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linux/drivers/rtc/rtc-stmp3xxx.c
Uwe Kleine-König 7f48b21bdf rtc: stmp3xxx: use optional crystal in low power states 
The rtc's status register allows to determine if a 32k crystal is
connected to keep the rtc running in low power states provided the
corresponding fuse bits were blown correctly during production.  (In case
they were not, the right frequency can be stated in the device tree.) If
there is no such crystal available force the 24 MHz XTAL clock to keep
running to retain the right date and time.  Otherwise use the crystal to
save some power.

It would be nice to only switch to the crystal when the XTAL clock is
about to be disabled and keep the crystal off when unneeded because XTAL
is always on while the chip is powered on.  But as sudden power loss isn't
detectable this is not save.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-17 09:03:59 -04:00

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/*
* Freescale STMP37XX/STMP378X Real Time Clock driver
*
* Copyright (c) 2007 Sigmatel, Inc.
* Peter Hartley, <peter.hartley@sigmatel.com>
*
* Copyright 2008 Freescale Semiconductor, Inc. All Rights Reserved.
* Copyright 2008 Embedded Alley Solutions, Inc All Rights Reserved.
* Copyright 2011 Wolfram Sang, Pengutronix e.K.
*/
/*
* The code contained herein is licensed under the GNU General Public
* License. You may obtain a copy of the GNU General Public License
* Version 2 or later at the following locations:
*
* http://www.opensource.org/licenses/gpl-license.html
* http://www.gnu.org/copyleft/gpl.html
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/rtc.h>
#include <linux/slab.h>
#include <linux/of_device.h>
#include <linux/of.h>
#include <linux/stmp_device.h>
#include <linux/stmp3xxx_rtc_wdt.h>
#define STMP3XXX_RTC_CTRL 0x0
#define STMP3XXX_RTC_CTRL_SET 0x4
#define STMP3XXX_RTC_CTRL_CLR 0x8
#define STMP3XXX_RTC_CTRL_ALARM_IRQ_EN 0x00000001
#define STMP3XXX_RTC_CTRL_ONEMSEC_IRQ_EN 0x00000002
#define STMP3XXX_RTC_CTRL_ALARM_IRQ 0x00000004
#define STMP3XXX_RTC_CTRL_WATCHDOGEN 0x00000010
#define STMP3XXX_RTC_STAT 0x10
#define STMP3XXX_RTC_STAT_STALE_SHIFT 16
#define STMP3XXX_RTC_STAT_RTC_PRESENT 0x80000000
#define STMP3XXX_RTC_STAT_XTAL32000_PRESENT 0x10000000
#define STMP3XXX_RTC_STAT_XTAL32768_PRESENT 0x08000000
#define STMP3XXX_RTC_SECONDS 0x30
#define STMP3XXX_RTC_ALARM 0x40
#define STMP3XXX_RTC_WATCHDOG 0x50
#define STMP3XXX_RTC_PERSISTENT0 0x60
#define STMP3XXX_RTC_PERSISTENT0_SET 0x64
#define STMP3XXX_RTC_PERSISTENT0_CLR 0x68
#define STMP3XXX_RTC_PERSISTENT0_CLOCKSOURCE (1 << 0)
#define STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE_EN (1 << 1)
#define STMP3XXX_RTC_PERSISTENT0_ALARM_EN (1 << 2)
#define STMP3XXX_RTC_PERSISTENT0_XTAL24MHZ_PWRUP (1 << 4)
#define STMP3XXX_RTC_PERSISTENT0_XTAL32KHZ_PWRUP (1 << 5)
#define STMP3XXX_RTC_PERSISTENT0_XTAL32_FREQ (1 << 6)
#define STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE (1 << 7)
#define STMP3XXX_RTC_PERSISTENT1 0x70
/* missing bitmask in headers */
#define STMP3XXX_RTC_PERSISTENT1_FORCE_UPDATER 0x80000000
struct stmp3xxx_rtc_data {
struct rtc_device *rtc;
void __iomem *io;
int irq_alarm;
};
#if IS_ENABLED(CONFIG_STMP3XXX_RTC_WATCHDOG)
/**
* stmp3xxx_wdt_set_timeout - configure the watchdog inside the STMP3xxx RTC
* @dev: the parent device of the watchdog (= the RTC)
* @timeout: the desired value for the timeout register of the watchdog.
* 0 disables the watchdog
*
* The watchdog needs one register and two bits which are in the RTC domain.
