[MIPS] Implement clockevents for R4000-style cp0 count/compare interrupt

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

4 files changed, 124 insertions, 139 deletions

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index aadd2cd5778c..f99bb4085430 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -11,6 +11,7 @@
 #include <linux/errno.h>
 #include <linux/module.h>
 #include <linux/sched.h>
+#include <linux/tick.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/stddef.h>
@@ -52,6 +53,7 @@ void __noreturn cpu_idle(void)
 {
         /* endless idle loop with no priority at all */
         while (1) {
+                tick_nohz_stop_sched_tick();
                 while (!need_resched()) {
 #ifdef CONFIG_SMTC_IDLE_HOOK_DEBUG
                         extern void smtc_idle_loop_hook(void);
@@ -61,6 +63,7 @@ void __noreturn cpu_idle(void)
                         if (cpu_wait)
                                 (*cpu_wait)();
                 }
+                tick_nohz_restart_sched_tick();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index 73b0dab02668..500a7ec2880f 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -38,6 +38,7 @@
 #include <asm/system.h>
 #include <asm/mmu_context.h>
 #include <asm/smp.h>
+#include <asm/time.h>
 
 #ifdef CONFIG_MIPS_MT_SMTC
 #include <asm/mipsmtregs.h>
@@ -70,6 +71,7 @@ asmlinkage __cpuinit void start_secondary(void)
         cpu_probe();
         cpu_report();
         per_cpu_trap_init();
+        mips_clockevent_init();
         prom_init_secondary();
 
         /*
diff --git a/arch/mips/kernel/smtc.c b/arch/mips/kernel/smtc.c
index a7afbf2c9710..137183bba54f 100644
--- a/arch/mips/kernel/smtc.c
+++ b/arch/mips/kernel/smtc.c
@@ -867,7 +867,7 @@ void ipi_decode(struct smtc_ipi *pipi)
 #ifdef CONFIG_SMTC_IDLE_HOOK_DEBUG
                 clock_hang_reported[dest_copy] = 0;
 #endif /* CONFIG_SMTC_IDLE_HOOK_DEBUG */
-                local_timer_interrupt(0);
+                local_timer_interrupt(0, NULL);
                 irq_exit();
                 break;
         case LINUX_SMP_IPI:
diff --git a/arch/mips/kernel/time.c b/arch/mips/kernel/time.c
index d23e6825e988..35988847c98a 100644
--- a/arch/mips/kernel/time.c
+++ b/arch/mips/kernel/time.c
@@ -11,6 +11,7 @@
  * Free Software Foundation;  either version 2 of the  License, or (at your
  * option) any later version.
  */
+#include <linux/clockchips.h>
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
@@ -34,6 +35,8 @@
 #include <asm/sections.h>
 #include <asm/time.h>
 
+#include <irq.h>
+
 /*
  * The integer part of the number of usecs per jiffy is taken from tick,
  * but the fractional part is not recorded, so we calculate it using the
@@ -70,10 +73,6 @@ int update_persistent_clock(struct timespec now)
 /* how many counter cycles in a jiffy */
 static unsigned long cycles_per_jiffy __read_mostly;
 
-/* expirelo is the count value for next CPU timer interrupt */
-static unsigned int expirelo;
-
-
 /*
  * Null timer ack for systems not needing one (e.g. i8254).
  */
@@ -92,18 +91,7 @@ static cycle_t null_hpt_read(void)
  */
 static void c0_timer_ack(void)
 {
-        unsigned int count;
-
-        /* Ack this timer interrupt and set the next one.  */
-        expirelo += cycles_per_jiffy;
-        write_c0_compare(expirelo);
-
-        /* Check to see if we have missed any timer interrupts.  */
-        while (((count = read_c0_count()) - expirelo) < 0x7fffffff) {
-                /* missed_timer_count++; */
-                expirelo = count + cycles_per_jiffy;
-                write_c0_compare(expirelo);
-        }
+        write_c0_compare(read_c0_compare());
 }
 
 /*
@@ -114,13 +102,6 @@ static cycle_t c0_hpt_read(void)
         return read_c0_count();
 }
 
-/* For use both as a high precision timer and an interrupt source.  */
-static void __init c0_hpt_timer_init(void)
-{
-        expirelo = read_c0_count() + cycles_per_jiffy;
-        write_c0_compare(expirelo);
-}
-
 int (*mips_timer_state)(void);
 void (*mips_timer_ack)(void);
 
@@ -140,35 +121,6 @@ void local_timer_interrupt(int irq, void *dev_id)
         update_process_times(user_mode(get_irq_regs()));
 }
 
