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// SPDX-License-Identifier: GPL-2.0
/*
* RTC interface for Wilco Embedded Controller with R/W abilities
*
* Copyright 2018 Google LLC
*
* The corresponding platform device is typically registered in
* drivers/platform/chrome/wilco_ec/core.c
*/
#include <linux/bcd.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/platform_data/wilco-ec.h>
#include <linux/rtc.h>
#include <linux/timekeeping.h>
#define EC_COMMAND_CMOS 0x7c
#define EC_CMOS_TOD_WRITE 0x02
#define EC_CMOS_TOD_READ 0x08
/* Message sent to the EC to request the current time. */
struct ec_rtc_read_request {
u8 command;
u8 reserved;
u8 param;
} __packed;
static struct ec_rtc_read_request read_rq = {
.command = EC_COMMAND_CMOS,
.param = EC_CMOS_TOD_READ,
};
/**
* struct ec_rtc_read_response - Format of RTC returned by EC.
* @reserved: Unused byte
* @second: Second value (0..59)
* @minute: Minute value (0..59)
* @hour: Hour value (0..23)
* @day: Day value (1..31)
* @month: Month value (1..12)
* @year: Year value (full year % 100)
* @century: Century value (full year / 100)
*
* All values are presented in binary (not BCD).
*/
struct ec_rtc_read_response {
u8 reserved;
u8 second;
u8 minute;
u8 hour;
u8 day;
u8 month;
u8 year;
u8 century;
} __packed;
/**
* struct ec_rtc_write_request - Format of RTC sent to the EC.
* @command: Always EC_COMMAND_CMOS
* @reserved: Unused byte
* @param: Always EC_CMOS_TOD_WRITE
* @century: Century value (full year / 100)
* @year: Year value (full year % 100)
* @month: Month value (1..12)
* @day: Day value (1..31)
* @hour: Hour value (0..23)
* @minute: Minute value (0..59)
* @second: Second value (0..59)
* @weekday: Day of the week (0=Saturday)
*
* All values are presented in BCD.
*/
struct ec_rtc_write_request {
u8 command;
u8 reserved;
u8 param;
u8 century;
u8 year;
u8 month;
u8 day;
u8 hour;
u8 minute;
u8 second;
u8 weekday;
} __packed;
static int wilco_ec_rtc_read(struct device *dev, struct rtc_time *tm)
{
struct wilco_ec_device *ec = dev_get_drvdata(dev->parent);
struct ec_rtc_read_response rtc;
struct wilco_ec_message msg;
int ret;
memset(&msg, 0, sizeof(msg));
msg.type = WILCO_EC_MSG_LEGACY;
msg.request_data = &read_rq;
msg.request_size = sizeof(read_rq);
msg.response_data = &rtc;
msg.response_size = sizeof(rtc);
ret = wilco_ec_mailbox(ec, &msg);
if (ret < 0)
return ret;
tm->tm_sec = rtc.second;
tm->tm_min = rtc.minute;
tm->tm_hour = rtc.hour;
tm->tm_mday = rtc.day;
tm->tm_mon = rtc.month - 1;
tm->tm_year = rtc.year + (rtc.century * 100) - 1900;
/* Ignore other tm fields, man rtc says userspace shouldn't use them. */
if (rtc_valid_tm(tm)) {
dev_err(dev, "Time from RTC is invalid: %ptRr\n", tm);
return -EIO;
}
return 0;
}
static int wilco_ec_rtc_write(struct device *dev, struct rtc_time *tm)
{
struct wilco_ec_device *ec = dev_get_drvdata(dev->parent);
struct ec_rtc_write_request rtc;
struct wilco_ec_message msg;
int year = tm->tm_year + 1900;
/*
* Convert from 0=Sunday to 0=Saturday for the EC
* We DO need to set weekday because the EC controls battery charging
* schedules that depend on the day of the week.
*/
int wday = tm->tm_wday == 6 ? 0 : tm->tm_wday + 1;
int ret;
rtc.command = EC_COMMAND_CMOS;
rtc.param = EC_CMOS_TOD_WRITE;
rtc.century = bin2bcd(year / 100);
rtc.year = bin2bcd(year % 100);
rtc.month = bin2bcd(tm->tm_mon + 1);
rtc.day = bin2bcd(tm->tm_mday);
rtc.hour = bin2bcd(tm->tm_hour);
rtc.minute = bin2bcd(tm->tm_min);
rtc.second = bin2bcd(tm->tm_sec);
rtc.weekday = bin2bcd(wday);
memset(&msg, 0, sizeof(msg));
msg.type = WILCO_EC_MSG_LEGACY;
msg.request_data = &rtc;
msg.request_size = sizeof(rtc);
ret = wilco_ec_mailbox(ec, &msg);
if (ret < 0)
return ret;
return 0;
}
static const struct rtc_class_ops wilco_ec_rtc_ops = {
.read_time = wilco_ec_rtc_read,
.set_time = wilco_ec_rtc_write,
};
static int wilco_ec_rtc_probe(struct platform_device *pdev)
{
struct rtc_device *rtc;
rtc = devm_rtc_allocate_device(&pdev->dev);
if (IS_ERR(rtc))
return PTR_ERR(rtc);
rtc->ops = &wilco_ec_rtc_ops;
/* EC only supports this century */
rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
rtc->range_max = RTC_TIMESTAMP_END_2099;
rtc->owner = THIS_MODULE;
return devm_rtc_register_device(rtc);
}
static struct platform_driver wilco_ec_rtc_driver = {
.driver = {
.name = "rtc-wilco-ec",
},
.probe = wilco_ec_rtc_probe,
};
module_platform_driver(wilco_ec_rtc_driver);
MODULE_ALIAS("platform:rtc-wilco-ec");
MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Wilco EC RTC driver");
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