gpio-cros-ec.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright 2024 Google LLC
  4 *
  5 * This driver provides the ability to control GPIOs on the Chrome OS EC.
  6 * There isn't any direction control, and setting values on GPIOs is only
  7 * possible when the system is unlocked.
  8 */
  9
 10#include <linux/bitops.h>
 11#include <linux/device.h>
 12#include <linux/errno.h>
 13#include <linux/gpio/driver.h>
 14#include <linux/kernel.h>
 15#include <linux/mod_devicetable.h>
 16#include <linux/module.h>
 17#include <linux/platform_data/cros_ec_commands.h>
 18#include <linux/platform_data/cros_ec_proto.h>
 19#include <linux/platform_device.h>
 20#include <linux/property.h>
 21#include <linux/slab.h>
 22
 23/* Prefix all names to avoid collisions with EC <-> AP nets */
 24static const char cros_ec_gpio_prefix[] = "EC:";
 25
 26/* Setting gpios is only supported when the system is unlocked */
 27static int cros_ec_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
 28{
 29	const char *name = gc->names[gpio] + strlen(cros_ec_gpio_prefix);
 30	struct cros_ec_device *cros_ec = gpiochip_get_data(gc);
 31	struct ec_params_gpio_set params = {
 32		.val = val,
 33	};
 34	ssize_t copied;
 35
 36	copied = strscpy(params.name, name, sizeof(params.name));
 37	if (copied < 0)
 38		return copied;
 39
 40	return cros_ec_cmd(cros_ec, 0, EC_CMD_GPIO_SET, &params,
 41			   sizeof(params), NULL, 0);
 42}
 43
 44static int cros_ec_gpio_get(struct gpio_chip *gc, unsigned int gpio)
 45{
 46	const char *name = gc->names[gpio] + strlen(cros_ec_gpio_prefix);
 47	struct cros_ec_device *cros_ec = gpiochip_get_data(gc);
 48	struct ec_params_gpio_get params;
 49	struct ec_response_gpio_get response;
 50	int ret;
 51	ssize_t copied;
 52
 53	copied = strscpy(params.name, name, sizeof(params.name));
 54	if (copied < 0)
 55		return -EINVAL;
 56
 57	ret = cros_ec_cmd(cros_ec, 0, EC_CMD_GPIO_GET, &params,
 58			  sizeof(params), &response, sizeof(response));
 59	if (ret < 0) {
 60		dev_err(gc->parent, "error getting gpio%d (%s) on EC: %d\n", gpio, name, ret);
 61		return ret;
 62	}
 63
 64	return response.val;
 65}
 66
 67#define CROS_EC_GPIO_INPUT         BIT(8)
 68#define CROS_EC_GPIO_OUTPUT        BIT(9)
 69
 70static int cros_ec_gpio_get_direction(struct gpio_chip *gc, unsigned int gpio)
 71{
 72	const char *name = gc->names[gpio] + strlen(cros_ec_gpio_prefix);
 73	struct cros_ec_device *cros_ec = gpiochip_get_data(gc);
 74	struct ec_params_gpio_get_v1 params = {
 75		.subcmd = EC_GPIO_GET_INFO,
 76		.get_info.index = gpio,
 77	};
 78	struct ec_response_gpio_get_v1 response;
 79	int ret;
 80
 81	ret = cros_ec_cmd(cros_ec, 1, EC_CMD_GPIO_GET, &params,
 82			  sizeof(params), &response, sizeof(response));
 83	if (ret < 0) {
 84		dev_err(gc->parent, "error getting direction of gpio%d (%s) on EC: %d\n", gpio, name, ret);
 85		return ret;
 86	}
 87
 88	if (response.get_info.flags & CROS_EC_GPIO_INPUT)
 89		return GPIO_LINE_DIRECTION_IN;
 90
 91	if (response.get_info.flags & CROS_EC_GPIO_OUTPUT)
 92		return GPIO_LINE_DIRECTION_OUT;
 93
 94	return -EINVAL;
 95}
 96
 97/* Query EC for all gpio line names */
 98static int cros_ec_gpio_init_names(struct cros_ec_device *cros_ec, struct gpio_chip *gc)
