[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>

4 files changed, 80 insertions, 191 deletions

diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index eb768ce88672..df033249f6b1 100644
--- a/arch/s390/kernel/process.c
+++ b/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();
diff --git a/arch/s390/kernel/s390_ext.c b/arch/s390/kernel/s390_ext.c
index 3a8772d3baea..947d8c74403b 100644
--- a/arch/s390/kernel/s390_ext.c
+++ b/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) {
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 22040d087d8a..7141147e6b63 100644
--- a/arch/s390/kernel/setup.c
+++ b/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;
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 925f9dc0b0a0..17c4de9e1b6b 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -30,7 +30,7 @@
 #include <linux/timex.h>
 #include <linux/notifier.h>
 #include <linux/clocksource.h>
-
+#include <linux/clockchips.h>
 #include <asm/uaccess.h>
 #include <asm/delay.h>
 #include <asm/s390_ext.h>
@@ -57,9 +57,9 @@
 
 static ext_int_info_t ext_int_info_cc;
 static ext_int_info_t ext_int_etr_cc;
-static u64 init_timer_cc;
 static u64 jiffies_timer_cc;
-static u64 xtime_cc;
+
+static DEFINE_PER_CPU(struct clock_event_device, comparators);
 
 /*
  * Scheduler clock - returns current time in nanosec units.
@@ -95,162 +95,40 @@ void tod_to_timeval(__u64 todval, struct timespec *xtime)
 #define s390_do_profile()       do { ; } while(0)
 #endif /* CONFIG_PROFILING */
 
-/*
- * Advance the per cpu tick counter up to the time given with the
- * "time" argument. The per cpu update consists of accounting
- * the virtual cpu time, calling update_process_times and calling
- * the profiling hook. If xtime is before time it is advanced as well.
- */
-void account_ticks(u64 time)
+void clock_comparator_work(void)
 {
-        __u32 ticks;
-        __u64 tmp;
-
-        /* Calculate how many ticks have passed. */
-        if (time < S390_lowcore.jiffy_timer)
-                return;
-        tmp = time - S390_lowcore.jiffy_timer;
-        if (tmp >= 2*CLK_TICKS_PER_JIFFY) {  /* more than two ticks ? */
-                ticks = __div(tmp, CLK_TICKS_PER_JIFFY) + 1;
-                S390_lowcore.jiffy_timer +=
-                        CLK_TICKS_PER_JIFFY * (__u64) ticks;
-        } else if (tmp >= CLK_TICKS_PER_JIFFY) {
-                ticks = 2;
-                S390_lowcore.jiffy_timer += 2*CLK_TICKS_PER_JIFFY;
-        } else {
-                ticks = 1;
-                S390_lowcore.jiffy_timer += CLK_TICKS_PER_JIFFY;
-        }
-
-#ifdef CONFIG_SMP
-        /*
-         * Do not rely on the boot cpu to do the calls to do_timer.
-         * Spread it over all cpus instead.
-         */
-        write_seqlock(&xtime_lock);
-        if (S390_lowcore.jiffy_timer > xtime_cc) {
-                __u32 xticks;
-                tmp = S390_lowcore.jiffy_timer - xtime_cc;
-                if (tmp >= 2*CLK_TICKS_PER_JIFFY) {
-                        xticks = __div(tmp, CLK_TICKS_PER_JIFFY);
-                        xtime_cc += (__u64) xticks * CLK_TICKS_PER_JIFFY;
-                } else {
-                        xticks = 1;
-                        xtime_cc += CLK_TICKS_PER_JIFFY;
-                }
-                do_timer(xticks);
-        }
-        write_sequnlock(&xtime_lock);
-#else
-        do_timer(ticks);
-#endif
-
-        while (ticks--)
-                update_process_times(user_mode(get_irq_regs()));
+        struct clock_event_device *cd;
 
+        S390_lowcore.clock_comparator = -1ULL;
+        set_clock_comparator(S390_lowcore.clock_comparator);
+        cd = &__get_cpu_var(comparators);
+        cd->event_handler(cd);
         s390_do_profile();
 }
 
