d54853ef8c
This patch adds support for clock synchronization to an external time reference (ETR). The external time reference sends an oscillator signal and a synchronization signal every 2^20 microseconds to keep the TOD clocks of all connected servers in sync. For availability two ETR units can be connected to a machine. If the clock deviates for more than the sync-check tolerance all cpus get a machine check that indicates that the clock is out of sync. For the lovely details how to get the clock back in sync see the code below. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
67 lines
1.9 KiB
C
67 lines
1.9 KiB
C
/*
|
|
* arch/s390/lib/delay.c
|
|
* Precise Delay Loops for S390
|
|
*
|
|
* S390 version
|
|
* Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
|
|
* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
|
|
*
|
|
* Derived from "arch/i386/lib/delay.c"
|
|
* Copyright (C) 1993 Linus Torvalds
|
|
* Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
|
|
*/
|
|
|
|
#include <linux/sched.h>
|
|
#include <linux/delay.h>
|
|
#include <linux/timex.h>
|
|
#include <linux/irqflags.h>
|
|
|
|
void __delay(unsigned long loops)
|
|
{
|
|
/*
|
|
* To end the bloody studid and useless discussion about the
|
|
* BogoMips number I took the liberty to define the __delay
|
|
* function in a way that that resulting BogoMips number will
|
|
* yield the megahertz number of the cpu. The important function
|
|
* is udelay and that is done using the tod clock. -- martin.
|
|
*/
|
|
asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
|
|
}
|
|
|
|
/*
|
|
* Waits for 'usecs' microseconds using the TOD clock comparator.
|
|
*/
|
|
void __udelay(unsigned long usecs)
|
|
{
|
|
u64 end, time, jiffy_timer = 0;
|
|
unsigned long flags, cr0, mask, dummy;
|
|
|
|
local_irq_save(flags);
|
|
if (raw_irqs_disabled_flags(flags)) {
|
|
jiffy_timer = S390_lowcore.jiffy_timer;
|
|
S390_lowcore.jiffy_timer = -1ULL - (4096 << 12);
|
|
__ctl_store(cr0, 0, 0);
|
|
dummy = (cr0 & 0xffff00e0) | 0x00000800;
|
|
__ctl_load(dummy , 0, 0);
|
|
mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
|
|
} else
|
|
mask = psw_kernel_bits | PSW_MASK_WAIT |
|
|
PSW_MASK_EXT | PSW_MASK_IO;
|
|
|
|
end = get_clock() + ((u64) usecs << 12);
|
|
do {
|
|
time = end < S390_lowcore.jiffy_timer ?
|
|
end : S390_lowcore.jiffy_timer;
|
|
set_clock_comparator(time);
|
|
trace_hardirqs_on();
|
|
__load_psw_mask(mask);
|
|
local_irq_disable();
|
|
} while (get_clock() < end);
|
|
|
|
if (raw_irqs_disabled_flags(flags)) {
|
|
__ctl_load(cr0, 0, 0);
|
|
S390_lowcore.jiffy_timer = jiffy_timer;
|
|
}
|
|
set_clock_comparator(S390_lowcore.jiffy_timer);
|
|
local_irq_restore(flags);
|
|
}
|