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/delay.h> 11 #include <asm/div64.h> 12 #include <asm/timex.h> 13 14 void __delay(unsigned long loops) 15 { 16 /* 17 * To end the bloody studid and useless discussion about the 18 * BogoMips number I took the liberty to define the __delay 19 * function in a way that that resulting BogoMips number will 20 * yield the megahertz number of the cpu. The important function 21 * is udelay and that is done using the tod clock. -- martin. 22 */ 23 asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1)); 24 } 25 EXPORT_SYMBOL(__delay); 26 27 static void delay_loop(unsigned long delta) 28 { 29 unsigned long end; 30 31 end = get_tod_clock_monotonic() + delta; 32 while (!tod_after(get_tod_clock_monotonic(), end)) 33 cpu_relax(); 34 } 35 36 void __udelay(unsigned long usecs) 37 { 38 delay_loop(usecs << 12); 39 } 40 EXPORT_SYMBOL(__udelay); 41 42 void __ndelay(unsigned long nsecs) 43 { 44 nsecs <<= 9; 45 do_div(nsecs, 125); 46 delay_loop(nsecs); 47 } 48 EXPORT_SYMBOL(__ndelay); 49