-#ifdef CONFIG_NO_IDLE_HZ
-
-#ifdef CONFIG_NO_IDLE_HZ_INIT
-int sysctl_hz_timer = 0;
-#else
-int sysctl_hz_timer = 1;
-#endif
-
-/*
- * Stop the HZ tick on the current CPU.
- * Only cpu_idle may call this function.
- */
-static void stop_hz_timer(void)
-{
-        unsigned long flags;
-        unsigned long seq, next;
-        __u64 timer, todval;
-        int cpu = smp_processor_id();
-
-        if (sysctl_hz_timer != 0)
-                return;
-
-        cpu_set(cpu, nohz_cpu_mask);
-
-        /*
-         * Leave the clock comparator set up for the next timer
-         * tick if either rcu or a softirq is pending.
-         */
-        if (rcu_needs_cpu(cpu) || local_softirq_pending()) {
-                cpu_clear(cpu, nohz_cpu_mask);
-                return;
-        }
-
-        /*
-         * This cpu is going really idle. Set up the clock comparator
-         * for the next event.
-         */
-        next = next_timer_interrupt();
-        do {
-                seq = read_seqbegin_irqsave(&xtime_lock, flags);
-                timer = ((__u64) next) - ((__u64) jiffies) + jiffies_64;
-        } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
-        todval = -1ULL;
-        /* Be careful about overflows. */
-        if (timer < (-1ULL / CLK_TICKS_PER_JIFFY)) {
-                timer = jiffies_timer_cc + timer * CLK_TICKS_PER_JIFFY;
-                if (timer >= jiffies_timer_cc)
-                        todval = timer;
-        }
-        set_clock_comparator(todval);
-}
-
 /*
- * Start the HZ tick on the current CPU.
- * Only cpu_idle may call this function.
+ * Fixup the clock comparator.
  */
-static void start_hz_timer(void)
+static void fixup_clock_comparator(unsigned long long delta)
 {
-        if (!cpu_isset(smp_processor_id(), nohz_cpu_mask))
+        /* If nobody is waiting there's nothing to fix. */
+        if (S390_lowcore.clock_comparator == -1ULL)
                 return;
-        account_ticks(get_clock());
-        set_clock_comparator(S390_lowcore.jiffy_timer + CPU_DEVIATION);
-        cpu_clear(smp_processor_id(), nohz_cpu_mask);
-}
-
-static int nohz_idle_notify(struct notifier_block *self,
-                            unsigned long action, void *hcpu)
-{
-        switch (action) {
-        case S390_CPU_IDLE:
-                stop_hz_timer();
-                break;
-        case S390_CPU_NOT_IDLE:
-                start_hz_timer();
-                break;
-        }
-        return NOTIFY_OK;
+        S390_lowcore.clock_comparator += delta;
+        set_clock_comparator(S390_lowcore.clock_comparator);
 }
 
-static struct notifier_block nohz_idle_nb = {
-        .notifier_call = nohz_idle_notify,
-};
-
-static void __init nohz_init(void)
+static int s390_next_event(unsigned long delta,
+                           struct clock_event_device *evt)
 {
-        if (register_idle_notifier(&nohz_idle_nb))
-                panic("Couldn't register idle notifier");
+        S390_lowcore.clock_comparator = get_clock() + delta;
+        set_clock_comparator(S390_lowcore.clock_comparator);
+        return 0;
 }
 
-#endif
-
-/*
- * Set up per cpu jiffy timer and set the clock comparator.
- */
-static void setup_jiffy_timer(void)
+static void s390_set_mode(enum clock_event_mode mode,
+                          struct clock_event_device *evt)
 {
-        /* Set up clock comparator to next jiffy. */
-        S390_lowcore.jiffy_timer =
-                jiffies_timer_cc + (jiffies_64 + 1) * CLK_TICKS_PER_JIFFY;
-        set_clock_comparator(S390_lowcore.jiffy_timer + CPU_DEVIATION);
 }
 
