[S390] Convert s390 to GENERIC_CLOCKEVENTS.

This way we get rid of s390's NO_IDLE_HZ and use the generic dynticks
variant instead. In addition we get high resolution timers for free.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

arch/s390/Kconfig

@@ -43,6 +43,9 @@ config GENERIC_HWEIGHT
 config GENERIC_TIME
 	def_bool y
 
+config GENERIC_CLOCKEVENTS
+	def_bool y
+
 config GENERIC_BUG
 	bool
 	depends on BUG
@@ -73,6 +76,8 @@ menu "Base setup"
 
 comment "Processor type and features"
 
+source "kernel/time/Kconfig"
+
 config 64BIT
 	bool "64 bit kernel"
 	help
@@ -487,25 +492,6 @@ config APPLDATA_NET_SUM
 
 source kernel/Kconfig.hz
 
-config NO_IDLE_HZ
-	bool "No HZ timer ticks in idle"
-	help
-	  Switches the regular HZ timer off when the system is going idle.
-	  This helps z/VM to detect that the Linux system is idle. VM can
-	  then "swap-out" this guest which reduces memory usage. It also
-	  reduces the overhead of idle systems.
-
-	  The HZ timer can be switched on/off via /proc/sys/kernel/hz_timer.
-	  hz_timer=0 means HZ timer is disabled. hz_timer=1 means HZ
-	  timer is active.
-
-config NO_IDLE_HZ_INIT
-	bool "HZ timer in idle off by default"
-	depends on NO_IDLE_HZ
-	help
-	  The HZ timer is switched off in idle by default. That means the
-	  HZ timer is already disabled at boot time.
-
 config S390_HYPFS_FS
 	bool "s390 hypervisor file system support"
 	select SYS_HYPERVISOR

arch/s390/kernel/process.c

@@ -36,6 +36,7 @@
 #include <linux/module.h>
 #include <linux/notifier.h>
 #include <linux/utsname.h>
+#include <linux/tick.h>
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
 #include <asm/system.h>
@@ -167,9 +168,10 @@ static void default_idle(void)
 void cpu_idle(void)
 {
 	for (;;) {
+		tick_nohz_stop_sched_tick();
 		while (!need_resched())
 			default_idle();
-
+		tick_nohz_restart_sched_tick();
 		preempt_enable_no_resched();
 		schedule();
 		preempt_disable();

arch/s390/kernel/s390_ext.c

@@ -120,12 +120,9 @@ void do_extint(struct pt_regs *regs, unsigned short code)
 	old_regs = set_irq_regs(regs);
 	irq_enter();
 	s390_idle_check();
-	if (S390_lowcore.int_clock >= S390_lowcore.jiffy_timer)
-		/**
-		 * Make sure that the i/o interrupt did not "overtake"
-		 * the last HZ timer interrupt.
-		 */
-		account_ticks(S390_lowcore.int_clock);
+	if (S390_lowcore.int_clock >= S390_lowcore.clock_comparator)
+		/* Serve timer interrupts first. */
+		clock_comparator_work();
 	kstat_cpu(smp_processor_id()).irqs[EXTERNAL_INTERRUPT]++;
         index = ext_hash(code);
 	for (p = ext_int_hash[index]; p; p = p->next) {

arch/s390/kernel/setup.c

@@ -428,7 +428,7 @@ setup_lowcore(void)
 	lc->io_new_psw.mask = psw_kernel_bits;
 	lc->io_new_psw.addr = PSW_ADDR_AMODE | (unsigned long) io_int_handler;
 	lc->ipl_device = S390_lowcore.ipl_device;
-	lc->jiffy_timer = -1LL;
+	lc->clock_comparator = -1ULL;
 	lc->kernel_stack = ((unsigned long) &init_thread_union) + THREAD_SIZE;
 	lc->async_stack = (unsigned long)
 		__alloc_bootmem(ASYNC_SIZE, ASYNC_SIZE, 0) + ASYNC_SIZE;