Problem with system time in lpc176x bsp
Joel Sherrill
joel at rtems.org
Mon Jan 11 18:16:34 UTC 2016
At this point, a ticket is needed for anything applied to 4.11 that is not
release
mechanics related.
--joel
On Mon, Jan 11, 2016 at 11:47 AM, Marcos Diaz <
marcos.diaz at tallertechnologies.com> wrote:
> Hi Sebastian,
>
> we did some more testing and found out what's causing the problem. Based
> on what
> I posted at
> https://lists.rtems.org/pipermail/devel/2015-December/013235.html,
> the problem arises when the ticker interrupt occurs while a task is
> executing
> one of the instructions that make up the following line:
>
> is_count_pending = (systick->csr & ARMV7M_SYSTICK_CSR_COUNTFLAG) != 0;
>
> which compiling with -O3 are:
>
> ldr.w r3, [r9]
> ubfx r5, r3, #16, #1
> strb.w r5, [r8, #64]
>
> If the SysTick counts to 0 and the ldr executes before the interrupt
> occurs,
> R3 will have the CSR.COUNTFLAG bit set. Even though _ARMV7M_TC_at_tick will
> clear the is_count_pending boolean, the task will still see it as true.
>
> The solution we found is to simply disable interrupts while reading that
> flag.
> We also use a local variable inside _ARMV7M_TC_is_pending instead of
> directly
> returning the current value of the is_count_pending global, just in case.
>
> Here's the patch that fixes it; this applies to the 4.11 branch.
> Do we have to open a new thread for it to be applied to the mainline, or
> will
> this suffice? Should we open a ticket for 4.11?
>
> ---
> .../arm/shared/armv7m/clock/armv7m-clock-config.c | 38
> +++++++++++++++-------
> c/src/lib/libbsp/shared/clockdrv_shell.h | 16 ++++++++-
> cpukit/rtems/src/clocktick.c | 6 +++-
> cpukit/sapi/include/rtems/timecounter.h | 35
> ++++++++++++++++----
> cpukit/score/include/rtems/score/timecounter.h | 37
> +++++++++++++++++++--
> cpukit/score/src/kern_tc.c | 16 ++++-----
> doc/bsp_howto/clock.t | 13 +++++++-
> 7 files changed, 130 insertions(+), 31 deletions(-)
>
> diff --git
> a/c/src/lib/libbsp/arm/shared/armv7m/clock/armv7m-clock-config.c
> b/c/src/lib/libbsp/arm/shared/armv7m/clock/armv7m-clock-config.c
> index e78684c..53bd7cf 100644
> --- a/c/src/lib/libbsp/arm/shared/armv7m/clock/armv7m-clock-config.c
> +++ b/c/src/lib/libbsp/arm/shared/armv7m/clock/armv7m-clock-config.c
> @@ -25,6 +25,8 @@ static void Clock_isr(void *arg);
>
> static rtems_timecounter_simple _ARMV7M_TC;
>
> +static bool is_count_pending = false;
> +
> static uint32_t _ARMV7M_TC_get(rtems_timecounter_simple *tc)
> {
> volatile ARMV7M_Systick *systick = _ARMV7M_Systick;
> @@ -34,9 +36,20 @@ static uint32_t _ARMV7M_TC_get(rtems_timecounter_simple
> *tc)
>
> static bool _ARMV7M_TC_is_pending(rtems_timecounter_simple *tc)
> {
> - volatile ARMV7M_SCB *scb = _ARMV7M_SCB;
> + volatile ARMV7M_Systick *systick = _ARMV7M_Systick;
> + ISR_lock_Context lock_context;
> +
> + _Timecounter_Acquire( &lock_context );
> + /* We use this bool since the hardware flag is reset each time it is
> read. */
> + if (!is_count_pending)
> + {
> + is_count_pending = ((systick->csr & ARMV7M_SYSTICK_CSR_COUNTFLAG) !=
> 0 );
> + }
>
> - return ((scb->icsr & ARMV7M_SCB_ICSR_PENDSTSET) != 0);
> + const bool is_pending_local = is_count_pending;
> +
> + _Timecounter_Release( &lock_context );
> + return is_pending_local;
> }
>
