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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* The Netronix embedded controller is a microcontroller found in some
* e-book readers designed by the original design manufacturer Netronix, Inc.
* It contains RTC, battery monitoring, system power management, and PWM
* functionality.
*
* This driver implements access to the RTC time and date.
*
* Copyright 2020 Jonathan Neuschäfer <j.neuschaefer@gmx.net>
*/
#include <linux/mfd/ntxec.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>
#include <linux/rtc.h>
#include <linux/types.h>
struct ntxec_rtc {
struct device *dev;
struct ntxec *ec;
};
#define NTXEC_REG_WRITE_YEAR 0x10
#define NTXEC_REG_WRITE_MONTH 0x11
#define NTXEC_REG_WRITE_DAY 0x12
#define NTXEC_REG_WRITE_HOUR 0x13
#define NTXEC_REG_WRITE_MINUTE 0x14
#define NTXEC_REG_WRITE_SECOND 0x15
#define NTXEC_REG_READ_YEAR_MONTH 0x20
#define NTXEC_REG_READ_MDAY_HOUR 0x21
#define NTXEC_REG_READ_MINUTE_SECOND 0x23
static int ntxec_read_time(struct device *dev, struct rtc_time *tm)
{
struct ntxec_rtc *rtc = dev_get_drvdata(dev);
unsigned int value;
int res;
retry:
res = regmap_read(rtc->ec->regmap, NTXEC_REG_READ_MINUTE_SECOND, &value);
if (res < 0)
return res;
tm->tm_min = value >> 8;
tm->tm_sec = value & 0xff;
res = regmap_read(rtc->ec->regmap, NTXEC_REG_READ_MDAY_HOUR, &value);
if (res < 0)
return res;
tm->tm_mday = value >> 8;
tm->tm_hour = value & 0xff;
res = regmap_read(rtc->ec->regmap, NTXEC_REG_READ_YEAR_MONTH, &value);
if (res < 0)
return res;
tm->tm_year = (value >> 8) + 100;
tm->tm_mon = (value & 0xff) - 1;
/*
* Read the minutes/seconds field again. If it changed since the first
* read, we can't assume that the values read so far are consistent,
* and should start from the beginning.
*/
res = regmap_read(rtc->ec->regmap, NTXEC_REG_READ_MINUTE_SECOND, &value);
if (res < 0)
return res;
if (tm->tm_min != value >> 8 || tm->tm_sec != (value & 0xff))
goto retry;
return 0;
}
static int ntxec_set_time(struct device *dev, struct rtc_time *tm)
{
struct ntxec_rtc *rtc = dev_get_drvdata(dev);
/*
* To avoid time overflows while we're writing the full date/time,
* set the seconds field to zero before doing anything else. For the
* next 59 seconds (plus however long it takes until the RTC's next
* update of the second field), the seconds field will not overflow
* into the other fields.
*/
struct reg_sequence regs[] = {
{ NTXEC_REG_WRITE_SECOND, ntxec_reg8(0) },
{ NTXEC_REG_WRITE_YEAR, ntxec_reg8(tm->tm_year - 100) },
{ NTXEC_REG_WRITE_MONTH, ntxec_reg8(tm->tm_mon + 1) },
{ NTXEC_REG_WRITE_DAY, ntxec_reg8(tm->tm_mday) },
{ NTXEC_REG_WRITE_HOUR, ntxec_reg8(tm->tm_hour) },
{ NTXEC_REG_WRITE_MINUTE, ntxec_reg8(tm->tm_min) },
{ NTXEC_REG_WRITE_SECOND, ntxec_reg8(tm->tm_sec) },
};
return regmap_multi_reg_write(rtc->ec->regmap, regs, ARRAY_SIZE(regs));
}
static const struct rtc_class_ops ntxec_rtc_ops = {
.read_time = ntxec_read_time,
.set_time = ntxec_set_time,
};
static int ntxec_rtc_probe(struct platform_device *pdev)
{
struct rtc_device *dev;
struct ntxec_rtc *rtc;
pdev->dev.of_node = pdev->dev.parent->of_node;
rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
if (!rtc)
return -ENOMEM;
rtc->dev = &pdev->dev;
rtc->ec = dev_get_drvdata(pdev->dev.parent);
platform_set_drvdata(pdev, rtc);
dev = devm_rtc_allocate_device(&pdev->dev);
if (IS_ERR(dev))
return PTR_ERR(dev);
dev->ops = &ntxec_rtc_ops;
dev->range_min = RTC_TIMESTAMP_BEGIN_2000;
dev->range_max = 9025257599LL; /* 2255-12-31 23:59:59 */
return devm_rtc_register_device(dev);
}
static struct platform_driver ntxec_rtc_driver = {
.driver = {
.name = "ntxec-rtc",
},
.probe = ntxec_rtc_probe,
};
module_platform_driver(ntxec_rtc_driver);
MODULE_AUTHOR("Jonathan Neuschäfer <j.neuschaefer@gmx.net>");
MODULE_DESCRIPTION("RTC driver for Netronix EC");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:ntxec-rtc");
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