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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * The Netronix embedded controller is a microcontroller found in some4 * e-book readers designed by the original design manufacturer Netronix, Inc.5 * It contains RTC, battery monitoring, system power management, and PWM6 * 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 0x1026#define NTXEC_REG_WRITE_MONTH 0x1127#define NTXEC_REG_WRITE_DAY 0x1228#define NTXEC_REG_WRITE_HOUR 0x1329#define NTXEC_REG_WRITE_MINUTE 0x1430#define NTXEC_REG_WRITE_SECOND 0x1531 32#define NTXEC_REG_READ_YEAR_MONTH 0x2033#define NTXEC_REG_READ_MDAY_HOUR 0x2134#define NTXEC_REG_READ_MINUTE_SECOND 0x2335 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 first66 * 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 the86 * next 59 seconds (plus however long it takes until the RTC's next87 * update of the second field), the seconds field will not overflow88 * 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");146