ene-kb3930",
+ .of_match_table = of_match_ptr(kb3930_dt_ids),
+ },
+};
+module_i2c_driver(kb3930_driver);
+
+MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
+MODULE_DESCRIPTION("ENE KB3930 Embedded Controller Driver");
+MODULE_LICENSE("Dual BSD/GPL");
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