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linux/drivers/rtc/rtc-s3c.c
Sam Protsenko a5feda3b36 rtc: s3c: Add time range 
This RTC driver starts counting from 2000 to avoid Y2K problem. Also it
only supports 100 years range for all RTCs.  Provide that info to RTC
framework. Also remove check for 100 years range in s3c_rtc_settime(),
as RTC core won't pass any invalid values to the driver, now that
correct range is set.

Here is the rationale on 100 years range limitation. Info on different
Samsung RTCs (credit goes to Krzysztof Kozlowski):
  - All S3C chips have only 8-bit wide year register (can store 100
    years range in BCD format)
  - S5Pv210 and Exynos chips have 12-bit year register (can store 1000
    years range in BCD format)

But in reality we usually can't make use of those 12 bits either:
  - RTCs might think that both 2000 and 2100 years are leap years. So
    when the YEAR register is 0, RTC goes from 28 Feb to 29 Feb, and
    when the YEAR register is 100, RTC also goes from 28 Feb to 29 Feb.
    This is of course incorrect: RTC breaks leap year criteria, which
    breaks the time contiguity, which leads to inability to use the RTC
    after year of 2099. It was found for example on Exynos850 SoC.
  - Despite having 12 bits for holding the year value, RTC might
    overflow the year value internally much earlier. For example, on
    Exynos850 the RTC overflows when YEAR=159, making the next YEAR=0.
    This way RTC actually has range of 160 years, not 1000 as one may
    think.

All that said, there is no sense in trying to increase the time range
for more than 100 years on RTCs that seem capable of that. It also
doesn't have too much practical value -- current hardware will be
probably obsolete by 2100.

Tested manually on Exynos850 RTC:

    $ date -s "1999-12-31 23:59:50"
    $ hwclock -w -f /dev/rtc0
    $ date -s "2100-01-01 00:00:00"
    $ hwclock -w -f /dev/rtc0
    $ date -s "2000-01-01 00:00:00"
    $ hwclock -w -f /dev/rtc0
    $ hwclock -r -f /dev/rtc0
    $ date -s "2099-12-31 23:59:50"
    $ hwclock -w -f /dev/rtc0
    $ hwclock -r -f /dev/rtc0

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20211021202256.28517-4-semen.protsenko@linaro.org
2021-10-23 23:57:23 +02:00

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// SPDX-License-Identifier: GPL-2.0-only
/* drivers/rtc/rtc-s3c.c
*
* Copyright (c) 2010 Samsung Electronics Co., Ltd.
* http://www.samsung.com/
*
* Copyright (c) 2004,2006 Simtec Electronics
* Ben Dooks, <ben@simtec.co.uk>
* http://armlinux.simtec.co.uk/
*
* S3C2410/S3C2440/S3C24XX Internal RTC Driver
*/
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <linux/rtc.h>
#include <linux/bcd.h>
#include <linux/clk.h>
#include <linux/log2.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <asm/irq.h>
#include "rtc-s3c.h"
struct s3c_rtc {
struct device *dev;
struct rtc_device *rtc;
void __iomem *base;
struct clk *rtc_clk;
struct clk *rtc_src_clk;
bool alarm_enabled;
const struct s3c_rtc_data *data;
int irq_alarm;
spinlock_t alarm_lock;
bool wake_en;
};
struct s3c_rtc_data {
bool needs_src_clk;
void (*irq_handler) (struct s3c_rtc *info, int mask);
void (*enable) (struct s3c_rtc *info);
void (*disable) (struct s3c_rtc *info);
};
static int s3c_rtc_enable_clk(struct s3c_rtc *info)
{
int ret;
ret = clk_enable(info->rtc_clk);
if (ret)
return ret;
if (info->data->needs_src_clk) {
ret = clk_enable(info->rtc_src_clk);
