From 3f5dc472965e6a5b8efe60e33c7b6c2d18d92008 Mon Sep 17 00:00:00 2001 From: Stefan Kerkmann Date: Mon, 11 Jul 2022 15:17:05 +0200 Subject: [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 --- platforms/chibios/drivers/serial.c | 3 ++- platforms/chibios/drivers/vendor/RP/RP2040/serial_vendor.c | 2 +- 2 files changed, 3 insertions(+), 2 deletions(-) (limited to 'platforms/chibios/drivers') diff --git a/platforms/chibios/drivers/serial.c b/platforms/chibios/drivers/serial.c index 3fae5cd3a4..0dd8e71ae8 100644 --- a/platforms/chibios/drivers/serial.c +++ b/platforms/chibios/drivers/serial.c @@ -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 diff --git a/platforms/chibios/drivers/vendor/RP/RP2040/serial_vendor.c b/platforms/chibios/drivers/vendor/RP/RP2040/serial_vendor.c index d933dc1f5d..338146dadd 100644 --- a/platforms/chibios/drivers/vendor/RP/RP2040/serial_vendor.c +++ b/platforms/chibios/drivers/vendor/RP/RP2040/serial_vendor.c @@ -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); -- cgit v1.2.3