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. */
25 struct ec_rtc_read_request {
26 	u8 command;
27 	u8 reserved;
28 	u8 param;
29 } __packed;
30 static 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  */
48 struct 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  */
75 struct 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 
wilco_ec_rtc_read(struct device * dev,struct rtc_time * tm)89 static 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 
wilco_ec_rtc_write(struct device * dev,struct rtc_time * tm)123 static 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 
160 static 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 
wilco_ec_rtc_probe(struct platform_device * pdev)165 static 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 
182 static struct platform_driver wilco_ec_rtc_driver = {
183 	.driver = {
184 		.name = "rtc-wilco-ec",
185 	},
186 	.probe = wilco_ec_rtc_probe,
187 };
188 
189 module_platform_driver(wilco_ec_rtc_driver);
190 
191 MODULE_ALIAS("platform:rtc-wilco-ec");
192 MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
193 MODULE_LICENSE("GPL v2");
194 MODULE_DESCRIPTION("Wilco EC RTC driver");
195