* To handle the resource conflict, the RTC driver will create another
* platform_device for the watchdog driver as a child of the RTC device.
* The watchdog driver is passed the below accessor function via platform_data
* to configure the watchdog. Locking is not needed because accessing SET/CLR
* registers is atomic.
*/
static void stmp3xxx_wdt_set_timeout(struct device *dev, u32 timeout)
{
struct stmp3xxx_rtc_data *rtc_data = dev_get_drvdata(dev);
if (timeout) {
writel(timeout, rtc_data->io + STMP3XXX_RTC_WATCHDOG);
writel(STMP3XXX_RTC_CTRL_WATCHDOGEN,
rtc_data->io + STMP3XXX_RTC_CTRL + STMP_OFFSET_REG_SET);
writel(STMP3XXX_RTC_PERSISTENT1_FORCE_UPDATER,
rtc_data->io + STMP3XXX_RTC_PERSISTENT1 + STMP_OFFSET_REG_SET);
} else {
writel(STMP3XXX_RTC_CTRL_WATCHDOGEN,
rtc_data->io + STMP3XXX_RTC_CTRL + STMP_OFFSET_REG_CLR);
writel(STMP3XXX_RTC_PERSISTENT1_FORCE_UPDATER,
rtc_data->io + STMP3XXX_RTC_PERSISTENT1 + STMP_OFFSET_REG_CLR);
}
}
static struct stmp3xxx_wdt_pdata wdt_pdata = {
.wdt_set_timeout = stmp3xxx_wdt_set_timeout,
};
static void stmp3xxx_wdt_register(struct platform_device *rtc_pdev)
{
struct platform_device *wdt_pdev =
platform_device_alloc("stmp3xxx_rtc_wdt", rtc_pdev->id);
if (wdt_pdev) {
wdt_pdev->dev.parent = &rtc_pdev->dev;
wdt_pdev->dev.platform_data = &wdt_pdata;
platform_device_add(wdt_pdev);
}
}
#else
static void stmp3xxx_wdt_register(struct platform_device *rtc_pdev)
{
}
#endif /* CONFIG_STMP3XXX_RTC_WATCHDOG */
static int stmp3xxx_wait_time(struct stmp3xxx_rtc_data *rtc_data)
{
int timeout = 5000; /* 3ms according to i.MX28 Ref Manual */
/*
* The i.MX28 Applications Processor Reference Manual, Rev. 1, 2010
* states:
* | The order in which registers are updated is
* | Persistent 0, 1, 2, 3, 4, 5, Alarm, Seconds.
* | (This list is in bitfield order, from LSB to MSB, as they would
* | appear in the STALE_REGS and NEW_REGS bitfields of the HW_RTC_STAT
* | register. For example, the Seconds register corresponds to
* | STALE_REGS or NEW_REGS containing 0x80.)
*/
do {
if (!(readl(rtc_data->io + STMP3XXX_RTC_STAT) &
(0x80 << STMP3XXX_RTC_STAT_STALE_SHIFT)))
return 0;
udelay(1);
} while (--timeout > 0);
return (readl(rtc_data->io + STMP3XXX_RTC_STAT) &
(0x80 << STMP3XXX_RTC_STAT_STALE_SHIFT)) ? -ETIME : 0;
}
/* Time read/write */
static int stmp3xxx_rtc_gettime(struct device *dev, struct rtc_time *rtc_tm)
{
int ret;
struct stmp3xxx_rtc_data *rtc_data = dev_get_drvdata(dev);
ret = stmp3xxx_wait_time(rtc_data);
if (ret)
return ret;
rtc_time_to_tm(readl(rtc_data->io + STMP3XXX_RTC_SECONDS), rtc_tm);
return 0;
}
static int stmp3xxx_rtc_set_mmss(struct device *dev, unsigned long t)
{
struct stmp3xxx_rtc_data *rtc_data = dev_get_drvdata(dev);
writel(t, rtc_data->io + STMP3XXX_RTC_SECONDS);
return stmp3xxx_wait_time(rtc_data);
}
/* interrupt(s) handler */
static irqreturn_t stmp3xxx_rtc_interrupt(int irq, void *dev_id)
{
struct stmp3xxx_rtc_data *rtc_data = dev_get_drvdata(dev_id);
u32 status = readl(rtc_data->io + STMP3XXX_RTC_CTRL);
if (status & STMP3XXX_RTC_CTRL_ALARM_IRQ) {
writel(STMP3XXX_RTC_CTRL_ALARM_IRQ,
rtc_data->io + STMP3XXX_RTC_CTRL_CLR);