> static uint32_t _ARMV7M_TC_get_timecount(struct timecounter *tc)
> @@ -48,19 +61,23 @@ static uint32_t _ARMV7M_TC_get_timecount(struct
> timecounter *tc)
> );
> }
>
> -static void _ARMV7M_TC_tick(void)
> -{
> - rtems_timecounter_simple_downcounter_tick(&_ARMV7M_TC, _ARMV7M_TC_get);
> -}
> -
> -static void _ARMV7M_Systick_at_tick(void)
> +static void _ARMV7M_TC_at_tick(rtems_timecounter_simple *tc)
> {
> volatile ARMV7M_Systick *systick = _ARMV7M_Systick;
> -
> + is_count_pending = false;
> /* Clear COUNTFLAG */
> systick->csr;
> }
>
> +static void _ARMV7M_TC_tick(void)
> +{
> + rtems_timecounter_simple_downcounter_tick(
> + &_ARMV7M_TC,
> + _ARMV7M_TC_get,
> + _ARMV7M_TC_at_tick
> + );
> +}
> +
> static void _ARMV7M_Systick_handler(void)
> {
> _ARMV7M_Interrupt_service_enter();
> @@ -111,9 +128,6 @@ static void _ARMV7M_Systick_cleanup(void)
>
> #define Clock_driver_timecounter_tick() _ARMV7M_TC_tick()
>
> -#define Clock_driver_support_at_tick() \
> - _ARMV7M_Systick_at_tick()
> -
> #define Clock_driver_support_initialize_hardware() \
> _ARMV7M_Systick_initialize()
>
> diff --git a/c/src/lib/libbsp/shared/clockdrv_shell.h
> b/c/src/lib/libbsp/shared/clockdrv_shell.h
> index d546fb8..96b962f 100644
> --- a/c/src/lib/libbsp/shared/clockdrv_shell.h
> +++ b/c/src/lib/libbsp/shared/clockdrv_shell.h
> @@ -44,6 +44,13 @@
> #define Clock_driver_support_find_timer()
> #endif
>
> +/**
> + * @brief Do nothing by default.
> + */
> +#ifndef Clock_driver_support_at_tick
> + #define Clock_driver_support_at_tick()
> +#endif
> +
> /*
> * A specialized clock driver may use for example
> rtems_timecounter_tick_simple()
> * instead of the default.
> @@ -108,7 +115,14 @@ rtems_isr Clock_isr(
> && _Thread_Executing->Start.entry_point
> == (Thread_Entry) rtems_configuration_get_idle_task()
> ) {
> - _Timecounter_Tick_simple(interval, (*tc->tc_get_timecount)(tc));
> + ISR_lock_Context lock_context;
> +
> + _Timecounter_Acquire(&lock_context);
> + _Timecounter_Tick_simple(
> + interval,
> + (*tc->tc_get_timecount)(tc),
> + &lock_context
> + );
> }
>
> Clock_driver_support_at_tick();
> diff --git a/cpukit/rtems/src/clocktick.c b/cpukit/rtems/src/clocktick.c
> index e2cd35f..a6bf26d 100644
> --- a/cpukit/rtems/src/clocktick.c
> +++ b/cpukit/rtems/src/clocktick.c
> @@ -23,9 +23,13 @@
>
> rtems_status_code rtems_clock_tick( void )
> {
> + ISR_lock_Context lock_context;
> +
> + _Timecounter_Acquire( &lock_context );
> _Timecounter_Tick_simple(
> rtems_configuration_get_microseconds_per_tick(),
> - 0
> + 0,
> + &lock_context
> );
>
> return RTEMS_SUCCESSFUL;
> diff --git a/cpukit/sapi/include/rtems/timecounter.h
> b/cpukit/sapi/include/rtems/timecounter.h
> index 04bc534..06b3973 100644
> --- a/cpukit/sapi/include/rtems/timecounter.h
> +++ b/cpukit/sapi/include/rtems/timecounter.h
> @@ -94,6 +94,13 @@ typedef struct {
> } rtems_timecounter_simple;
>
> /**
> + * @brief At tick handling done under protection of the timecounter lock.
> + */
> +typedef uint32_t rtems_timecounter_simple_at_tick(
> + rtems_timecounter_simple *tc
> +);
> +
> +/**
> * @brief Returns the current value of a simple timecounter.
> */
> typedef uint32_t rtems_timecounter_simple_get(
> @@ -199,20 +206,28 @@ RTEMS_INLINE_ROUTINE uint32_t
> rtems_timecounter_simple_scale(
> *
> * @param[in] tc The simple timecounter.
