1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Precise Delay Loops for Meta 4 * 5 * Copyright (C) 1993 Linus Torvalds 6 * Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz> 7 * Copyright (C) 2007,2009 Imagination Technologies Ltd. 8 * 9 */ 10 11 #include <linux/export.h> 12 #include <linux/sched.h> 13 #include <linux/delay.h> 14 15 #include <asm/core_reg.h> 16 #include <asm/processor.h> 17 18 /* 19 * TXTACTCYC is only 24 bits, so on chips with fast clocks it will wrap 20 * many times per-second. If it does wrap __delay will return prematurely, 21 * but this is only likely with large delay values. 22 * 23 * We also can't implement read_current_timer() with TXTACTCYC due to 24 * this wrapping behaviour. 25 */ 26 #define rdtimer(t) t = __core_reg_get(TXTACTCYC) 27 __delay(unsigned long loops)28void __delay(unsigned long loops) 29 { 30 unsigned long bclock, now; 31 32 rdtimer(bclock); 33 do { 34 asm("NOP"); 35 rdtimer(now); 36 } while ((now-bclock) < loops); 37 } 38 EXPORT_SYMBOL(__delay); 39 __const_udelay(unsigned long xloops)40inline void __const_udelay(unsigned long xloops) 41 { 42 u64 loops = (u64)xloops * (u64)loops_per_jiffy * HZ; 43 __delay(loops >> 32); 44 } 45 EXPORT_SYMBOL(__const_udelay); 46 __udelay(unsigned long usecs)47void __udelay(unsigned long usecs) 48 { 49 __const_udelay(usecs * 0x000010c7); /* 2**32 / 1000000 (rounded up) */ 50 } 51 EXPORT_SYMBOL(__udelay); 52 __ndelay(unsigned long nsecs)53void __ndelay(unsigned long nsecs) 54 { 55 __const_udelay(nsecs * 0x00005); /* 2**32 / 1000000000 (rounded up) */ 56 } 57 EXPORT_SYMBOL(__ndelay); 58