| /* |
| * Precise Delay Loops for i386 |
| * |
| * Copyright (C) 1993 Linus Torvalds |
| * Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz> |
| * Copyright (C) 2008 Jiri Hladky <hladky _dot_ jiri _at_ gmail _dot_ com> |
| * |
| * The __delay function must _NOT_ be inlined as its execution time |
| * depends wildly on alignment on many x86 processors. The additional |
| * jump magic is needed to get the timing stable on all the CPU's |
| * we have to worry about. |
| */ |
| |
| #include <linux/module.h> |
| #include <linux/sched.h> |
| #include <linux/timex.h> |
| #include <linux/preempt.h> |
| #include <linux/delay.h> |
| #include <linux/init.h> |
| |
| #include <asm/processor.h> |
| #include <asm/delay.h> |
| #include <asm/timer.h> |
| |
| #ifdef CONFIG_SMP |
| # include <asm/smp.h> |
| #endif |
| |
| /* simple loop based delay: */ |
| static void delay_loop(unsigned long loops) |
| { |
| asm volatile( |
| " test %0,%0 \n" |
| " jz 3f \n" |
| " jmp 1f \n" |
| |
| ".align 16 \n" |
| "1: jmp 2f \n" |
| |
| ".align 16 \n" |
| "2: dec %0 \n" |
| " jnz 2b \n" |
| "3: dec %0 \n" |
| |
| : /* we don't need output */ |
| :"a" (loops) |
| ); |
| } |
| |
| /* TSC based delay: */ |
| static void delay_tsc(unsigned long loops) |
| { |
| unsigned long bclock, now; |
| int cpu; |
| |
| preempt_disable(); |
| cpu = smp_processor_id(); |
| rdtsc_barrier(); |
| rdtscl(bclock); |
| for (;;) { |
| rdtsc_barrier(); |
| rdtscl(now); |
| if ((now - bclock) >= loops) |
| break; |
| |
| /* Allow RT tasks to run */ |
| preempt_enable(); |
| rep_nop(); |
| preempt_disable(); |
| |
| /* |
| * It is possible that we moved to another CPU, and |
| * since TSC's are per-cpu we need to calculate |
| * that. The delay must guarantee that we wait "at |
| * least" the amount of time. Being moved to another |
| * CPU could make the wait longer but we just need to |
| * make sure we waited long enough. Rebalance the |
| * counter for this CPU. |
| */ |
| if (unlikely(cpu != smp_processor_id())) { |
| loops -= (now - bclock); |
| cpu = smp_processor_id(); |
| rdtsc_barrier(); |
| rdtscl(bclock); |
| } |
| } |
| preempt_enable(); |
| } |
| |
| /* |
| * Since we calibrate only once at boot, this |
| * function should be set once at boot and not changed |
| */ |
| static void (*delay_fn)(unsigned long) = delay_loop; |
| |
| void use_tsc_delay(void) |
| { |
| delay_fn = delay_tsc; |
| } |
| |
| int __devinit read_current_timer(unsigned long *timer_val) |
| { |
| if (delay_fn == delay_tsc) { |
| rdtscll(*timer_val); |
| return 0; |
| } |
| return -1; |
| } |
| |
| void __delay(unsigned long loops) |
| { |
| delay_fn(loops); |
| } |
| EXPORT_SYMBOL(__delay); |
| |
| inline void __const_udelay(unsigned long xloops) |
| { |
| int d0; |
| |
| xloops *= 4; |
| asm("mull %%edx" |
| :"=d" (xloops), "=&a" (d0) |
| :"1" (xloops), "0" |
| (this_cpu_read(cpu_info.loops_per_jiffy) * (HZ/4))); |
| |
| __delay(++xloops); |
| } |
| EXPORT_SYMBOL(__const_udelay); |
| |
| void __udelay(unsigned long usecs) |
| { |
| __const_udelay(usecs * 0x000010c7); /* 2**32 / 1000000 (rounded up) */ |
| } |
| EXPORT_SYMBOL(__udelay); |
| |
| void __ndelay(unsigned long nsecs) |
| { |
| __const_udelay(nsecs * 0x00005); /* 2**32 / 1000000000 (rounded up) */ |
| } |
| EXPORT_SYMBOL(__ndelay); |