8c071b0f19
The result of the store-clock-fast (STCKF) instruction is a bit fuzzy. It can happen that the value stored on one CPU is smaller than the value stored on another CPU, although the order of the stores is the other way around. This can cause deltas of get_tod_clock() values to become negative when they should not be. We need to be more careful with store-clock-fast, this patch partially reverts git commit e4b7b4238e666682555461fa52eecd74652f36bb "time: always use stckf instead of stck if available". The get_tod_clock() function now uses the store-clock-extended (STCKE) instruction. get_tod_clock_fast() can be used if the fuzziness of store-clock-fast is acceptable e.g. for wait loops local to a CPU. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
130 lines
2.9 KiB
C
130 lines
2.9 KiB
C
/*
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* Precise Delay Loops for S390
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*
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* Copyright IBM Corp. 1999, 2008
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* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
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* Heiko Carstens <heiko.carstens@de.ibm.com>,
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*/
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#include <linux/sched.h>
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#include <linux/delay.h>
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#include <linux/timex.h>
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#include <linux/module.h>
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#include <linux/irqflags.h>
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#include <linux/interrupt.h>
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#include <asm/vtimer.h>
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#include <asm/div64.h>
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void __delay(unsigned long loops)
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{
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/*
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* To end the bloody studid and useless discussion about the
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* BogoMips number I took the liberty to define the __delay
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* function in a way that that resulting BogoMips number will
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* yield the megahertz number of the cpu. The important function
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* is udelay and that is done using the tod clock. -- martin.
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*/
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asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
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}
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static void __udelay_disabled(unsigned long long usecs)
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{
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unsigned long cr0, cr6, new;
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u64 clock_saved, end;
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end = get_tod_clock() + (usecs << 12);
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clock_saved = local_tick_disable();
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__ctl_store(cr0, 0, 0);
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__ctl_store(cr6, 6, 6);
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new = (cr0 & 0xffff00e0) | 0x00000800;
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__ctl_load(new , 0, 0);
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new = 0;
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__ctl_load(new, 6, 6);
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lockdep_off();
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do {
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set_clock_comparator(end);
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vtime_stop_cpu();
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} while (get_tod_clock_fast() < end);
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lockdep_on();
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__ctl_load(cr0, 0, 0);
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__ctl_load(cr6, 6, 6);
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local_tick_enable(clock_saved);
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}
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static void __udelay_enabled(unsigned long long usecs)
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{
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u64 clock_saved, end;
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end = get_tod_clock_fast() + (usecs << 12);
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do {
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clock_saved = 0;
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if (end < S390_lowcore.clock_comparator) {
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clock_saved = local_tick_disable();
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set_clock_comparator(end);
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}
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vtime_stop_cpu();
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if (clock_saved)
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local_tick_enable(clock_saved);
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} while (get_tod_clock_fast() < end);
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}
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/*
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* Waits for 'usecs' microseconds using the TOD clock comparator.
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*/
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void __udelay(unsigned long long usecs)
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{
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unsigned long flags;
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preempt_disable();
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local_irq_save(flags);
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if (in_irq()) {
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__udelay_disabled(usecs);
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goto out;
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}
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if (in_softirq()) {
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if (raw_irqs_disabled_flags(flags))
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__udelay_disabled(usecs);
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else
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__udelay_enabled(usecs);
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goto out;
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}
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if (raw_irqs_disabled_flags(flags)) {
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local_bh_disable();
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__udelay_disabled(usecs);
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_local_bh_enable();
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goto out;
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}
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__udelay_enabled(usecs);
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out:
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local_irq_restore(flags);
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preempt_enable();
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}
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EXPORT_SYMBOL(__udelay);
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/*
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* Simple udelay variant. To be used on startup and reboot
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* when the interrupt handler isn't working.
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*/
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void udelay_simple(unsigned long long usecs)
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{
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u64 end;
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end = get_tod_clock_fast() + (usecs << 12);
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while (get_tod_clock_fast() < end)
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cpu_relax();
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}
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void __ndelay(unsigned long long nsecs)
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{
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u64 end;
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nsecs <<= 9;
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do_div(nsecs, 125);
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end = get_tod_clock_fast() + nsecs;
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if (nsecs & ~0xfffUL)
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__udelay(nsecs >> 12);
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while (get_tod_clock_fast() < end)
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barrier();
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}
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EXPORT_SYMBOL(__ndelay);
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