Remove support for busy-wait millisecond delays with IRQs disabled

The current implementation of Pybricks does not disable IRQs for any significant
length of time, which means that we can remove clock driver code supporting it.

Author: ArcaneNibble

bricks/_common_stm32/mphalport.c

@@ -22,22 +22,17 @@
 extern volatile uint32_t pbdrv_clock_ticks;
 
 // Core delay function that does an efficient sleep and may switch thread context.
-// If IRQs are enabled then we must have the GIL.
+// We must have the GIL.
 void mp_hal_delay_ms(mp_uint_t Delay) {
-    if (pbdrv_clock_is_ticking()) {
-        // IRQs enabled, so can use systick counter to do the delay
-        uint32_t start = pbdrv_clock_ticks;
-        // Wraparound of tick is taken care of by 2's complement arithmetic.
-        do {
-            // This macro will execute the necessary idle behaviour.  It may
-            // raise an exception, switch threads or enter sleep mode (waiting for
-            // (at least) the SysTick interrupt).
-            MICROPY_EVENT_POLL_HOOK
-        } while (pbdrv_clock_ticks - start < Delay);
-    } else {
-        // IRQs disabled, so need to use a busy loop for the delay.
-        pbdrv_clock_busy_delay_ms(Delay);
-    }
+    // Use systick counter to do the delay
+    uint32_t start = pbdrv_clock_ticks;
+    // Wraparound of tick is taken care of by 2's complement arithmetic.
+    do {
+        // This macro will execute the necessary idle behaviour.  It may
+        // raise an exception, switch threads or enter sleep mode (waiting for
+        // (at least) the SysTick interrupt).
+        MICROPY_EVENT_POLL_HOOK
+    } while (pbdrv_clock_ticks - start < Delay);
 }
 
 uintptr_t mp_hal_stdio_poll(uintptr_t poll_flags) {

bricks/ev3/mphalport.c

@@ -19,9 +19,9 @@
 #include "py/stream.h"
 
 // Core delay function that does an efficient sleep and may switch thread context.
-// If IRQs are enabled then we must have the GIL.
+// We must have the GIL.
 void mp_hal_delay_ms(mp_uint_t Delay) {
-    // IRQs enabled, so can use systick counter to do the delay
+    // Use systick counter to do the delay
     uint32_t start = pbdrv_clock_get_ms();
     // Wraparound of tick is taken care of by 2's complement arithmetic.
     do {

bricks/nxt/mphalport.c

@@ -18,28 +18,18 @@
 #include "py/mpconfig.h"
 #include "py/stream.h"
 
-// TODO
-static bool interrupts_get(void) {
-    return true;
-}
-
 // Core delay function that does an efficient sleep and may switch thread context.
-// If IRQs are enabled then we must have the GIL.
+// We must have the GIL.
 void mp_hal_delay_ms(mp_uint_t Delay) {
-    if (interrupts_get()) {
-        // IRQs enabled, so can use systick counter to do the delay
-        uint32_t start = pbdrv_clock_get_ms();
-        // Wraparound of tick is taken care of by 2's complement arithmetic.
-        do {
-            // This macro will execute the necessary idle behaviour.  It may
-            // raise an exception, switch threads or enter sleep mode (waiting for
-            // (at least) the SysTick interrupt).
-            MICROPY_EVENT_POLL_HOOK
-        } while (pbdrv_clock_get_ms() - start < Delay);
-    } else {
-        // IRQs disabled, so need to use a busy loop for the delay.
-        nx_systick_wait_ms(Delay);
-    }
+    // Use systick counter to do the delay
+    uint32_t start = pbdrv_clock_get_ms();
+    // Wraparound of tick is taken care of by 2's complement arithmetic.
+    do {
+        // This macro will execute the necessary idle behaviour.  It may
+        // raise an exception, switch threads or enter sleep mode (waiting for
+        // (at least) the SysTick interrupt).
+        MICROPY_EVENT_POLL_HOOK
+    } while (pbdrv_clock_get_ms() - start < Delay);
 }
 
 // delay for given number of microseconds

lib/pbio/drv/clock/clock_ev3.c

@@ -119,13 +119,4 @@ uint32_t pbdrv_clock_get_100us(void) {
     return pbdrv_clock_get_ms() * 10;
 }
 