rtc_update_irq(rtc_data->rtc, 1, RTC_AF | RTC_IRQF);
return IRQ_HANDLED;
}
return IRQ_NONE;
}
static int stmp3xxx_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
struct stmp3xxx_rtc_data *rtc_data = dev_get_drvdata(dev);
if (enabled) {
writel(STMP3XXX_RTC_PERSISTENT0_ALARM_EN |
STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE_EN,
rtc_data->io + STMP3XXX_RTC_PERSISTENT0_SET);
writel(STMP3XXX_RTC_CTRL_ALARM_IRQ_EN,
rtc_data->io + STMP3XXX_RTC_CTRL_SET);
} else {
writel(STMP3XXX_RTC_PERSISTENT0_ALARM_EN |
STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE_EN,
rtc_data->io + STMP3XXX_RTC_PERSISTENT0_CLR);
writel(STMP3XXX_RTC_CTRL_ALARM_IRQ_EN,
rtc_data->io + STMP3XXX_RTC_CTRL_CLR);
}
return 0;
}
static int stmp3xxx_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
{
struct stmp3xxx_rtc_data *rtc_data = dev_get_drvdata(dev);
rtc_time_to_tm(readl(rtc_data->io + STMP3XXX_RTC_ALARM), &alm->time);
return 0;
}
static int stmp3xxx_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
{
unsigned long t;
struct stmp3xxx_rtc_data *rtc_data = dev_get_drvdata(dev);
rtc_tm_to_time(&alm->time, &t);
writel(t, rtc_data->io + STMP3XXX_RTC_ALARM);
stmp3xxx_alarm_irq_enable(dev, alm->enabled);
return 0;
}
static struct rtc_class_ops stmp3xxx_rtc_ops = {
.alarm_irq_enable =
stmp3xxx_alarm_irq_enable,
.read_time = stmp3xxx_rtc_gettime,
.set_mmss = stmp3xxx_rtc_set_mmss,
.read_alarm = stmp3xxx_rtc_read_alarm,
.set_alarm = stmp3xxx_rtc_set_alarm,
};
static int stmp3xxx_rtc_remove(struct platform_device *pdev)
{
struct stmp3xxx_rtc_data *rtc_data = platform_get_drvdata(pdev);
if (!rtc_data)
return 0;
writel(STMP3XXX_RTC_CTRL_ALARM_IRQ_EN,
rtc_data->io + STMP3XXX_RTC_CTRL_CLR);
return 0;
}
static int stmp3xxx_rtc_probe(struct platform_device *pdev)
{
struct stmp3xxx_rtc_data *rtc_data;
struct resource *r;
u32 rtc_stat;
u32 pers0_set, pers0_clr;
u32 crystalfreq = 0;
int err;
rtc_data = devm_kzalloc(&pdev->dev, sizeof(*rtc_data), GFP_KERNEL);
if (!rtc_data)
return -ENOMEM;
r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!r) {
dev_err(&pdev->dev, "failed to get resource\n");
return -ENXIO;
}
rtc_data->io = devm_ioremap(&pdev->dev, r->start, resource_size(r));
if (!rtc_data->io) {
dev_err(&pdev->dev, "ioremap failed\n");
return -EIO;
}
rtc_data->irq_alarm = platform_get_irq(pdev, 0);
rtc_stat = readl(rtc_data->io + STMP3XXX_RTC_STAT);
if (!(rtc_stat & STMP3XXX_RTC_STAT_RTC_PRESENT)) {
dev_err(&pdev->dev, "no device onboard\n");
return -ENODEV;
}
platform_set_drvdata(pdev, rtc_data);
err = stmp_reset_block(rtc_data->io);
if (err) {
dev_err(&pdev->dev, "stmp_reset_block failed: %d\n", err);
return err;
}
/*
* Obviously the rtc needs a clock input to be able to run.
* This clock can be provided by an external 32k crystal. If that one is
* missing XTAL must not be disabled in suspend which consumes a
* lot of power. Normally the presence and exact frequency (supported
* are 32000 Hz and 32768 Hz) is detectable from fuses, but as reality
* proves these fuses are not blown correctly on all machines, so the
* frequency can be overridden in the device tree.