 99{
100	struct ec_params_gpio_get_v1 params = {
101		.subcmd = EC_GPIO_GET_INFO,
102	};
103	struct ec_response_gpio_get_v1 response;
104	int ret, i;
105	/* EC may not NUL terminate */
106	size_t name_len = strlen(cros_ec_gpio_prefix) + sizeof(response.get_info.name) + 1;
107	ssize_t copied;
108	const char **names;
109	char *str;
110
111	names = devm_kcalloc(gc->parent, gc->ngpio, sizeof(*names), GFP_KERNEL);
112	if (!names)
113		return -ENOMEM;
114	gc->names = names;
115
116	str = devm_kcalloc(gc->parent, gc->ngpio, name_len, GFP_KERNEL);
117	if (!str)
118		return -ENOMEM;
119
120	/* Get gpio line names one at a time */
121	for (i = 0; i < gc->ngpio; i++) {
122		params.get_info.index = i;
123		ret = cros_ec_cmd(cros_ec, 1, EC_CMD_GPIO_GET, &params,
124				  sizeof(params), &response, sizeof(response));
125		if (ret < 0) {
126			dev_err_probe(gc->parent, ret, "error getting gpio%d info\n", i);
127			return ret;
128		}
129
130		names[i] = str;
131		copied = scnprintf(str, name_len, "%s%s", cros_ec_gpio_prefix,
132				   response.get_info.name);
133		if (copied < 0)
134			return copied;
135
136		str += copied + 1;
137	}
138
139	return 0;
140}
141
142/* Query EC for number of gpios */
143static int cros_ec_gpio_ngpios(struct cros_ec_device *cros_ec)
144{
145	struct ec_params_gpio_get_v1 params = {
146		.subcmd = EC_GPIO_GET_COUNT,
147	};
148	struct ec_response_gpio_get_v1 response;
149	int ret;
150
151	ret = cros_ec_cmd(cros_ec, 1, EC_CMD_GPIO_GET, &params,
152			  sizeof(params), &response, sizeof(response));
153	if (ret < 0)
154		return ret;
155
156	return response.get_count.val;
157}
158
159static int cros_ec_gpio_probe(struct platform_device *pdev)
160{
161	struct device *dev = &pdev->dev;
162	struct device *parent = dev->parent;
163	struct cros_ec_dev *ec_dev = dev_get_drvdata(parent);
164	struct cros_ec_device *cros_ec = ec_dev->ec_dev;
165	struct gpio_chip *gc;
166	int ngpios;
167	int ret;
168
169	/* Use the fwnode from the protocol device, e.g. cros-ec-spi */
170	device_set_node(dev, dev_fwnode(cros_ec->dev));
171
172	ngpios = cros_ec_gpio_ngpios(cros_ec);
173	if (ngpios < 0) {
174		dev_err_probe(dev, ngpios, "error getting gpio count\n");
175		return ngpios;
176	}
177
178	gc = devm_kzalloc(dev, sizeof(*gc), GFP_KERNEL);
179	if (!gc)
180		return -ENOMEM;
181
182	gc->ngpio = ngpios;
183	gc->parent = dev;
184	ret = cros_ec_gpio_init_names(cros_ec, gc);
185	if (ret)
186		return ret;
187
188	gc->can_sleep = true;
189	gc->label = dev_name(dev);
190	gc->base = -1;
191	gc->set = cros_ec_gpio_set;
192	gc->get = cros_ec_gpio_get;
193	gc->get_direction = cros_ec_gpio_get_direction;
194
195	return devm_gpiochip_add_data(dev, gc, cros_ec);
196}
197
198static const struct platform_device_id cros_ec_gpio_id[] = {
199	{ "cros-ec-gpio", 0 },
200	{}
201};
202MODULE_DEVICE_TABLE(platform, cros_ec_gpio_id);
203
204static struct platform_driver cros_ec_gpio_driver = {
205	.probe = cros_ec_gpio_probe,
206	.driver = {
207		.name = "cros-ec-gpio",
208	},
209	.id_table = cros_ec_gpio_id,
210};
211module_platform_driver(cros_ec_gpio_driver);
212
213MODULE_DESCRIPTION("ChromeOS EC GPIO Driver");
214MODULE_LICENSE("GPL");