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 * Heiko Carstens <heiko.carstens@de.ibm.com>, 8 */ 9 10 #include <linux/processor.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 * To end the bloody studid and useless discussion about the 19 * BogoMips number I took the liberty to define the __delay 20 * function in a way that that resulting BogoMips number will 21 * yield the megahertz number of the cpu. The important function 22 * is udelay and that is done using the tod clock. -- martin. 23 */ 24 asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1)); 25 } 26 EXPORT_SYMBOL(__delay); 27 28 static void delay_loop(unsigned long delta) 29 { 30 unsigned long end; 31 32 end = get_tod_clock_monotonic() + delta; 33 while (!tod_after(get_tod_clock_monotonic(), end)) 34 cpu_relax(); 35 } 36 37 void __udelay(unsigned long usecs) 38 { 39 delay_loop(usecs << 12); 40 } 41 EXPORT_SYMBOL(__udelay); 42 43 void __ndelay(unsigned long nsecs) 44 { 45 nsecs <<= 9; 46 do_div(nsecs, 125); 47 delay_loop(nsecs); 48 } 49 EXPORT_SYMBOL(__ndelay); 50