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 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 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 }; 107 108 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