1// SPDX-License-Identifier: BSD-2-Clause OR GPL-2.0-or-later
  2/*
  3 * ENE KB3930 Embedded Controller Driver
  4 *
  5 * Copyright (C) 2020 Lubomir Rintel
  6 */
  7
  8#include <linux/delay.h>
  9#include <linux/gpio/consumer.h>
 10#include <linux/i2c.h>
 11#include <linux/mfd/core.h>
 12#include <linux/module.h>
 13#include <linux/reboot.h>
 14#include <linux/regmap.h>
 15
 16/* I2C registers that are multiplexing access to the EC RAM. */
 17enum {
 18	EC_DATA_IN	= 0x00,
 19	EC_RAM_OUT	= 0x80,
 20	EC_RAM_IN	= 0x81,
 21};
 22
 23/* EC RAM registers. */
 24enum {
 25	EC_MODEL	= 0x30,
 26	EC_VERSION_MAJ	= 0x31,
 27	EC_VERSION_MIN	= 0x32,
 28};
 29
 30struct kb3930 {
 31	struct i2c_client *client;
 32	struct regmap *ram_regmap;
 33	struct gpio_descs *off_gpios;
 34};
 35
 36static struct kb3930 *kb3930_power_off;
 37
 38#define EC_GPIO_WAVE		0
 39#define EC_GPIO_OFF_MODE	1
 40
 41#define EC_OFF_MODE_REBOOT	0
 42#define EC_OFF_MODE_POWER	1
 43
 44static void kb3930_off(struct kb3930 *ddata, int off_mode)
 45{
 46	gpiod_direction_output(ddata->off_gpios->desc[EC_GPIO_OFF_MODE],
 47			       off_mode);
 48
 49	/*
 50	 * This creates a 10 Hz wave on EC_GPIO_WAVE that signals a
 51	 * shutdown request to the EC. Once the EC detects it, it will
 52	 * proceed to turn the power off or reset the board depending on
 53	 * the value of EC_GPIO_OFF_MODE.
 54	 */
 55	while (1) {
 56		mdelay(50);
 57		gpiod_direction_output(ddata->off_gpios->desc[EC_GPIO_WAVE], 0);
 58		mdelay(50);
 59		gpiod_direction_output(ddata->off_gpios->desc[EC_GPIO_WAVE], 1);
 60	}
 61}
 62
 63static int kb3930_restart(struct notifier_block *this,
 64			  unsigned long mode, void *cmd)
 65{
 66	kb3930_off(kb3930_power_off, EC_OFF_MODE_REBOOT);
 67	return NOTIFY_DONE;
 68}
 69
 70static void kb3930_pm_power_off(void)
 71{
 72	kb3930_off(kb3930_power_off, EC_OFF_MODE_POWER);
 73}
 74
 75static struct notifier_block kb3930_restart_nb = {
 76	.notifier_call = kb3930_restart,
 77};
 78
 79static const struct mfd_cell ariel_ec_cells[] = {
 80	{ .name = "dell-wyse-ariel-led", },
 81	{ .name = "dell-wyse-ariel-power", },
 82};
 83
 84static int kb3930_ec_ram_reg_write(void *context, unsigned int reg,
 85				   unsigned int val)
 86{
 87	struct kb3930 *ddata = context;
 88
 89	return i2c_smbus_write_word_data(ddata->client, EC_RAM_OUT,
 90					 (val << 8) | reg);
 91}
 92
 93static int kb3930_ec_ram_reg_read(void *context, unsigned int reg,
 94				  unsigned int *val)
 95{
 96	struct kb3930 *ddata = context;
 97	int ret;
 98
 99	ret = i2c_smbus_write_word_data(ddata->client, EC_RAM_IN, reg);
100	if (ret < 0)
101		return ret;
102
103	ret = i2c_smbus_read_word_data(ddata->client, EC_DATA_IN);
104	if (ret < 0)
105		return ret;
106
107	*val = ret >> 8;
108	return 0;
109}
110
111static const struct regmap_config kb3930_ram_regmap_config = {
112	.name = "ec_ram",
113	.reg_bits = 8,
114	.val_bits = 8,
115	.reg_stride = 1,
116	.max_register = 0xff,
117	.reg_write = kb3930_ec_ram_reg_write,
118	.reg_read = kb3930_ec_ram_reg_read,
119	.fast_io = false,
120};
121
122static int kb3930_probe(struct i2c_client *client)
123{
124	struct device *dev = &client->dev;
125	struct device_node *np = dev->of_node;
126	struct kb3930 *ddata;
127	unsigned int model;
128	int ret;
129
130	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
131	if (!ddata)
132		return -ENOMEM;
133
134	kb3930_power_off = ddata;
135	ddata->client = client;
136	i2c_set_clientdata(client, ddata);
137
138	ddata->ram_regmap = devm_regmap_init(dev, NULL, ddata,
139					     &kb3930_ram_regmap_config);
140	if (IS_ERR(ddata->ram_regmap))
141		return PTR_ERR(ddata->ram_regmap);
142
143	ret = regmap_read(ddata->ram_regmap, EC_MODEL, &model);
144	if (ret < 0)
145		return ret;
146
147	/* Currently we only support the cells present on Dell Ariel model. */
148	if (model != 'J') {
149		dev_err(dev, "unknown board model: %02x\n", model);
150		return -ENODEV;
151	}
152
153	ret = devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO,
154				   ariel_ec_cells,
155				   ARRAY_SIZE(ariel_ec_cells),
156				   NULL, 0, NULL);
157	if (ret)
158		return ret;
159
160	if (of_property_read_bool(np, "system-power-controller")) {
161		ddata->off_gpios =
162			devm_gpiod_get_array_optional(dev, "off", GPIOD_IN);
163		if (IS_ERR(ddata->off_gpios))
164			return PTR_ERR(ddata->off_gpios);
165		if (ddata->off_gpios->ndescs < 2) {
166			dev_err(dev, "invalid off-gpios property\n");
167			return -EINVAL;
168		}
169	}
170
171	if (ddata->off_gpios) {
172		register_restart_handler(&kb3930_restart_nb);
173		if (!pm_power_off)
174			pm_power_off = kb3930_pm_power_off;
175	}
176
177	return 0;
178}
179
180static void kb3930_remove(struct i2c_client *client)
181{
182	struct kb3930 *ddata = i2c_get_clientdata(client);
183
184	if (ddata->off_gpios) {
185		if (pm_power_off == kb3930_pm_power_off)
186			pm_power_off = NULL;
187		unregister_restart_handler(&kb3930_restart_nb);
188	}
189	kb3930_power_off = NULL;
190}
191
192static const struct of_device_id kb3930_dt_ids[] = {
193	{ .compatible = "ene,kb3930" },
194	{ }
195};
196MODULE_DEVICE_TABLE(of, kb3930_dt_ids);
197
198static struct i2c_driver kb3930_driver = {
199	.probe = kb3930_probe,
200	.remove = kb3930_remove,
201	.driver = {
202		.name = "ene-kb3930",
203		.of_match_table = kb3930_dt_ids,
204	},
205};
206module_i2c_driver(kb3930_driver);
207
208MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
209MODULE_DESCRIPTION("ENE KB3930 Embedded Controller Driver");
210MODULE_LICENSE("Dual BSD/GPL");