*/
if (rtc_stat & STMP3XXX_RTC_STAT_XTAL32000_PRESENT)
crystalfreq = 32000;
else if (rtc_stat & STMP3XXX_RTC_STAT_XTAL32768_PRESENT)
crystalfreq = 32768;
of_property_read_u32(pdev->dev.of_node, "stmp,crystal-freq",
&crystalfreq);
switch (crystalfreq) {
case 32000:
/* keep 32kHz crystal running in low-power mode */
pers0_set = STMP3XXX_RTC_PERSISTENT0_XTAL32_FREQ |
STMP3XXX_RTC_PERSISTENT0_XTAL32KHZ_PWRUP |
STMP3XXX_RTC_PERSISTENT0_CLOCKSOURCE;
pers0_clr = STMP3XXX_RTC_PERSISTENT0_XTAL24MHZ_PWRUP;
break;
case 32768:
/* keep 32.768kHz crystal running in low-power mode */
pers0_set = STMP3XXX_RTC_PERSISTENT0_XTAL32KHZ_PWRUP |
STMP3XXX_RTC_PERSISTENT0_CLOCKSOURCE;
pers0_clr = STMP3XXX_RTC_PERSISTENT0_XTAL24MHZ_PWRUP |
STMP3XXX_RTC_PERSISTENT0_XTAL32_FREQ;
break;
default:
dev_warn(&pdev->dev,
"invalid crystal-freq specified in device-tree. Assuming no crystal\n");
/* fall-through */
case 0:
/* keep XTAL on in low-power mode */
pers0_set = STMP3XXX_RTC_PERSISTENT0_XTAL24MHZ_PWRUP;
pers0_clr = STMP3XXX_RTC_PERSISTENT0_XTAL32KHZ_PWRUP |
STMP3XXX_RTC_PERSISTENT0_CLOCKSOURCE;
}
writel(pers0_set, rtc_data->io + STMP3XXX_RTC_PERSISTENT0_SET);
writel(STMP3XXX_RTC_PERSISTENT0_ALARM_EN |
STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE_EN |
STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE | pers0_clr,
rtc_data->io + STMP3XXX_RTC_PERSISTENT0_CLR);
writel(STMP3XXX_RTC_CTRL_ONEMSEC_IRQ_EN |
STMP3XXX_RTC_CTRL_ALARM_IRQ_EN,
rtc_data->io + STMP3XXX_RTC_CTRL_CLR);
rtc_data->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
&stmp3xxx_rtc_ops, THIS_MODULE);
if (IS_ERR(rtc_data->rtc))
return PTR_ERR(rtc_data->rtc);
err = devm_request_irq(&pdev->dev, rtc_data->irq_alarm,
stmp3xxx_rtc_interrupt, 0, "RTC alarm", &pdev->dev);
if (err) {
dev_err(&pdev->dev, "Cannot claim IRQ%d\n",
rtc_data->irq_alarm);
return err;
}
stmp3xxx_wdt_register(pdev);
return 0;
}
#ifdef CONFIG_PM_SLEEP
static int stmp3xxx_rtc_suspend(struct device *dev)
{
return 0;
}
static int stmp3xxx_rtc_resume(struct device *dev)
{
struct stmp3xxx_rtc_data *rtc_data = dev_get_drvdata(dev);
stmp_reset_block(rtc_data->io);
writel(STMP3XXX_RTC_PERSISTENT0_ALARM_EN |
STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE_EN |
STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE,
rtc_data->io + STMP3XXX_RTC_PERSISTENT0_CLR);
return 0;
}
#endif
static SIMPLE_DEV_PM_OPS(stmp3xxx_rtc_pm_ops, stmp3xxx_rtc_suspend,
stmp3xxx_rtc_resume);
static const struct of_device_id rtc_dt_ids[] = {
{ .compatible = "fsl,stmp3xxx-rtc", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, rtc_dt_ids);
static struct platform_driver stmp3xxx_rtcdrv = {
.probe = stmp3xxx_rtc_probe,
.remove = stmp3xxx_rtc_remove,
.driver = {
.name = "stmp3xxx-rtc",
.pm = &stmp3xxx_rtc_pm_ops,
.of_match_table = rtc_dt_ids,
},
};
module_platform_driver(stmp3xxx_rtcdrv);
MODULE_DESCRIPTION("STMP3xxx RTC Driver");
MODULE_AUTHOR("dmitry pervushin <dpervushin@embeddedalley.com> and "
"Wolfram Sang <w.sang@pengutronix.de>");
MODULE_LICENSE("GPL");
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