[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: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/lib/delay.c b/arch/s390/lib/delay.c
index 027c474..0285444 100644
--- a/arch/s390/lib/delay.c
+++ b/arch/s390/lib/delay.c
@@ -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 @@
}
/*
- * 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);
}