diff options
Diffstat (limited to 'drivers/rtc/rtc-wilco-ec.c')
| -rw-r--r-- | drivers/rtc/rtc-wilco-ec.c | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-wilco-ec.c b/drivers/rtc/rtc-wilco-ec.c new file mode 100644 index 000000000..ff46066a6 --- /dev/null +++ b/drivers/rtc/rtc-wilco-ec.c @@ -0,0 +1,194 @@ +// 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 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"); |