if (ret) {
clk_disable(info->rtc_clk);
return ret;
}
}
return 0;
}
static void s3c_rtc_disable_clk(struct s3c_rtc *info)
{
if (info->data->needs_src_clk)
clk_disable(info->rtc_src_clk);
clk_disable(info->rtc_clk);
}
/* IRQ Handler */
static irqreturn_t s3c_rtc_alarmirq(int irq, void *id)
{
struct s3c_rtc *info = (struct s3c_rtc *)id;
if (info->data->irq_handler)
info->data->irq_handler(info, S3C2410_INTP_ALM);
return IRQ_HANDLED;
}
/* Update control registers */
static int s3c_rtc_setaie(struct device *dev, unsigned int enabled)
{
struct s3c_rtc *info = dev_get_drvdata(dev);
unsigned long flags;
unsigned int tmp;
int ret;
dev_dbg(info->dev, "%s: aie=%d\n", __func__, enabled);
ret = s3c_rtc_enable_clk(info);
if (ret)
return ret;
tmp = readb(info->base + S3C2410_RTCALM) & ~S3C2410_RTCALM_ALMEN;
if (enabled)
tmp |= S3C2410_RTCALM_ALMEN;
writeb(tmp, info->base + S3C2410_RTCALM);
spin_lock_irqsave(&info->alarm_lock, flags);
if (info->alarm_enabled && !enabled)
s3c_rtc_disable_clk(info);
else if (!info->alarm_enabled && enabled)
ret = s3c_rtc_enable_clk(info);
info->alarm_enabled = enabled;
spin_unlock_irqrestore(&info->alarm_lock, flags);
s3c_rtc_disable_clk(info);
return ret;
}
/* Read time from RTC and convert it from BCD */
static int s3c_rtc_read_time(struct s3c_rtc *info, struct rtc_time *tm)
{
unsigned int have_retried = 0;
int ret;
ret = s3c_rtc_enable_clk(info);
if (ret)
return ret;
retry_get_time:
tm->tm_min = readb(info->base + S3C2410_RTCMIN);
tm->tm_hour = readb(info->base + S3C2410_RTCHOUR);
tm->tm_mday = readb(info->base + S3C2410_RTCDATE);
tm->tm_mon = readb(info->base + S3C2410_RTCMON);
tm->tm_year = readb(info->base + S3C2410_RTCYEAR);
tm->tm_sec = readb(info->base + S3C2410_RTCSEC);
/*
* The only way to work out whether the system was mid-update
* when we read it is to check the second counter, and if it
* is zero, then we re-try the entire read
*/
if (tm->tm_sec == 0 && !have_retried) {
have_retried = 1;
goto retry_get_time;
}
s3c_rtc_disable_clk(info);
tm->tm_sec = bcd2bin(tm->tm_sec);
tm->tm_min = bcd2bin(tm->tm_min);
tm->tm_hour = bcd2bin(tm->tm_hour);
tm->tm_mday = bcd2bin(tm->tm_mday);
tm->tm_mon = bcd2bin(tm->tm_mon);
tm->tm_year = bcd2bin(tm->tm_year);
return 0;
}
/* Convert time to BCD and write it to RTC */
static int s3c_rtc_write_time(struct s3c_rtc *info, const struct rtc_time *tm)
{
int ret;
ret = s3c_rtc_enable_clk(info);
if (ret)
return ret;
writeb(bin2bcd(tm->tm_sec), info->base + S3C2410_RTCSEC);
writeb(bin2bcd(tm->tm_min), info->base + S3C2410_RTCMIN);
writeb(bin2bcd(tm->tm_hour), info->base + S3C2410_RTCHOUR);
writeb(bin2bcd(tm->tm_mday), info->base + S3C2410_RTCDATE);
writeb(bin2bcd(tm->tm_mon), info->base + S3C2410_RTCMON);
writeb(bin2bcd(tm->tm_year), info->base + S3C2410_RTCYEAR);
s3c_rtc_disable_clk(info);
return 0;
}
static int s3c_rtc_gettime(struct device *dev, struct rtc_time *tm)
{
struct s3c_rtc *info = dev_get_drvdata(dev);
int ret;
ret = s3c_rtc_read_time(info, tm);
if (ret)
return ret;
/* Convert internal representation to actual date/time */
tm->tm_year += 100;
tm->tm_mon -= 1;
dev_dbg(dev, "read time %ptR\n", tm);
return 0;
}
static int s3c_rtc_settime(struct device *dev, struct rtc_time *tm)
{
struct s3c_rtc *info = dev_get_drvdata(dev);
struct rtc_time rtc_tm = *tm;
dev_dbg(dev, "set time %ptR\n", tm);
/*
* Convert actual date/time to internal representation.
* We get around Y2K by simply not supporting it.
