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[Core] Use polled waiting on ChibiOS platforms that support it (#17607)

* Use polled waiting on platforms that support it

Due to context switching overhead waiting a very short amount of time on
a sleeping thread is often not accurate and in fact not usable for timing
critical usage i.e. in a driver. Thus we use polled waiting for ranges
in the us range on platforms that support it instead. The fallback is
the thread sleeping mechanism.

This includes:

* ARM platforms with CYCCNT register (ARMv7, ARMv8) this is
  incremented at CPU clock frequency
* GD32VF103 RISC-V port with CSR_MCYCLE register this is incremented at
  CPU clock frequency
* RP2040 ARMv6 port which uses the integrated timer peripheral which is
  incremented with a fixed 1MHz frequency

* Use wait_us() instead of chSysPolledDelayX

...as it is powered by busy waiting now.

* Add chibios waiting methods test bench
This commit is contained in:
Stefan Kerkmann 2022-07-11 15:17:05 +02:00 committed by GitHub
parent 57021d6358
commit 3f5dc47296
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
14 changed files with 126 additions and 31 deletions

View file

@ -30,6 +30,11 @@
#ifdef WAIT_US_TIMER
void wait_us(uint16_t duration);
#elif PORT_SUPPORTS_RT == TRUE
# define wait_us(us) \
do { \
chSysPolledDelayX(US2RTC(REALTIME_COUNTER_CLOCK, us)); \
} while (0)
#else
# define wait_us(us) \
do { \

View file

@ -43,9 +43,8 @@ void __late_init(void) {
if (magic_location != magic_token) {
magic_location = magic_token;
// ChibiOS is not initialized at this point, so sleeping is only
// possible via busy waiting. The internal timer peripheral is running
// at this point with a precision of 1us.
chSysPolledDelayX(MS2RTC(1 * MHZ, RP2040_BOOTLOADER_DOUBLE_TAP_RESET_TIMEOUT));
// possible via busy waiting.
wait_us(RP2040_BOOTLOADER_DOUBLE_TAP_RESET_TIMEOUT * 1000U);
magic_location = 0;
return;
}

View file

@ -21,6 +21,9 @@
#if defined(MCU_RP)
# define CPU_CLOCK RP_CORE_CLK
// ChibiOS uses the RP2040 timer peripheral as its real time counter, this timer
// is monotonic and running at 1MHz.
# define REALTIME_COUNTER_CLOCK 1000000
# define USE_GPIOV1
# define PAL_OUTPUT_TYPE_OPENDRAIN _Static_assert(0, "RP2040 has no Open Drain GPIO configuration, setting this is not possible");
@ -102,6 +105,11 @@
# endif
#endif
#if defined(MCU_MIMXRT1062)
# include "clock_config.h"
# define CPU_CLOCK BOARD_BOOTCLOCKRUN_CORE_CLOCK
#endif
#if defined(HT32)
# define CPU_CLOCK HT32_CK_SYS_FREQUENCY
# define PAL_MODE_ALTERNATE PAL_HT32_MODE_AF
@ -109,3 +117,7 @@
# define PAL_OUTPUT_TYPE_PUSHPULL PAL_HT32_MODE_DIR
# define PAL_OUTPUT_SPEED_HIGHEST 0
#endif
#if !defined(REALTIME_COUNTER_CLOCK)
# define REALTIME_COUNTER_CLOCK CPU_CLOCK
#endif

View file

@ -20,7 +20,8 @@
# error "chSysPolledDelayX method not supported on this platform"
#else
# undef wait_us
# define wait_us(x) chSysPolledDelayX(US2RTC(CPU_CLOCK, x))
// Force usage of polled waiting - in case WAIT_US_TIMER is activated
# define wait_us(us) chSysPolledDelayX(US2RTC(REALTIME_COUNTER_CLOCK, us))
#endif
#ifndef SELECT_SOFT_SERIAL_SPEED

View file

@ -152,7 +152,7 @@ static inline void enter_rx_state(void) {
}
// Wait for ~11 bits, 1 start bit + 8 data bits + 1 stop bit + 1 bit
// headroom.
chSysPolledDelayX(US2RTC(1 * MHZ, (1000000U * 11 / SERIAL_USART_SPEED)));
wait_us(1000000U * 11U / SERIAL_USART_SPEED);
// Disable tx state machine to not interfere with our tx pin manipulation
pio_sm_set_enabled(pio, tx_state_machine, false);
gpio_set_drive_strength(SERIAL_USART_TX_PIN, GPIO_DRIVE_STRENGTH_2MA);