linux/drivers/rtc/rtc-bfin.c
Mike Frysinger 9980060bad bfin: delay IRQ registration until driver is ready
Make sure we do not actually request the RTC IRQ until the device driver
is fully ready to handle and process any interrupt.  This way a spurious
interrupt won't crash the system (which may happen if the bootloader was
poking the RTC right before booting Linux).

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-06-30 18:56:01 -07:00

474 lines
13 KiB
C

/*
* Blackfin On-Chip Real Time Clock Driver
* Supports BF51x/BF52x/BF53[123]/BF53[467]/BF54x
*
* Copyright 2004-2009 Analog Devices Inc.
*
* Enter bugs at http://blackfin.uclinux.org/
*
* Licensed under the GPL-2 or later.
*/
/* The biggest issue we deal with in this driver is that register writes are
* synced to the RTC frequency of 1Hz. So if you write to a register and
* attempt to write again before the first write has completed, the new write
* is simply discarded. This can easily be troublesome if userspace disables
* one event (say periodic) and then right after enables an event (say alarm).
* Since all events are maintained in the same interrupt mask register, if
* we wrote to it to disable the first event and then wrote to it again to
* enable the second event, that second event would not be enabled as the
* write would be discarded and things quickly fall apart.
*
* To keep this delay from significantly degrading performance (we, in theory,
* would have to sleep for up to 1 second everytime we wanted to write a
* register), we only check the write pending status before we start to issue
* a new write. We bank on the idea that it doesnt matter when the sync
* happens so long as we don't attempt another write before it does. The only
* time userspace would take this penalty is when they try and do multiple
* operations right after another ... but in this case, they need to take the
* sync penalty, so we should be OK.
*
* Also note that the RTC_ISTAT register does not suffer this penalty; its
* writes to clear status registers complete immediately.
*/
/* It may seem odd that there is no SWCNT code in here (which would be exposed
* via the periodic interrupt event, or PIE). Since the Blackfin RTC peripheral
* runs in units of seconds (N/HZ) but the Linux framework runs in units of HZ
* (2^N HZ), there is no point in keeping code that only provides 1 HZ PIEs.
* The same exact behavior can be accomplished by using the update interrupt
* event (UIE). Maybe down the line the RTC peripheral will suck less in which
* case we can re-introduce PIE support.
*/
#include <linux/bcd.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/seq_file.h>
#include <asm/blackfin.h>
#define dev_dbg_stamp(dev) dev_dbg(dev, "%s:%i: here i am\n", __func__, __LINE__)
struct bfin_rtc {
struct rtc_device *rtc_dev;
struct rtc_time rtc_alarm;
u16 rtc_wrote_regs;
};
/* Bit values for the ISTAT / ICTL registers */
#define RTC_ISTAT_WRITE_COMPLETE 0x8000
#define RTC_ISTAT_WRITE_PENDING 0x4000
#define RTC_ISTAT_ALARM_DAY 0x0040
#define RTC_ISTAT_24HR 0x0020
#define RTC_ISTAT_HOUR 0x0010
#define RTC_ISTAT_MIN 0x0008
#define RTC_ISTAT_SEC 0x0004
#define RTC_ISTAT_ALARM 0x0002
#define RTC_ISTAT_STOPWATCH 0x0001
/* Shift values for RTC_STAT register */
#define DAY_BITS_OFF 17
#define HOUR_BITS_OFF 12
#define MIN_BITS_OFF 6
#define SEC_BITS_OFF 0
/* Some helper functions to convert between the common RTC notion of time
* and the internal Blackfin notion that is encoded in 32bits.
