1 /* 2 * Precise Delay Loops for S390 3 * 4 * Copyright IBM Corp. 1999,2008 5 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>, 6 * Heiko Carstens <heiko.carstens@de.ibm.com>, 7 */ 8 9 #include <linux/sched.h> 10 #include <linux/delay.h> 11 #include <linux/timex.h> 12 #include <linux/irqflags.h> 13 #include <linux/interrupt.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 27 static void __udelay_disabled(unsigned long usecs) 28 { 29 unsigned long mask, cr0, cr0_saved; 30 u64 clock_saved; 31 32 clock_saved = local_tick_disable(); 33 set_clock_comparator(get_clock() + ((u64) usecs << 12)); 34 __ctl_store(cr0_saved, 0, 0); 35 cr0 = (cr0_saved & 0xffff00e0) | 0x00000800; 36 __ctl_load(cr0 , 0, 0); 37 mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT; 38 trace_hardirqs_on(); 39 __load_psw_mask(mask); 40 local_irq_disable(); 41 __ctl_load(cr0_saved, 0, 0); 42 local_tick_enable(clock_saved); 43 set_clock_comparator(S390_lowcore.clock_comparator); 44 } 45 46 static void __udelay_enabled(unsigned long usecs) 47 { 48 unsigned long mask; 49 u64 end, time; 50 51 mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO; 52 end = get_clock() + ((u64) usecs << 12); 53 do { 54 time = end < S390_lowcore.clock_comparator ? 55 end : S390_lowcore.clock_comparator; 56 set_clock_comparator(time); 57 trace_hardirqs_on(); 58 __load_psw_mask(mask); 59 local_irq_disable(); 60 } while (get_clock() < end); 61 set_clock_comparator(S390_lowcore.clock_comparator); 62 } 63 64 /* 65 * Waits for 'usecs' microseconds using the TOD clock comparator. 66 */ 67 void __udelay(unsigned long usecs) 68 { 69 unsigned long flags; 70 71 preempt_disable(); 72 local_irq_save(flags); 73 if (in_irq()) { 74 __udelay_disabled(usecs); 75 goto out; 76 } 77 if (in_softirq()) { 78 if (raw_irqs_disabled_flags(flags)) 79 __udelay_disabled(usecs); 80 else 81 __udelay_enabled(usecs); 82 goto out; 83 } 84 if (raw_irqs_disabled_flags(flags)) { 85 local_bh_disable(); 86 __udelay_disabled(usecs); 87 _local_bh_enable(); 88 goto out; 89 } 90 __udelay_enabled(usecs); 91 out: 92 local_irq_restore(flags); 93 preempt_enable(); 94 } 95 96 /* 97 * Simple udelay variant. To be used on startup and reboot 98 * when the interrupt handler isn't working. 99 */ 100 void udelay_simple(unsigned long usecs) 101 { 102 u64 end; 103 104 end = get_clock() + ((u64) usecs << 12); 105 while (get_clock() < end) 106 cpu_relax(); 107 } 108