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-rw-r--r--arch/mips/kernel/cevt-smtc.c324
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diff --git a/arch/mips/kernel/cevt-smtc.c b/arch/mips/kernel/cevt-smtc.c
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--- a/arch/mips/kernel/cevt-smtc.c
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-/*
- * This file is subject to the terms and conditions of the GNU General Public
- * License. See the file "COPYING" in the main directory of this archive
- * for more details.
- *
- * Copyright (C) 2007 MIPS Technologies, Inc.
- * Copyright (C) 2007 Ralf Baechle <ralf@linux-mips.org>
- * Copyright (C) 2008 Kevin D. Kissell, Paralogos sarl
- */
-#include <linux/clockchips.h>
-#include <linux/interrupt.h>
-#include <linux/percpu.h>
-#include <linux/smp.h>
-#include <linux/irq.h>
-
-#include <asm/smtc_ipi.h>
-#include <asm/time.h>
-#include <asm/cevt-r4k.h>
-
-/*
- * Variant clock event timer support for SMTC on MIPS 34K, 1004K
- * or other MIPS MT cores.
- *
- * Notes on SMTC Support:
- *
- * SMTC has multiple microthread TCs pretending to be Linux CPUs.
- * But there's only one Count/Compare pair per VPE, and Compare
- * interrupts are taken opportunisitically by available TCs
- * bound to the VPE with the Count register. The new timer
- * framework provides for global broadcasts, but we really
- * want VPE-level multicasts for best behavior. So instead
- * of invoking the high-level clock-event broadcast code,
- * this version of SMTC support uses the historical SMTC
- * multicast mechanisms "under the hood", appearing to the
- * generic clock layer as if the interrupts are per-CPU.
- *
- * The approach taken here is to maintain a set of NR_CPUS
- * virtual timers, and track which "CPU" needs to be alerted
- * at each event.
- *
- * It's unlikely that we'll see a MIPS MT core with more than
- * 2 VPEs, but we *know* that we won't need to handle more
- * VPEs than we have "CPUs". So NCPUs arrays of NCPUs elements
- * is always going to be overkill, but always going to be enough.
- */
-
-unsigned long smtc_nexttime[NR_CPUS][NR_CPUS];
-static int smtc_nextinvpe[NR_CPUS];
-
-/*
- * Timestamps stored are absolute values to be programmed
- * into Count register. Valid timestamps will never be zero.
- * If a Zero Count value is actually calculated, it is converted
- * to be a 1, which will introduce 1 or two CPU cycles of error
- * roughly once every four billion events, which at 1000 HZ means
- * about once every 50 days. If that's actually a problem, one
- * could alternate squashing 0 to 1 and to -1.
- */
-
-#define MAKEVALID(x) (((x) == 0L) ? 1L : (x))
-#define ISVALID(x) ((x) != 0L)
-
-/*
- * Time comparison is subtle, as it's really truncated
- * modular arithmetic.
- */
-
-#define IS_SOONER(a, b, reference) \
- (((a) - (unsigned long)(reference)) < ((b) - (unsigned long)(reference)))
-
-/*
- * CATCHUP_INCREMENT, used when the function falls behind the counter.
- * Could be an increasing function instead of a constant;
- */
-
-#define CATCHUP_INCREMENT 64
-
-static int mips_next_event(unsigned long delta,
- struct clock_event_device *evt)
-{
- unsigned long flags;
- unsigned int mtflags;
- unsigned long timestamp, reference, previous;
- unsigned long nextcomp = 0L;
- int vpe = current_cpu_data.vpe_id;
- int cpu = smp_processor_id();
- local_irq_save(flags);
- mtflags = dmt();
-
- /*
- * Maintain the per-TC virtual timer
- * and program the per-VPE shared Count register
- * as appropriate here...
- */
- reference = (unsigned long)read_c0_count();
- timestamp = MAKEVALID(reference + delta);
- /*
- * To really model the clock, we have to catch the case
- * where the current next-in-VPE timestamp is the old
- * timestamp for the calling CPE, but the new value is
- * in fact later. In that case, we have to do a full
- * scan and discover the new next-in-VPE CPU id and
- * timestamp.
- */
- previous = smtc_nexttime[vpe][cpu];
- if (cpu == smtc_nextinvpe[vpe] && ISVALID(previous)
- && IS_SOONER(previous, timestamp, reference)) {
- int i;
- int soonest = cpu;
-
- /*
- * Update timestamp array here, so that new
- * value gets considered along with those of
- * other virtual CPUs on the VPE.
- */
- smtc_nexttime[vpe][cpu] = timestamp;
- for_each_online_cpu(i) {
- if (ISVALID(smtc_nexttime[vpe][i])
- && IS_SOONER(smtc_nexttime[vpe][i],
- smtc_nexttime[vpe][soonest], reference)) {
- soonest = i;
- }
- }
- smtc_nextinvpe[vpe] = soonest;
- nextcomp = smtc_nexttime[vpe][soonest];
- /*
- * Otherwise, we don't have to process the whole array rank,
- * we just have to see if the event horizon has gotten closer.
- */
- } else {
- if (!ISVALID(smtc_nexttime[vpe][smtc_nextinvpe[vpe]]) ||
- IS_SOONER(timestamp,
- smtc_nexttime[vpe][smtc_nextinvpe[vpe]], reference)) {
- smtc_nextinvpe[vpe] = cpu;
- nextcomp = timestamp;
- }
- /*
- * Since next-in-VPE may me the same as the executing
- * virtual CPU, we update the array *after* checking
- * its value.