-/*
- * High-level timer interrupt service routines.  This function
- * is set as irqaction->handler and is invoked through do_IRQ.
- */
-static irqreturn_t timer_interrupt(int irq, void *dev_id)
-{
-        write_seqlock(&xtime_lock);
-
-        mips_timer_ack();
-
-        /*
-         * call the generic timer interrupt handling
-         */
-        do_timer(1);
-
-        write_sequnlock(&xtime_lock);
-
-        /*
-         * In UP mode, we call local_timer_interrupt() to do profiling
-         * and process accouting.
-         *
-         * In SMP mode, local_timer_interrupt() is invoked by appropriate
-         * low-level local timer interrupt handler.
-         */
-        local_timer_interrupt(irq, dev_id);
-
-        return IRQ_HANDLED;
-}
-
 int null_perf_irq(void)
 {
         return 0;
@@ -209,81 +161,6 @@ static inline int handle_perf_irq (int r2)
                 !r2;
 }
 
-void ll_timer_interrupt(int irq, void *dev_id)
-{
-        int cpu = smp_processor_id();
-
-#ifdef CONFIG_MIPS_MT_SMTC
-        /*
-         *  In an SMTC system, one Count/Compare set exists per VPE.
-         *  Which TC within a VPE gets the interrupt is essentially
-         *  random - we only know that it shouldn't be one with
-         *  IXMT set. Whichever TC gets the interrupt needs to
-         *  send special interprocessor interrupts to the other
-         *  TCs to make sure that they schedule, etc.
-         *
-         *  That code is specific to the SMTC kernel, not to
-         *  the a particular platform, so it's invoked from
-         *  the general MIPS timer_interrupt routine.
-         */
-
-        /*
-         * We could be here due to timer interrupt,
-         * perf counter overflow, or both.
-         */
-        (void) handle_perf_irq(1);
-
-        if (read_c0_cause() & (1 << 30)) {
-                /*
-                 * There are things we only want to do once per tick
-                 * in an "MP" system.   One TC of each VPE will take
-                 * the actual timer interrupt.  The others will get
-                 * timer broadcast IPIs. We use whoever it is that takes
-                 * the tick on VPE 0 to run the full timer_interrupt().
-                 */
-                if (cpu_data[cpu].vpe_id == 0) {
-                        timer_interrupt(irq, NULL);
-                } else {
-                        write_c0_compare(read_c0_count() +
-                                         (mips_hpt_frequency/HZ));
-                        local_timer_interrupt(irq, dev_id);
-                }
-                smtc_timer_broadcast(cpu_data[cpu].vpe_id);
-        }
-#else /* CONFIG_MIPS_MT_SMTC */
-        int r2 = cpu_has_mips_r2;
-
-        if (handle_perf_irq(r2))
-                return;
-
-        if (r2 && ((read_c0_cause() & (1 << 30)) == 0))
-                return;
-
-        if (cpu == 0) {
-                /*
-                 * CPU 0 handles the global timer interrupt job and process
-                 * accounting resets count/compare registers to trigger next
-                 * timer int.
-                 */
-                timer_interrupt(irq, NULL);
-        } else {
-                /* Everyone else needs to reset the timer int here as
-                   ll_local_timer_interrupt doesn't */
-                /*
-                 * FIXME: need to cope with counter underflow.
-                 * More support needs to be added to kernel/time for
-                 * counter/timer interrupts on multiple CPU's
-                 */
-                write_c0_compare(read_c0_count() + (mips_hpt_frequency/HZ));
-
-                /*
-                 * Other CPUs should do profiling and process accounting
-                 */
-                local_timer_interrupt(irq, dev_id);
-        }
-#endif /* CONFIG_MIPS_MT_SMTC */
-}
-
 /*
  * time_init() - it does the following things.
  *
@@ -301,12 +178,6 @@ void ll_timer_interrupt(int irq, void *dev_id)
 
 unsigned int mips_hpt_frequency;
 