> * @param[in] get The method to get the value of the simple timecounter.
> + * @param[in] at_tick The method to perform work under timecounter lock
> + * protection at this tick, e.g. clear a pending flag.
> */
> RTEMS_INLINE_ROUTINE void rtems_timecounter_simple_downcounter_tick(
> - rtems_timecounter_simple *tc,
> - rtems_timecounter_simple_get get
> + rtems_timecounter_simple *tc,
> + rtems_timecounter_simple_get get,
> + rtems_timecounter_simple_at_tick at_tick
> )
> {
> + ISR_lock_Context lock_context;
> uint32_t current;
>
> + _Timecounter_Acquire( &lock_context );
> +
> + ( *at_tick )( tc );
> +
> current = rtems_timecounter_simple_scale(
> tc,
> tc->real_interval - ( *get )( tc )
> );
>
> - _Timecounter_Tick_simple( tc->binary_interval, current );
> + _Timecounter_Tick_simple( tc->binary_interval, current, &lock_context );
> }
>
> /**
> @@ -220,17 +235,25 @@ RTEMS_INLINE_ROUTINE void
> rtems_timecounter_simple_downcounter_tick(
> *
> * @param[in] tc The simple timecounter.
> * @param[in] get The method to get the value of the simple timecounter.
> + * @param[in] at_tick The method to perform work under timecounter lock
> + * protection at this tick, e.g. clear a pending flag.
> */
> RTEMS_INLINE_ROUTINE void rtems_timecounter_simple_upcounter_tick(
> - rtems_timecounter_simple *tc,
> - rtems_timecounter_simple_get get
> + rtems_timecounter_simple *tc,
> + rtems_timecounter_simple_get get,
> + rtems_timecounter_simple_at_tick at_tick
> )
> {
> + ISR_lock_Context lock_context;
> uint32_t current;
>
> + _Timecounter_Acquire( &lock_context );
> +
> + ( *at_tick )( tc );
> +
> current = rtems_timecounter_simple_scale( tc, ( *get )( tc ) );
>
> - _Timecounter_Tick_simple( tc->binary_interval, current );
> + _Timecounter_Tick_simple( tc->binary_interval, current, &lock_context );
> }
>
> /**
> diff --git a/cpukit/score/include/rtems/score/timecounter.h
> b/cpukit/score/include/rtems/score/timecounter.h
> index 0d17cc7..0e611b5 100644
> --- a/cpukit/score/include/rtems/score/timecounter.h
> +++ b/cpukit/score/include/rtems/score/timecounter.h
> @@ -26,6 +26,8 @@
> #include <sys/time.h>
> #include <sys/timetc.h>
>
> +#include <rtems/score/isrlock.h>
> +
> #ifdef __cplusplus
> extern "C" {
> #endif /* __cplusplus */
> @@ -161,6 +163,31 @@ void _Timecounter_Install( struct timecounter *tc );
> void _Timecounter_Tick( void );
>
> /**
> + * @brief Lock to protect the timecounter mechanic.
> + */
> +ISR_LOCK_DECLARE( extern, _Timecounter_Lock )
> +
> +/**
> + * @brief Acquires the timecounter lock.
> + *
> + * @param[in] lock_context The lock context.
> + *
> + * See _Timecounter_Tick_simple().
> + */
> +#define _Timecounter_Acquire( lock_context ) \
> + _ISR_lock_ISR_disable_and_acquire( &_Timecounter_Lock, lock_context )
> +
> +/**
> + * @brief Releases the timecounter lock.
> + *
> + * @param[in] lock_context The lock context.
> + *
> + * See _Timecounter_Tick_simple().
> + */
> +#define _Timecounter_Release(lock_context) \
> + _ISR_lock_Release_and_ISR_enable(&_Timecounter_Lock, lock_context)
> +
> +/**
> * @brief Performs a simple timecounter tick.
> *
> * This is a special purpose tick function for simple timecounter to
> support
> @@ -169,8 +196,14 @@ void _Timecounter_Tick( void );
> * @param[in] delta The time in timecounter ticks elapsed since the last
> call
> * to _Timecounter_Tick_simple().
> * @param[in] offset The current value of the timecounter.
> - */
> -void _Timecounter_Tick_simple( uint32_t delta, uint32_t offset );
> + * @param[in] lock_context The lock context of the corresponding
> + * _Timecounter_Acquire().
