implement mp_hal_delay_us() to not need interrupts, and use it

ports/atmel-samd/mphalport.c

@@ -99,10 +99,7 @@ void mp_hal_delay_ms(mp_uint_t delay) {
     }
 }
 
-void mp_hal_delay_us(mp_uint_t delay) {
-    tick_delay(delay);
-}
-
+// Use mp_hal_delay_us() for timing of less than 1ms.
 // Do a simple timing loop to wait for a certain number of microseconds.
 // Can be used when interrupts are disabled, which makes tick_delay() unreliable.
 //
@@ -115,8 +112,8 @@ void mp_hal_delay_us(mp_uint_t delay) {
 #define DELAY_LOOP_ITERATIONS_PER_US ( (30U*120000000U) / common_hal_mcu_processor_get_frequency())
 #endif
 
-void mp_hal_delay_us_loop(uint32_t us) {
-    for (uint32_t i = us*DELAY_LOOP_ITERATIONS_PER_US; i > 0; i--) {
+void mp_hal_delay_us(mp_uint_t delay) {
+    for (uint32_t i = delay*DELAY_LOOP_ITERATIONS_PER_US; i > 0; i--) {
         asm volatile("nop");
     }
 }

ports/atmel-samd/mphalport.h

@@ -50,6 +50,4 @@ void mp_hal_set_interrupt_char(int c);
 void mp_hal_disable_all_interrupts(void);
 void mp_hal_enable_all_interrupts(void);
 
-void mp_hal_delay_us_loop(uint32_t us);
-
 #endif // MICROPY_INCLUDED_ATMEL_SAMD_MPHALPORT_H

ports/esp8266/Makefile

@@ -92,7 +92,6 @@ SRC_C = \
 	machine_hspi.c \
 	modesp.c \
 	modnetwork.c \
-	mphalport.c \
 	ets_alt_task.c \
 	fatfs_port.c \
 	posix_helpers.c \

ports/nrf/common-hal/microcontroller/__init__.c

@@ -33,6 +33,8 @@
 #include "shared-bindings/microcontroller/Processor.h"
 
 // TODO porting common_hal_mcu
+// This routine should work even when interrupts are disabled. Used by OneWire
+// for precise timing.
 void common_hal_mcu_delay_us(uint32_t delay) {
 //    os_delay_us(delay);
 }
@@ -58,4 +60,3 @@ const mcu_processor_obj_t common_hal_mcu_processor_obj = {
         .type = &mcu_processor_type,
     },
 };
-

ports/nrf/mphalport.c

@@ -85,17 +85,3 @@ void mp_hal_stdout_tx_strn_cooked(const char *str, mp_uint_t len) {
 void mp_hal_stdout_tx_str(const char *str) {
     mp_hal_stdout_tx_strn(str, strlen(str));
 }
-
-// Do a simple timing loop to wait for a certain number of microseconds.
-// Can be used when interrupts are disabled, which makes tick_delay() unreliable.
-//
-// Testing done at 48 MHz on SAMD21 and 120 MHz on SAMD51 (cache on).
-// TODO: Test on NRF. For now, use SAMD51 calibration, even though nRF52 runs slower.
-// Fraction should compensate.
-#define DELAY_LOOP_ITERATIONS_PER_US ( (30U*120000000U) / common_hal_mcu_processor_get_frequency())
-
-void mp_hal_delay_us_loop(uint32_t us) {
-    for (uint32_t i = us*DELAY_LOOP_ITERATIONS_PER_US; i > 0; i--) {
-        asm volatile("nop");
-    }
-}

ports/nrf/mphalport.h

@@ -52,7 +52,6 @@ static inline uint32_t hal_tick_fake(void) {
 
 extern const unsigned char mp_hal_status_to_errno_table[4];
 
-
 NORETURN void mp_hal_raise(HAL_StatusTypeDef status);
 void mp_hal_set_interrupt_char(int c); // -1 to disable
 
