linux/drivers/rtc/rtc-wilco-ec.c
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   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. */
  25struct ec_rtc_read_request {
  26        u8 command;
  27        u8 reserved;
  28        u8 param;
  29} __packed;
  30static 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 */
  48struct 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 */
  75struct 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
  89static 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
 123static 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
 160static 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
 165static 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
 182static struct platform_driver wilco_ec_rtc_driver = {
 183        .driver = {
 184                .name = "rtc-wilco-ec",
 185        },
 186        .probe = wilco_ec_rtc_probe,
 187};
 188
 189module_platform_driver(wilco_ec_rtc_driver);
 190
 191MODULE_ALIAS("platform:rtc-wilco-ec");
 192MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
 193MODULE_LICENSE("GPL v2");
 194MODULE_DESCRIPTION("Wilco EC RTC driver");
 195