*/
static inline u32 rtc_time_to_bfin(unsigned long now)
{
u32 sec = (now % 60);
u32 min = (now % (60 * 60)) / 60;
u32 hour = (now % (60 * 60 * 24)) / (60 * 60);
u32 days = (now / (60 * 60 * 24));
return (sec << SEC_BITS_OFF) +
(min << MIN_BITS_OFF) +
(hour << HOUR_BITS_OFF) +
(days << DAY_BITS_OFF);
}
static inline unsigned long rtc_bfin_to_time(u32 rtc_bfin)
{
return (((rtc_bfin >> SEC_BITS_OFF) & 0x003F)) +
(((rtc_bfin >> MIN_BITS_OFF) & 0x003F) * 60) +
(((rtc_bfin >> HOUR_BITS_OFF) & 0x001F) * 60 * 60) +
(((rtc_bfin >> DAY_BITS_OFF) & 0x7FFF) * 60 * 60 * 24);
}
static inline void rtc_bfin_to_tm(u32 rtc_bfin, struct rtc_time *tm)
{
rtc_time_to_tm(rtc_bfin_to_time(rtc_bfin), tm);
}
/**
* bfin_rtc_sync_pending - make sure pending writes have complete
*
* Wait for the previous write to a RTC register to complete.
* Unfortunately, we can't sleep here as that introduces a race condition when
* turning on interrupt events. Consider this:
* - process sets alarm
* - process enables alarm
* - process sleeps while waiting for rtc write to sync
* - interrupt fires while process is sleeping
* - interrupt acks the event by writing to ISTAT
* - interrupt sets the WRITE PENDING bit
* - interrupt handler finishes
* - process wakes up, sees WRITE PENDING bit set, goes to sleep
* - interrupt fires while process is sleeping
* If anyone can point out the obvious solution here, i'm listening :). This
* shouldn't be an issue on an SMP or preempt system as this function should
* only be called with the rtc lock held.
*
* Other options:
* - disable PREN so the sync happens at 32.768kHZ ... but this changes the
* inc rate for all RTC registers from 1HZ to 32.768kHZ ...
* - use the write complete IRQ
*/
/*
static void bfin_rtc_sync_pending_polled(void)
{
while (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_COMPLETE))
if (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING))
break;
bfin_write_RTC_ISTAT(RTC_ISTAT_WRITE_COMPLETE);
}
*/
static DECLARE_COMPLETION(bfin_write_complete);
static void bfin_rtc_sync_pending(struct device *dev)
{
dev_dbg_stamp(dev);
while (bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING)
wait_for_completion_timeout(&bfin_write_complete, HZ * 5);
dev_dbg_stamp(dev);
}
/**
* bfin_rtc_reset - set RTC to sane/known state
*
* Initialize the RTC. Enable pre-scaler to scale RTC clock
* to 1Hz and clear interrupt/status registers.
*/
static void bfin_rtc_reset(struct device *dev, u16 rtc_ictl)
{
struct bfin_rtc *rtc = dev_get_drvdata(dev);
dev_dbg_stamp(dev);
bfin_rtc_sync_pending(dev);
bfin_write_RTC_PREN(0x1);
bfin_write_RTC_ICTL(rtc_ictl);
bfin_write_RTC_ALARM(0);
bfin_write_RTC_ISTAT(0xFFFF);
rtc->rtc_wrote_regs = 0;
}
/**
* bfin_rtc_interrupt - handle interrupt from RTC
*
* Since we handle all RTC events here, we have to make sure the requested
* interrupt is enabled (in RTC_ICTL) as the event status register (RTC_ISTAT)
* always gets updated regardless of the interrupt being enabled. So when one
* even we care about (e.g. stopwatch) goes off, we don't want to turn around
* and say that other events have happened as well (e.g. second). We do not
* have to worry about pending writes to the RTC_ICTL register as interrupts
* only fire if they are enabled in the RTC_ICTL register.
