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Add rollover protection to the STM32 RTC sampling logic

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git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3963 42af7a65-404d-4744-a932-0658087f49c3
This commit is contained in:
patacongo 2011-09-19 17:00:49 +00:00
parent 417ae9969a
commit cb518b3a04
1 changed files with 43 additions and 18 deletions
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61
arch/arm/src/stm32/stm32_rtc.c
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@ -83,7 +83,6 @@
#define RTC_TIMEMSB_REG STM32_BKP_DR1
/************************************************************************************
* Private Data
************************************************************************************/
@ -93,8 +92,8 @@
* - on start-up
* - during operation, reported by LSE interrupt
*/
volatile bool g_rtc_enabled = false;
volatile bool g_rtc_enabled = false;
/************************************************************************************
* Private Functions
@ -109,13 +108,11 @@ static inline void stm32_rtc_beginwr(void)
modifyreg16(STM32_RTC_CRL, 0, RTC_CRL_CNF);
}
static inline void stm32_rtc_endwr(void)
{
modifyreg16(STM32_RTC_CRL, RTC_CRL_CNF, 0);
}
/** Wait for registerred to synchronise with RTC module, call after power-up only */
static inline void stm32_rtc_wait4rsf(void)
{
@ -123,8 +120,6 @@ static inline void stm32_rtc_wait4rsf(void)
while( !(getreg16(STM32_RTC_CRL) & RTC_CRL_RSF) ) up_waste();
}
/************************************************************************************
* Interrupt Service Routines
************************************************************************************/
@ -147,7 +142,6 @@ static int stm32_rtc_overflow_isr(int irq, void *context)
return 0;
}
/************************************************************************************
* Public Function - Initialization
************************************************************************************/
@ -175,13 +169,13 @@ int up_rtcinitialize(void)
// \todo Get state from this function, if everything is
// okay and whether it is already enabled (if it was disabled
// reset upper time register
// reset upper time register)
g_rtc_enabled = true;
// \todo Possible stall? should we set the timeout period? and return with -1
stm32_rtc_wait4rsf();
/* Configure prescaler, note that this are write-only registers */
/* Configure prescaler, note that these are write-only registers */
stm32_rtc_beginwr();
putreg16(prescaler >> 16, STM32_RTC_PRLH);
@ -206,17 +200,53 @@ int up_rtcinitialize(void)
return OK;
}
/** Get time (counter) value
*
* \return time, where the unit depends on the prescaler value
**/
clock_t up_rtc_getclock(void)
{
return ( (uint32_t)getreg16(STM32_RTC_CNTH) << 16) |
(uint32_t)getreg16(STM32_RTC_CNTL);
}
irqstate_t flags;
uint16_t cnth;
uint16_t cntl;
uint16_t tmp;
/* The RTC counter is read from two 16-bit registers to form one 32-bit
* value. Because these are non-atomic operations, many things can happen
* between the two reads: This thread could get suspended or interrrupted
* or the lower 16-bit counter could rollover between reads. Disabling
* interrupts will prevent suspensions and interruptions:
*/
flags = irqsave();
/* And the following loop will handle any clock rollover events that may
* happen between samples. Most of the time (like 99.9%), the following
* loop will execute only once. In the rare rollover case, it should
* execute no more than 2 times.
*/
do
{
tmp = getreg16(STM32_RTC_CNTL);
cnth = getreg16(STM32_RTC_CNTH);
cntl = getreg16(STM32_RTC_CNTL);
}
/* The second sample of CNTL could be less than the first sample of CNTL
* only if rollover occurred. In that case, CNTH may or may not be out
* of sync. The best thing to do is try again until we know that no
* rollover occurred.
*/
while (cntl < tmp);
irqrestore(flags);
/* Then return the full 32-bit counter value */
return ((uint32_t)cnth << 16) | (uint32_t)cntl;
}
/** Set time (counter) value
*
@ -231,7 +261,6 @@ void up_rtc_setclock(clock_t newclock)
stm32_rtc_endwr();
}
time_t up_rtc_gettime(void)
{
/* Fetch time from LSB (hardware counter) and MSB (backup domain)
@ -263,7 +292,6 @@ time_t up_rtc_gettime(void)
return time_msb | time_lsb;
}
void up_rtc_settime(time_t newtime)
{
/* Do reverse compared to gettime above */
@ -281,7 +309,6 @@ void up_rtc_settime(time_t newtime)
irqrestore( irqs );
}
/** Set ALARM at which time ALARM callback is going to be generated
*
* The function sets the alarm and return present time at the time
@ -304,12 +331,10 @@ clock_t up_rtc_setalarm(clock_t atclock)
return up_rtc_getclock();
}
/** Set alarm output pin */
void stm32_rtc_settalarmpin(bool activate)
{
}
#endif // defined(CONFIG_STM32_BKP)
/** \} */