qmk-firmware/platforms/chibios/_wait.h
Stefan Kerkmann 3f5dc47296
[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
2022-07-11 15:17:05 +02:00

66 lines
2.5 KiB
C

/* Copyright 2021 QMK
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
#include <ch.h>
#include <hal.h>
/* chThdSleepX of zero maps to infinite - so we map to a tiny delay to still yield */
#define wait_ms(ms) \
do { \
if (ms != 0) { \
chThdSleepMilliseconds(ms); \
} else { \
chThdSleepMicroseconds(1); \
} \
} while (0)
#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 { \
if (us != 0) { \
chThdSleepMicroseconds(us); \
} else { \
chThdSleepMicroseconds(1); \
} \
} while (0)
#endif
#include "_wait.c"
/* For GPIOs on ARM-based MCUs, the input pins are sampled by the clock of the bus
* to which the GPIO is connected.
* The connected buses differ depending on the various series of MCUs.
* And since the instruction execution clock of the CPU and the bus clock of GPIO are different,
* there is a delay of several clocks to read the change of the input signal.
*
* Define this delay with the GPIO_INPUT_PIN_DELAY macro.
* If the GPIO_INPUT_PIN_DELAY macro is not defined, the following default values will be used.
* (A fairly large value of 0.25 microseconds is set.)
*/
#ifndef GPIO_INPUT_PIN_DELAY
# define GPIO_INPUT_PIN_DELAY (CPU_CLOCK / 1000000L / 4)
#endif
#define waitInputPinDelay() wait_cpuclock(GPIO_INPUT_PIN_DELAY)