linux/drivers/rtc/rtc-ntxec.c
Jonathan Neuschäfer 435af89786 rtc: New driver for RTC in Netronix embedded controller
With this driver, mainline Linux can keep its time and date in sync with
the vendor kernel.

Advanced functionality like alarm and automatic power-on is not yet
supported.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
2021-03-10 11:06:33 +00:00

146 lines
3.9 KiB
C

// 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");