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drivers/rtc/rtc-at91rm9200.c: use a variable for storing IMR
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On some revisions of AT91 SoCs, the RTC IMR register is not working.
Instead of elaborating a workaround for that specific SoC or IP version,
we simply use a software variable to store the Interrupt Mask Register
and modify it for each enabling/disabling of an interrupt.  The overhead
of this is negligible anyway.

The interrupt mask register (IMR) for the RTC is broken on the AT91SAM9x5
sub-family of SoCs (good overview of the members here:
http://www.eewiki.net/display/linuxonarm/AT91SAM9x5 ).  The "user visible
effect" is the RTC doesn't work.

That sub-family is less than two years old and only has devicetree (DT)
support and came online circa lk 3.7 .  The dust is yet to settle on the
DT stuff at least for AT91 SoCs (translation: lots of stuff is still
broken, so much that it is hard to know where to start).

The fix in the patch is pretty simple: just shadow the silicon IMR
register with a variable in the driver.  Some older SoCs (pre-DT) use the
the rtc-at91rm9200 driver (e.g.  obviously the AT91RM9200) and they should
not be impacted by the change.  There shouldn't be a large volume of
interrupts associated with a RTC.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Reported-by: Douglas Gilbert <dgilbert@interlog.com>
Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: Ludovic Desroches <ludovic.desroches@atmel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Nicolas Ferre authored and torvalds committed Mar 22, 2013
1 parent e66b058 commit 0ef1594
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Showing 2 changed files with 31 additions and 20 deletions.
50 changes: 31 additions & 19 deletions drivers/rtc/rtc-at91rm9200.c
View file
Expand Up @@ -44,6 +44,7 @@ static DECLARE_COMPLETION(at91_rtc_updated);
static unsigned int at91_alarm_year = AT91_RTC_EPOCH;
static void __iomem *at91_rtc_regs;
static int irq;
static u32 at91_rtc_imr;

/*
* Decode time/date into rtc_time structure
Expand Down Expand Up @@ -108,9 +109,11 @@ static int at91_rtc_settime(struct device *dev, struct rtc_time *tm)
cr = at91_rtc_read(AT91_RTC_CR);
at91_rtc_write(AT91_RTC_CR, cr | AT91_RTC_UPDCAL | AT91_RTC_UPDTIM);

at91_rtc_imr |= AT91_RTC_ACKUPD;
at91_rtc_write(AT91_RTC_IER, AT91_RTC_ACKUPD);
wait_for_completion(&at91_rtc_updated); /* wait for ACKUPD interrupt */
at91_rtc_write(AT91_RTC_IDR, AT91_RTC_ACKUPD);
at91_rtc_imr &= ~AT91_RTC_ACKUPD;

at91_rtc_write(AT91_RTC_TIMR,
bin2bcd(tm->tm_sec) << 0
Expand Down Expand Up @@ -142,7 +145,7 @@ static int at91_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
tm->tm_yday = rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
tm->tm_year = at91_alarm_year - 1900;

alrm->enabled = (at91_rtc_read(AT91_RTC_IMR) & AT91_RTC_ALARM)
alrm->enabled = (at91_rtc_imr & AT91_RTC_ALARM)
? 1 : 0;

dev_dbg(dev, "%s(): %4d-%02d-%02d %02d:%02d:%02d\n", __func__,
Expand All @@ -168,6 +171,7 @@ static int at91_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
tm.tm_sec = alrm->time.tm_sec;

at91_rtc_write(AT91_RTC_IDR, AT91_RTC_ALARM);
at91_rtc_imr &= ~AT91_RTC_ALARM;
at91_rtc_write(AT91_RTC_TIMALR,
bin2bcd(tm.tm_sec) << 0
| bin2bcd(tm.tm_min) << 8
Expand All @@ -180,6 +184,7 @@ static int at91_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)

if (alrm->enabled) {
at91_rtc_write(AT91_RTC_SCCR, AT91_RTC_ALARM);
at91_rtc_imr |= AT91_RTC_ALARM;
at91_rtc_write(AT91_RTC_IER, AT91_RTC_ALARM);
}

