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arch/arm/src/rp23xx: correct NVIC and PendSV priority initialisation #18865

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arch/arm/src/rp23xx: correct NVIC and PendSV priority initialisation #18865

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4fa4e58
arch/arm/src/rp23xx: fix NVIC priority init missing IRQs 12-51
dfanache May 8, 2026
fcc1772
arch/arm/src/rp23xx: place PendSV at the lowest NVIC priority
dfanache May 11, 2026
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27 changes: 25 additions & 2 deletions arch/arm/src/rp23xx/rp23xx_irq.c
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Original file line number Diff line number Diff line change
Expand Up @@ -249,6 +249,7 @@ static inline void rp23xx_clrpend(int irq)
void up_irqinitialize(void)
{
uint32_t regaddr;
uint32_t regval;
int i;

/* Disable all interrupts */
Expand Down Expand Up @@ -280,9 +281,14 @@ void up_irqinitialize(void)
arm_ramvec_initialize();
#endif

/* Now set all of the interrupt lines to the default priority */
/* Set all of the interrupt lines to the default priority.
* NVIC_IRQ_PRIORITY(n) maps IRQ number n to its IPR register via
* (n >> 2); each 32-bit IPR covers four IRQs. Step by four and bound
* the loop by RP23XX_IRQ_NEXTINT so that every IPR (covering IRQs
* 0..51) is written exactly once.
*/

for (i = 0; i < 12; i++)
for (i = 0; i < RP23XX_IRQ_NEXTINT; i += 4)
{
regaddr = NVIC_IRQ_PRIORITY(i);
putreg32(DEFPRIORITY32, regaddr);
Expand All @@ -299,6 +305,23 @@ void up_irqinitialize(void)

rp23xx_prioritize_syscall(NVIC_SYSH_SVCALL_PRIORITY);

/* Place PendSV at the lowest NVIC priority. This is the deferred
* half of the Cortex-M context-switch path: a higher-priority ISR
* that wakes a task sets PendSV pending and returns; after that
* PendSV does the actual register save/restore. For this pattern to
* work safely PendSV must run only after all peripheral ISRs have
* finished, i.e. at the lowest priority.
*
* Read-modify-write SHPR3 to lower just the PendSV byte to MIN
* (0XF0) without disturbing the SysTick and DebugMon bytes that
* share the same register.
*/

regval = getreg32(NVIC_SYSH12_15_PRIORITY);
regval &= ~NVIC_SYSH_PRIORITY_PR14_MASK;
regval |= (NVIC_SYSH_PRIORITY_MIN << NVIC_SYSH_PRIORITY_PR14_SHIFT);
putreg32(regval, NVIC_SYSH12_15_PRIORITY);

/* Attach all other processor exceptions (except reset and sys tick) */

#ifdef CONFIG_DEBUG_FEATURES
Expand Down
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