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

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* 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
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14 changed files with 126 additions and 31 deletions
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5
platforms/chibios/bootloaders/rp2040.c
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@ -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;
}