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add systick example port and cleanups
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- some f303 port cleanups
- add port using generic ARM SysTick with explained limitations

only lightly tested!
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@diggit
diggit committed May 2, 2020
1 parent 060ce54 commit da2b0b3
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Showing 4 changed files with 246 additions and 128 deletions.
28 changes: 25 additions & 3 deletions src/ar_internal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -173,11 +173,10 @@ extern ar_kernel_t g_ar;
//@{
void ar_port_init_system();
void ar_port_init_tick_timer();
uint32_t ar_port_set_time_delay(bool enable, uint32_t delay_us);
uint16_t ar_port_get_time_since_alignment_us();
void ar_port_set_time_delay(bool enable, uint32_t delay_us);
uint32_t ar_port_get_time_absolute_ticks();
uint64_t ar_port_get_time_absolute_us();
uint32_t ar_port_get_time_absolute_ms();
uint64_t ar_port_get_time_absolute_us();
void ar_port_prepare_stack(ar_thread_t * thread, uint32_t stackSize, void * param);
void ar_port_service_call();
bool ar_port_get_irq_state();
Expand Down Expand Up @@ -292,6 +291,29 @@ class KernelGuard
typedef KernelGuard<true> KernelLock; //!< Lock kernel.
typedef KernelGuard<false> KernelUnlock; //!< Unlock kernel.

// when there is no other way and you really have to disable interrupt for short moment in some scope
class IrqGuard
{
private:
// in fact we really need just one bit to store,
uint32_t cpuSR; // occupies 4B on stack but saves 3 masking instruction
// uint8_t cpuSR; // occupies 1B on stack (depends on alignment of surrounding data), adds cca 2 masking instructions
public:
IrqGuard(void)
{
asm ( \
"mrs %[output], PRIMASK\n\t" \
"cpsid I\n\t" \
: [output] "=r" (cpuSR) ::);
}
~IrqGuard(void)
{
asm ( \
"msr PRIMASK, %[input];\n\t" \
::[input] "r" (cpuSR) : );
};
};

#endif // _AR_INTERNAL_H_
//------------------------------------------------------------------------------
// EOF
Expand Down
26 changes: 9 additions & 17 deletions src/cortex_m/ar_port_f303_chained.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@
#include <string.h>
#include <iterator>

#include "clock.h"
#include "ar_config.h"

using namespace Ar;
Expand All @@ -59,21 +60,21 @@ enum _exception_priorities
#define F_uTIM F_TIM3
#define uTIM TIM3
#define uTIM_IRQn TIM3_IRQn
#define sTIM_MAX UINT16_MAX
#define uTIM_MAX UINT16_MAX
#define uTIM_CLK_EN() do{RCC->APB1ENR |= RCC_APB1ENR_TIM3EN; (void)RCC->APB1ENR;}while(0)

//sTIM counts system ticks
#define F_sTIM F_TIM2
#define sTIM TIM2
#define sTIM_IRQn TIM2_IRQn
#define sTIM_IRQHandler TIM2_IRQHandler
#define sTIM_MAX UINT32_MAX

#define sTIM_CLK_EN() do{RCC->APB1ENR |= RCC_APB1ENR_TIM2EN; (void)RCC->APB1ENR;}while(0)

//------------------------------------------------------------------------------
// Prototypes
//------------------------------------------------------------------------------

extern "C" void SysTick_Handler(void);
extern "C" uint32_t ar_port_yield_isr(uint32_t topOfStack, uint32_t isExtendedFrame);

//------------------------------------------------------------------------------
Expand Down Expand Up @@ -114,9 +115,9 @@ void ar_port_init_system()

void ar_port_init_tick_timer()
{
//DBGMCU->APB1FZ |= DBGMCU_APB1_FZ_DBG_TIM3_STOP; //stop timer in debug, useful for stepping
RCC->APB1ENR |= RCC_APB1ENR_TIM3EN;
RCC->APB1ENR |= RCC_APB1ENR_TIM2EN;
//se corresponding bits in DBGMCU->APBxFZ to stop timer in debug, useful for stepping
sTIM_CLK_EN();
uTIM_CLK_EN();
// NVIC_ClearPendingIRQ
uTIM->CR1 = 0;
uTIM->CR2 = (2 << TIM_CR2_MMS_Pos); //UPDATE EVENT as TRGO
Expand Down Expand Up @@ -151,36 +152,27 @@ void ar_port_init_tick_timer()
//! @return real value of delay, because clamping may occur
//! returns 0 when timer does not run or is delay:_us is 0
//! and interrupt is fired up immediately
uint32_t ar_port_set_time_delay(bool enable, uint32_t delay_us)
void ar_port_set_time_delay(bool enable, uint32_t delay_us)
{
if (enable)
{
uint32_t delay_ticks = delay_us/1000 / kSchedulerQuanta_ms;
// If the delay is 0, just make the SysTick interrupt pending.
if (delay_ticks == 0)
{
//disable compare interrupts
sTIM->DIER &= ~TIM_DIER_CC1IE;
NVIC_SetPendingIRQ(sTIM_IRQn);
return 0;
return;
}

