1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * The Netronix embedded controller is a microcontroller found in some
4 * e-book readers designed by the original design manufacturer Netronix, Inc.
5 * It contains RTC, battery monitoring, system power management, and PWM
6 * functionality.
7 *
8 * This driver implements access to the RTC time and date.
9 *
10 * Copyright 2020 Jonathan Neuschäfer <j.neuschaefer@gmx.net>
11 */
12
13 #include <linux/mfd/ntxec.h>
14 #include <linux/module.h>
15 #include <linux/platform_device.h>
16 #include <linux/regmap.h>
17 #include <linux/rtc.h>
18 #include <linux/types.h>
19
20 struct ntxec_rtc {
21 struct device *dev;
22 struct ntxec *ec;
23 };
24
25 #define NTXEC_REG_WRITE_YEAR 0x10
26 #define NTXEC_REG_WRITE_MONTH 0x11
27 #define NTXEC_REG_WRITE_DAY 0x12
28 #define NTXEC_REG_WRITE_HOUR 0x13
29 #define NTXEC_REG_WRITE_MINUTE 0x14
30 #define NTXEC_REG_WRITE_SECOND 0x15
31
32 #define NTXEC_REG_READ_YEAR_MONTH 0x20
33 #define NTXEC_REG_READ_MDAY_HOUR 0x21
34 #define NTXEC_REG_READ_MINUTE_SECOND 0x23
35
ntxec_read_time(struct device * dev,struct rtc_time * tm)36 static int ntxec_read_time(struct device *dev, struct rtc_time *tm)
37 {
38 struct ntxec_rtc *rtc = dev_get_drvdata(dev);
39 unsigned int value;
40 int res;
41
42 retry:
43 res = regmap_read(rtc->ec->regmap, NTXEC_REG_READ_MINUTE_SECOND, &value);
44 if (res < 0)
45 return res;
46
47 tm->tm_min = value >> 8;
48 tm->tm_sec = value & 0xff;
49
50 res = regmap_read(rtc->ec->regmap, NTXEC_REG_READ_MDAY_HOUR, &value);
51 if (res < 0)
52 return res;
53
54 tm->tm_mday = value >> 8;
55 tm->tm_hour = value & 0xff;
56
57 res = regmap_read(rtc->ec->regmap, NTXEC_REG_READ_YEAR_MONTH, &value);
58 if (res < 0)
59 return res;
60
61 tm->tm_year = (value >> 8) + 100;
62 tm->tm_mon = (value & 0xff) - 1;
63
64 /*
65 * Read the minutes/seconds field again. If it changed since the first
66 * read, we can't assume that the values read so far are consistent,
67 * and should start from the beginning.
68 */
69 res = regmap_read(rtc->ec->regmap, NTXEC_REG_READ_MINUTE_SECOND, &value);
70 if (res < 0)
71 return res;
72
73 if (tm->tm_min != value >> 8 || tm->tm_sec != (value & 0xff))
74 goto retry;
75
76 return 0;
77 }
78
ntxec_set_time(struct device * dev,struct rtc_time * tm)79 static int ntxec_set_time(struct device *dev, struct rtc_time *tm)
80 {
81 struct ntxec_rtc *rtc = dev_get_drvdata(dev);
82
83 /*
84 * To avoid time overflows while we're writing the full date/time,
85 * set the seconds field to zero before doing anything else. For the
86 * next 59 seconds (plus however long it takes until the RTC's next
87 * update of the second field), the seconds field will not overflow
88 * into the other fields.
89 */
90 struct reg_sequence regs[] = {
91 { NTXEC_REG_WRITE_SECOND, ntxec_reg8(0) },
92 { NTXEC_REG_WRITE_YEAR, ntxec_reg8(tm->tm_year - 100) },
93 { NTXEC_REG_WRITE_MONTH, ntxec_reg8(tm->tm_mon + 1) },
94 { NTXEC_REG_WRITE_DAY, ntxec_reg8(tm->tm_mday) },
95 { NTXEC_REG_WRITE_HOUR, ntxec_reg8(tm->tm_hour) },
96 { NTXEC_REG_WRITE_MINUTE, ntxec_reg8(tm->tm_min) },
97 { NTXEC_REG_WRITE_SECOND, ntxec_reg8(tm->tm_sec) },
98 };
99
100 return regmap_multi_reg_write(rtc->ec->regmap, regs, ARRAY_SIZE(regs));
101 }
102
103 static const struct rtc_class_ops ntxec_rtc_ops = {
104 .read_time = ntxec_read_time,
105 .set_time = ntxec_set_time,
106 };
107
ntxec_rtc_probe(struct platform_device * pdev)108 static int ntxec_rtc_probe(struct platform_device *pdev)
109 {
110 struct rtc_device *dev;
111 struct ntxec_rtc *rtc;
112
113 pdev->dev.of_node = pdev->dev.parent->of_node;
114
115 rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
116 if (!rtc)
117 return -ENOMEM;
118
119 rtc->dev = &pdev->dev;
120 rtc->ec = dev_get_drvdata(pdev->dev.parent);
121 platform_set_drvdata(pdev, rtc);
122
123 dev = devm_rtc_allocate_device(&pdev->dev);
124 if (IS_ERR(dev))
125 return PTR_ERR(dev);
126
127 dev->ops = &ntxec_rtc_ops;
128 dev->range_min = RTC_TIMESTAMP_BEGIN_2000;
129 dev->range_max = 9025257599LL; /* 2255-12-31 23:59:59 */
130
131 return devm_rtc_register_device(dev);
132 }
133
134 static struct platform_driver ntxec_rtc_driver = {
135 .driver = {
136 .name = "ntxec-rtc",
137 },
138 .probe = ntxec_rtc_probe,
139 };
140 module_platform_driver(ntxec_rtc_driver);
141
142 MODULE_AUTHOR("Jonathan Neuschäfer <j.neuschaefer@gmx.net>");
143 MODULE_DESCRIPTION("RTC driver for Netronix EC");
144 MODULE_LICENSE("GPL");
145 MODULE_ALIAS("platform:ntxec-rtc");
146