*/
static irqreturn_t bfin_rtc_interrupt(int irq, void *dev_id)
{
struct device *dev = dev_id;
struct bfin_rtc *rtc = dev_get_drvdata(dev);
unsigned long events = 0;
bool write_complete = false;
u16 rtc_istat, rtc_ictl;
dev_dbg_stamp(dev);
rtc_istat = bfin_read_RTC_ISTAT();
rtc_ictl = bfin_read_RTC_ICTL();
if (rtc_istat & RTC_ISTAT_WRITE_COMPLETE) {
bfin_write_RTC_ISTAT(RTC_ISTAT_WRITE_COMPLETE);
write_complete = true;
complete(&bfin_write_complete);
}
if (rtc_ictl & (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY)) {
if (rtc_istat & (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY)) {
bfin_write_RTC_ISTAT(RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY);
events |= RTC_AF | RTC_IRQF;
}
}
if (rtc_ictl & RTC_ISTAT_SEC) {
if (rtc_istat & RTC_ISTAT_SEC) {
bfin_write_RTC_ISTAT(RTC_ISTAT_SEC);
events |= RTC_UF | RTC_IRQF;
}
}
if (events)
rtc_update_irq(rtc->rtc_dev, 1, events);
if (write_complete || events)
return IRQ_HANDLED;
else
return IRQ_NONE;
}
static void bfin_rtc_int_set(u16 rtc_int)
{
bfin_write_RTC_ISTAT(rtc_int);
bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() | rtc_int);
}
static void bfin_rtc_int_clear(u16 rtc_int)
{
bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() & rtc_int);
}
static void bfin_rtc_int_set_alarm(struct bfin_rtc *rtc)
{
/* Blackfin has different bits for whether the alarm is
* more than 24 hours away.
*/
bfin_rtc_int_set(rtc->rtc_alarm.tm_yday == -1 ? RTC_ISTAT_ALARM : RTC_ISTAT_ALARM_DAY);
}
static int bfin_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
{
struct bfin_rtc *rtc = dev_get_drvdata(dev);
int ret = 0;
dev_dbg_stamp(dev);
bfin_rtc_sync_pending(dev);
switch (cmd) {
case RTC_UIE_ON:
dev_dbg_stamp(dev);
bfin_rtc_int_set(RTC_ISTAT_SEC);
break;
case RTC_UIE_OFF:
dev_dbg_stamp(dev);
bfin_rtc_int_clear(~RTC_ISTAT_SEC);
break;
case RTC_AIE_ON:
dev_dbg_stamp(dev);
bfin_rtc_int_set_alarm(rtc);
break;
case RTC_AIE_OFF:
dev_dbg_stamp(dev);
bfin_rtc_int_clear(~(RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY));
break;
default:
dev_dbg_stamp(dev);
ret = -ENOIOCTLCMD;
}
return ret;
}
static int bfin_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
struct bfin_rtc *rtc = dev_get_drvdata(dev);
dev_dbg_stamp(dev);
if (rtc->rtc_wrote_regs & 0x1)
bfin_rtc_sync_pending(dev);
rtc_bfin_to_tm(bfin_read_RTC_STAT(), tm);
return 0;
}
static int bfin_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
struct bfin_rtc *rtc = dev_get_drvdata(dev);
int ret;
unsigned long now;
dev_dbg_stamp(dev);
ret = rtc_tm_to_time(tm, &now);
if (ret == 0) {
if (rtc->rtc_wrote_regs & 0x1)
bfin_rtc_sync_pending(dev);
bfin_write_RTC_STAT(rtc_time_to_bfin(now));
rtc->rtc_wrote_regs = 0x1;
}
return ret;
}
static int bfin_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct bfin_rtc *rtc = dev_get_drvdata(dev);
dev_dbg_stamp(dev);
alrm->time = rtc->rtc_alarm;
bfin_rtc_sync_pending(dev);
alrm->enabled = !!(bfin_read_RTC_ICTL() & (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY));
return 0;
}
static int bfin_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct bfin_rtc *rtc = dev_get_drvdata(dev);
unsigned long rtc_alarm;
dev_dbg_stamp(dev);
if (rtc_tm_to_time(&alrm->time, &rtc_alarm))
return -EINVAL;
rtc->rtc_alarm = alrm->time;
