[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;

arch/s390/lib/delay.c

@@ -34,7 +34,7 @@ void __delay(unsigned long loops)
  */
 void __udelay(unsigned long usecs)
 {
-	u64 end, time, jiffy_timer = 0;
+	u64 end, time, old_cc = 0;
 	unsigned long flags, cr0, mask, dummy;
 	int irq_context;
 
@@ -43,8 +43,8 @@ void __udelay(unsigned long usecs)
 		local_bh_disable();
 	local_irq_save(flags);
 	if (raw_irqs_disabled_flags(flags)) {
-		jiffy_timer = S390_lowcore.jiffy_timer;
-		S390_lowcore.jiffy_timer = -1ULL - (4096 << 12);
+		old_cc = S390_lowcore.clock_comparator;
+		S390_lowcore.clock_comparator = -1ULL;
 		__ctl_store(cr0, 0, 0);
 		dummy = (cr0 & 0xffff00e0) | 0x00000800;
 		__ctl_load(dummy , 0, 0);
@@ -55,8 +55,8 @@ void __udelay(unsigned long usecs)
 
 	end = get_clock() + ((u64) usecs << 12);
 	do {
-		time = end < S390_lowcore.jiffy_timer ?
-			end : S390_lowcore.jiffy_timer;
+		time = end < S390_lowcore.clock_comparator ?
+			end : S390_lowcore.clock_comparator;
 		set_clock_comparator(time);
 		trace_hardirqs_on();
 		__load_psw_mask(mask);
@@ -65,10 +65,10 @@ void __udelay(unsigned long usecs)
 
 	if (raw_irqs_disabled_flags(flags)) {
 		__ctl_load(cr0, 0, 0);
-		S390_lowcore.jiffy_timer = jiffy_timer;
+		S390_lowcore.clock_comparator = old_cc;
 	}
 	if (!irq_context)
 		_local_bh_enable();
-	set_clock_comparator(S390_lowcore.jiffy_timer);
+	set_clock_comparator(S390_lowcore.clock_comparator);
 	local_irq_restore(flags);
 }

drivers/s390/cio/cio.c

@@ -651,12 +651,9 @@ do_IRQ (struct pt_regs *regs)
 	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();
 	/*
 	 * Get interrupt information from lowcore
 	 */

include/asm-s390/hardirq.h

@@ -32,6 +32,6 @@ typedef struct {
 
 #define HARDIRQ_BITS	8
 
-extern void account_ticks(u64 time);
+void clock_comparator_work(void);
 
 #endif /* __ASM_HARDIRQ_H */

include/asm-s390/lowcore.h

@@ -80,7 +80,6 @@
 #define __LC_CPUID                      0xC60
 #define __LC_CPUADDR                    0xC68
 #define __LC_IPLDEV                     0xC7C
-#define __LC_JIFFY_TIMER		0xC80
 #define __LC_CURRENT			0xC90
 #define __LC_INT_CLOCK			0xC98
 #else /* __s390x__ */
@@ -103,7 +102,6 @@
 #define __LC_CPUID			0xD80
 #define __LC_CPUADDR			0xD88
 #define __LC_IPLDEV                     0xDB8
-#define __LC_JIFFY_TIMER		0xDC0
 #define __LC_CURRENT			0xDD8
 #define __LC_INT_CLOCK			0xDE8
 #endif /* __s390x__ */
@@ -276,7 +274,7 @@ struct _lowcore
 	/* entry.S sensitive area end */
 
         /* SMP info area: defined by DJB */
-        __u64        jiffy_timer;              /* 0xc80 */
+	__u64	     clock_comparator;	       /* 0xc80 */
 	__u32        ext_call_fast;            /* 0xc88 */
 	__u32        percpu_offset;            /* 0xc8c */
 	__u32        current_task;	       /* 0xc90 */
@@ -368,7 +366,7 @@ struct _lowcore
 	/* entry.S sensitive area end */
 
         /* SMP info area: defined by DJB */
-        __u64        jiffy_timer;              /* 0xdc0 */
+	__u64	     clock_comparator;	       /* 0xdc0 */
 	__u64        ext_call_fast;            /* 0xdc8 */
 	__u64        percpu_offset;            /* 0xdd0 */
 	__u64        current_task;	       /* 0xdd8 */