@@ -70,7 +69,6 @@ bool mp_hal_stdin_any(void);
 #define mp_hal_pin_od_high(p)    mp_hal_pin_high(p)
 #define mp_hal_pin_open_drain(p) hal_gpio_cfg_pin(p->port, p->pin, HAL_GPIO_MODE_INPUT, HAL_GPIO_PULL_DISABLED)
 
-void mp_hal_delay_us_loop(uint32_t us);
 
 // TODO: empty implementation for now. Used by machine_spi.c:69
 #define mp_hal_delay_us_fast(p)

shared-module/bitbangio/OneWire.c

@@ -24,8 +24,6 @@
  * THE SOFTWARE.
  */
 
-#include "mphalport.h"
-
 #include "common-hal/microcontroller/Pin.h"
 #include "shared-bindings/bitbangio/OneWire.h"
 #include "shared-bindings/microcontroller/__init__.h"
@@ -51,17 +49,17 @@ void shared_module_bitbangio_onewire_deinit(bitbangio_onewire_obj_t* self) {
     common_hal_digitalio_digitalinout_deinit(&self->pin);
 }
 
-// We can't use common_hal_mcu_delay_us() here because it needs interrupts to be accurate
-// due to SysTick rollover checking, done by an interrupt.
+// We use common_hal_mcu_delay_us(). It should not be dependent on interrupts
+// to do accurate timekeeping, since we disable interrupts during the delays below.
 
 bool shared_module_bitbangio_onewire_reset(bitbangio_onewire_obj_t* self) {
     common_hal_mcu_disable_interrupts();
     common_hal_digitalio_digitalinout_switch_to_output(&self->pin, false, DRIVE_MODE_OPEN_DRAIN);
-    mp_hal_delay_us_loop(480);
+    common_hal_mcu_delay_us(480);
     common_hal_digitalio_digitalinout_switch_to_input(&self->pin, PULL_NONE);
-    mp_hal_delay_us_loop(70);
+    common_hal_mcu_delay_us(70);
     bool value = common_hal_digitalio_digitalinout_get_value(&self->pin);
-    mp_hal_delay_us_loop(410);
+    common_hal_mcu_delay_us(410);
     common_hal_mcu_enable_interrupts();
     return value;
 }
@@ -69,14 +67,14 @@ bool shared_module_bitbangio_onewire_reset(bitbangio_onewire_obj_t* self) {
 bool shared_module_bitbangio_onewire_read_bit(bitbangio_onewire_obj_t* self) {
     common_hal_mcu_disable_interrupts();
     common_hal_digitalio_digitalinout_switch_to_output(&self->pin, false, DRIVE_MODE_OPEN_DRAIN);
-    mp_hal_delay_us_loop(6);
+    common_hal_mcu_delay_us(6);
     common_hal_digitalio_digitalinout_switch_to_input(&self->pin, PULL_NONE);
     // TODO(tannewt): Test with more devices and maybe make the delays
     // configurable. This should be 9 by the datasheet but all bits read as 1
     // then.
-    mp_hal_delay_us_loop(6);
+    common_hal_mcu_delay_us(6);
     bool value = common_hal_digitalio_digitalinout_get_value(&self->pin);
-    mp_hal_delay_us_loop(55);
+    common_hal_mcu_delay_us(55);
     common_hal_mcu_enable_interrupts();
     return value;
 }
@@ -85,8 +83,8 @@ void shared_module_bitbangio_onewire_write_bit(bitbangio_onewire_obj_t* self,
         bool bit) {
     common_hal_mcu_disable_interrupts();
     common_hal_digitalio_digitalinout_switch_to_output(&self->pin, false, DRIVE_MODE_OPEN_DRAIN);
-    mp_hal_delay_us_loop(bit? 6 : 60);
+    common_hal_mcu_delay_us(bit? 6 : 60);
     common_hal_digitalio_digitalinout_switch_to_input(&self->pin, PULL_NONE);
-    mp_hal_delay_us_loop(bit? 64 : 10);
+    common_hal_mcu_delay_us(bit? 64 : 10);
     common_hal_mcu_enable_interrupts();
 }