bfin_rtc_sync_pending(dev);
bfin_write_RTC_ALARM(rtc_time_to_bfin(rtc_alarm));
if (alrm->enabled)
bfin_rtc_int_set_alarm(rtc);
return 0;
}
static int bfin_rtc_proc(struct device *dev, struct seq_file *seq)
{
#define yesno(x) ((x) ? "yes" : "no")
u16 ictl = bfin_read_RTC_ICTL();
dev_dbg_stamp(dev);
seq_printf(seq,
"alarm_IRQ\t: %s\n"
"wkalarm_IRQ\t: %s\n"
"seconds_IRQ\t: %s\n",
yesno(ictl & RTC_ISTAT_ALARM),
yesno(ictl & RTC_ISTAT_ALARM_DAY),
yesno(ictl & RTC_ISTAT_SEC));
return 0;
#undef yesno
}
static struct rtc_class_ops bfin_rtc_ops = {
.ioctl = bfin_rtc_ioctl,
.read_time = bfin_rtc_read_time,
.set_time = bfin_rtc_set_time,
.read_alarm = bfin_rtc_read_alarm,
.set_alarm = bfin_rtc_set_alarm,
.proc = bfin_rtc_proc,
};
static int __devinit bfin_rtc_probe(struct platform_device *pdev)
{
struct bfin_rtc *rtc;
struct device *dev = &pdev->dev;
int ret = 0;
unsigned long timeout = jiffies + HZ;
dev_dbg_stamp(dev);
/* Allocate memory for our RTC struct */
rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
if (unlikely(!rtc))
return -ENOMEM;
platform_set_drvdata(pdev, rtc);
device_init_wakeup(dev, 1);
/* Register our RTC with the RTC framework */
rtc->rtc_dev = rtc_device_register(pdev->name, dev, &bfin_rtc_ops,
THIS_MODULE);
if (unlikely(IS_ERR(rtc->rtc_dev))) {
ret = PTR_ERR(rtc->rtc_dev);
goto err;
}
/* Grab the IRQ and init the hardware */
ret = request_irq(IRQ_RTC, bfin_rtc_interrupt, IRQF_SHARED, pdev->name, dev);
if (unlikely(ret))
goto err_reg;
/* sometimes the bootloader touched things, but the write complete was not
* enabled, so let's just do a quick timeout here since the IRQ will not fire ...
*/
while (bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING)
if (time_after(jiffies, timeout))
break;
bfin_rtc_reset(dev, RTC_ISTAT_WRITE_COMPLETE);
bfin_write_RTC_SWCNT(0);
return 0;
err_reg:
rtc_device_unregister(rtc->rtc_dev);
err:
kfree(rtc);
return ret;
}
static int __devexit bfin_rtc_remove(struct platform_device *pdev)
{
struct bfin_rtc *rtc = platform_get_drvdata(pdev);
struct device *dev = &pdev->dev;
bfin_rtc_reset(dev, 0);
free_irq(IRQ_RTC, dev);
rtc_device_unregister(rtc->rtc_dev);
platform_set_drvdata(pdev, NULL);
kfree(rtc);
return 0;
}
#ifdef CONFIG_PM
static int bfin_rtc_suspend(struct platform_device *pdev, pm_message_t state)
{
if (device_may_wakeup(&pdev->dev)) {
enable_irq_wake(IRQ_RTC);
bfin_rtc_sync_pending(&pdev->dev);
} else
bfin_rtc_int_clear(-1);
return 0;
}
static int bfin_rtc_resume(struct platform_device *pdev)
{
if (device_may_wakeup(&pdev->dev))
disable_irq_wake(IRQ_RTC);
else
bfin_write_RTC_ISTAT(-1);
return 0;
}
#else
# define bfin_rtc_suspend NULL
# define bfin_rtc_resume NULL
#endif
static struct platform_driver bfin_rtc_driver = {
.driver = {
.name = "rtc-bfin",
.owner = THIS_MODULE,
},
.probe = bfin_rtc_probe,
.remove = __devexit_p(bfin_rtc_remove),
.suspend = bfin_rtc_suspend,
.resume = bfin_rtc_resume,
};
static int __init bfin_rtc_init(void)
{
return platform_driver_register(&bfin_rtc_driver);
}
static void __exit bfin_rtc_exit(void)
{
platform_driver_unregister(&bfin_rtc_driver);
}
module_init(bfin_rtc_init);
module_exit(bfin_rtc_exit);
MODULE_DESCRIPTION("Blackfin On-Chip Real Time Clock Driver");
MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:rtc-bfin");