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 /* Message sent to the EC to request the current time. */
  25 struct ec_rtc_read_request {
  26         u8 command;
  27         u8 reserved;
  28         u8 param;
  29 } __packed;
  30 static struct ec_rtc_read_request read_rq = {
  31         .command = EC_COMMAND_CMOS,
  32         .param = EC_CMOS_TOD_READ,
  33 };
  34
  35 /**
  36  * struct ec_rtc_read_response - Format of RTC returned by EC.
  37  * @reserved: Unused byte
  38  * @second: Second value (0..59)
  39  * @minute: Minute value (0..59)
  40  * @hour: Hour value (0..23)
  41  * @day: Day value (1..31)
  42  * @month: Month value (1..12)
  43  * @year: Year value (full year % 100)
  44  * @century: Century value (full year / 100)
  45  *
  46  * All values are presented in binary (not BCD).
  47  */
  48 struct ec_rtc_read_response {
  49         u8 reserved;
  50         u8 second;
  51         u8 minute;
  52         u8 hour;
  53         u8 day;
  54         u8 month;
  55         u8 year;
  56         u8 century;
  57 } __packed;
  58
  59 /**
  60  * struct ec_rtc_write_request - Format of RTC sent to the EC.
  61  * @command: Always EC_COMMAND_CMOS
  62  * @reserved: Unused byte
  63  * @param: Always EC_CMOS_TOD_WRITE
  64  * @century: Century value (full year / 100)
  65  * @year: Year value (full year % 100)
  66  * @month: Month value (1..12)
  67  * @day: Day value (1..31)
  68  * @hour: Hour value (0..23)
  69  * @minute: Minute value (0..59)
  70  * @second: Second value (0..59)
  71  * @weekday: Day of the week (0=Saturday)
  72  *
  73  * All values are presented in BCD.
  74  */
  75 struct ec_rtc_write_request {
  76         u8 command;
  77         u8 reserved;
  78         u8 param;
  79         u8 century;
  80         u8 year;
  81         u8 month;
  82         u8 day;
  83         u8 hour;
  84         u8 minute;
  85         u8 second;
  86         u8 weekday;
  87 } __packed;
  88
  89 static int wilco_ec_rtc_read(struct device *dev, struct rtc_time *tm)
  90 {
  91         struct wilco_ec_device *ec = dev_get_drvdata(dev->parent);
  92         struct ec_rtc_read_response rtc;
  93         struct wilco_ec_message msg;
  94         int ret;
  95
  96         memset(&msg, 0, sizeof(msg));
  97         msg.type = WILCO_EC_MSG_LEGACY;
  98         msg.request_data = &read_rq;
  99         msg.request_size = sizeof(read_rq);
 100         msg.response_data = &rtc;
 101         msg.response_size = sizeof(rtc);
 102
 103         ret = wilco_ec_mailbox(ec, &msg);
 104         if (ret < 0)
 105                 return ret;
 106
 107         tm->tm_sec      = rtc.second;
 108         tm->tm_min      = rtc.minute;
 109         tm->tm_hour     = rtc.hour;
 110         tm->tm_mday     = rtc.day;
 111         tm->tm_mon      = rtc.month - 1;
 112         tm->tm_year     = rtc.year + (rtc.century * 100) - 1900;
 113         /* Ignore other tm fields, man rtc says userspace shouldn't use them. */
 114
 115         if (rtc_valid_tm(tm)) {
 116                 dev_err(dev, "Time from RTC is invalid: %ptRr\n", tm);
 117                 return -EIO;
 118         }
 119
 120         return 0;
 121 }
 122
 123 static int wilco_ec_rtc_write(struct device *dev, struct rtc_time *tm)
 124 {
 125         struct wilco_ec_device *ec = dev_get_drvdata(dev->parent);
 126         struct ec_rtc_write_request rtc;
 127         struct wilco_ec_message msg;
 128         int year = tm->tm_year + 1900;
 129         /*
 130          * Convert from 0=Sunday to 0=Saturday for the EC
 131          * We DO need to set weekday because the EC controls battery charging
 132          * schedules that depend on the day of the week.
 133          */
 134         int wday = tm->tm_wday == 6 ? 0 : tm->tm_wday + 1;
 135         int ret;
 136
 137         rtc.command     = EC_COMMAND_CMOS;
 138         rtc.param       = EC_CMOS_TOD_WRITE;
 139         rtc.century     = bin2bcd(year / 100);
 140         rtc.year        = bin2bcd(year % 100);
 141         rtc.month       = bin2bcd(tm->tm_mon + 1);
 142         rtc.day         = bin2bcd(tm->tm_mday);
 143         rtc.hour        = bin2bcd(tm->tm_hour);
 144         rtc.minute      = bin2bcd(tm->tm_min);
 145         rtc.second      = bin2bcd(tm->tm_sec);
 146         rtc.weekday     = bin2bcd(wday);
 147
 148         memset(&msg, 0, sizeof(msg));
 149         msg.type = WILCO_EC_MSG_LEGACY;
 150         msg.request_data = &rtc;
 151         msg.request_size = sizeof(rtc);
 152
 153         ret = wilco_ec_mailbox(ec, &msg);
 154         if (ret < 0)
 155                 return ret;
 156
 157         return 0;
 158 }
 159
 160 static const struct rtc_class_ops wilco_ec_rtc_ops = {
 161         .read_time = wilco_ec_rtc_read,
 162         .set_time = wilco_ec_rtc_write,
 163 };
 164
 165 static int wilco_ec_rtc_probe(struct platform_device *pdev)
 166 {
 167         struct rtc_device *rtc;
 168
 169         rtc = devm_rtc_allocate_device(&pdev->dev);
 170         if (IS_ERR(rtc))
 171                 return PTR_ERR(rtc);
 172
 173         rtc->ops = &wilco_ec_rtc_ops;
 174         /* EC only supports this century */
 175         rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
 176         rtc->range_max = RTC_TIMESTAMP_END_2099;
 177         rtc->owner = THIS_MODULE;
 178
 179         return devm_rtc_register_device(rtc);
 180 }
 181
 182 static struct platform_driver wilco_ec_rtc_driver = {
 183         .driver = {
 184                 .name = "rtc-wilco-ec",
 185         },
 186         .probe = wilco_ec_rtc_probe,
 187 };
 188
 189 module_platform_driver(wilco_ec_rtc_driver);
 190
 191 MODULE_ALIAS("platform:rtc-wilco-ec");
 192 MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
 193 MODULE_LICENSE("GPL v2");
 194 MODULE_DESCRIPTION("Wilco EC RTC driver");