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. */

arch/s390/kernel/time.c

+1117 −62

File changed.

Preview size limit exceeded, changes collapsed.

arch/s390/kernel/vtime.c

+4 −4
Original line number Diff line number Diff line
@@ -524,16 +524,15 @@ EXPORT_SYMBOL(del_virt_timer); 
void init_cpu_vtimer(void)

{

	struct vtimer_queue *vt_list;

	unsigned long cr0;



	/* kick the virtual timer */

	S390_lowcore.exit_timer = VTIMER_MAX_SLICE;

	S390_lowcore.last_update_timer = VTIMER_MAX_SLICE;

	asm volatile ("SPT %0" : : "m" (S390_lowcore.last_update_timer));

	asm volatile ("STCK %0" : "=m" (S390_lowcore.last_update_clock));

	__ctl_store(cr0, 0, 0);

	cr0 |= 0x400;

	__ctl_load(cr0, 0, 0);



	/* enable cpu timer interrupts */

	__ctl_set_bit(0,10);



	vt_list = &per_cpu(virt_cpu_timer, smp_processor_id());

	INIT_LIST_HEAD(&vt_list->list);
@@ -572,6 +571,7 @@ void __init vtime_init(void) 
	if (register_idle_notifier(&vtimer_idle_nb))

		panic("Couldn't register idle notifier");



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

	init_cpu_vtimer();

}

arch/s390/lib/delay.c

+34 −14
Original line number Diff line number Diff line 
/*

 *  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;



	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;



        if (usecs == 0)

                return;

	start_cc = get_clock();

	end = get_clock() + ((u64) usecs << 12);

	do {

		cpu_relax();

	} while (((get_clock() - start_cc)/4096) < usecs);

		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);

}

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