ports/stm32: Use PRIMASK for complete interrupt masking in Zephyr threading.

Replace arch_irq_lock/unlock with direct PRIMASK manipulation in IRQ
management functions. PRIMASK masks ALL interrupts including priority 0,
ensuring critical sections are not interrupted by Zephyr's scheduler or
any IRQs. This provides more complete protection than BASEPRI which only
masks interrupts at or above a specific priority threshold.

Signed-off-by: Andrew Leech <andrew@alelec.net>
Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>

Author: pi-anl

ports/stm32/irq.h

@@ -60,21 +60,23 @@ extern uint32_t irq_stats[IRQ_STATS_MAX];
 // value from disable_irq back to enable_irq.
 
 #if MICROPY_ZEPHYR_THREADING
-// Zephyr IRQ management
-#include <zephyr/arch/cpu.h>
+// Zephyr IRQ management using PRIMASK for complete interrupt masking
+// PRIMASK masks ALL interrupts (including NMI-like priority 0), ensuring
+// critical sections are not interrupted by Zephyr's scheduler or any IRQs.
+// This is more complete than BASEPRI which only masks priority >= threshold.
 
 static inline uint32_t query_irq(void) {
-    // For Zephyr, assume IRQs are enabled when not in atomic section
-    // This is a simplification - Zephyr manages IRQs via arch_irq_lock/unlock
-    return IRQ_STATE_ENABLED;
+    return __get_PRIMASK();
 }
 
 static inline void enable_irq(mp_uint_t state) {
-    arch_irq_unlock(state);
+    __set_PRIMASK(state);
 }
 
 static inline mp_uint_t disable_irq(void) {
-    return arch_irq_lock();
+    mp_uint_t state = __get_PRIMASK();
+    __disable_irq();
+    return state;
 }
 
 #else