*/
rtc_tm.tm_year -= 100;
rtc_tm.tm_mon += 1;
return s3c_rtc_write_time(info, &rtc_tm);
}
static int s3c_rtc_getalarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct s3c_rtc *info = dev_get_drvdata(dev);
struct rtc_time *alm_tm = &alrm->time;
unsigned int alm_en;
int ret;
ret = s3c_rtc_enable_clk(info);
if (ret)
return ret;
alm_tm->tm_sec = readb(info->base + S3C2410_ALMSEC);
alm_tm->tm_min = readb(info->base + S3C2410_ALMMIN);
alm_tm->tm_hour = readb(info->base + S3C2410_ALMHOUR);
alm_tm->tm_mon = readb(info->base + S3C2410_ALMMON);
alm_tm->tm_mday = readb(info->base + S3C2410_ALMDATE);
alm_tm->tm_year = readb(info->base + S3C2410_ALMYEAR);
alm_en = readb(info->base + S3C2410_RTCALM);
s3c_rtc_disable_clk(info);
alrm->enabled = (alm_en & S3C2410_RTCALM_ALMEN) ? 1 : 0;
dev_dbg(dev, "read alarm %d, %ptR\n", alm_en, alm_tm);
/* decode the alarm enable field */
if (alm_en & S3C2410_RTCALM_SECEN)
alm_tm->tm_sec = bcd2bin(alm_tm->tm_sec);
if (alm_en & S3C2410_RTCALM_MINEN)
alm_tm->tm_min = bcd2bin(alm_tm->tm_min);
if (alm_en & S3C2410_RTCALM_HOUREN)
alm_tm->tm_hour = bcd2bin(alm_tm->tm_hour);
if (alm_en & S3C2410_RTCALM_DAYEN)
alm_tm->tm_mday = bcd2bin(alm_tm->tm_mday);
if (alm_en & S3C2410_RTCALM_MONEN) {
alm_tm->tm_mon = bcd2bin(alm_tm->tm_mon);
alm_tm->tm_mon -= 1;
}
if (alm_en & S3C2410_RTCALM_YEAREN)
alm_tm->tm_year = bcd2bin(alm_tm->tm_year);
return 0;
}
static int s3c_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct s3c_rtc *info = dev_get_drvdata(dev);
struct rtc_time *tm = &alrm->time;
unsigned int alrm_en;
int ret;
dev_dbg(dev, "s3c_rtc_setalarm: %d, %ptR\n", alrm->enabled, tm);
ret = s3c_rtc_enable_clk(info);
if (ret)
return ret;
alrm_en = readb(info->base + S3C2410_RTCALM) & S3C2410_RTCALM_ALMEN;
writeb(0x00, info->base + S3C2410_RTCALM);
if (tm->tm_sec < 60 && tm->tm_sec >= 0) {
alrm_en |= S3C2410_RTCALM_SECEN;
writeb(bin2bcd(tm->tm_sec), info->base + S3C2410_ALMSEC);
}
if (tm->tm_min < 60 && tm->tm_min >= 0) {
alrm_en |= S3C2410_RTCALM_MINEN;
writeb(bin2bcd(tm->tm_min), info->base + S3C2410_ALMMIN);
}
if (tm->tm_hour < 24 && tm->tm_hour >= 0) {
alrm_en |= S3C2410_RTCALM_HOUREN;
writeb(bin2bcd(tm->tm_hour), info->base + S3C2410_ALMHOUR);
}
if (tm->tm_mon < 12 && tm->tm_mon >= 0) {
alrm_en |= S3C2410_RTCALM_MONEN;
writeb(bin2bcd(tm->tm_mon + 1), info->base + S3C2410_ALMMON);
}
if (tm->tm_mday <= 31 && tm->tm_mday >= 1) {
alrm_en |= S3C2410_RTCALM_DAYEN;
writeb(bin2bcd(tm->tm_mday), info->base + S3C2410_ALMDATE);
}
dev_dbg(dev, "setting S3C2410_RTCALM to %08x\n", alrm_en);
writeb(alrm_en, info->base + S3C2410_RTCALM);
s3c_rtc_setaie(dev, alrm->enabled);
s3c_rtc_disable_clk(info);
return 0;
}
static const struct rtc_class_ops s3c_rtcops = {
.read_time = s3c_rtc_gettime,
.set_time = s3c_rtc_settime,
.read_alarm = s3c_rtc_getalarm,
.set_alarm = s3c_rtc_setalarm,
.alarm_irq_enable = s3c_rtc_setaie,
};
static void s3c24xx_rtc_enable(struct s3c_rtc *info)
{
unsigned int con, tmp;
con = readw(info->base + S3C2410_RTCCON);
/* re-enable the device, and check it is ok */
if ((con & S3C2410_RTCCON_RTCEN) == 0) {
dev_info(info->dev, "rtc disabled, re-enabling\n");
tmp = readw(info->base + S3C2410_RTCCON);
