/* 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/>. */ #ifndef __OPTIMIZE__ # pragma message "Compiler optimizations disabled; wait_cpuclock() won't work as designed" #endif #define CLOCK_DELAY_NOP8 "nop\n\t nop\n\t nop\n\t nop\n\t nop\n\t nop\n\t nop\n\t nop\n\t" __attribute__((always_inline)) static inline void wait_cpuclock(unsigned int n) { /* n: 1..135 */ /* The argument n must be a constant expression. * That way, compiler optimization will remove unnecessary code. */ if (n < 1) { return; } if (n > 8) { unsigned int n8 = n / 8; n = n - n8 * 8; switch (n8) { case 16: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 15: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 14: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 13: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 12: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 11: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 10: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 9: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 8: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 7: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 6: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 5: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 4: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 3: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 2: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 1: asm volatile(CLOCK_DELAY_NOP8::: "memory"); case 0: break; } } switch (n) { case 8: asm volatile("nop" ::: "memory"); case 7: asm volatile("nop" ::: "memory"); case 6: asm volatile("nop" ::: "memory"); case 5: asm volatile("nop" ::: "memory"); case 4: asm volatile("nop" ::: "memory"); case 3: asm volatile("nop" ::: "memory"); case 2: asm volatile("nop" ::: "memory"); case 1: asm volatile("nop" ::: "memory"); case 0: break; } }