1
0
Fork 0

[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

@ -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);