1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Precise Delay Loops for S390 4 * 5 * Copyright IBM Corp. 1999, 2008 6 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>, 7 */ 8 9 #include <linux/processor.h> 10 #include <linux/export.h> 11 #include <linux/delay.h> 12 #include <asm/div64.h> 13 #include <asm/timex.h> 14 15 void __delay(unsigned long loops) 16 { 17 /* 18 * Loop 'loops' times. Callers must not assume a specific 19 * amount of time passes before this function returns. 20 */ 21 asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1)); 22 } 23 EXPORT_SYMBOL(__delay); 24 25 static void delay_loop(unsigned long delta) 26 { 27 unsigned long end; 28 29 end = get_tod_clock_monotonic() + delta; 30 while (!tod_after(get_tod_clock_monotonic(), end)) 31 cpu_relax(); 32 } 33 34 void __udelay(unsigned long usecs) 35 { 36 delay_loop(usecs << 12); 37 } 38 EXPORT_SYMBOL(__udelay); 39 40 void __ndelay(unsigned long nsecs) 41 { 42 nsecs <<= 9; 43 do_div(nsecs, 125); 44 delay_loop(nsecs); 45 } 46 EXPORT_SYMBOL(__ndelay); 47