writew(tmp | S3C2410_RTCCON_RTCEN, info->base + S3C2410_RTCCON);
}
if (con & S3C2410_RTCCON_CNTSEL) {
dev_info(info->dev, "removing RTCCON_CNTSEL\n");
tmp = readw(info->base + S3C2410_RTCCON);
writew(tmp & ~S3C2410_RTCCON_CNTSEL,
info->base + S3C2410_RTCCON);
}
if (con & S3C2410_RTCCON_CLKRST) {
dev_info(info->dev, "removing RTCCON_CLKRST\n");
tmp = readw(info->base + S3C2410_RTCCON);
writew(tmp & ~S3C2410_RTCCON_CLKRST,
info->base + S3C2410_RTCCON);
}
}
static void s3c24xx_rtc_disable(struct s3c_rtc *info)
{
unsigned int con;
con = readw(info->base + S3C2410_RTCCON);
con &= ~S3C2410_RTCCON_RTCEN;
writew(con, info->base + S3C2410_RTCCON);
con = readb(info->base + S3C2410_TICNT);
con &= ~S3C2410_TICNT_ENABLE;
writeb(con, info->base + S3C2410_TICNT);
}
static void s3c6410_rtc_disable(struct s3c_rtc *info)
{
unsigned int con;
con = readw(info->base + S3C2410_RTCCON);
con &= ~S3C64XX_RTCCON_TICEN;
con &= ~S3C2410_RTCCON_RTCEN;
writew(con, info->base + S3C2410_RTCCON);
}
static int s3c_rtc_remove(struct platform_device *pdev)
{
struct s3c_rtc *info = platform_get_drvdata(pdev);
s3c_rtc_setaie(info->dev, 0);
if (info->data->needs_src_clk)
clk_unprepare(info->rtc_src_clk);
clk_unprepare(info->rtc_clk);
return 0;
}
static int s3c_rtc_probe(struct platform_device *pdev)
{
struct s3c_rtc *info = NULL;
int ret;
info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
if (!info)
return -ENOMEM;
info->dev = &pdev->dev;
info->data = of_device_get_match_data(&pdev->dev);
if (!info->data) {
dev_err(&pdev->dev, "failed getting s3c_rtc_data\n");
return -EINVAL;
}
spin_lock_init(&info->alarm_lock);
platform_set_drvdata(pdev, info);
info->irq_alarm = platform_get_irq(pdev, 0);
if (info->irq_alarm < 0)
return info->irq_alarm;
dev_dbg(&pdev->dev, "s3c2410_rtc: alarm irq %d\n", info->irq_alarm);
/* get the memory region */
info->base = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(info->base))
return PTR_ERR(info->base);
info->rtc_clk = devm_clk_get(&pdev->dev, "rtc");
if (IS_ERR(info->rtc_clk)) {
ret = PTR_ERR(info->rtc_clk);
if (ret != -EPROBE_DEFER)
dev_err(&pdev->dev, "failed to find rtc clock\n");
else
dev_dbg(&pdev->dev, "probe deferred due to missing rtc clk\n");
return ret;
}
ret = clk_prepare_enable(info->rtc_clk);
if (ret)
return ret;
if (info->data->needs_src_clk) {
info->rtc_src_clk = devm_clk_get(&pdev->dev, "rtc_src");
if (IS_ERR(info->rtc_src_clk)) {
ret = dev_err_probe(&pdev->dev, PTR_ERR(info->rtc_src_clk),
"failed to find rtc source clock\n");
goto err_src_clk;
}
ret = clk_prepare_enable(info->rtc_src_clk);
if (ret)
goto err_src_clk;
}
/* disable RTC enable bits potentially set by the bootloader */
if (info->data->disable)
info->data->disable(info);
/* check to see if everything is setup correctly */
if (info->data->enable)
info->data->enable(info);
dev_dbg(&pdev->dev, "s3c2410_rtc: RTCCON=%02x\n",
readw(info->base + S3C2410_RTCCON));
device_init_wakeup(&pdev->dev, 1);
info->rtc = devm_rtc_allocate_device(&pdev->dev);
if (IS_ERR(info->rtc)) {
ret = PTR_ERR(info->rtc);
goto err_nortc;
}
info->rtc->ops = &s3c_rtcops;
info->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