-static struct irqaction timer_irqaction = {
-        .handler = timer_interrupt,
-        .flags = IRQF_DISABLED | IRQF_PERCPU,
-        .name = "timer",
-};
-
 static unsigned int __init calibrate_hpt(void)
 {
         cycle_t frequency, hpt_start, hpt_end, hpt_count, hz;
@@ -355,6 +226,65 @@ struct clocksource clocksource_mips = {
         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
+static int mips_next_event(unsigned long delta,
+                           struct clock_event_device *evt)
+{
+        unsigned int cnt;
+
+        cnt = read_c0_count();
+        cnt += delta;
+        write_c0_compare(cnt);
+
+        return ((long)(read_c0_count() - cnt ) > 0) ? -ETIME : 0;
+}
+
+static void mips_set_mode(enum clock_event_mode mode,
+                          struct clock_event_device *evt)
+{
+        /* Nothing to do ...  */
+}
+
+struct clock_event_device mips_clockevent;
+
+static struct clock_event_device *global_cd[NR_CPUS];
+static int cp0_timer_irq_installed;
+
+static irqreturn_t timer_interrupt(int irq, void *dev_id)
+{
+        const int r2 = cpu_has_mips_r2;
+        struct clock_event_device *cd;
+        int cpu = smp_processor_id();
+
+        /*
+         * Suckage alert:
+         * Before R2 of the architecture there was no way to see if a
+         * performance counter interrupt was pending, so we have to run
+         * the performance counter interrupt handler anyway.
+         */
+        if (handle_perf_irq(r2))
+                goto out;
+
+        /*
+         * The same applies to performance counter interrupts.  But with the
+         * above we now know that the reason we got here must be a timer
+         * interrupt.  Being the paranoiacs we are we check anyway.
+         */
+        if (!r2 || (read_c0_cause() & (1 << 30))) {
+                c0_timer_ack();
+                cd = global_cd[cpu];
+                cd->event_handler(cd);
+        }
+
+out:
+        return IRQ_HANDLED;
+}
+
+static struct irqaction timer_irqaction = {
+        .handler = timer_interrupt,
+        .flags = IRQF_DISABLED | IRQF_PERCPU,
+        .name = "timer",
+};
+
 static void __init init_mips_clocksource(void)
 {
         u64 temp;
@@ -382,6 +312,56 @@ void __init __weak plat_time_init(void)
 {
 }
 
+void __init __weak plat_timer_setup(struct irqaction *irq)
+{
+}
+
+void __cpuinit mips_clockevent_init(void)
+{
+        uint64_t mips_freq = mips_hpt_frequency;
+        unsigned int cpu = smp_processor_id();
+        struct clock_event_device *cd;
+        unsigned int irq = MIPS_CPU_IRQ_BASE + 7;
+
+        if (!cpu_has_counter)
+                return;
+
+        if (cpu == 0)
+                cd = &mips_clockevent;
+        else
+                cd = kzalloc(sizeof(*cd), GFP_ATOMIC);
+        if (!cd)
+                return;         /* We're probably roadkill ...  */
+
+        cd->name                = "MIPS";
+        cd->features            = CLOCK_EVT_FEAT_ONESHOT;
+
+        /* Calculate the min / max delta */
+        cd->mult        = div_sc((unsigned long) mips_freq, NSEC_PER_SEC, 32);
+        cd->shift               = 32;
+        cd->max_delta_ns        = clockevent_delta2ns(0x7fffffff, cd);
+        cd->min_delta_ns        = clockevent_delta2ns(0x30, cd);
+
+        cd->rating              = 300;
+        cd->irq                 = irq;
+        cd->cpumask             = cpumask_of_cpu(cpu);
+        cd->set_next_event      = mips_next_event;
+        cd->set_mode            = mips_set_mode;
+
+        global_cd[cpu] = cd;
+        clockevents_register_device(cd);
+
+        if (!cp0_timer_irq_installed) {
+#ifdef CONFIG_MIPS_MT_SMTC
+#define CPUCTR_IMASKBIT (0x100 << cp0_compare_irq)
+                setup_irq_smtc(irq, &timer_irqaction, CPUCTR_IMASKBIT);
+#else
+                setup_irq(irq, &timer_irqaction);
+#endif /* CONFIG_MIPS_MT_SMTC */
+                cp0_timer_irq_installed = 1;
+        }
+}
+
 void __init time_init(void)
 {
         plat_time_init();
@@ -407,11 +387,6 @@ void __init time_init(void)
                                 /* Calculate cache parameters.  */
                                 cycles_per_jiffy =
                                         (mips_hpt_frequency + HZ / 2) / HZ;
-                                /*
-                                 * This sets up the high precision
-                                 * timer for the first interrupt.
-                                 */
-                                c0_hpt_timer_init();
                         }
                 }
                 if (!mips_hpt_frequency)
@@ -421,6 +396,10 @@ void __init time_init(void)
                 printk("Using %u.%03u MHz high precision timer.\n",
                        ((mips_hpt_frequency + 500) / 1000) / 1000,
                        ((mips_hpt_frequency + 500) / 1000) % 1000);
+
+#ifdef CONFIG_IRQ_CPU
+                setup_irq(MIPS_CPU_IRQ_BASE + 7, &timer_irqaction);
+#endif
         }
 
         if (!mips_timer_ack)
@@ -441,4 +420,5 @@ void __init time_init(void)
         plat_timer_setup(&timer_irqaction);
 
         init_mips_clocksource();
+        mips_clockevent_init();
 }