> + */
> +void _Timecounter_Tick_simple(
> + uint32_t delta,
> + uint32_t offset,
> + ISR_lock_Context *lock_context
> +);
>
> /**
> * @brief The wall clock time in seconds.
> diff --git a/cpukit/score/src/kern_tc.c b/cpukit/score/src/kern_tc.c
> index f6a1136..4257533 100644
> --- a/cpukit/score/src/kern_tc.c
> +++ b/cpukit/score/src/kern_tc.c
> @@ -64,7 +64,9 @@ __FBSDID("$FreeBSD r284178 2015-06-09T11:49:56Z$");
> #ifdef __rtems__
> #include <limits.h>
> #include <rtems.h>
> -ISR_LOCK_DEFINE(static, _Timecounter_Lock, "Timecounter");
> +ISR_LOCK_DEFINE(, _Timecounter_Lock, "Timecounter")
> +#define _Timecounter_Release(lock_context) \
> + _ISR_lock_Release_and_ISR_enable(&_Timecounter_Lock, lock_context)
> #define hz rtems_clock_get_ticks_per_second()
> #define printf(...)
> #define log(...)
> @@ -1383,7 +1385,7 @@ tc_windup(void)
> #ifdef __rtems__
> ISR_lock_Context lock_context;
>
> - _ISR_lock_ISR_disable_and_acquire(&_Timecounter_Lock,
> &lock_context);
> + _Timecounter_Acquire(&lock_context);
> #endif /* __rtems__ */
>
> /*
> @@ -1538,7 +1540,7 @@ tc_windup(void)
> timekeep_push_vdso();
> #endif /* __rtems__ */
> #ifdef __rtems__
> - _ISR_lock_Release_and_ISR_enable(&_Timecounter_Lock,
> &lock_context);
> + _Timecounter_Release(&lock_context);
> #endif /* __rtems__ */
> }
>
> @@ -1963,14 +1965,12 @@ _Timecounter_Tick(void)
> }
> #ifdef __rtems__
> void
> -_Timecounter_Tick_simple(uint32_t delta, uint32_t offset)
> +_Timecounter_Tick_simple(uint32_t delta, uint32_t offset,
> + ISR_lock_Context *lock_context)
> {
> struct bintime bt;
> struct timehands *th;
> uint32_t ogen;
> - ISR_lock_Context lock_context;
> -
> - _ISR_lock_ISR_disable_and_acquire(&_Timecounter_Lock,
> &lock_context);
>
> th = timehands;
> ogen = th->th_generation;
> @@ -1997,7 +1997,7 @@ _Timecounter_Tick_simple(uint32_t delta, uint32_t
> offset)
> time_second = th->th_microtime.tv_sec;
> time_uptime = th->th_offset.sec;
>
> - _ISR_lock_Release_and_ISR_enable(&_Timecounter_Lock,
> &lock_context);
> + _Timecounter_Release(lock_context);
>
> _Watchdog_Tick();
> }
> diff --git a/doc/bsp_howto/clock.t b/doc/bsp_howto/clock.t
> index f58b898..2891bb2 100644
> --- a/doc/bsp_howto/clock.t
> +++ b/doc/bsp_howto/clock.t
> @@ -89,6 +89,13 @@ static uint32_t some_tc_get( rtems_timecounter_simple
> *tc )
> return some.counter;
> @}
>
> +static void some_tc_at_tick( rtems_timecounter_simple *tc )
> +@{
> + /*
> + * Do work necessary at the clock tick interrupt, e.g. clear a pending
> flag.
> + */
> +@}
> +
> static bool some_tc_is_pending( rtems_timecounter_simple *tc )
> @{
> return some.is_pending;
> @@ -105,7 +112,11 @@ static uint32_t some_tc_get_timecount( struct
> timecounter *tc )
>
> static void some_tc_tick( void )
> @{
> - rtems_timecounter_simple_downcounter_tick( &some_tc, some_tc_get );
> + rtems_timecounter_simple_downcounter_tick(
> + &some_tc,
> + some_tc_get,
> + some_tc_at_tick
> + );
> @}
>
> static void some_support_initialize_hardware( void )
> --
> 2.7.0
>
> _______________________________________________
> devel mailing list
> devel at rtems.org
> http://lists.rtems.org/mailman/listinfo/devel
>
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