info->rtc->range_max = RTC_TIMESTAMP_END_2099;
ret = devm_rtc_register_device(info->rtc);
if (ret)
goto err_nortc;
ret = devm_request_irq(&pdev->dev, info->irq_alarm, s3c_rtc_alarmirq,
0, "s3c2410-rtc alarm", info);
if (ret) {
dev_err(&pdev->dev, "IRQ%d error %d\n", info->irq_alarm, ret);
goto err_nortc;
}
s3c_rtc_disable_clk(info);
return 0;
err_nortc:
if (info->data->disable)
info->data->disable(info);
if (info->data->needs_src_clk)
clk_disable_unprepare(info->rtc_src_clk);
err_src_clk:
clk_disable_unprepare(info->rtc_clk);
return ret;
}
#ifdef CONFIG_PM_SLEEP
static int s3c_rtc_suspend(struct device *dev)
{
struct s3c_rtc *info = dev_get_drvdata(dev);
int ret;
ret = s3c_rtc_enable_clk(info);
if (ret)
return ret;
if (info->data->disable)
info->data->disable(info);
if (device_may_wakeup(dev) && !info->wake_en) {
if (enable_irq_wake(info->irq_alarm) == 0)
info->wake_en = true;
else
dev_err(dev, "enable_irq_wake failed\n");
}
return 0;
}
static int s3c_rtc_resume(struct device *dev)
{
struct s3c_rtc *info = dev_get_drvdata(dev);
if (info->data->enable)
info->data->enable(info);
s3c_rtc_disable_clk(info);
if (device_may_wakeup(dev) && info->wake_en) {
disable_irq_wake(info->irq_alarm);
info->wake_en = false;
}
return 0;
}
#endif
static SIMPLE_DEV_PM_OPS(s3c_rtc_pm_ops, s3c_rtc_suspend, s3c_rtc_resume);
static void s3c24xx_rtc_irq(struct s3c_rtc *info, int mask)
{
rtc_update_irq(info->rtc, 1, RTC_AF | RTC_IRQF);
}
static void s3c6410_rtc_irq(struct s3c_rtc *info, int mask)
{
rtc_update_irq(info->rtc, 1, RTC_AF | RTC_IRQF);
writeb(mask, info->base + S3C2410_INTP);
}
static struct s3c_rtc_data const s3c2410_rtc_data = {
.irq_handler = s3c24xx_rtc_irq,
.enable = s3c24xx_rtc_enable,
.disable = s3c24xx_rtc_disable,
};
static struct s3c_rtc_data const s3c2416_rtc_data = {
.irq_handler = s3c24xx_rtc_irq,
.enable = s3c24xx_rtc_enable,
.disable = s3c24xx_rtc_disable,
};
static struct s3c_rtc_data const s3c2443_rtc_data = {
.irq_handler = s3c24xx_rtc_irq,
.enable = s3c24xx_rtc_enable,
.disable = s3c24xx_rtc_disable,
};
static struct s3c_rtc_data const s3c6410_rtc_data = {
.needs_src_clk = true,
.irq_handler = s3c6410_rtc_irq,
.enable = s3c24xx_rtc_enable,
.disable = s3c6410_rtc_disable,
};
static const __maybe_unused struct of_device_id s3c_rtc_dt_match[] = {
{
.compatible = "samsung,s3c2410-rtc",
.data = &s3c2410_rtc_data,
}, {
.compatible = "samsung,s3c2416-rtc",
.data = &s3c2416_rtc_data,
}, {
.compatible = "samsung,s3c2443-rtc",
.data = &s3c2443_rtc_data,
}, {
.compatible = "samsung,s3c6410-rtc",
.data = &s3c6410_rtc_data,
}, {
.compatible = "samsung,exynos3250-rtc",
.data = &s3c6410_rtc_data,
},
{ /* sentinel */ },
};
MODULE_DEVICE_TABLE(of, s3c_rtc_dt_match);
static struct platform_driver s3c_rtc_driver = {
.probe = s3c_rtc_probe,
.remove = s3c_rtc_remove,
.driver = {
.name = "s3c-rtc",
.pm = &s3c_rtc_pm_ops,
.of_match_table = of_match_ptr(s3c_rtc_dt_match),
},
};
module_platform_driver(s3c_rtc_driver);
MODULE_DESCRIPTION("Samsung S3C RTC Driver");
MODULE_AUTHOR("Ben Dooks <ben@simtec.co.uk>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:s3c2410-rtc");
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