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Commit d54853ef authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

[S390] ETR support. 



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: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent c1821c2e

arch/s390/kernel/s390_ext.c

+3 −5
Original line number Diff line number Diff line
@@ -125,15 +125,13 @@ void do_extint(struct pt_regs *regs, unsigned short code) 
		 * Make sure that the i/o interrupt did not "overtake"

		 * the last HZ timer interrupt.

		 */

		account_ticks();

		account_ticks(S390_lowcore.int_clock);

	kstat_cpu(smp_processor_id()).irqs[EXTERNAL_INTERRUPT]++;

        index = ext_hash(code);

	for (p = ext_int_hash[index]; p; p = p->next) {

		if (likely(p->code == code)) {

			if (likely(p->handler))

		if (likely(p->code == code))

			p->handler(code);

	}

	}

	irq_exit();

	set_irq_regs(old_regs);

}

arch/s390/kernel/smp.c

+2 −1
Original line number Diff line number Diff line
@@ -457,9 +457,10 @@ int __devinit start_secondary(void *cpuvoid) 
        /* Setup the cpu */

        cpu_init();

	preempt_disable();

        /* init per CPU timer */

	/* Enable TOD clock interrupts on the secondary cpu. */

        init_cpu_timer();

#ifdef CONFIG_VIRT_TIMER

	/* Enable cpu timer interrupts on the secondary cpu. */

        init_cpu_vtimer();

#endif

	/* Enable pfault pseudo page faults on this cpu. */