1// SPDX-License-Identifier: GPL-2.0
2/*
3 * RTC interface for Wilco Embedded Controller with R/W abilities
4 *
5 * Copyright 2018 Google LLC
6 *
7 * The corresponding platform device is typically registered in
8 * drivers/platform/chrome/wilco_ec/core.c
9 */
10
11#include <linux/bcd.h>
12#include <linux/err.h>
13#include <linux/kernel.h>
14#include <linux/module.h>
15#include <linux/platform_device.h>
16#include <linux/platform_data/wilco-ec.h>
17#include <linux/rtc.h>
18#include <linux/timekeeping.h>
19
20#define EC_COMMAND_CMOS			0x7c
21#define EC_CMOS_TOD_WRITE		0x02
22#define EC_CMOS_TOD_READ		0x08
23
24/* Message sent to the EC to request the current time. */
25struct ec_rtc_read_request {
26	u8 command;
27	u8 reserved;
28	u8 param;
29} __packed;
30static struct ec_rtc_read_request read_rq = {
31	.command = EC_COMMAND_CMOS,
32	.param = EC_CMOS_TOD_READ,
33};
34
35/**
36 * struct ec_rtc_read_response - Format of RTC returned by EC.
37 * @reserved: Unused byte
38 * @second: Second value (0..59)
39 * @minute: Minute value (0..59)
40 * @hour: Hour value (0..23)
41 * @day: Day value (1..31)
42 * @month: Month value (1..12)
43 * @year: Year value (full year % 100)
44 * @century: Century value (full year / 100)
45 *
46 * All values are presented in binary (not BCD).
47 */
48struct ec_rtc_read_response {
49	u8 reserved;
50	u8 second;
51	u8 minute;
52	u8 hour;
53	u8 day;
54	u8 month;
55	u8 year;
56	u8 century;
57} __packed;
58
59/**
60 * struct ec_rtc_write_request - Format of RTC sent to the EC.
61 * @command: Always EC_COMMAND_CMOS
62 * @reserved: Unused byte
63 * @param: Always EC_CMOS_TOD_WRITE
64 * @century: Century value (full year / 100)
65 * @year: Year value (full year % 100)
66 * @month: Month value (1..12)
67 * @day: Day value (1..31)
68 * @hour: Hour value (0..23)
69 * @minute: Minute value (0..59)
70 * @second: Second value (0..59)
71 * @weekday: Day of the week (0=Saturday)
72 *
73 * All values are presented in BCD.
74 */
75struct ec_rtc_write_request {
76	u8 command;
77	u8 reserved;
78	u8 param;
79	u8 century;
80	u8 year;
81	u8 month;
82	u8 day;
83	u8 hour;
84	u8 minute;
85	u8 second;
86	u8 weekday;
87} __packed;
88
89static int wilco_ec_rtc_read(struct device *dev, struct rtc_time *tm)
90{
91	struct wilco_ec_device *ec = dev_get_drvdata(dev->parent);
92	struct ec_rtc_read_response rtc;
93	struct wilco_ec_message msg;
94	int ret;
95
96	memset(&msg, 0, sizeof(msg));
97	msg.type = WILCO_EC_MSG_LEGACY;
98	msg.request_data = &read_rq;
99	msg.request_size = sizeof(read_rq);
100	msg.response_data = &rtc;
101	msg.response_size = sizeof(rtc);
102
103	ret = wilco_ec_mailbox(ec, &msg);
104	if (ret < 0)
105		return ret;
106
107	tm->tm_sec	= rtc.second;
108	tm->tm_min	= rtc.minute;
109	tm->tm_hour	= rtc.hour;
110	tm->tm_mday	= rtc.day;
111	tm->tm_mon	= rtc.month - 1;
112	tm->tm_year	= rtc.year + (rtc.century * 100) - 1900;
113	/* Ignore other tm fields, man rtc says userspace shouldn't use them. */
114
115	if (rtc_valid_tm(tm)) {
116		dev_err(dev, "Time from RTC is invalid: %ptRr\n", tm);
117		return -EIO;
118	}
119
120	return 0;
121}
122
123static int wilco_ec_rtc_write(struct device *dev, struct rtc_time *tm)
124{
125	struct wilco_ec_device *ec = dev_get_drvdata(dev->parent);
126	struct ec_rtc_write_request rtc;
127	struct wilco_ec_message msg;
128	int year = tm->tm_year + 1900;
129	/*
130	 * Convert from 0=Sunday to 0=Saturday for the EC
131	 * We DO need to set weekday because the EC controls battery charging
132	 * schedules that depend on the day of the week.
133	 */
134	int wday = tm->tm_wday == 6 ? 0 : tm->tm_wday + 1;
135	int ret;
136
137	rtc.command	= EC_COMMAND_CMOS;
138	rtc.param	= EC_CMOS_TOD_WRITE;
139	rtc.century	= bin2bcd(year / 100);
140	rtc.year	= bin2bcd(year % 100);
141	rtc.month	= bin2bcd(tm->tm_mon + 1);
142	rtc.day		= bin2bcd(tm->tm_mday);
143	rtc.hour	= bin2bcd(tm->tm_hour);
144	rtc.minute	= bin2bcd(tm->tm_min);
145	rtc.second	= bin2bcd(tm->tm_sec);
146	rtc.weekday	= bin2bcd(wday);
147
148	memset(&msg, 0, sizeof(msg));
149	msg.type = WILCO_EC_MSG_LEGACY;
150	msg.request_data = &rtc;
151	msg.request_size = sizeof(rtc);
152
153	ret = wilco_ec_mailbox(ec, &msg);
154	if (ret < 0)
155		return ret;
156
157	return 0;
158}
159
160static const struct rtc_class_ops wilco_ec_rtc_ops = {
161	.read_time = wilco_ec_rtc_read,
162	.set_time = wilco_ec_rtc_write,
163};
164
165static int wilco_ec_rtc_probe(struct platform_device *pdev)
166{
167	struct rtc_device *rtc;
168
169	rtc = devm_rtc_allocate_device(&pdev->dev);
170	if (IS_ERR(rtc))
171		return PTR_ERR(rtc);
172
173	rtc->ops = &wilco_ec_rtc_ops;
174	/* EC only supports this century */
175	rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
176	rtc->range_max = RTC_TIMESTAMP_END_2099;
177	rtc->owner = THIS_MODULE;
178
179	return devm_rtc_register_device(rtc);
180}
181
182static struct platform_driver wilco_ec_rtc_driver = {
183	.driver = {
184		.name = "rtc-wilco-ec",
185	},
186	.probe = wilco_ec_rtc_probe,
187};
188
189module_platform_driver(wilco_ec_rtc_driver);
190
191MODULE_ALIAS("platform:rtc-wilco-ec");
192MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
193MODULE_LICENSE("GPL v2");
194MODULE_DESCRIPTION("Wilco EC RTC driver");
195