drivers/rtc/rtc-wilco-ec.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * RTC interface for Wilco Embedded Controller with R/W abilities
   4  *
   5  * Copyright 2018 Google LLC
   6  *
   7  * The corresponding platform device is typically registered in
   8  * drivers/platform/chrome/wilco_ec/core.c
   9  */
  10
  11 #include <linux/bcd.h>
  12 #include <linux/err.h>
  13 #include <linux/kernel.h>
  14 #include <linux/module.h>
  15 #include <linux/platform_device.h>
  16 #include <linux/platform_data/wilco-ec.h>
  17 #include <linux/rtc.h>
  18 #include <linux/timekeeping.h>
  19
  20 #define EC_COMMAND_CMOS                 0x7c
  21 #define EC_CMOS_TOD_WRITE               0x02
  22 #define EC_CMOS_TOD_READ                0x08
  23
  24 /**
  25  * struct ec_rtc_read - Format of RTC returned by EC.
  26  * @second: Second value (0..59)
  27  * @minute: Minute value (0..59)
  28  * @hour: Hour value (0..23)
  29  * @day: Day value (1..31)
  30  * @month: Month value (1..12)
  31  * @year: Year value (full year % 100)
  32  * @century: Century value (full year / 100)
  33  *
  34  * All values are presented in binary (not BCD).
  35  */
  36 struct ec_rtc_read {
  37         u8 second;
  38         u8 minute;
  39         u8 hour;
  40         u8 day;
  41         u8 month;
  42         u8 year;
  43         u8 century;
  44 } __packed;
  45
  46 /**
  47  * struct ec_rtc_write - Format of RTC sent to the EC.
  48  * @param: EC_CMOS_TOD_WRITE
  49  * @century: Century value (full year / 100)
  50  * @year: Year value (full year % 100)
  51  * @month: Month value (1..12)
  52  * @day: Day value (1..31)
  53  * @hour: Hour value (0..23)
  54  * @minute: Minute value (0..59)
  55  * @second: Second value (0..59)
  56  * @weekday: Day of the week (0=Saturday)
  57  *
  58  * All values are presented in BCD.
  59  */
  60 struct ec_rtc_write {
  61         u8 param;
  62         u8 century;
  63         u8 year;
  64         u8 month;
  65         u8 day;
  66         u8 hour;
  67         u8 minute;
  68         u8 second;
  69         u8 weekday;
  70 } __packed;
  71
  72 static int wilco_ec_rtc_read(struct device *dev, struct rtc_time *tm)
  73 {
  74         struct wilco_ec_device *ec = dev_get_drvdata(dev->parent);
  75         u8 param = EC_CMOS_TOD_READ;
  76         struct ec_rtc_read rtc;
  77         struct wilco_ec_message msg = {
  78                 .type = WILCO_EC_MSG_LEGACY,
  79                 .flags = WILCO_EC_FLAG_RAW_RESPONSE,
  80                 .command = EC_COMMAND_CMOS,
  81                 .request_data = &param,
  82                 .request_size = sizeof(param),
  83                 .response_data = &rtc,
  84                 .response_size = sizeof(rtc),
  85         };
  86         int ret;
  87
  88         ret = wilco_ec_mailbox(ec, &msg);
  89         if (ret < 0)
  90                 return ret;
  91
  92         tm->tm_sec      = rtc.second;
  93         tm->tm_min      = rtc.minute;
  94         tm->tm_hour     = rtc.hour;
  95         tm->tm_mday     = rtc.day;
  96         tm->tm_mon      = rtc.month - 1;
  97         tm->tm_year     = rtc.year + (rtc.century * 100) - 1900;
  98         tm->tm_yday     = rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
  99
 100         /* Don't compute day of week, we don't need it. */
 101         tm->tm_wday = -1;
 102
 103         return 0;
 104 }
 105
 106 static int wilco_ec_rtc_write(struct device *dev, struct rtc_time *tm)
 107 {
 108         struct wilco_ec_device *ec = dev_get_drvdata(dev->parent);
 109         struct ec_rtc_write rtc;
 110         struct wilco_ec_message msg = {
 111                 .type = WILCO_EC_MSG_LEGACY,
 112                 .flags = WILCO_EC_FLAG_RAW_RESPONSE,
 113                 .command = EC_COMMAND_CMOS,
 114                 .request_data = &rtc,
 115                 .request_size = sizeof(rtc),
 116         };
 117         int year = tm->tm_year + 1900;
 118         /*
 119          * Convert from 0=Sunday to 0=Saturday for the EC
 120          * We DO need to set weekday because the EC controls battery charging
 121          * schedules that depend on the day of the week.
 122          */
 123         int wday = tm->tm_wday == 6 ? 0 : tm->tm_wday + 1;
 124         int ret;
 125
 126         rtc.param       = EC_CMOS_TOD_WRITE;
 127         rtc.century     = bin2bcd(year / 100);
 128         rtc.year        = bin2bcd(year % 100);
 129         rtc.month       = bin2bcd(tm->tm_mon + 1);
 130         rtc.day         = bin2bcd(tm->tm_mday);
 131         rtc.hour        = bin2bcd(tm->tm_hour);
 132         rtc.minute      = bin2bcd(tm->tm_min);
 133         rtc.second      = bin2bcd(tm->tm_sec);
 134         rtc.weekday     = bin2bcd(wday);
 135
 136         ret = wilco_ec_mailbox(ec, &msg);
 137         if (ret < 0)
 138                 return ret;
 139
 140         return 0;
 141 }
 142
 143 static const struct rtc_class_ops wilco_ec_rtc_ops = {
 144         .read_time = wilco_ec_rtc_read,
 145         .set_time = wilco_ec_rtc_write,
 146 };
 147
 148 static int wilco_ec_rtc_probe(struct platform_device *pdev)
 149 {
 150         struct rtc_device *rtc;
 151
 152         rtc = devm_rtc_allocate_device(&pdev->dev);
 153         if (IS_ERR(rtc))
 154                 return PTR_ERR(rtc);
 155
 156         rtc->ops = &wilco_ec_rtc_ops;
 157         /* EC only supports this century */
 158         rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
 159         rtc->range_max = RTC_TIMESTAMP_END_2099;
 160         rtc->owner = THIS_MODULE;
 161
 162         return rtc_register_device(rtc);
 163 }
 164
 165 static struct platform_driver wilco_ec_rtc_driver = {
 166         .driver = {
 167                 .name = "rtc-wilco-ec",
 168         },
 169         .probe = wilco_ec_rtc_probe,
 170 };
 171
 172 module_platform_driver(wilco_ec_rtc_driver);
 173
 174 MODULE_ALIAS("platform:rtc-wilco-ec");
 175 MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
 176 MODULE_LICENSE("GPL v2");
 177 MODULE_DESCRIPTION("Wilco EC RTC driver");