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[S390] ETR support.

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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>
This commit is contained in:
Martin Schwidefsky 2007-02-05 21:18:19 +01:00
parent c1821c2e97
commit d54853ef8c
13 changed files with 1488 additions and 109 deletions
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48
arch/s390/lib/delay.c
View file

@ -1,5 +1,5 @@
/*
* arch/s390/kernel/delay.c
* arch/s390/lib/delay.c
* Precise Delay Loops for S390
*
* S390 version
@ -13,10 +13,8 @@
#include <linux/sched.h>
#include <linux/delay.h>
#ifdef CONFIG_SMP
#include <asm/smp.h>
#endif
#include <linux/timex.h>
#include <linux/irqflags.h>
void __delay(unsigned long loops)
{
@ -31,17 +29,39 @@ void __delay(unsigned long loops)
}
/*
* Waits for 'usecs' microseconds using the tod clock, giving up the time slice
* of the virtual PU inbetween to avoid congestion.
* Waits for 'usecs' microseconds using the TOD clock comparator.
*/
void __udelay(unsigned long usecs)
{
uint64_t start_cc;
u64 end, time, jiffy_timer = 0;
unsigned long flags, cr0, mask, dummy;
if (usecs == 0)
return;
start_cc = get_clock();
do {
cpu_relax();
} while (((get_clock() - start_cc)/4096) < usecs);
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);
}