xref: /openbmc/linux/drivers/rtc/rtc-ntxec.c (revision 435af897)
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