Commit 357ec64b authored Sep 15, 2021 by Berend Ozceri Committed by Christopher Friedt Sep 20, 2021

drivers: timer: Fix RISC-V machine timer count drift due integer math

If CYC_PER_TICK does not divide the (now - last_count) quantity exactly with integer math, the subsequent multiplication before incrementing last_count causes a drift. This commit eliminates the redundant division-followed-by-multiplication and fixes https://github.com/zephyrproject-rtos/zephyr/issues/37852



Signed-off-by: Berend Ozceri <berend@recogni.com>

parent 123be4f1

drivers/timer/riscv_machine_timer.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -64,7 +64,7 @@ static void timer_isr(const void *arg)
		uint64_t now = mtime();
		uint32_t dticks = (uint32_t)((now - last_count) / CYC_PER_TICK);

		last_count += dticks * CYC_PER_TICK;
		last_count = now;

		if (!TICKLESS) {
		uint64_t next = last_count + CYC_PER_TICK;

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