Expand All @@ -196,9 +201,12 @@ static int at91_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)

if (enabled) {
at91_rtc_write(AT91_RTC_SCCR, AT91_RTC_ALARM);
at91_rtc_imr |= AT91_RTC_ALARM;
at91_rtc_write(AT91_RTC_IER, AT91_RTC_ALARM);
} else
} else {
at91_rtc_write(AT91_RTC_IDR, AT91_RTC_ALARM);
at91_rtc_imr &= ~AT91_RTC_ALARM;
}

return 0;
}
Expand All @@ -207,12 +215,10 @@ static int at91_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
*/
static int at91_rtc_proc(struct device *dev, struct seq_file *seq)
{
unsigned long imr = at91_rtc_read(AT91_RTC_IMR);

seq_printf(seq, "update_IRQ\t: %s\n",
(imr & AT91_RTC_ACKUPD) ? "yes" : "no");
(at91_rtc_imr & AT91_RTC_ACKUPD) ? "yes" : "no");
seq_printf(seq, "periodic_IRQ\t: %s\n",
(imr & AT91_RTC_SECEV) ? "yes" : "no");
(at91_rtc_imr & AT91_RTC_SECEV) ? "yes" : "no");

return 0;
}
Expand All @@ -227,7 +233,7 @@ static irqreturn_t at91_rtc_interrupt(int irq, void *dev_id)
unsigned int rtsr;
unsigned long events = 0;

rtsr = at91_rtc_read(AT91_RTC_SR) & at91_rtc_read(AT91_RTC_IMR);
rtsr = at91_rtc_read(AT91_RTC_SR) & at91_rtc_imr;
if (rtsr) { /* this interrupt is shared! Is it ours? */
if (rtsr & AT91_RTC_ALARM)
events |= (RTC_AF | RTC_IRQF);
Expand Down Expand Up @@ -291,6 +297,7 @@ static int __init at91_rtc_probe(struct platform_device *pdev)
at91_rtc_write(AT91_RTC_IDR, AT91_RTC_ACKUPD | AT91_RTC_ALARM |
AT91_RTC_SECEV | AT91_RTC_TIMEV |
AT91_RTC_CALEV);
at91_rtc_imr = 0;

ret = request_irq(irq, at91_rtc_interrupt,
IRQF_SHARED,
Expand Down Expand Up @@ -329,6 +336,7 @@ static int __exit at91_rtc_remove(struct platform_device *pdev)
at91_rtc_write(AT91_RTC_IDR, AT91_RTC_ACKUPD | AT91_RTC_ALARM |
AT91_RTC_SECEV | AT91_RTC_TIMEV |
AT91_RTC_CALEV);
at91_rtc_imr = 0;
free_irq(irq, pdev);

rtc_device_unregister(rtc);
Expand All @@ -341,31 +349,35 @@ static int __exit at91_rtc_remove(struct platform_device *pdev)

/* AT91RM9200 RTC Power management control */

static u32 at91_rtc_imr;
static u32 at91_rtc_bkpimr;


static int at91_rtc_suspend(struct device *dev)
{
/* this IRQ is shared with DBGU and other hardware which isn't
* necessarily doing PM like we are...
*/
at91_rtc_imr = at91_rtc_read(AT91_RTC_IMR)
& (AT91_RTC_ALARM|AT91_RTC_SECEV);
if (at91_rtc_imr) {
if (device_may_wakeup(dev))
at91_rtc_bkpimr = at91_rtc_imr & (AT91_RTC_ALARM|AT91_RTC_SECEV);
if (at91_rtc_bkpimr) {
if (device_may_wakeup(dev)) {
enable_irq_wake(irq);
else
at91_rtc_write(AT91_RTC_IDR, at91_rtc_imr);
}
} else {
at91_rtc_write(AT91_RTC_IDR, at91_rtc_bkpimr);
at91_rtc_imr &= ~at91_rtc_bkpimr;
}
}
return 0;
}

static int at91_rtc_resume(struct device *dev)
{
if (at91_rtc_imr) {
if (device_may_wakeup(dev))
if (at91_rtc_bkpimr) {
if (device_may_wakeup(dev)) {
disable_irq_wake(irq);
else
at91_rtc_write(AT91_RTC_IER, at91_rtc_imr);
} else {
at91_rtc_imr |= at91_rtc_bkpimr;
at91_rtc_write(AT91_RTC_IER, at91_rtc_bkpimr);
}
}
return 0;
}
Expand Down
1 change: 0 additions & 1 deletion drivers/rtc/rtc-at91rm9200.h
View file
Expand Up @@ -64,7 +64,6 @@
#define AT91_RTC_SCCR 0x1c /* Status Clear Command Register */
#define AT91_RTC_IER 0x20 /* Interrupt Enable Register */
#define AT91_RTC_IDR 0x24 /* Interrupt Disable Register */
#define AT91_RTC_IMR 0x28 /* Interrupt Mask Register */

#define AT91_RTC_VER 0x2c /* Valid Entry Register */
#define AT91_RTC_NVTIM (1 << 0) /* Non valid Time */
Expand Down

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