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  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
 20struct 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
 36static 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
 42retry:
 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
 79static 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
103static const struct rtc_class_ops ntxec_rtc_ops = {
104	.read_time = ntxec_read_time,
105	.set_time = ntxec_set_time,
106};
107
108static 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
134static struct platform_driver ntxec_rtc_driver = {
135	.driver = {
136		.name = "ntxec-rtc",
137	},
138	.probe = ntxec_rtc_probe,
139};
140module_platform_driver(ntxec_rtc_driver);
141
142MODULE_AUTHOR("Jonathan Neuschäfer <j.neuschaefer@gmx.net>");
143MODULE_DESCRIPTION("RTC driver for Netronix EC");
144MODULE_LICENSE("GPL");
145MODULE_ALIAS("platform:ntxec-rtc");
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