/*
* Blackfin On-Chip Real Time Clock Driver
* Supports BF51x/BF52x/BF53[123]/BF53[467]/BF54x
*
* Copyright 2004-2010 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 every time 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 doesn't 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 <linux/slab.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_istat_clear, rtc_ictl, bits;
dev_dbg_stamp(dev);
rtc_istat = bfin_read_RTC_ISTAT();
rtc_ictl = bfin_read_RTC_ICTL();
rtc_istat_clear = 0;
bits = RTC_ISTAT_WRITE_COMPLETE;
if (rtc_istat & bits) {
rtc_istat_clear |= bits;
write_complete = true;
complete(&bfin_write_complete);
}
bits = (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY);
if (rtc_ictl & bits) {
if (rtc_istat & bits) {
rtc_istat_clear |= bits;
events |= RTC_AF | RTC_IRQF;
}
}
bits = RTC_ISTAT_SEC;
if (rtc_ictl & bits) {
if (rtc_istat & bits) {
rtc_istat_clear |= bits;
events |= RTC_UF | RTC_IRQF;
}
}
if (events)
rtc_update_irq(rtc->rtc_dev, 1, events);
if (write_complete || events) {
bfin_write_RTC_ISTAT(rtc_istat_clear);
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_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
struct bfin_rtc *rtc = dev_get_drvdata(dev);
dev_dbg_stamp(dev);
if (enabled)
bfin_rtc_int_set_alarm(rtc);
else
bfin_rtc_int_clear(~(RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY));
return 0;
}
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 = {
.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,
.alarm_irq_enable = bfin_rtc_alarm_irq_enable,
};
static int 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 = devm_kzalloc(dev, 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 = devm_rtc_device_register(dev, pdev->name, &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 = devm_request_irq(dev, IRQ_RTC, bfin_rtc_interrupt, 0,
pdev->name, dev);
if (unlikely(ret))
goto err;
/* 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:
return ret;
}
static int bfin_rtc_remove(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
bfin_rtc_reset(dev, 0);
return 0;
}
#ifdef CONFIG_PM_SLEEP
static int bfin_rtc_suspend(struct device *dev)
{
dev_dbg_stamp(dev);
if (device_may_wakeup(dev)) {
enable_irq_wake(IRQ_RTC);
bfin_rtc_sync_pending(dev);
} else
bfin_rtc_int_clear(0);
return 0;
}
static int bfin_rtc_resume(struct device *dev)
{
dev_dbg_stamp(dev);
if (device_may_wakeup(dev))
disable_irq_wake(IRQ_RTC);
/*
* Since only some of the RTC bits are maintained externally in the
* Vbat domain, we need to wait for the RTC MMRs to be synced into
* the core after waking up. This happens every RTC 1HZ. Once that
* has happened, we can go ahead and re-enable the important write
* complete interrupt event.
*/
while (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_SEC))
continue;
bfin_rtc_int_set(RTC_ISTAT_WRITE_COMPLETE);
return 0;
}
#endif
static SIMPLE_DEV_PM_OPS(bfin_rtc_pm_ops, bfin_rtc_suspend, bfin_rtc_resume);
static struct platform_driver bfin_rtc_driver = {
.driver = {
.name = "rtc-bfin",
.owner = THIS_MODULE,
.pm = &bfin_rtc_pm_ops,
},
.probe = bfin_rtc_probe,
.remove = bfin_rtc_remove,
};
module_platform_driver(bfin_rtc_driver);
MODULE_DESCRIPTION("Blackfin On-Chip Real Time Clock Driver");
MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:rtc-bfin");
