1 files changed, 321 insertions, 0 deletions

diff --git a/arch/mips/kernel/cevt-smtc.c b/arch/mips/kernel/cevt-smtc.c
new file mode 100644
index 000000000000..5162fe4b5952
--- /dev/null
+++ b/arch/mips/kernel/cevt-smtc.c
@@ -0,0 +1,321 @@
+/*
+ * 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 <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 = 0L;
+        unsigned long reference;
+
+
+repeat:
+        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 __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;
+        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(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;
+}