 /*
@@ -259,7 +137,26 @@ static void setup_jiffy_timer(void)
  */
 void init_cpu_timer(void)
 {
-        setup_jiffy_timer();
+        struct clock_event_device *cd;
+        int cpu;
+
+        S390_lowcore.clock_comparator = -1ULL;
+        set_clock_comparator(S390_lowcore.clock_comparator);
+
+        cpu = smp_processor_id();
+        cd = &per_cpu(comparators, cpu);
+        cd->name                = "comparator";
+        cd->features            = CLOCK_EVT_FEAT_ONESHOT;
+        cd->mult                = 16777;
+        cd->shift               = 12;
+        cd->min_delta_ns        = 1;
+        cd->max_delta_ns        = LONG_MAX;
+        cd->rating              = 400;
+        cd->cpumask             = cpumask_of_cpu(cpu);
+        cd->set_next_event      = s390_next_event;
+        cd->set_mode            = s390_set_mode;
+
+        clockevents_register_device(cd);
 
         /* Enable clock comparator timer interrupt. */
         __ctl_set_bit(0,11);
@@ -270,8 +167,6 @@ void init_cpu_timer(void)
 
 static void clock_comparator_interrupt(__u16 code)
 {
-        /* set clock comparator for next tick */
-        set_clock_comparator(S390_lowcore.jiffy_timer + CPU_DEVIATION);
 }
 
 static void etr_reset(void);
@@ -316,8 +211,9 @@ static struct clocksource clocksource_tod = {
  */
 void __init time_init(void)
 {
+        u64 init_timer_cc;
+
         init_timer_cc = reset_tod_clock();
-        xtime_cc = init_timer_cc + CLK_TICKS_PER_JIFFY;
         jiffies_timer_cc = init_timer_cc - jiffies_64 * CLK_TICKS_PER_JIFFY;
 
         /* set xtime */
@@ -342,10 +238,6 @@ void __init time_init(void)
         /* Enable TOD clock interrupts on the boot cpu. */
         init_cpu_timer();
 
-#ifdef CONFIG_NO_IDLE_HZ
-        nohz_init();
-#endif
-
 #ifdef CONFIG_VIRT_TIMER
         vtime_init();
 #endif
@@ -699,53 +591,49 @@ static int etr_aib_follows(struct etr_aib *a1, struct etr_aib *a2, int p)
 }
 
 /*
- * The time is "clock". xtime is what we think the time is.
+ * The time is "clock". old is what we think the time is.
  * Adjust the value by a multiple of jiffies and add the delta to ntp.
  * "delay" is an approximation how long the synchronization took. If
  * the time correction is positive, then "delay" is subtracted from
  * the time difference and only the remaining part is passed to ntp.
  */
-static void etr_adjust_time(unsigned long long clock, unsigned long long delay)
+static unsigned long long etr_adjust_time(unsigned long long old,
+                                          unsigned long long clock,
+                                          unsigned long long delay)
 {
         unsigned long long delta, ticks;
         struct timex adjust;
 
-        /*
-         * We don't have to take the xtime lock because the cpu
-         * executing etr_adjust_time is running disabled in
-         * tasklet context and all other cpus are looping in
-         * etr_sync_cpu_start.
-         */
-        if (clock > xtime_cc) {
+        if (clock > old) {
                 /* It is later than we thought. */
-                delta = ticks = clock - xtime_cc;
+                delta = ticks = clock - old;
                 delta = ticks = (delta < delay) ? 0 : delta - delay;
                 delta -= do_div(ticks, CLK_TICKS_PER_JIFFY);
-                init_timer_cc = init_timer_cc + delta;
-                jiffies_timer_cc = jiffies_timer_cc + delta;
-                xtime_cc = xtime_cc + delta;
                 adjust.offset = ticks * (1000000 / HZ);
         } else {
                 /* It is earlier than we thought. */
-                delta = ticks = xtime_cc - clock;
+                delta = ticks = old - clock;
                 delta -= do_div(ticks, CLK_TICKS_PER_JIFFY);
-                init_timer_cc = init_timer_cc - delta;
-                jiffies_timer_cc = jiffies_timer_cc - delta;
-                xtime_cc = xtime_cc - delta;
+                delta = -delta;
                 adjust.offset = -ticks * (1000000 / HZ);
         }
+        jiffies_timer_cc += delta;
         if (adjust.offset != 0) {
                 printk(KERN_NOTICE "etr: time adjusted by %li micro-seconds\n",
                        adjust.offset);
                 adjust.modes = ADJ_OFFSET_SINGLESHOT;
                 do_adjtimex(&adjust);
         }
+        return delta;
 }
 