-void pbdrv_clock_busy_delay_ms(uint32_t ms) {
-    // TODO
-}
-
-bool pbdrv_clock_is_ticking(void) {
-    // TODO
-    return true;
-}
-
 #endif // PBDRV_CONFIG_CLOCK_TIAM1808

lib/pbio/drv/clock/clock_linux.c

@@ -112,14 +112,4 @@ uint32_t pbdrv_clock_get_us(void) {
     return time_val.tv_sec * 1000000 + time_val.tv_nsec / 1000;
 }
 
-void pbdrv_clock_busy_delay_ms(uint32_t ms) {
-    uint32_t start = pbdrv_clock_get_ms();
-    while (pbdrv_clock_get_ms() - start < ms) {
-    }
-}
-
-bool pbdrv_clock_is_ticking(void) {
-    return true;
-}
-
 #endif // PBDRV_CONFIG_CLOCK_LINUX

lib/pbio/drv/clock/clock_none.c

@@ -22,11 +22,4 @@ uint32_t pbdrv_clock_get_100us(void) {
     return 0;
 }
 
-void pbdrv_clock_busy_delay_ms(uint32_t ms) {
-}
-
-bool pbdrv_clock_is_ticking(void) {
-    return false;
-}
-
 #endif // PBDRV_CONFIG_CLOCK_NONE

lib/pbio/drv/clock/clock_nxt.c

@@ -98,10 +98,6 @@ void nx_systick_wait_ms(uint32_t ms) {
     }
 }
 
-void pbdrv_clock_busy_delay_ms(uint32_t ms) {
-    nx_systick_wait_ms(ms);
-}
-
 void nx_systick_wait_ns(uint32_t ns) {
     volatile uint32_t x = (ns >> 7) + 1;
 
@@ -110,9 +106,4 @@ void nx_systick_wait_ns(uint32_t ns) {
     }
 }
 
-bool pbdrv_clock_is_ticking(void) {
-    // TODO
-    return true;
-}
-
 #endif // PBDRV_CONFIG_CLOCK_NXT

lib/pbio/drv/clock/clock_stm32.c

@@ -92,6 +92,8 @@ uint32_t HAL_GetTick(void) {
 // We provide our own version of HAL_Delay that calls __WFI while waiting,
 // and works when interrupts are disabled.  This function is intended to be
 // used only by the ST HAL functions.
+//
+// TODO: Is anything actually still calling this?
 void HAL_Delay(uint32_t Delay) {
     if (__get_PRIMASK() == 0) {
         // IRQs enabled, so can use systick counter to do the delay
@@ -112,14 +114,4 @@ void HAL_Delay(uint32_t Delay) {
     }
 }
 
-void pbdrv_clock_busy_delay_ms(uint32_t ms) {
-    HAL_Delay(ms);
-}
-
-bool pbdrv_clock_is_ticking(void) {
-    // Init already completed in SystemInit(), so we just need to check if
-    // interrupts are enabled.
-    return __get_PRIMASK() == 0;
-}
-
 #endif // PBDRV_CONFIG_CLOCK_STM32

lib/pbio/drv/clock/clock_test.c

@@ -41,12 +41,5 @@ uint32_t pbdrv_clock_get_us(void) {
     return clock_ticks * 1000;
 }
 
-void pbdrv_clock_busy_delay_ms(uint32_t ms) {
-}
-
-bool pbdrv_clock_is_ticking(void) {
-    return true;
-}
-
 
 #endif // PBDRV_CONFIG_CLOCK_TEST

lib/pbio/include/pbdrv/clock.h

@@ -37,26 +37,6 @@ uint32_t pbdrv_clock_get_us(void);
  */
 void pbdrv_clock_busy_delay_us(uint32_t us);
 
-/**
- * Busy wait delay for several milliseconds. May not be accurate.
- *
- * NB: Should not be used in any driver code. This exists only as a hook for
- * APIs that need a blocking delay to work when interrupts could be disabled.
- *
- * @param [in]  ms  The number of milliseconds to delay.
- */
-void pbdrv_clock_busy_delay_ms(uint32_t ms);
-
-/**
- * Tests if the millisecond clock is ticking.
- *
- * On embedded systems, this means that the clock was initialized and IRQs are
- * enabled.
- *
- * @return True if the clock is ticking, false otherwise.
- */
-bool pbdrv_clock_is_ticking(void);
-
 #endif /* _PBDRV_CLOCK_H_ */
 
 /** @} */