sTIM->CCR1 = sTIM->CNT + delay_ticks;
sTIM->DIER |= TIM_DIER_CC1IE;

return delay_ticks * (kSchedulerQuanta_ms * 1000);
}
else
{
sTIM->DIER &= ~TIM_DIER_CC1IE; //just don't fire interrupts on compare
return 0;
}
}

uint16_t ar_port_get_time_since_alignment_us()
{
return uTIM->CNT;
}

uint32_t ar_port_get_time_absolute_ticks()
{
Expand Down
110 changes: 53 additions & 57 deletions src/cortex_m/ar_port_f303_single.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -60,16 +60,16 @@ enum _exception_priorities
#define sTIM TIM3
#define sTIM_IRQn TIM3_IRQn
#define sTIM_IRQHandler TIM3_IRQHandler
#define sTIM_MAX UINT16_MAX
#define sTIM_MAX (UINT16_MAX)
#define sTIM_MAX_QUANTAS (sTIM_MAX/(kSchedulerQuanta_ms * 1000))
#define sTIM_MAX_ALIGNED_us (sTIM_MAX_QUANTAS*(kSchedulerQuanta_ms * 1000))
#define sTIM_CLK_EN() do{RCC->APB1ENR |= RCC_APB1ENR_TIM3EN; (void)RCC->APB1ENR;}while(0)


//------------------------------------------------------------------------------
// Prototypes
//------------------------------------------------------------------------------

extern "C" void SysTick_Handler(void);
extern "C" uint32_t ar_port_yield_isr(uint32_t topOfStack, uint32_t isExtendedFrame);

//------------------------------------------------------------------------------
Expand Down Expand Up @@ -105,7 +105,6 @@ void ar_port_init_system()
// Set priorities for the exceptions we use in the kernel.
NVIC_SetPriority(SVCall_IRQn, kHandlerPriority);
NVIC_SetPriority(PendSV_IRQn, kHandlerPriority);
//TODO: config timers priority irq
//TODO: use uTIM overflow irq in tick mode
NVIC_EnableIRQ(sTIM_IRQn);
NVIC_SetPriority(sTIM_IRQn, kHandlerPriority);
Expand All @@ -115,9 +114,8 @@ void ar_port_init_system()

void ar_port_init_tick_timer()
{
//DBGMCU->APB1FZ |= DBGMCU_APB1_FZ_DBG_TIM3_STOP; //stop timer in debug, useful for stepping
RCC->APB1ENR |= RCC_APB1ENR_TIM3EN;
(void)RCC->APB1ENR;//force on tick before accessing timer
//se corresponding bits in DBGMCU->APBxFZ to stop timer in debug, useful for stepping
sTIM_CLK_EN();
sTIM->CR1 = TIM_CR1_URS;// | TIM_CR1_ARPE; //only ovf generated Update IRQ, enable preload on ARR
sTIM->CR2 = 0;
sTIM->PSC = (F_sTIM / 1000000UL)-1;//psc to have 1Mhz (1us) ticking
Expand All @@ -143,29 +141,26 @@ void ar_port_init_tick_timer()
//! @return real value of delay, because clamping may occur
//! returns 0 when timer does not run or is delay:_us is 0
//! and interrupt is fired up immediately
uint32_t ar_port_set_time_delay(bool enable, uint32_t delay_us)
void ar_port_set_time_delay(bool enable, uint32_t delay_us)
{
//self preemption never happen here (called only from scheduler[IRQ] or tick[IRQ] which share same priority)
propagateTicksToArgon = enable;

if (enable)
{
// sTIM->CR1 &= ~TIM_CR1_CEN;//temporary timer stop, just for debug
if (delay_us == 100000U) {
asm("NOP");
}
uint32_t delay_ticks = delay_us/1000 / kSchedulerQuanta_ms;
// If the delay is 0, just make the SysTick interrupt pending.
if (delay_ticks == 0)
{
_halt();//this really should not happen, this will trigger unaligned tick and that is BAD
return 0;
}
if (delay_ticks == 9) {
asm("NOP");
} else {
asm("NOP");
asm("NOP");
if (sTIM->SR & TIM_SR_UIF)
{
return; // already pending interrupt, that is fine
}
assert(1);
return;
}