- */
- smtc_nexttime[vpe][cpu] = timestamp;
- }
-
- /*
- * It may be that, in fact, we don't need to update Compare,
- * but if we do, we want to make sure we didn't fall into
- * a crack just behind Count.
- */
- if (ISVALID(nextcomp)) {
- write_c0_compare(nextcomp);
- ehb();
- /*
- * We never return an error, we just make sure
- * that we trigger the handlers as quickly as
- * we can if we fell behind.
- */
- while ((nextcomp - (unsigned long)read_c0_count())
- > (unsigned long)LONG_MAX) {
- nextcomp += CATCHUP_INCREMENT;
- write_c0_compare(nextcomp);
- ehb();
- }
- }
- emt(mtflags);
- local_irq_restore(flags);
- return 0;
-}
-
-
-void smtc_distribute_timer(int vpe)
-{
- unsigned long flags;
- unsigned int mtflags;
- int cpu;
- struct clock_event_device *cd;
- unsigned long nextstamp;
- unsigned long reference;
-
-
-repeat:
- nextstamp = 0L;
- for_each_online_cpu(cpu) {
- /*
- * Find virtual CPUs within the current VPE who have
- * unserviced timer requests whose time is now past.
- */
- local_irq_save(flags);
- mtflags = dmt();
- if (cpu_data[cpu].vpe_id == vpe &&
- ISVALID(smtc_nexttime[vpe][cpu])) {
- reference = (unsigned long)read_c0_count();
- if ((smtc_nexttime[vpe][cpu] - reference)
- > (unsigned long)LONG_MAX) {
- smtc_nexttime[vpe][cpu] = 0L;
- emt(mtflags);
- local_irq_restore(flags);
- /*
- * We don't send IPIs to ourself.
- */
- if (cpu != smp_processor_id()) {
- smtc_send_ipi(cpu, SMTC_CLOCK_TICK, 0);
- } else {
- cd = &per_cpu(mips_clockevent_device, cpu);
- cd->event_handler(cd);
- }
- } else {
- /* Local to VPE but Valid Time not yet reached. */
- if (!ISVALID(nextstamp) ||
- IS_SOONER(smtc_nexttime[vpe][cpu], nextstamp,
- reference)) {
- smtc_nextinvpe[vpe] = cpu;
- nextstamp = smtc_nexttime[vpe][cpu];
- }
- emt(mtflags);
- local_irq_restore(flags);
- }
- } else {
- emt(mtflags);
- local_irq_restore(flags);
-
- }
- }
- /* Reprogram for interrupt at next soonest timestamp for VPE */
- if (ISVALID(nextstamp)) {
- write_c0_compare(nextstamp);
- ehb();
- if ((nextstamp - (unsigned long)read_c0_count())
- > (unsigned long)LONG_MAX)
- goto repeat;
- }
-}
-
-
-irqreturn_t c0_compare_interrupt(int irq, void *dev_id)
-{
- int cpu = smp_processor_id();
-
- /* If we're running SMTC, we've got MIPS MT and therefore MIPS32R2 */
- handle_perf_irq(1);
-
- if (read_c0_cause() & (1 << 30)) {
- /* Clear Count/Compare Interrupt */
- write_c0_compare(read_c0_compare());
- smtc_distribute_timer(cpu_data[cpu].vpe_id);
- }
- return IRQ_HANDLED;
-}
-
-
-int smtc_clockevent_init(void)
-{
- uint64_t mips_freq = mips_hpt_frequency;
- unsigned int cpu = smp_processor_id();
- struct clock_event_device *cd;
- unsigned int irq;
- int i;
- int j;
-
- if (!cpu_has_counter || !mips_hpt_frequency)
- return -ENXIO;
- if (cpu == 0) {
- for (i = 0; i < num_possible_cpus(); i++) {
- smtc_nextinvpe[i] = 0;
- for (j = 0; j < num_possible_cpus(); j++)
- smtc_nexttime[i][j] = 0L;
- }
- /*
- * SMTC also can't have the usablility test
- * run by secondary TCs once Compare is in use.
- */
- if (!c0_compare_int_usable())
- return -ENXIO;
- }
-
- /*
- * With vectored interrupts things are getting platform specific.
- * get_c0_compare_int is a hook to allow a platform to return the
- * interrupt number of it's liking.
- */
- irq = MIPS_CPU_IRQ_BASE + cp0_compare_irq;
- if (get_c0_compare_int)
- irq = get_c0_compare_int();
-
- cd = &per_cpu(mips_clockevent_device, cpu);
-
- 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(0x300, cd);
-
- cd->rating = 300;
- cd->irq = irq;
- cd->cpumask = cpumask_of(cpu);
- cd->set_next_event = mips_next_event;
- cd->set_mode = mips_set_clock_mode;
- cd->event_handler = mips_event_handler;
-
- clockevents_register_device(cd);
-
- /*
- * On SMTC we only want to do the data structure
- * initialization and IRQ setup once.
- */
- if (cpu)
- return 0;
- /*
- * And we need the hwmask associated with the c0_compare
- * vector to be initialized.
- */
- irq_hwmask[irq] = (0x100 << cp0_compare_irq);
- if (cp0_timer_irq_installed)
- return 0;
-
- cp0_timer_irq_installed = 1;
-
- setup_irq(irq, &c0_compare_irqaction);
-
- return 0;
-}