+static struct {
+        int in_sync;
+        unsigned long long fixup_cc;
+} etr_sync;
+
 static void etr_sync_cpu_start(void *dummy)
 {
-        int *in_sync = dummy;
-
         etr_enable_sync_clock();
         /*
          * This looks like a busy wait loop but it isn't. etr_sync_cpus
@@ -753,7 +641,7 @@ static void etr_sync_cpu_start(void *dummy)
          * __udelay will stop the cpu on an enabled wait psw until the
          * TOD is running again.
          */
-        while (*in_sync == 0) {
+        while (etr_sync.in_sync == 0) {
                 __udelay(1);
                 /*
                  * A different cpu changes *in_sync. Therefore use
@@ -761,14 +649,14 @@ static void etr_sync_cpu_start(void *dummy)
                  */
                 barrier();
         }
-        if (*in_sync != 1)
+        if (etr_sync.in_sync != 1)
                 /* Didn't work. Clear per-cpu in sync bit again. */
                 etr_disable_sync_clock(NULL);
         /*
          * This round of TOD syncing is done. Set the clock comparator
          * to the next tick and let the processor continue.
          */
-        setup_jiffy_timer();
+        fixup_clock_comparator(etr_sync.fixup_cc);
 }
 
 static void etr_sync_cpu_end(void *dummy)
@@ -783,8 +671,8 @@ static void etr_sync_cpu_end(void *dummy)
 static int etr_sync_clock(struct etr_aib *aib, int port)
 {
         struct etr_aib *sync_port;
-        unsigned long long clock, delay;
-        int in_sync, follows;
+        unsigned long long clock, old_clock, delay, delta;
+        int follows;
         int rc;
 
         /* Check if the current aib is adjacent to the sync port aib. */
@@ -799,9 +687,9 @@ static int etr_sync_clock(struct etr_aib *aib, int port)
          * successfully synced the clock. smp_call_function will
          * return after all other cpus are in etr_sync_cpu_start.
          */
-        in_sync = 0;
+        memset(&etr_sync, 0, sizeof(etr_sync));
         preempt_disable();
-        smp_call_function(etr_sync_cpu_start,&in_sync,0,0);
+        smp_call_function(etr_sync_cpu_start, NULL, 0, 0);
         local_irq_disable();
         etr_enable_sync_clock();
 
@@ -809,6 +697,7 @@ static int etr_sync_clock(struct etr_aib *aib, int port)
         __ctl_set_bit(14, 21);
         __ctl_set_bit(0, 29);
         clock = ((unsigned long long) (aib->edf2.etv + 1)) << 32;
+        old_clock = get_clock();
         if (set_clock(clock) == 0) {
                 __udelay(1);    /* Wait for the clock to start. */
                 __ctl_clear_bit(0, 29);
@@ -817,16 +706,17 @@ static int etr_sync_clock(struct etr_aib *aib, int port)
                 /* Adjust Linux timing variables. */
                 delay = (unsigned long long)
                         (aib->edf2.etv - sync_port->edf2.etv) << 32;
-                etr_adjust_time(clock, delay);
-                setup_jiffy_timer();
+                delta = etr_adjust_time(old_clock, clock, delay);
+                etr_sync.fixup_cc = delta;
+                fixup_clock_comparator(delta);
                 /* Verify that the clock is properly set. */
                 if (!etr_aib_follows(sync_port, aib, port)) {
                         /* Didn't work. */
                         etr_disable_sync_clock(NULL);
-                        in_sync = -EAGAIN;
+                        etr_sync.in_sync = -EAGAIN;
                         rc = -EAGAIN;
                 } else {
-                        in_sync = 1;
+                        etr_sync.in_sync = 1;
                         rc = 0;
                 }
         } else {
@@ -834,7 +724,7 @@ static int etr_sync_clock(struct etr_aib *aib, int port)
                 __ctl_clear_bit(0, 29);
                 __ctl_clear_bit(14, 21);
                 etr_disable_sync_clock(NULL);
-                in_sync = -EAGAIN;
+                etr_sync.in_sync = -EAGAIN;
                 rc = -EAGAIN;
         }
         local_irq_enable();