//never alter CNT
Expand All @@ -177,19 +172,11 @@ uint32_t ar_port_set_time_delay(bool enable, uint32_t delay_us)
delay_ticks = sTIM_MAX_QUANTAS - alignmentsSinceTimerStart;
}
nextWakeup_tick = lastTick + ovfTicks + alignmentsSinceTimerStart + delay_ticks;
// sTIM->CR1 &= ~TIM_CR1_ARPE;//disable shadowing, to get access to active register
sTIM->ARR = (alignmentsSinceTimerStart + delay_ticks) * (kSchedulerQuanta_ms * 1000) - 1;
// sTIM->CR1 |= TIM_CR1_ARPE;//reenable shadowing, to prepare backup value to load after ovf (in case system can't handle ovf soon)
// sTIM->ARR = sTIM_MAX_ALIGNED_us - 1; //after overflow, timer reconfigures to maximal value (allows for quite late handling of overflow)
// sTIM->CR1 |= TIM_CR1_CEN;//temporary timer stop, just for debug
return delay_ticks * (kSchedulerQuanta_ms * 1000);
}
else
{
// sTIM->CR1 &= ~TIM_CR1_ARPE;//disable shadowing, to get access to active register
sTIM->ARR = sTIM_MAX_ALIGNED_us - 1; //maximum length ticking
// sTIM->CR1 |= TIM_CR1_ARPE;//TODO: not necessary?
return 0;
}
}

Expand All @@ -204,32 +191,32 @@ uint32_t ar_port_get_time_absolute_ticks()
return ar_port_get_time_absolute_ms()/kSchedulerQuanta_ms;
}

// uint64_t ar_port_get_time_absolute_us()
// {
// auto cnt = sTIM->CNT;
// auto ticks = lastTick;
// auto ovf = sTIM->SR & TIM_SR_UIF;
// auto nextTick = nextWakeup_tick;

// decltype(cnt) preread_cnt;
// decltype(ticks) preread_ticks;
// decltype(ovf) preread_ovf;
// decltype(nextTick) preread_nextTick;
// do {
// preread_cnt = cnt;
// preread_ticks = ticks;
// preread_ovf = ovf;
// preread_nextTick = nextTick;
// cnt = sTIM->CNT;
// ticks = lastTick;
// ovf = sTIM->SR & TIM_SR_UIF;
// nextTick = nextWakeup_tick;

// }while(preread_cnt > cnt || preread_ticks != ticks || preread_ovf != ovf || nextTick!= preread_nextTick);
// //TODO: is this contraption enough to have synced 3 variables?

// return static_cast<uint64_t>(ovf ? nextTick : ticks) * (kSchedulerQuanta_ms * 1000) + cnt;
// }
uint64_t ar_port_get_time_absolute_us()
{
auto cnt = sTIM->CNT;
auto ticks = lastTick;
auto ovf = sTIM->SR & TIM_SR_UIF;
auto nextTick = nextWakeup_tick;

decltype(cnt) preread_cnt;
decltype(ticks) preread_ticks;
decltype(ovf) preread_ovf;
decltype(nextTick) preread_nextTick;
do {
preread_cnt = cnt;
preread_ticks = ticks;
preread_ovf = ovf;
preread_nextTick = nextTick;
cnt = sTIM->CNT;
ticks = lastTick;
ovf = sTIM->SR & TIM_SR_UIF;
nextTick = nextWakeup_tick;

}while(preread_cnt > cnt || preread_ticks != ticks || preread_ovf != ovf || nextTick!= preread_nextTick);
//TODO: is this contraption enough to have synced 3 variables?

return static_cast<uint64_t>(ovf ? nextTick : ticks) * (kSchedulerQuanta_ms * 1000) + cnt;
}

//TODO: is return type sufficient?
uint32_t ar_port_get_time_absolute_ms()
Expand Down Expand Up @@ -406,19 +393,28 @@ bool ar_atomic_cas32(volatile int32_t * value, int32_t expectedValue, int32_t ne

extern "C" void sTIM_IRQHandler(void)
{
sTIM->SR &= ~TIM_SR_UIF;
lastTick = nextWakeup_tick + sTIM->CNT/(kSchedulerQuanta_ms * 1000);
bool ticked = sTIM->SR & TIM_SR_UIF;
if (ticked)
{
sTIM->SR &= ~TIM_SR_UIF;
// update lastTick only on interrupd due to overflow (non SW trigger)
lastTick = nextWakeup_tick + sTIM->CNT/(kSchedulerQuanta_ms * 1000);
}

if (propagateTicksToArgon)
{
ar_kernel_periodic_timer_isr();
}
if (nextWakeup_tick == lastTick)

if (ticked)
{
//not updated next tick
if (targetedNextWakeup_tick > nextWakeup_tick)
if (nextWakeup_tick == lastTick) //this is time when we scheduled next tick
{
// and still not there
ar_port_set_time_delay(true, (targetedNextWakeup_tick - nextWakeup_tick) * kSchedulerQuanta_ms * 1000);
if (targetedNextWakeup_tick > nextWakeup_tick) //but it is not target wakeup time (limited by timer may delay capability)
{
// reconfigure delay again
ar_port_set_time_delay(true, (targetedNextWakeup_tick - nextWakeup_tick) * kSchedulerQuanta_ms * 1000);
}
}
}
}
Expand Down
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